All Abstracts

OPTICAL CHARACTERIZATION OF AN EDDY INDUCED DIATOM BLOOM IN THE LEE OF HAWAII

Nencioli, Francesco¹; Chang Spada, Grace¹; Twardowski, Michael<sup>2

1</sup>SEA Lab 5092 Rhoads ave. #a, Santa Barbara, CA, 93111, United States; ²Dep. of Research, WET Labs Inc., Narragansett, RI, 02882, United States

Optical measurements were collected during the E-FluxIII field experiment in the lee of Hawaii. The focus of the experiment was the cyclonic eddy Opal. Vertical profiles of chlorophyll fluorescence and beam attenuation at the center of the eddy show a relatively sharp Deep Chlorophyll Maximum, and broader peaks in beam transmission that extended to shallower depths. Microscopy of collected water samples revealed that the DCM was diatom dominated, and that the broader peak in beam transmission was due to a layer of unhealthy diatoms and empty frustules on top of the DCM. Here we investigate the relationship between scattering ratio (bbp/bp) and chlorophyll to attenuation coefficient ratio (Chl/cp) to optically characterize this interesting feature.

Our preliminary results show that an inverse relationship between bbp/bp and Chl/cp, also reported by others, is respected only up to the DCM. There, Chl/cp increases whereas bbp/bp remains similar to values found in the empty frustule layer. We hypothesize that this is the result of a packaging effect, i.e. frustule concentrations in the two layers are similar; however chlorophyll concentrations within the DCM with diatoms increases, therefore we observe progressively higher values of Chl/Cp for constant values of bbp/bp.

Increased values of both ratios are observed below the DCM. Vertical profiles of chlorophyll and attenuation coefficient show that here, cp decreases to values much lower than the values found above the DCM for similar chlorophyll concentrations. This might indicate that at these depths remineralization becomes a dominant process. Lower values of cp for similar values of chlorophyll concentrations found in the upper layer is consistent with cells that are degraded and thus reduced in size as they sink from the DCM to the deep ocean.

USE OF MODIS OCEAN COLOR IMAGERY FOR IMPROVED DETECTION AND MONITORING OF KARENIA BREVIS BLOOMS IN THE GULF OF MEXICO

Amin, Ruhul¹; Zhou, Jing¹; Gilerson, Alex ¹; Gross, Barry¹; Moshary, Fred¹; Ahmed, Sam<sup>1

1</sup>140 St @ Convent Ave, New York, NY, 10031, United States

Karenia brevis (K. brevis) blooms are of great interest and have been commonly reported throughout the Gulf of Mexico. However, detection still remains a challenge from space with standard bio-optical algorithms due to the uncertainty of atmospheric correction, and interference from high concentrations of organic and inorganic materials in optically complex coastal waters. We propose a simple normalized difference technique, which for convenience we call the K. brevis bloom index KBBI = (Rrs(678)-Rrs(667))/ (Rrs(678)+Rrs(667)), capable of detecting potential areas of K. brevis blooms from MODIS ocean color measurements. This index takes advantage of low backscattering efficiency of K. brevis. Remote sensing reflectance has a local minimum around 667nm (MODIS band 13) which is less than the signal at 678nm (MODIS band 14) when chlorophyll fluorescence is a significant fraction of water leaving radiance in the red bands; this increases the KBBI numerator. At the same time, lower reflectance values reduce the index denominator. As a result, the KBBI as a function of chlorophyll concentration for K. brevis differs from the similar function for the non- K. brevis blooms allowing K. brevis bloom detection to be more accurate and reliable. To assess the index, simulations including chlorophyll fluorescence based on the non-K. brevis bloom and K. brevis bloom were performed to determine the threshold of the detection conditions for possible K. brevis bloom using this technique. The approach was successfully applied to well documented blooms of K. brevis in the Gulf of Mexico and compared to other detection techniques, including FLH. Initial comparison indicates that this technique is generally capable of defining the area of K. brevis blooms more precisely and with fewer false alarms in the highly scattering and/or CDOM rich waters.

IMPROVED FLUORESCENCE MODELING AND RETRIEVAL IN COASTAL ZONES

Gilerson, Alexander¹; Zhou, Jing¹; Hlaing, Soe¹; Ioannou, Ioannis¹; Gross, Barry¹; Moshary, Fred¹; Ahmed, Sam<sup>1

1</sup>City College of the City University of New York 140 St @ Convent Ave, New York, NY, 10031, United States

Results of simulations and field measurements on the contribution of chlorophyll fluorescence to the reflectance spectra in coastal waters with a wide variety of water components are presented. This includes parameterization of fluorescence amplitude as a function of concentrations of water constituents, performance of fluorescence height (FLH) algorithms, their sensitivity to types of phytoplankton species and atmospheric correction models, dependence on illumination and viewing angles. Based on this parameterized model, near surface fluorescence quantum yield was indirectly estimated through a statistical analysis of the relationship between the chlorophyll concentration [Chl] and the shift of the total NIR peak from the fluorescence peak at 685 nm on reflectance spectra. On the other hand, a more direct measurement approach for the quantum yield was obtained by direct comparison of measured spectra with simulated spectra constructed from underwater attenuation and absorption spectral data (measured by WET Labs ac-s) together with fluorescence amplitude models based on insitu [Chl] measurements. Both approaches point to a smaller than expected quantum efficiency (0.3% – 0.5%) with less variability than normally believed. In addition, our modified FLH model applied to both MODIS and MERIS sensor bands are used to explore retrieval performance over a wide range of conditions. Performance based on actual MODIS and MERIS satellite imagery will also be presented.

A NEW ALGORITHM FOR CALCULATING PRODUCTIVITY FROM OCEAN COLOR DERIVED CHLOROPHYLL-A

Marra, John¹; Hyde, Kimberly²; O'Reilly, Jay<sup>2

1</sup>Brooklyn College/CUNY 2900 Bedford Ave, Brooklyn, NY, 11210, United States; ²NOAA, Narragansett, Rhode Island, 02883, Afghanistan

We investigate the use of a new model, Ocean Productivity from Absorption and Light (OPAL) in calculating primary productivity from ocean color. (2003). The OPAL model generates profiles of chlorophyll estimated from the SeaWiFS chlorophyll using the algorithm from the literature and uses the absorption properties in the water column to vertically resolve estimates of light attenuation in approximately 100 strata within the euphotic zone. Absorption by pure water is assumed to be a constant value over PAR wavelengths; chlorophyll-specific phytoplankton absorption is parameterized empirically; absorption by photosynthetic pigments is distinguished from total absorption; and absorption by colored dissolved organic matter (CDOM) is calculated based on the idea that upwelled water will have a high CDOM, which then becomes photo-oxidized with time near the surface. The chlorophyll-specific phytoplankton absorption is used to calculate productivity, while absorption by pigments, water, and CDOM are used to vertically resolve light attenuation. SST, which is used as a proxy for seasonal changes in the phytoplankton community, is related to the chlorophyll-specific absorption coefficient. The quantum efficiency is obtained from a hyperbolic tangent and a constant φmax. The model is tested using in situ productivity data from our database. A global map of productivity will be shown.

MATCHING THE TOTAL AND POLARIZED WATERLEAVING RADIANCE CONTRIBUTIONS TO THE MULTIANGLE AND MULTISPECTRAL REMOTE SENSING MEASUREMENT CAPABILITIES OF THE 2009 NASA/GLORY MISSION

Chowdhary, Jacek¹; Cairns, Brian¹; Travis, Larry¹; Mishchenko, Michael<sup>1

1</sup>NASA/GISS & Columbia University 2880 Broadway, New York, NY, 10025, United States

The polarization intensity of light scattered by particles exhibits features as a function of wavelength and of scattering angle that are distinctively different from the features for the total intensity of this light. The polarized and total intensity features exhibit also very different sensitivities to particle properties such as size, shape, and composition. Finally, these sensitivities vary themselves with particle properties. For example, the polarization of light scattered by low-refractive particles (relative to the surrounding medium) such as marine particulates shows less features with scattering angle, and less variation with shape and size, than the corresponding features for light scattered by high-refractive particles such as atmospheric aerosols. This suggests that for observations over the ocean, one can use the different variations of polarized and total intensity features with observation angle and wavelength to separate aerosol signatures from changes in the ocean color and retrieve both these atmosphere-ocean system properties simultaneously.

However, the success of such retrievals depends strongly on the ability to measure total and polarized intensity features accurately, and on the numerical tools to match such features for observations over the ocean. This sets the stage for his talk as follows. First, we introduce the multi-angle, multi-spectral measuring capabilities of the polarimeter onboard the NASA/Glory mission scheduled for launch in 2009. Secondly, we present the Case-1 water hydrosol model developed for this mission to compute realistic underwater light scattering contributions of total and polarized light to observations from space. Thirdly, we describe simulations of such contributions as a function of viewing angle, wavelength, and Chlorophyll a concentration, and illustrate the underlying potential for separating aerosol and ocean color retrievals. And fourthly, we discuss actual measurements and analyses of such contributions with an airborne version of the NASA/Glory polarimeter deployed at low (65 m) and high (4 km) altitudes.

SEASONAL VARIABILITY IN THE LIGHT ABSORPTION COEFFICIENT OF PHYTOPLANKTON, NON-ALGAL PARTICLES, AND COLORED DISSOLVED ORGANIC MATTER FOR WESTERN ARCTIC WATERS: IMPLICATIONS FOR DERIVING THE INDIVIDUAL COMPONENTS OF ABSORPTION USING OCEAN COLOR

Matsuoka, Atsushi¹; Hill, Victoria²; Babin, Marcel<sup>1

1</sup>Laboratoire d'Oceanographie de Villefranche (LOV) 06238 Villefranche-sur-mer Cedex, France, Villefranche-sur-mer, --, 06238, France; ²Earth and atmospheric sciences, the department of ocean, Norfolk, VA, 23529, United States

The light absorption properties of particulate and dissolved materials determine the behavior of visible light in oceanic waters and therefore, the accuracy of ocean color based algorithms. While the general absorption properties of these materials have been reported for western Arctic waters, their seasonal variability remains unknown. This is of particular importance as recent declines in sea ice cover have made possible longer seasonal ocean color observations of the western Arctic and the performance of global and regional algorithms needs to be assessed to allow analysis of biogeochemical processes. We investigated the light absorption coefficients of phytoplankton [a_φ(λ)], non-algal particles [a_NAP(λ)], and colored dissolved organic matter [a_CDOM(λ)] through all ice-free periods (from May to October) in the western Arctic. a_φ(440) covaried strongly with chlorophyll a (chl a), although the chl a specific a_φ(440) [a_φ(440)*] declined significantly from spring to autumn. The lower a_φ(440)* can be explained by the seasonal succession from smaller to larger sized phytoplankton species. Despite the seasonal variability, the a_φ(440) was also highly correlated with a_φ(λ) at other wavelengths (i.e., 410, 490, 510, 555, 620, and 670 nm) which approximately correspond to the band of SeaWiFS, MODIS and MERIS ocean color sensors. The spectral slope of a_NAP(λ) from the blue to the red was relatively constant, while that of a_CDOM(λ) from the blue to the green showed inverse correlation with a_CDOM(440). Variability in these two components was significantly different among seasons. These results suggest that when chl a and the related absorption coefficients of constituents in waters are derived from ocean color, the seasonal variability in a_φ(λ), a_NAP(λ), and a_CDOM(λ) should be considered.

DEVELOPMENT OF SIMULTANEOUS MULTI-WAVELENGTH EXCITATION FLUOROMETER

Oishi, Tomohiko¹; Tanaka, Akihiko¹; Yano, Shintaro¹; Ebata, Hiroki¹; Takahashi, Yo-hei¹; Kondo, Naotake¹; Tan, Hiroyuki²; Doerffer, Roland<sup>2

1</sup>Tokai University Orido 3-20-1, Shimizu-Ku, Shizuoka City, --, 424-8610, Japan; ²GKSS Research Centre, Geestchacht/Max-Plank Strasse, Hamburg, 21502, Germany

A simple and cost effective Simultaneous Multi-wavelength Excitation Fluorometer is presented. Using a newly developed excitation method, we show that the wavelength dependence of fluorescence at a given excitation wavelength can be easily retrieved. Our proposed method is that the fluorescence from a sample detected by a single sensor is excited simultaneously with different wavelength. Another advantage of the method is that the measurement time is independent with the number of excitation wavelength we use.

Further, by extending this method, we demonstrate that we can easily realize an in-situ type fluorometer, which obtain the excitation-emission fluorescence contour map of phytoplankton. The results show that we could determine theclass of phytoplankton by utilizing the difference of the excitation-emission fluorescence contour map, although it is first trial. It is promising method for used in field validations concerning ocean colour remote sensing

INFLUENCE OF MEASUREMENT AND ENVIRONMENTAL CONDITIONS ON BOTTOM REFLECTANCE MEASUREMENTS

Pinnel, Nicole¹; Gege, Peter <sup>2

1</sup>Murdoch University South St , Murdoch , --, WA, 6150, Australia; ²German Aerospace Center (DLR), Wessling, Oberpfaffenhofen, 82234, Germany

Bottom albedo measurements are often used as input of optical inversion models for shallow water habitat mapping as e.g. macrophytes species, seagrass and coral reef habitats. Spectral discrimination of various species underwater have first to be understood before they can be mapped using physical based remote sensing techniques. To make quantitative conclusions about species discrimination, spectral libraries are essential to extract these fingerprints of various substrate types. However such spectral libraries generally contain errors as they often are highly influenced by environmental conditions, such as changing illumination, sunangle, wave action, watercolumn and varying substrate densities, often leading to high exclusion of valuable spectral readings and/or time intensive statistical corrections. This results in major difficulties in making them transferable to other shallow water systems or comparison with other spectral libraries. Physical understanding of various factors which influence bottom albedo is therefore essential. Radiance and irradiance reflectance spectra of homogeneous freshwater macrophytes measured with a submersible spectroradiometer in 2003 and 2004 at two different lakes were used to investigate these influencing factors. The aim is to provide better understanding of underwater measurements, improve spectral separability between classes and achieve a better comparison between spectral libraries making exchange of such databases more reliable.

RADIANCE REFLECTED FROM A WIND BLOWN SURFACE CALCULATED FROM MEASUREMENTS

Høkedal, Jo<sup>1

1</sup>Narvik University College PO Box 385, Narvik, --, 8505, Norway

A set of measured radiance has been used to compute the reflected radiance on a wind blown sea-surface. Direct solar radiance and diffuse sky radiance have been measured on clear sky occations at different wavelengths, solar elevations and directions. Using a numerically modelled surface, with slopes as described by Cox and Munk, the surface reflected radiance has been calculated for numerous conditions. The calculated reflected radiances are then studied as function of direction, incident radiance and wind conditions.

LONG TERM STATISTICS OF REMOTELY SENSED PARAMETERS IN THE BALTIC SEA WITH MERIS-DATA

Krawczyk, Harald¹; Neumann, Andreas¹; Riha, Stefan<sup>1

1</sup>German Aerospace Center Rutherfordstreet 2, Berlin, --, D-12489, Germany

The Baltic Sea is an important ecological factor for all the riparian states. Therefore there is a high interest to continuously obtain detailed information about its ecological state. Due to a pan-European interest in the survey of the marine and coastal environment - ESA funded the GMES Service Element project MARCOAST started in 2005. Within the frame of this project a regular (daily) service of the determination of water properties basing on the interpretation of MERIS data was established. It allows a routine estimation of the quality of all relevant European water basins/areas. DLR developed a number of algorithms allowing the interpretation of water constituent parameters with special focus to the specific inherent bio-optical properties of the Baltic Sea. They allow the provision of quantitative maps of Chlorophyll, Suspended Matter, Gelbstoff and Water Transparency. The results are regularly provided to the State Ministry for the Environment, Nature Conservation and Geology of the state Mecklenburg-Vorpommern (LUNG). Since the start of the project in 2005 a large number of data could be collected and can now be subjected to a broad statistical analysis. The current presentation will describe the used interpretation scheme and algorithms and investigate the long-term statistical behavior of the mentioned parameters for different years. This gives interesting inputs for climatologic data bases and can be a valuable contribution for the estimation of the time development of the Baltic Sea water quality. Additionally a number of comparisons of remotely sensed parameters with in-situ measurements will be shown and discussed.

VALIDATION OF VARIOUS REMOTE SENSING ALGORITHMS FOR ESTIMATION OF ABSORPTION BY COLORED DISSOLVED ORGANIC MATTER IN THE BALTIC SEA FROM SEAWIFS AND MODIS IMAGERY

Kowalczuk, Piotr¹; Darecki, Miroslaw¹; Zablocka, Monika²; Gorecka, Izabela<sup>1

1</sup>Institute of Oceanology PAS Powstancow Warszawy 55, Sopot, --, 81-712, Poland; ²Institute of Oceanography, University of Gdansk /al. Marszalka Pilsudskiego 46, Gdynia, POMORSKIE, PL 81 - 378, Poland

Colored dissolved organic matter (CDOM) is one of the major determinants of the optical properties of natural waters and it directly affects both the availability and spectral quality of light in the water column. The CDOM is a part of the Dissolved Organic Matter pool and through its optical signatures its possible to estimate the concentration of Dissolved Organic Carbon in coastal areas. Thus ocean color remote sensing may be applied in carbon cycle studies in the coastal ocean and semi-enclosed seas. An extensive bio-optical data set from field measurements was used to evaluate the performance of two semi-analytical: GSM01 (Maritorena et al., 2002) and Carder et al., (1999) and one empirical (Kowalczuk et al., 2005) algorithms for estimation of CDOM absorption have been validated in the Baltic Sea. The data set includes coincident measurements of radiometric quantities, and absorption coefficient of CDOM, which were taken on 33 cruises between 2000 and 2006. At first stage of the analysis the accuracy of the empirical algorithm by Kowalczuk et al., (2005) has been assessed using in situ measurements of the remote sensing reflectance. The CDOM absorption coefficient, aCDOM(400), has been estimated with an error that exceeded 155% (RMS). Validation results improved greatly, when matching points located in Gulf of Gdansk close to Vistula River outlet have been eliminated from the data set: errors in a_CDOM(400) estimation were: Bias = 5%, RMS = 54%, R² = 0.43. In the second stage of the analysis the empirical algorithm has been tested on the satellite data from SeaWiFS and MODIS imagery. The satellite data were atmospherically corrected with the MUMM algorithm designed for turbid coastal and inland waters and implemented in the SeaDAS software. Results of the best case scenario of estimation of CDOM absorption coefficient, a_CDOM(400), based on the SeaWiFS data were: Bias = -1.7%, RMS = 23.6%, R² = 0.50. Application of MODIS data leads to less accurate estimation of the a_CDOM(400): Bias = -3.3%, RMS = 19.4%, R² = 0.38. Accuracy assessment of performance of standard semi-analytical algorithms available in the SeaWiFS and MODIS imagery processing software has revealed that both algorithms (GSM_01 and Carder) underestimate the CDOM absorption in the Baltic Sea with mean systematic and random errors that exceed 70%.

EXPLOITATION OF MULTIANGULAR AND POLARIMETRIC REMOTELY SENSED DATA FROM SPACE FOR OCEAN COLOR RETRIEVAL IN OPEN OCEAN WATERS

Harmel, tristan¹; Chami, malik<sup>1

1</sup>LOV-UPMC LOV, B.P. 08 , Villefranche sur Mer, --, 06230, France

PARASOL (Polarization and Anisotropy of Reflectance for Atmospheric Sciences coupled with Observations from a Lidar) satellite instrument has been deployed in 2005 to provide complete observations of radiative properties of the atmosphere and ocean. The PARASOL sensor is currently the only one which is able to perform multiangular and polarized acquisitions combined with the spectral information. Our study focuses on the exploitation of the polarized and directional measurements carried out by PARASOL for remote sensing of the ocean color in open ocean waters. First, the variations in the polarized signal acquired in a visible spectral band (namely 490 nm) with water constituents are analyzed using radiative transfer modeling together with satellite data. The analysis reveals the property of invariance of the polarized satellite radiance at 490 nm with respect to phytoplankton concentration for the open ocean water case. Second, an original atmospheric correction algorithm is developed based on the latter results to improve the retrieval accuracy of oceanic parameters.. The new atmospheric correction algorithm consists in two steps. The first step focuses on the retrieval of atmospheric parameters using the influence of directional properties of the aerosols (including the non spherical aerosols) on the polarized and unpolarized radiance. the second step of the algorithm deals with the retrieval of the marine reflectance using a coupled atmosphere-ocean radiative transfer model that includes the polarization state of light. As a validation, the comparison of marine reflectances derived from one year PARASOL atmospherically corrected images with in situ measurements which are routinely collected by the BOUSSOLE buoy in the Mediterranean Sea, will be performed. Note that the proposed atmospheric correction algorithm might be extended to any sensors capable of measuring the directionality and polarization from space such as the Aerosol Polarimetry Sensor which will be shortly launched on the Glory (NASA) satellite.

OCEAN COLOUR, BIO-OPTICS AND HARMFUL ALGAL BLOOMS: A GEOHAB PERSPECTIVE

Bernard, Stewart¹; Babin, Marcel²; Kudela, Raphael M³; Allen, Icarus<sup>4

1</sup>GEOHAB SSC and CSIR, 1 Jan Cilliers Street, Stellenbosch, --, 7599, South Africa; ²GEOHAB SSC & Laboratoire d'Océanographie de Villefranche, Villefranche-Sur-Mer, Provence-Alpes-Cote d'Azur, 06238, France; ³GEOHAB SSC & University of California Santa Cruz 1156 High Street, Santa Cruz, CA, 95064, United States; ⁴GEOHAB SSC and Plymouth Marine Laboratory, Prospect Place, Plymouth, Devon, PL1 3DH, United Kingdom

he GEOHAB programme seeks to address the development of improved remote observation systems for harmful algae: identifying gaps in knowledge, and stimulating development and improved application of relevant techniques. Ocean colour remote sensing has demonstrated considerable potential for the observation of harmful algal blooms (HABs). However, there are still fundamental problems with the application of rigorous ocean colour techniques in optically complex coastal waters. The high levels of uncertainty currently associated with coastal products compromise many HAB applications seeking to make use of remotely sensed data e.g. bloom detection and tracking, empirical ecological studies, and coupled ecological-hydrodynamic models. The challenges facing ocean colour based harmful algal applications are reviewed here, using studies from a variety of coastal ecosystems. Atmospheric correction schemes considered suitable for the open ocean often perform poorly in turbid, atmospherically complex coastal waters, where a lack of suitable validation data hampers improvement. In addition, the often high biomass associated with many HAB events, and Case-2 water problems, lead to the failure of standard ocean colour products. Better coastal data and new specific products are needed, and some new approaches are discussed - fluorescence line height, and analytical and red wavelength based algorithms. HAB detection places rigorous demands on our understanding of causal processes; radiative transfer and empirical studies examining the potential and problems for the detection of algal community change in different systems are discussed. In situ bio-optical instrumentation similarly has considerable potential in harmful algal focused observations systems, and HAB applications are often used as development and marketing motivators. However, there is a need for robust, inexpensive instrumentation that can be easily implemented by coastal groups globally, and potential approaches for achieving this are discussed.

BIOGEO-OPTICS: THEORETICAL AND APPLIED ASPECTS OF MINERAL AND ORGANIC MASS-SPECIFIC SCATTERING CROSS-SECTIONS

Stavn, Robert Hans¹; Richter, Scott<sup>2

1</sup>University of North Carolina/Greensboro PO Box 26174, Greensboro, NC, 27402-6174, United States; ²PO Box 26174, Greensboro, NC, 27402-6174, United States

There are more and more uses of mass-specific scattering cross sections of suspended particulates being discovered, such as the inversion of remote-sensing reflectance to determine concentrations of suspended mater. It is therefore important to explore the theoretical limits of this parameter. It is conveniently measured in the field and it has significant theoretical content. The choice of particle size distribution significantly affects the mass-specific scattering cross section and we will explore the theoretical consequences of choosing realistic and unrealistic particle size distributions in determining these limits.

Recently we described a new method of partitioning the particle scattering coefficient into two major components, mineral and organic. The method employs mass-specific scattering cross sections determined from a new Model II multiple linear regression model. We demonstrate the characteristics of this regression model that make it an optimum estimator of mass-specific scattering cross sections. The Model I estimate of the first independent variable (mineral mass-specific scattering cross section) is always an underestimate of the mass-specific scattering cross section. The second independent variable (organic mass-specific scattering cross section) can be either an overestimate or an underestimate of the mass-specific scattering cross section, which has not been observed before.

There are significant differences in the suspended mineral matter of the western and eastern portions of the northern Gulf of Mexico. Variations in the content of suspended particulate mineral matter in the northern Gulf of Mexico and its effect on the mass-specific mineral scattering cross sections and remote-sensing reflectance will be demonstrated.

CHARACTERIZING WATER MASS PROPERTIES IN RIVER DOMINATED COASTAL WATERS USING UNDERWAY HYPERSPECTRAL REMOTE SENSING REFLECTANCE

Lohrenz, Steven¹; Cai, Wei-Jun²; Chen, Xiaogang¹; Tuel, Merritt<sup>1

1</sup>University of Southern Mississippi 1020 Balch Boulevard, Stennis Space Center, MS, 39529, United States; ²University of Georgia, Athens, Georgia, 30602, United States

A focus of current research in aquatic optics is to improve our understanding of the diverse processes that influence optical properties and their relationship to key constituents including algal pigments, chromophoric dissolved organic matter and suspended particulate matter. Optically complex coastal waters represent a challenge for ocean color remote sensing because of the high degree of spatial heterogeneity and limitations in the performance of algorithms. Ship-based underway hyperspectral observations of remote sensing reflectance provide a means for improved spatial resolution and greater degrees of freedom for semi-analytical algorithms. Here we describe a series of complementary observations of surface hyperspectral radiance and irradiance and in situ measurements of apparent and inherent optical properties and key constituents in coastal waters of the northern Gulf of Mexico. The HyerSAS-UV system was used to provide above-water measurements of radiance and irradiance, as well as extended spectral range into the UV-B, thereby yielding broad spatial and temporal coverage and higher frequency sampling. Results illustrate the utility of remote sensing reflectance as means of tracking water mass properties in an optically complex coastal regime, the Mississippi River plume.

UNDERWATER IMAGERY, A MEASURING TOOL TO EXTEND OUR SPATIO-TEMPORAL UNDERSTANDING OF BENTHIC ORGANISMS DYNAMICS: CASE STUDY OF A 2 YEARS LONG MONITORING OF THE MACROALGAE CODIUM ELISABETHAE IN THE AZORES

Sirjacobs, Damien¹; Tempera, Fernando²; Cardigos, Frederico²; Santos, Ricardo Serrao²; Bouquegneau, Jean-Marie<sup>3

1</sup>Mare Center, University of Liège GHER, Allée de la Physique, B5, Sart-Tilman, Liège, --, 4000, Belgium; ²Department of Oceanography and Fisheries, University of the Azores; Cais de santa Cruz, Horta, Azores, PT-9901-862 , Portugal; ³Mare Center, Laboratory of Oceanology, University of Liège, Allée de la Chimie B6c, Sart-Tilman, Liège, Liège, 4000, Belgium

Foreseeing a time when Autonomous Underwater Vehicles will be used for regular monitoring of biological ressources over large areas (Pascoal et al, 2000), benthic habitat mapping studies exploits underwater imagery to complete bathymetric and substrate informations by biological occupation maps (Santos et al.; 2001). Still, images are not frequently used as real measurement tool over large areas and population estimates are generally qualitative.

Benthic long living macroalgae are potential indicators of coastal environmental changes (Duarte, 1999). The present work focused on a quantitative underwater imagery monitoring of the macro algae Codium elisabethae in an Azorean Site of Community Importance of the Natura 2000 network (Tempera et al., 2001). Two study sites were selected for this, the first being classified as no-go reserve and shelters very high population density, the second site holds a rather sparse population in an environmentally exposed area.

Between august 2003 and november 2005, 15 imagery covers were acquired from scuba-diving. Image processing allowed mosaicking, automatic or interactive detection of individuals and extraction of population structure (Sirjacobs, 2002; Sirjacobs et al., 2006). Chi-square test with in situ measurements confirmed the validity of a centimeter precision estimation of population structure for individuals above 4 cm diameter. Seasonal variations of density, biomass and cover rate were quantified. Population reduction was sharp in the fall 2003 and density didn’t recover completely in spring and summer 2004. During the following year, population of the protected site maintained density and biomass, while at the exposed site population density dropped. Important variability of structures and densities were observed at small spatial scale. Automatic change detection at individual level yielded dynamical parameters as growth, recrutement, and mortality. In biological population statistics, it is mandatory to produce such information from thousands of individuals, and the imagery approach turned it possible regarding the limitations of scuba-diving work-time.

This study is the first long term monitoring of benthic macroalgae dynamics with underwater imagery and quantified both the unexpected intensity of summer growth rate of the Azorean Codium elisabethae populations, as well as the seasonal fluctuations of their primary production.

References:

Duarte, C. M., Agusti, S, Kennedy, H; Vaqué, D. (1999) The mediterranean climate as a template for Mediterranean marine ecosystems: the example of the northeast Spanish littoral. Progress in Oceanography 44, pp 245-270.

Pascoal, A., P. Oliveira, C. Silvestre, L. Sebastião, M. Rufino, V. Barroso, J. Gomes, G. Ayela, P. Coince, M. Cardew, A. Ryan, H. Braithwaite, N. Cardew, J. Trepte, N. Seube, J. Champeau, P. Dhaussy, V. Sauce, R. Moitié, R. Santos, F. Cardigos, M. Brussieux, P. Dando (2000). Robotic Ocean Vehicles for Marine Science Applications: the European ASIMOV Project. Presented at OCEANS'2000.

Santos, R.S., F. Tempera, F. Cardigos & A. Pascoal (2001) Mapping SACs for Management Purposes in the Azores. Presented in the Habitat Mapping ICES Workshop in Bergen, Norway: "Mapping the Sea-floor", February 2001.

http://www.horta.uac.pt/projectos/marov/Media/Bergen.jpg

Sirjacobs, D. (2002). Matlab designed Image analysis software for detection of Codium elisabethae and calculation of population statistics. Summer training work realised within the MAROV Project (Mapping of Marine Habitats of the Azores using Robotic Ocean Vehicles), co-ordinated by the Department of Oceanography and Fisheries, University of the Azores, Faial Island . ERASMUS grant report. University of Liège, 31 p.

http://www.horta.uac.pt/projectos/marov/reports/Final/Damien_2002.pdf

Sirjacobs, D.; Tempera, F.; Cardigos, F.; Gobert, S.; Lepoint, G.; Santos, R.S.; Bouquegneau, J.-M. (2006). Study of the structure, distribution and dynamics of Codium elisabethae populations in the reef ecosystem of Faial Island (Azores), use of submarine image analysis, in: Mees, J.; Seys, J. (Ed.) (2006). VLIZ Young Scientists’ Day, Brugge, Belgium 31 March 2006: book of abstracts. VLIZ Special Publication, 30: pp. 56.

Tempera , F., P. Afonso, T. Morato, R. Prieto, M. Silva, A. Cruz, J. Gonçalves & R. Serrão Santos (2001). Biological Assemblages of the Faial-Pico Channel SACs (in Portuguese). Departamento de Oceanografia e Pescas da Universidade dos Açores, Horta. Arquivos do DOP, Série Relatórios Internos, nº 7/2001, vi+95 pp.

TOWARD THE DEVELOPMENT OF AN OIL SLICK DETECTION SYSTEM USING OPTICAL DATA

Bignami, Francesco¹; Pisano, Andrea ¹; Santoleri, Rosalia¹; Evans, Robert<sup>2

1</sup>Via Fosso del Cavaliere 100, Rome, --, 00133, Italy; ²RSMAS, UMIAMI , Miami, florida, FL 33149-1098, United States

The object of this work is to present the first results of the Italian Space Agency-funded project PRIMI for the development a modular system for the operational monitoring (observation via SAR and optical remote sensing, forecasting, report generation) of marine pollution caused by hydrocarbon spills in the Mediterranean Sea. We present a new methodology for the detection of oil spills at sea using MODIS data. The methodology was developed using the imagery relative to a set of known oil spill cases (Lebanon coastal oil spills of July-August 2006). This technique consists in oil/water contrast enhancement via the elimination of the oceanic, Rayleigh scattering and part of the aerosol signals in the TOA reflectances (MODIS rhot_nnn product) in selected visible and near infrared bands. The elimination of the above natural variability leaves a ‘flattened’ version of the input reflectance image in each band, in which oil slicks tend to stand out more distinctly than in the original rhot_nnn image. These flattened images in the selected bands are then fed to a segmentation/clustering algorithm, which identifies a variable number reflectance mode values in each scene, thus classifying the latter in a set of sub-regions, some of which contain the oil slicks. The simplification of the original image with a continuous variability into a clustered image with a restricted number of modes encodable into colors enables a trained operator to more readily identify oil slicks. Also, the possibility of completely automatizing the detection process is discussed.

VARIABILITY IN GLOBAL OCEAN PHYTOPLANKTON DISTRIBUTION OVER 1979-2006

MASOTTI, Italo¹; ALVAIN, Severine²; MOULIN, Cyril¹; ANTOINE, David<sup>3

1</sup>LSCE/IPSL (CEA-CNRS-UVSQ) CEA Saclay - bat. 712, Gif-sur-Yvette, --, 91191, France; ²LOG (CNRS-ULCO-USTL), Wimereux, Nord, 62930, France; ³LOV (CNRS-UPMC), Villefranche-sur-Mer, Sud, 06238, France

Recently, reanalysis of long-term ocean color data (CZCS and SeaWiFS; Antoine et al., 2005) has shown that world ocean average phytoplankton chlorophyll levels show an increase of 20% over the last two decades. It is however unknown whether this increase is associated with a change in the distribution of phytoplankton groups or if it simply corresponds to an increase of the productivity. Within the framework of the GLOBPHY project, the distribution of the phytoplankton groups was monitored by applying the PHYSAT method (Alvain et al., 2005) to the historical ocean color data series from CZCS, OCTS and SeaWiFS sensors. The PHYSAT algorithm allows identification of several phytoplankton, like nanoeucaryotes, prochlorococcus, synechococcus and diatoms. Because both sensors (OCTS-SeaWiFS) are very similar, OCTS data were processed with the standard PHYSAT algorithm to cover the 1996-1997 period during which a large El Niño event occurred, just before the SeaWiFS era. Our analysis of this dataset (1996-2006) evidences a strong variability in the distribution of phytoplankton groups at both regional and global scales. In the equatorial region (0°-5°S), a three-fold increase of nanoeucaryotes frequency was detected in opposition to a two-fold decrease of synechococcus during the early stages of El Niño conditions (May-June 1997, OCTS). The impact of this El Niño is however not confined to the Equatorial Pacific and has affected the global ocean. The processing of CZCS data with PHYSAT has required several adaptations of this algorithm due to the lower performances and the reduced number of spectral bands of the sensor. Despites higher uncertainties, the phytoplankton groups distribution obtained with CZCS is globally consistent with that of SeaWiFS. A comparison of variability in global phytoplankton distribution between 1979-1982 (CZCS) and 1999-2002 (SeaWiFS) suggests an increase in nanoeucaryotes at high latitudes (>40°) and in the equatorial region (10°S-10°N ) for prochlorococcus and synechococcus during 1999-2002. Our results show variability in global ocean phytoplankton distribution over a 20-year timescale. Strong variability observed over the inter-annual and inter-decadal scales must be explained in order to understand which environmental variables control this shifting phytoplankton distribution.

COMPARISON OF GLOBAL PFT DISTRIBUTIONS OBTAINED WITH VARIOUS EXISTING ALGORITHMS

MOULIN, Cyril¹; ALVAIN, Severine²; BRICAUD, Annick³; CIOTTI, Aurea⁴; CLAUSTRE, Hervé³; DESSAILLY, David²; GENTILI, Bernard³; LOISEL, Hubert²; UITZ, Julia<sup>5

1</sup>LSCE/IPSL (CEA-CNRS-UVSQ) CEA Saclay - bat. 712, Gif-sur-Yvette, --, 91191, France; ²LOG (CNRS-ULCO-USTL), Wimereux, Nord, 62930, France; ³LOV (CNRS-UPMC), Villefranche-sur-Mer, Sud, 06238, France; ⁴AQUARELA, Sao Vicente, n, n, Brazil; ⁵SIO (UCSD), La Jolla, Ca, 92093, United States

Recently, several bio-optical algorithms have been proposed to detect or characterize Phytoplankton Functional Types (PFT) from global ocean color measurements. Despite their common goal, these algorithms are very different in terms of both approach and products, so that dedicated processing are required to perform a quantitative comparison of these new parameters. Two of these algorithms allow retrieving information about the phytoplankton size. The Uitz et al. (2006) algorithm relies on statistical relationships to spread the total chlorophyll-a concentration (Chl-a) into three classes of cell size (i.e., micro-, nano- and pico-phytoplankton), whereas the Ciotti and Bricaud (2006) algorithm examines the phytoplankton absorption spectrum to estimate a continuous size index that gives the ratio between micro- and pico-phytoplankton. Here we have used this index to spread Chl-a between the two classes in order to allow the comparison with the Uitz et al. (2006) product. The third algorithm that has been considered is that of Alvain et al. (2005), PHYSAT, which allows the identification of the dominant phytoplankton group among nanoeukaryotes, prochlorococcus, Synechococcus and diatoms. In order to compare these various PFT to the Inherent Optical Properties (IOP) of the waterbody, we also used the Loisel and Stramski (2000) algorithm to compute the absorption and particulate backscattering coefficients. The spectral slope of the backscattering coefficient, gamma, is known to be a proxy of the particle size. We present here a comparison of all these products for different regions. Despite the difference in terms of approaches, there is generally a remarkable similarity between the two “size” algorithms, in terms of both seasonal cycle and geographical distribution. The comparison with the PHYSAT results is more complicated. For most periods and for most regions, there are good agreements between the micro-phytoplankton class and Diatoms, especially during the periods of maximum Chl-a, and between the pico-phytoplankton class and Prochlorococcus or Synechococcus during the periods of minimum Chl-a. On the contrary, less correlation is observed between the nano-phytoplankton class and nanoeukaryotes, suggesting that this latter PFT might account for phytoplankton cells of various size. The comparison with IOP products shows that gamma is related to the variation of the relative proportion between small and larger particles (including phytoplankton as well as other particles, like detritus) and that its variability is well correlated with that of the phytoplankton size classes.

BIO-OPTICAL CONTROL ON REFLECTANCE IN THE NORTH EASTERN MEDITERRANEAN

Örek, Hasan¹; Beşiktepe, Şükrü Turan<sup>2

1</sup>METU-IMS Middle East Tech. Univ. Inst. of Marine Sciences. Erdemli, Mersin, --, tr33731, Turkey; ²NATO Undersea Research Centre, Viale San Bartolomeo, Genova, La Spezia, 19126, Italy

Comprehensive set of data collected during 2001-2005 reveal seasonal and inter annual variability in the bio-optical properties of the Northeastern Mediterranean. The data set includes upward and downward spectral irradiances, particle (Phytoplankton and Detritus), and CDOM absorption and phyto-pigment composition measured by HPLC. Irradiance measurements have done by Li-core UW1800 spectroradiometer both upward and downward. Irradiance reflectance was calculated from these measurements. Optical properties like diffusivity, reflectance, are controlled by particle or CDOM absorption or phytoplankton composition. Temporal and spatial variability of reflectance between offshore and coastal regions are observed. It was found that usually phytoplankton activity is controlling the reflectance properties at offshore; however concentration is not only controlling mechanism. Species composition is main reason reflectance variability. Reflectance peak values are changing between 400 to 500 nm in both offshore and coastal regions, but peak position in coastal regions are usually occurring between 450-500 nm. In offshore, peak shape and position are very variable according to phytoplankton composition. In summer period (May-August) system is usually dominated by Cyanobacteria and reflectance peaks are appearing around 410-420 nm. In winter, starting from late autumn, peak shape became broaden between 400-500 nm. Different than single peak shape reflectance, broaden and double peak shapes are observed in winter, where chlorophyll values are higher also. The main difference in this period is the species composition of phytoplankton. Whereas, in transition periods like in April both high CDOM and Chlorophyll and Phytoplankton absorption values observed with same reflectance peak shape in summer, that chlorophyll, CDOM etc. are relatively low. However, similar to summer period Cyanobacteria were dominating during April. As a conclusion; spatial and temporal variability of the optical properties of the N.E. Mediterranean is also controlled by species composition.

OCEAN COLOUR SENSORS CHARACTERISATION AND ERROR ESTIMATES OF RETRIEVED MERGED PARAMETERS FROM THE GLOBCOLOUR PROJECT

Fanton d'Andon, Odile Hembise¹; Antoine, David²; Mangin, Antoine³; Maritorena, Stéphane⁴; Durand, Dominique⁵; Pradhan, Yaswant⁶; Lavender, Samantha Jane⁷; Morel, André<sup>2

1</sup>ACRI 260 Route du Pin Montard, Sophia Antipolis, --, 06 904, France; ²Laboratoire d'Océanographie de Villefranche, Quai de La Darse, BP 8 , Villefranche sur Mer Cedex, PACA, 06238 , France; ³260 Route du Pin Montard, Sophia Antipolis, --, 06 904, France; ⁴University of California at Santa Barbara, 6841 Ellison Hall, Santa Barbara, CA 93106-3060, 93106-3060, United States; ⁵NIVA, Nordnesboder 5, PoBox 2026, Bergen, Bergen, N-5817 , Norway; ⁶University of Plymouth, Portland Square A403, Drake Circus, Plymouth, Devon, PL4 8AA, United Kingdom; ⁷ARGANS Limited, Tamar Science Park, 1 Davy Road, Derriford, Plymouth, Devon, PL6 8BX, United Kingdom

The ESA GlobColour project has produced a ten year time series of merged ocean colour products from available sensors (SeaWiFS, MODIS-Aqua, MERIS). The complete data set is available to the scientific community ( www.globcolour.info) and to the key users of the project (IOCCP, IOCCG and UKMO) in particular. Before the production of such a data set, a significant effort has been put on merging strategies and the characterisation of the input data. This analysis was conducted through an exhaustive match-up analysis for each of the sensors which has allowed the estimation of the uncertainties associated with each sensor as well as cross-comparisons among sensors. Error statistics from the initial sensor characterisation are used as an input to both the weighted averaging and the GSM merging methods, and propagate through the merging process to provide error estimates on the output merged products. The error estimates resulting from both merging methods and affecting the final bio-geophysical products were estimated and are presented and commented.

BIO-OPTICAL STUDIES ALONG THE PATAGONIAN SHELF-BREAK ZONE

Garcia, Carlos Alberto Eiras¹; Garcia, Virginia M. T.¹; Romero, Silvia I.²; Ferreira, Amábile¹; Dogliotti, Ana I.¹; Signorini, Sergio³; McClain, Charles R.<sup>3

1</sup>Federal University of Rio Grande Av Itália km 8, Rio Grande, --, 96201-900, Brazil; ²Servicio de Hidrografía Naval (SHN), Buenos Ayres, Ciudad de Buenos Aires, C1270 AVB, Argentina; ³Goddard Space Flight Center, Greenbelt, Maryland, MD 20771, United States

Ocean color images from the Patagonia shelf break in the Southwestern Atlantic Ocean, usually show high phytoplankton biomass patches during spring and summer periods.. The PATagonia EXperiment (PATEX) was specially designed to investigate the environmental factors that control the occurrence of these blooms, to characterize the phytoplankton assemblage and primary production rates, to determine the main nutrient levels and ratios associated with the bloom waters, to determine their bio-optical characteristics and the CO₂ fluxes in the studied area. Five cruises were conducted in November 2004, October 2006, March 2007, October 2007 and January 2008 when more than 120 oceanographic stations were occupied for physical, biogeochemical and optical studies along the large bloom extent in the Patagonian shelf-break (approximately 55,000 Km² of chlorophyll concentration >2 mg m^-3 chlorophyll patch). In this article, we report the physical environmental setting for biological production and the seawater bio-optical properties (spectral reflectance, backscattering, absorption of particles, beam attenuation, phytoplankton and colored dissolved organic matter, and chlorophyll-a concentration) measured during these five cruises. We found a remarkable bloom of diatoms and flagellates (~ 1,200 Km extension) in spring, which precedes the summer coccolithophore bloom in the frontal region. Primary production rates during the spring blooms were comparable with maxima seasonal productivity at Eastern Boundary Currents. Surface chlorophyll concentration ranged from 0.2 to 20 mg/m^-3 during the cruises. Particle (phytoplankton and detritus) and CDOM absorption coefficients measured in these waters were highly variable and showed a seasonal dependence. Comparisons between in-situ and satellite measurements (MODIS and SeaWiFS) of remote sensing reflectance, surface chlorophyll and inherent optical properties are also made in this work.

DERIVATIVE ANALYSIS OF LIGHT ABSORBANCE IN THE OPTICAL PHYTOPLANKTON DISCRIMINATOR

Kirkpatrick, Gary¹; Lohrenz, Steven ²; Moline, Mark³; Schofield, Oscar<sup>4

1</sup>Mote Marine Laboratory 1600 Ken Thompson Parkway, Sarasota, FL, 34236, United States; ²University of Southern Mississippi, Stennis Space Center, MS, 39529, United States; ³California Polytechnic State University, San Luis Obispo, CA, 93407, United States; ⁴Rutgers University, New Brunswick, NJ, 08903, United States

The Optical Phytoplankton Discriminator (OPD), first developed in the late 1990s as a harmful algal bloom detector (BreveBuster), has demonstrated applicability for CDOM mapping, phytoplankton community structure analysis and is currently being assessed for factoring the components of absorption in whole water. It has been adapted for deployment on ships, buoyancy and propeller driven autonomous underwater vehicles, buoyancy driven vertical profilers, buoys, channel marker and piers. The data stream from this network of instruments is received, processed and distributed by the Sarasota Operations of the Coastal Ocean Observation Laboratories to appropriate end users and displayed on the Web. The OPD is a hyperspectral device operating in the wavelength range from 300 to 800 nm with a spectrometer dispersion of 0.32 nm/pixel and an optical resolution of approximately 2.1 nm. Hence, the acquired particle absorbance spectra have high information content. The key to extracting the available information about pigmented particles has been the use of fourth derivative analysis. The application of multiple derivatives strongly attenuates monotonic and near-monotonic functions such as scattering and detrital absorption. Therefore, the spectra resulting from fourth derivative analyses represent only the pigment ensemble of the observed phytoplankton. These pigment spectra have been applied to correlation analyses against target harmful algal species as a non quantitative estimate of presence/absence. They have also been factored using a least-squares multiple regression routine of algal class libraries to obtain quantitative estimates of phytoplankton community taxonomic structure. Most recently, an attempt is being made to estimate the other components of light loss including scattering and detrital absorption in the instrument. This effort is utilizing iterative multiple regression and multiple integration routines.

PERFORMANCE PREDICTION FOR UNDERWATER ELECTRO-OPTICAL MINE IDENTIFICATION SYSTEMS

Giddings, Thomas¹; Shirron, Joseph<sup>1

1</sup>Metron, Inc. 11911 Freedom Dr., Reston, VA, 20190-5602, United States

Several electro-optical identification (EOID) systems are currently being incorporated into mine countermeasures (MCM) operations. The inclusion of these systems in fleet operations is accompanied by the need for accurate, robust, and timely EOID system performance predictions for effective mission planning. EODES software provides high-fidelity, validated models for several underwater EOID systems, including tools to compute performance estimates, determine optimal operational settings, and generate simulated images. The performance analysis products provide several key performance parameters required by tactical decision aids to assist in the development, planning, and execution of MCM missions. In particular, the performance prediction products may be used to guide asset allocation, track planning, and lane spacing decisions, and also to estimate MCM timelines, risk to MCM platforms, and the residual threat to maritime forces.

The performance of EOID systems is highly dependent on the optical properties of the operational environment. An accurate characterization of the optical properties in the areas of operations is therefore an important input to the EODES models. New developments in environmental sensing and computer modeling are making high-quality meteorological and oceanographic (METOC) data available to systems analysis tools such as EODES. Here we describe the physical and numerical models used to predict the environmental impact on EOID system performance, and show results from recent fleet exercises to illustrate how model outputs are used to aid in the development of operational tactics. In addition to operational applications, these performance estimates are also used in the design and evaluation of prospective systems and to inform investment and acquisition decisions to help ensure that an effective array of MCM assets is available to forces in the field.

DYNAMICS OF COLLOIDAL PARTICLES ASSOCIATED WITH VIRAL INFECTION OF MARINE BACTERIA

Uitz, Julia¹; Baudoux, Anne-Claire²; Wright, Vanessa M.¹; Malfatti, Francesca ²; Dubranna, Jean¹; Stramski, Dariusz¹; Azam, Farooq <sup>2

1</sup>Scripps Institution of Oceanography - Marine Physical Lab 9500 Gilman Drive, La Jolla, CA, 92093-0238, United States; ²Scripps Institution of Oceanography - Marine Microbiology Lab 9500 Gilman Drive, La Jolla, CA, 92093-0202, United States

Although viruses are among the most abundant colloidal particles in the ocean, their direct impact on ocean optics is thought to be of minor importance. Nonetheless, the particles produced by the lysis of bacteria or phytoplankton following viral infection may significantly affect marine optical properties, especially light backscattering. Furthermore, viral-induced lysis products could serve as “seeds” for particle aggregation, which in turn may supply hotspots for microbial processes and promote sinking of particulate matter into the deep ocean. An experiment was conducted to examine the formation of colloidal particles resulting from the viral infection of the antagonist marine bacteria SWAT-3, over a 3-day period. Our approach relies primarily on the use of a flow field-flow fractionation (Fl FFF) system integrated with a multi-angle light scattering meter. Fl FFF allows a size-based fractionation of macromolecules and colloids, while the scattering sensor measures the volume scattering function of the fractionated samples. The angle-dependent light scattering signal is then inverted to determine the size distribution of colloids. Our measurements were supplemented with other analyses, including the enumeration of viruses and bacteria by epifluorescence microscopy and particle counting with an electrical resistive particle sizer (Coulter). An increase in the abundance of viruses was detected 6 hours after infection, and most of bacterial cells underwent lysis within 12 hours. The increase in viral abundance was accompanied by the formation of significant amounts of colloids, primarily within the size range 100-300 nm (equivalent spherical diameter). In contrast, colloidal particles remained undetectable in the non-infected bacteria (control) samples. Our results indicate that viral infection stimulates the production of small colloidal particles which could aggregate to form larger-sized colloids and microparticles on time scales from several hours to a few days.

POLARIZATION MEASUREMENTS IN COASTAL WATERS USING HYPERSPECTRAL MULTI-ANGULAR SENSOR

Tonizzo, Alberto¹; Zhou, Jing¹; Gilerson, Alex ¹; Iijima, Takako¹; Twardowski, Michael²; Gray, Deric³; Arnone, Robert³; Gross, Barry¹; Moshary, Fred¹; Ahmed, Sam<sup>1

1</sup>City College of the City University of New York 160 Convent Ave., New York, NY, 10031, United States; ²Department of Research, WET Labs, Inc., Narragansett, Rhode Island, 02882, United States; ³Naval Research Laboratory, Code 7333, Stennis Space Center, Mississippi, 39529, United States

Polarization characteristics of coastal waters are of great interest since they can be used in retrieval algorithms for the separation of organic and inorganic particulates, in improving underwater visibility, in understandingthe physics of light propagation of ocean lidar and in other active techniques and applications. To study these characteristics a new Stokes vector instrument has been developed by the Optical Remote Sensing Laboratory at CCNY. The instrumentusesthree hyperspectral Satlantic radiance sensors eachwith a polarizer positioned in front of it and with polarizationaxes aligned at 0, 90 and 45 deg. The sensors are mounted on ascanning systemwhich is rotated by a stepping motor, so the sensors canchange their angular positionin the range 0-180 deg in respect to the direction of the incoming sun light. Downwelling irradiance is also monitored by a fourth hyperspectral sensor positioned on the deck of the boat. Results of measurements of water polarization properties using this instrument during a recent cruise on R/V "Connecticut" in the coastal areas of New York Harbor- Sandy Hook, NJ region are presented for waters with chlorophyll concentrations 1-10 mg/m³, minerals concentrations1-2 mg/l, and CDOM absorption at 400 nm approximately 0.5 m^-1. Components of the Stokes vector and values of degree of polarization measured in the main scattering plane are compared with simulated ones using a Monte Carlo radiative transfer codefor theatmosphere-ocean system showing reasonable agreement.

OPTICAL OBSERVATIONS OF LARGE DIATOMS AND SINKING PARTICLES DURING THE NORTH ATLANTIC SPRING BLOOM MADE FROM SEAGLIDERS, FLOATS, AND A SHIP

Perry, Mary Jane¹; Briggs, Nathan¹; Gray, Amanda²; Lee, Craig M²; Rehm, Eric²; D'Asaro, Eric A²; Gudmundsson, Kristinn³; Kallin, Emily¹; Lampitt, Richard ⁴; Poulton, Nicole ⁵; Rynearson, Tatiana⁶; Sieracki, Michael E<sup>5

1</sup>University of Maine Darling Marine Center, 193 Clark's Cove Road, Walpole, ME, 04573-3307, United States; ²University of Washington, Seattle, Washington, 98105, United States; ³Hafrannsoknastofnunin, Reykjavick, Reykjavik, 121 , Iceland; ⁴National Oceanography Centre, Southampton, Southampton, Southampton, SO14 3ZH, United Kingdom; ⁵Bigelow Laboratory for Ocean Sciences, West Boothbay Harbor, Maine, 04575, United States; ⁶University of Rhode Island, Narragansett, Rhode Island, 02882-1197, United States

Using optically-instrumented autonomous platforms, NAB08 provided continuous observation of the North Atlantic spring bloom – from pre-bloom to post-bloom. In early April when chlorophyll concentrations were still low (<0.3 mg m^-3), four Seagliders and two Lagrangian floats were deployed around 59ºN, 20ºW. In May, the R/V Knorr rendezvoused with the autonomous platforms, that by then had moved several degrees northeast. The three-week process cruise had two major goals: (1) to collect optical, biological, and chemical measurements to validate autonomous sensors, and (2) to enable more comprehensive interpretation of optical data. The Knorr arrived just as the bloom began. By mid-May, mixed layer depths shoaled and the bloom was maximal: chlorophyll concentrations were high (to 5 mg m^-3) and the phytoplankton assemblage was dominated by large and chain-forming diatoms, as documented by FlowCAM and microscopy. The large cells resulted in high-frequency variability in measurements of chlorophyll fluorescence, optical backscatter, and beam transmission due to movement of large particles in and out of the optical-sensing volume. Later, discrete spikes in chlorophyll fluorescence, optical backscatter, and beam transmission began to appear below the mixed layer, first extending to 250 m and then progressively deeper (deepest depth sampled was 900 m, by Seaglider). These optical spikes were associated with sinking organic particles; the largest catch of sinking cells, based on visual observations by PELAGRA floating sediments traps, coincided with a horizontally and vertically wide-spread distribution of optical spikes observed both by ship and Seagliders. Throughout the experiment, mapping of bloom optical signatures by Seagliders, floats and ships revealed km-scale patchiness with an amplitude (O(factor of two)), as well as larger scale patchiness and eddies. These observations show the power of coordinated autonomous and ship-based sampling, using complementary bio-optical and biogeochemical measurements to measure coupled biophysical processes controlling ocean carbon fluxes.

BIO-OPTICAL OBSERVATIONS OF THE NORTH ATLANTIC SPRING BLOOM

Westberry, Toby K.¹; Dall'Olmo, Giorgio¹; Behrenfeld, Michael J.¹; Boss, Emmanuel<sup>2

1</sup>Oregon State University 2082 Cordley Hall, Corvallis, OR, 97331-2902, United States; ²School of Marine Sciences, University of Maine, Orono, ME, 04469, United States

The evolution of the North Atlantic Spring Bloom was observed using continuous, underway measurements of particle absorption and scattering indices in a ~10000 km² area centered on 61N, 26W. Spectral particulate beam attenuation (c_p), absorption (a_p), and backscattering (b_bp) were measured simultaneously using a novel flow-through system with an actuated valve and timer to intermittently direct seawater flow through 0.2 um filters. Initially, the phytoplankton community was dominated by large chain-forming diatoms, which were then succeeded by dinoflagellates and ultimately by picoeukaryotes, as revealed by flow cytometry, microscopy, and HPLC pigment analysis. Despite the wide range in taxonomic variability, consistent relationships between c_p and b_bp were observed. Further, the slope of this relationship was similar to that obtained in very different oceanic environments (from oligotrophic to mesotrophic). This covariability of the two scattering indices suggests that they are, in large part, sensitive to the same pool of particles or that the particle size distribution is relatively conserved across large gradients in bulk chlorophyll (and presumably chlorophyll degradation products, as well). Coulter counter-based particle size distributions ranged from perfectly Junge-like to having pronounced peaks over the size range investigated (2-60um). In contrast to previous studies in the region, the bio-optical imprint of coccolithophorids was not observed in any of the quantities measured. Empirical relationships between c_p, a_p, and b_bp with coincident biogeochemical measurements such as chlorophyll, particulate organic carbon, and biovolume-estimated phytoplankton specific carbon will also be discussed.

PHYTOPLANKTON BIO-OPTICAL MODELS USING POPULATIONS OF TWO-LAYERED SPHERES

Bernard, Stewart¹; Probyn, Trevor ²; Shillington, Frank<sup>3

1</sup>Council for Scientific and Industrial Research 11 Jan Cilliers Street, Stellenbosch, --, 7599, South Africa; ²Marine and Coastal Management, Bag X1, Roggebaai, Cape Town, Western Cape, 8001, South Africa; ³University of Cape Town, Private Bag, Rondebosch, Cape Town, Western Cape, 7701, South Africa

Inherent optical property and reflectance inversion models are presented, using a two-layered spherical geometry and equivalent size distribution scheme to simulate the optical properties of phytoplankton populations. The two-layered geometry is chosen as the simplest heterogeneous structure potentially capable of simulating algal angular scattering properties. Simple, single cell models are used to demonstrate the optical effects of varying cellular geometry, chloroplast volume and complex refractive index. The approach is expanded to polydispersed populations using equivalent size distribution models to demonstrate variability in simulated inherent optical properties for phytoplankton assemblages of changing dominant cell size and functional type. This algal population model is then used as a component of a forward reflectance model to compare modeled and measured reflectance data from high biomass blooms in the Benguela system. The approach is expanded to construct reflectance inversion algorithms for use with data from hyper-spectral in water reflectance, and multi-spectral satellite derived ocean colour. Preliminary validation, with an independent bio-optical data set from the southern Benguela, shows the algorithm capable of deriving Chl a concentrations through several orders of magnitude and an algal size descriptor under high biomass conditions. Algorithm performance is used to to briefly discuss returned phytoplankton backscattering characteristics. Finally, the algorithm is used with data from the MERIS sensor during several high biomass algal bloom events in the Benguela system to demonstrate potential utility for monitoring algal dynamics and detecting harmful algal blooms.

EVALUATION OF A SUBMERGED REMOTE SENSING (SRS) TECHNIQUE

Trees, Charles C.¹; Pennucci, Giuliana¹; Austin, Ros²; Petzold (Deceased), Ted<sup>3

1</sup>NATO Undersea Research Centre Viale San Bartolomeo 400, 19126 La Spezia, Italy, --, 19126, Italy; ²Center for Hydro-Optics & Remote Sensing/SDSU , San Diego, CA, 92120, United States; ³Visibility Laboratory/ SIO, San Diego, CA, 92120, United States

Currently, there are efforts at using autonomous underwater vehicles, gliders and moorings to extend the spatial and temporal measurement capabilities in oceanographic research. These platforms either operate at fixed depths, programmed to change depths, sea saw, undulated or profile through the water column. Sensor data collected by these platforms is usually internally recorded and then transmitted via satellite-based communications when at the surface or dump via a cable when retrieved by a vessel. A variety of optical instruments have been deployed on these observing platforms with most of them measuring inherent optical properties (IOPs) because day/night illumination differences does not affect these measurements, they can be directly related to in situ properties and are not sensitive to vehicle orientation. Fluorescence sensors also have provided very valuable information related to the biological and dissolved components in the ocean. Disadvantages of IOP measurements, such as absorption, scattering and attenuation measurements as well as fluorescence, are that they measure a small volume and in order to obtain a vertical distribution the platform must profile or undulate. The ability to measure integrated optical properties from the surface to the depth of a platform would be highly advantageous for moorings and AUVs. The Submerged Remote Sensing (SRS) technique takes downwelling irradiance at two wavelengths at a known depth below the ocean surface, and given time, date, position and the extra-terrestrial solar spectral irradiance, computes the total water and atmospheric attenuation above the sensor. Using irradiance profiles from the North Atlantic, the integrated diffuse attenuation (490 nm) was predicted for depths from 20 to 120 m. Mean K(490) ranged from 0.028 to 0.4 m-1 with the average ratio between the SRS to measured K(490) being 0.986 m-1, with a standard deviation of 0.073 m-1. The SRS technique was only published as an SIO Technical Memo 87-18 and is not easily available to the optical community. We plan to explore the robust nature of SRS algorithm using a much larger optical database that has been collected since 1988 at the Visibility Laboratory/SIO and Center for Hydro-Optics and Remote Sensing/SDSU, as well as attempt to extraplote this in to coastal areas.

DEVELOPMENT OF MERIS LAKE WATER ALGORITHMS: VALIDATION RESULTS

Koponen, Sampsa¹; Ruiz-Verdu, Antonio Ruiz-Verdú²; Heege, Thomas Heege³; Doerffer, Roland⁴; Brockmann, Carsten Brockmann⁵; Kallio, Kari ⁶; Pyhälahti, Timo ⁶; Pena, Ramon²; Polvorinos, Angel ⁷; Heblinski, Jörg Heblinski³; Ylöstalo, Pasi ⁶; Conde, Laura ²; Odermatt, Daniel ⁸; Estelles, Victor ⁹; Pulliainen, Jouni ¹⁰; Moreno, Jose⁹; Sorensen, Kai <sup>11

1</sup>Helsinki University of Technology (TKK) Otakaari 5a, Espoo, --, 02015, Finland; ²Centre for Hydrographic Studies - CEDEX, Pº Bajo de la Virgen del Puerto, 3, Madrid, 28005 , Spain; ³GKSS Forschungszentrum Geesthacht, Airport Oberpfaffenhofen, Gilching, D-82205 , Germany; ⁴GKSS Forschungszentrum Geesthacht, Max-Planck-Str., Geesthacht, 21502 , Germany; ⁵Brockmann Consult, Max-Planck-Str., Geesthacht, 21502 , Germany; ⁶Finnish Environment Institute (SYKE), Mechelininkatu 34a, Helsinki , 00251, Finland; ⁷University of Sevilla, Profesor García González, s/n, Sevilla, 41012 , Spain; ⁸University of Zurich, Winterthurerstr. 190, Zurich, CH-8057, Switzerland; ⁹University of Valencia, Dr. Moliner 50, Valencia, 46100 , Spain; ¹⁰Finnish Meteorological Institute (FMI), Erik Palménin aukio, Helsinki, 00560 , Finland; ¹¹Norwegian Institute for water research (NIVA), Gaustadalléen 21 , Oslo, NO-0349, Norway

During the ESA project “Development of MERIS Lake Water Algorithms” (Jan. 2007 – June 2008) two plug-in processors for deriving water quality information from lakes with MERIS data were developed and validated. The processors were developed for the BEAM toolbox and are based on the architecture of the MERIS Case 2 Regional –processor. They include an enhanced algorithm for atmospheric correction and new bio-optical algorithms for deriving inherent optical properties (IOP) and concentration (chl a and total suspended matter) data from atmospherically corrected reflectances. The neural networks for interpreting water bio-optical properties in boreal and eutrophic lakes were developed with IOP data from Finnish and Spanish lakes. Correction for the adjacency effect is tested with the ICOL-processor.

The processors were validated with in situ data collected from eleven lakes in Finland, Spain and Germany during April – August 2007. The lakes cover a wide range of water types from oligotrophic to hypereutrophic and to humic. The validation data include water leaving radiance reflectances, IOPs and concentrations of chl a and total suspended matter. Validation was also performed in Africa (Lake Victoria and Lake Manzalah).

The main results of the validation activities are presented and the applicability of the processor in different types of lakes is discussed. The results indicate the necessity of proper adjacency effect correction as well as necessity of algorithms trained to cover the observed water optical variability for different lake types.

BLENDING DISCRETE BIO-OPTICAL ALGORITHMS: A UNIFIED APPROACH TOWARDS REDUCING ERROR IN CHLOROPHYLL RETRIEVALS

Moore, Timothy¹; Campbell, Janet<sup>1

1</sup>University of New Hampshire OPAL, 142 Morse Hall, UNH, Durham, NH, 03824-3525, United States

Phytoplankton are the primary source of optical variability in the ocean, and thus their concentration in surface waters can be observed by ocean color sensors. Currently, there are two families of algorithms that derive chlorophyll a concentration (Chl) – a proxy for phytoplankton biomass. These are the empirical and semi-analytic algorithms. Such algorithms, parameterized from in-situ data, are currently used operationally to produce global maps of Chl. However, it is generally accepted that a single universal algorithm is not accurate everywhere, regardless of which type of algorithm is used.

Regional differences in the global empirical algorithm (OC4v4) have been shown to exhibit biases specific to the geographic ocean basin (e.g., Southern Ocean, North Atlantic). Similarly, semi-analytic algorithms require empirical parameterizations derived from in-situ data. Most models parameterize the relationship between the inherent optical properties (IOPs) of the water (absorption, scattering) and its constituents. On the global scale, IOPs vary over two orders of magnitude (Barnard et al. 1998) due to variations in particle size, pigment composition and packaging of algal cells, and overall particle composition. Since the constituents can vary from place to place and seasonally, it is believed that model parameterizations have to be locally derived for a particular water type, thus requiring the algorithm to decide when and where to use appropriate parameters.

Little attention has been given to the challenge of working with a suite of algorithms that switch at natural oceanic boundaries. How does one decide when to choose one algorithm over another? How can we avoid artificial discontinuities at boundaries where two algorithms meet? The work reported here develops a concept of blending algorithms for different water types using a fuzzy logic approach, and is shown to work with both families of algorithms.

INHERENT OPTICAL PROPERTY MEASUREMENTS AND MODELING IN THE GREAT BARRIER REEF WORLD HERITAGE AREA

Slivkoff, Matthew¹; Mckinna, Lachlan²; Furnas, Miles<sup>3

1</sup>Curtin University / Australian Institute of Marine Science Kent St, Bentley, Perth, Western Australia, --, 6152, Australia; ²James Cook University, Townsville, Queensland, 4810, Australia; ³Australian Institute of Marine Science, Cape Ferguson, Queensland, 4810, Australia

There has been considerable interest in recent times to utilise data from polar orbiting SeaWiFS and MODIS sensors to assess and manage anthropogenic land runoff into the Great Barrier Reef system. The often turbid and complex nature of terrestrially-sourced materials demands ocean colour remote sensing algorithm approaches where the remotely sensed signal is decomposed into the water constituent Inherent Optical Properties (IOPS). Due to the latitudinal extent of the Great Barrier Reef and the geographical variability of the coastline that interacts with the reef, inherent optical property sampling was performed in an attempt to understand the regional and temporal variability of optically significant water constituents and how these optical properties relate to historically-measured water quality parameters in the region including Chlorophyll-a concentration, Total Suspended Solids and Dissolved Organic Carbon.

Phytoplankton and non-algal particulate absorption coefficients were determined from a modified Quantitative Filter Technique (QFT), along with spectrophotometric Coloured Dissolved Organic Matter (CDOM) absorption measurements. An ac-9 was used to verify the pathlength amplification factor of the modified QFT technique and to determine the total scattering coefficients for clear reef waters and turbid flood-plume waters. Backscattering measurements were also made using a Hydroscat-6.

Based on these measurements, a set of spectral IOP models were derived with the intention of using a radiative transfer model optimization technique to invert hyperspectral remote sensing reflectance measurements to determine three water quality parameters simultaneously (Chlorophyll-a, Total Suspended Solids, Dissolved Organic Carbon).

CDOM- ABSORPTION FROM TROPICAL BLACK WATER RIVERS TO OPEN OCEAN -CONTRIBUTIONS OF COLLOIDAL SIZE FRACTIONS

Siegel, Herbert¹; Gerth, Monika¹; Stottmeister, Iris¹; Alling, Vanja<sup>2

1</sup>Leibniz Institute for Baltic Sea Research Warnemünde Seestrasse 15, Rostock-Warnemünde, --, D-18119, Germany; ²University of Stockholm, Stockholm, Stockholm, Frescativägen 54 a, Sweden

Absorption of coloured dissolved organic substances (CDOM) was measured in different regions of the world ocean from tropical black water rivers, over enclosed seas to the open ocean. The highest absorption coefficients ever measured was recognised in tropical peat draining rivers of central Sumatra Island of Indonesia. Enclosed seas covered the Black-, North-, and the Baltic Seas. Lowest absorptions were determined in the open parts of the Indian and Atlantic Oceans including the Caribbean Sea. In the Baltic Sea horizontal gradients with a north-south decrease are stronger pronounced than seasonal variations. By partial thawing of the permafrost soil in northern Europe high CDOM content is transported into the Bothnian Bay the northern most part of the Baltic Sea. Therefore, the highest absorptions in the Baltic occurred in this area. Because of the strong ice coverage during the measuring campaign the rivers could not be sampled. The different ice layers in the ice cores contained also CDOM. Samples of that region were used to split the colloids into different size fractions by ultra filtration. The fraction < 0.01µm (<1kDa) delivered the highest contribution in the absorption coefficients. This systematisation presents not only the highest variation range of CDOM absorption coefficients ever published but also the spectral behaviour of a wide range of water masses.

LIGHT-DRIVEN CARBON FLUXES IN THE ARCTIC OCEAN: THE BALANCE BETWEEN PHOTO-OXIDATION AND PHOTOSYNTHESIS IN THE CONTEXT OF CLIMATE CHANGE

Simon, Bélanger¹; Babin, Marcel<sup>2

1</sup>Département de biologie, chimie et géographie, Université du Québec à Rimouski, Rimouski, Québec, G5L 3A1, Canada; ²CNRS - Villefranche LOV, BP 8, Villefranche-sur-Mer Cedex, --, 06238, France

Primary production and CDOM photo-oxidation have opposing impacts on carbon fluxes in the ocean. The balance between the two processes may be significantly affected in the near future by climate change. This is especially true for the Arctic Ocean, which is increasingly exposed to light as perennial ice recedes, and which receives increasing amounts of terrigenous dissolved organic matter (tDOM) as the permafrost thaws and river discharges increase. In this study, we used remote sensing data to estimate the pan-Arctic distributions of primary production and CDOM photo-oxidation, and how they evolved from 1998 to now. Ocean color (merged data from SeaWiFS, MERIS and MODIS), ozone, cloud (ISCCP) and ice (SSMI) data are combined to run a UV-visible atmospheric radiative transfer code, and primary production and photo-oxidation models. We used state-of-the-art optical models for Case 2 waters, some being specific to the Arctic Ocean. A sensitivity analysis is conducted to assess the impact of chosen ocean color algorithms and of various model parameters on results. Our results provide the first pan-Arctic combined estimates of primary production and CDOM photo-oxidation based on remote sensing, and allow determining how these two processes compare. They indicate that CDOM photo-oxidation accounts for a major fraction of allochthonous organic carbon mineralization in the Arctic Ocean, and is comparable in magnitude to the fraction of gross primary production that ends up sequestered within the ocean bottom sediments. The ratio between photo-oxidation and primary production turns out being highly variable, which indicates significant competition for light between CDOM and phytoplankton. As a response to sea ice decline, both photo-oxidation and primary production showed increasing trends from 1998 to 2007. We speculate that the increasing photomineralization of tDOM is boosting the productivity of whole microbial communities and the food-web dynamics of the Arctic Ocean coastal.

SEASONAL VARIABILITY OF REMOTE SENSING FLUORESCENCE OVER THE SOUTHEAST BRAZILIAN CONTINENTAL SHELF

Ciotti, Aurea Maria¹; Barbosa, Fabiana Pestana<sup>1

1</sup>UNESP- CLP Praça Infante Dom Henrique S/N, Parque Bitaru, São Vicente, --, 01223-000, Brazil

Remote sensing natural fluorescence is a potential tool to estimate phytoplankton biomass over optical complex waters. Here we present a winter/summer analysis MODIS FLH (Fluorescence Line Height) variability over the continental shelf area between Cabo de São Tomé (RJ) and Cananéia (SP), were several sources of non-algal material exist. Biological production is moderate and nutrient input include continental outflow in the south and both costal and eddy-induced upwelling in the north. Previous studies show that CDOM is the major component for in situ light absorption. Global, weekly, level 3 MODIS-aqua and SeaWIFS images, with 4 km and 9 km spatial resolution respectively, were acquired from March 2005 to July 2007. Using SEADAS, maps of FLH, Chlorophyll-a, Sea Surface Temperature (SST), Normalized water-leaving radiance at 551 nm (nLw551) and Photosynthetically Active Radiation (PAR) were generated, and the interest area was divided into four main sub areas based on hydrographic features reported in the literature. For each sub area, the FLH was statistically related to all other estimated products, to identify the respective degrees of optical complexity. Results confirm an expected non-linear relationship between FLH and Chlorophyll-a in all sub areas and seasons, with smaller ratio values over the continental shelf during winter. However, FLH over the shelf decreased with the decrease of both SST and PAR, suggesting additional factors regulating FLH.

RESOLVING SURF ZONE PARTICLE DYNAMICS WITH HIGH SAMPLING RATE VOLUME SCATTERING FUNCTION MEASUREMENTS

Twardowski, Michael¹; Freeman, Scott¹; Vagle, Svein ²; Zhang, Xiadong³; Zaneveld, Ronald<sup>4

1</sup>WET Labs 165 Dean Knauss Dr, Narragansett, RI, 02882, United States; ²Institue of Ocean Sciences, Sidney, British Columbia, V8L 4B2, Canada; ³University of North Dakota, Grand Forks, North Dakota, 58202-9011, United States; ⁴WET Labs, Philomath, Oregon, 97370, United States

The surf zone is a dynamic and unique environment optically. Breaking waves generate submerged bubble particle populations at the air-sea interface which evolve rapidly over time and space. Wave action suspends sediment while surf zone currents continually redistribute water column particle fields. The physics driving these processes is not well understood. Optical property measurements were made off Scripps Pier, La Jolla, CA in January 2008 to better elucidate surf zone particle dynamics and the resulting optical impacts. Volume scattering function (VSF) measurements were resolved at 20 Hz at angles spanning 10 to 170 degrees in 10 degree increments with a prototype MASCOT device, and at 1 Hz with several multi-channel ECO sensors at angles in the backward direction between 100 and 150 degrees. The near-forward portion of the VSF from 0.1 to 20 degrees in 32 logarithmically spaced intervals was also measured at 1 Hz with a LISST device. Acoustic measurements of bubble size distributions were made concurrently with a bubble resonator affixed to the same instrument package. All measurements were made just below the air-sea interface by suspending the package over the side of the pier while the ebbing tide moved the surf zone past the package. Unique modification of the phase function was observed in passing suspended sediment plumes, in wave-injected bubble plumes, and combinations of these particle populations relative to the background. Specifically, sediment plumes exhibited higher relative backscattering levels than the background, while a clear phase function enhancement in the 60 to 80 degree range was observed in association with bubble plumes. Both features are consistent with theoretical predictions. Acoustic measurements corroborated the presence of bubbles. Phase function specificity for particle subpopulations should enable inversion of the VSF measured in the bulk sample to derive information such as size distribution and concentration of the primary subfractions as long as theoretical and/or empirical representations of the subfraction phase functions are accurate.

VARIATIONS OF PHOTOACCLIMATION RELATED TO ENVIRONMENTAL CONDITIONS

Comeau, Adam Joseph¹; Craig, Susanne¹; Babin, Marcel²; Lewis, Marlon¹; Bruyant, Flavienne¹; Cullen, John<sup>1

1</sup>Dalhousie University 1355 Oxford street, Department of Oceanography, Dalhousie University, Halifax, NS, B3H4J1, Canada; ²Laboratoire d’Océanographie de Villefranche, Villefranche-sur-Mer, France, 06238, France

By understanding factors that influence parameters related to photosynthesis, better estimates of primary productivity and particle dynamics can be obtained. We describe a new method to estimate photoacclimation, a physiological process that influences both photosynthesis vs. irradiance (P vs. E) parameters and chemical composition of phytoplankton, based on profiles of in situ fluorescence and irradiance and apply it to a variety of datasets collected all over the world, to examine its variability in relation to environmental variables. Profiles of in situ chlorophyll fluorescence have been routinely measured during oceanographic surveys for several decades. Near surface decreases of fluorescence yield, chlorophyll fluorescence normalized to some measure of phytoplankton biomass, are commonly observed during daytime profiles. This decrease in fluorescence is due to physiological processes, activated in high irradiance, which act to dissipate light energy absorbed by phytoplankton. Lab studies show that the irradiance at which this quenching of fluorescence yield begins is related to the light saturation parameter, of P vs E curves. With the simple requirements of irradiance and fluorescence yield profiles, this method can be applied to many existing datasets. Examining variations of the light level where fluorescence quenching begins in response to environmental variables such as average light in the mixed layer, will provide new information on how phytoplankton acclimate to their environment.

AN IMPROVED T-R SYSTEM FOR FILTERPAD MEASUREMENT OF PHYTOPLANKTON SPECTRAL ABSORPTION

Hargreaves, Bruce R.¹; Lance, Veronica P.²; Vaillancourt, Robert D.²; Marra, John F.<sup>2

1</sup>Lehigh University 31 Williams Drive, Bethlehem, PA, 18015, United States; ²Lamont-Doherty Earth Observatory, Columbia University, 61 Route 9W, PO Box 1000, Palisades, New York, 10964-8000, United States

The Transmittance-Reflectance (T-R) method for measuring spectral absorption of phytoplankton and other suspended particles in natural waters was introduced by Tassan and Ferrari in 1995 and subsequently improved by these authors.Their improved version of the venerable “Quantitative Filterpad Technique (QFT)” has the potential to dramatically increase the accuracy of particle absorption but it has not been widely adopted. Presented here is a new instrument plus modifications of the published T-R method representing additional improvements (pQFT-TR). This portable QFT-TR system provides battery-powered, rapid, compact, and accurate measurement of particle spectral absorption over UV, VIS, and NIR wavelengths and should facilitate wider adoption and new applications of the T-R approach.The new T-R system (designed to work with a portable computer and 25mm diameter glass fiber filters) includes reflectance integrating sphere, fiber optic diode array spectrometer, xenon flash lamp, optical filters & standards, and 12-volt DC power.Procedures have been developed to create and test a universal calibration of the system while removing various inherent artifacts caused by fluorescence, stray light, detector nonlinearity, and spectrometer wavelength errors. The new system has recently been tested by making hundreds of underway measurements of samples collected during the Southern Ocean GASEX cruise (February-April 2008, NASA award NNX07AV23G).Pigment absorption of cruise samples was determined by subtracting bleached particle spectra from the corresponding unbleached spectra as recommended by Tassan and Ferrari (1995) but using bleach diluted in isotonic sodium sulfate.Analysis of SO-GASEX cruise samples showed extremely high correspondence (r² greater than 95%) between the red peak pigment absorption (a_ph675 nm) and extracted chlorophyll-a concentration (determined by chlorophyll-a fluorescence measurements after methanol extraction). Correction of fluorescence artifacts in both %T and %R data increased a_ph675 by 44-50% (highest with low sample loading) compared to uncorrected measurements, and yielded average chlorophyll-specific absorption at 675 nm of 0.023 m² mg^-1.

FAST AND ACCURATE RETRIEVAL OF AEROSOL AND MARINE PARAMETERS FOR COASTAL WATERS

Hamre, Børge¹; Stamnes, Jakob J.¹; Li, Wei²; Stamnes, Knut²; Spurr, Rob<sup>3

1</sup>University of Bergen Allegaten 55, Bergen, --, 5007 Bergen, Norway; ²Stevens Institute of Technology, Hoboken, NJ, 07030, United States; ³RT Solutions Inc, Cambridge, MA, 02138, United States

Recently the retrieval of two aerosol parameters and three marine parameters from eight SEAWifs channels was demonstrated [W. Li, K. Stamnes, R. Spurr, and J.J. Stamnes, Simultaneous retrieval of aerosol prperties and ocean properties by optimal estimation: SeaWiFS case studies for the Santa Barbara Channel, Int. J. Remote. Sens., in press (2008)]. The two aerosol parameters are the optical depth at 865 nm and the bimodal fraction of large vs small particles, and the three marine parameters are the chlorophyll content, the CDOM absorption, and the backscattering coefficient. The retrieval was based on forward simulations using a linearized discrete ordinate method for the coupled atmosphere-ocean system and optimal estimation theory to solve the inverse or retrieval problem. Since the forward simulations are time consuming, we demonstrate in this paper that the retrieval speed can be increased by a factor of about one thousand using interpolation by means of a radial basis function neural net. As a result, we obtain accurate retrievals of aerosol and marine parameters for coastal waters at an operational speed.

SEASONAL VARIATIONS IN THE OPTICAL AND PHOTOSYNTHETIC CHARACTERISTICS OF A COASTAL INLET

Bouman, Heather¹; Platt, Trevor²; Sathyendranath, Shubha<sup>3

1</sup>Oxford University Dept of Earth Sciences, Oxford University, Parks Rd, Oxford, --, OX1 3PR, United Kingdom; ²Bedford Institute of Oceanography, Dartmouth, Nova Scotia, B2Y 4A2, Canada; ³Plymouth Marine Laboratory, Prospect Place, The Hoe, Plymouth, PL1 3DH, United Kingdom

Coastal ecosystems are subject to high levels of anthropogenic activity and therefore play an important role in issues of resource management. Continual monitoring of these waters is necessary to assess how human activity impacts the structure and function of these ecosystems and to estimate year-to-year fluctuations in their productivity. In situ optical sensors provide scientists with the potential of continual monitoring of changes in the ecological status of coastal waters over a range of spatial scales. By virtue of their close proximity to land, coastal waters are heavily influenced by optical components that are terrestrial in origin, which make the task of estimating the spectral quality and quality of irradiance available for photosynthesis difficult.

In this study, optical and photosynthetic characteristics of a coastal embayment (Bedford Basin, Nova Scotia) were measured with a nominal sampling frequency of once per week. Variability in the spectral shapes and magnitudes of absorption by CDOM, detritus and phytoplankton are assessed and their relationships with the physico-chemical and biological properties of the water column are examined. The influence of CDOM and phytoplankton absorption on the diffuse attenuation coefficients of spectral downwelling irradiance is discussed. In addition, changes in the photosynthetic properties of the phytoplankton community as they relate to variation in the optical and physical characteristics of the basin are explored. The implications of these findings for modelling primary production in coastal environments will also be addressed.

LONG-TERM GLOBAL OBSERVATIONS OF THE PARTICULATE BACKSCATTERING COEFFICIENT AND PARTICULATE ORGANIC CARBON IN THE FRAMEWORK OF THE GLOBPHY PROJECT

Duforet-Gaurier, Lucile¹; Loisel, Hubert¹; Dessailly, David¹; Nordkvist, Karin¹; Antoine, David<sup>2

1</sup>CNRS UMR 8187 LOG/ULCO 32 avenue Foch, Wimereux, --, 62930, France; ²LOV, Quai de la Darse, BP8 , Villefranche sur Mer, 06238, France

This study is proposed in the framework of the GLOBPHY project dedicated to the analysis of the decadal changes in the global ocean phytoplankton. A consistent time series of chlorophyll concentration, at global scale, was produced from the CZCS era (1979-1983) to the SeaWiFS era (1998-2002) by Antoine et al, 2005. The final data set showed an overall increase of the world ocean average phytoplankton chlorophyll (Chl) by as much as 22%. The general objective of the GLOBPHY project is to confirm and interpret these changes, by looking at the coherence between the phytoplankton changes and those of other physical and biogeochemical parameters. Therefore, we propose to derive, from the marine reflectance, other indicators than the chlorophyll concentration Chl. The geographic distribution and seasonal evolution of the particulate backscattering coefficient bbp is described over the whole ocean for the SeaWiFS and CZCS era. The monitoring of Chl and bbp is analyzed and compared to provide complementary information about the biogeo-chemical status of surface waters. Indeed, while Chl is a good index of the phytoplankton biomass, the particle backscattering coefficient bbp may be used to describe the spatio-temporal variability of the particulate organic carbon (POC) (Loisel et al, 2002). Until now, POC content obtained from space-borne observations are restricted to the surface. In this study, a relationship between the surface POC and the column-integrated POC is established from a statistical analysis of 563 in situ profiles collected in various oceanic areas. This empirical relationship is tested successfully against an independent in situ dataset composed of 197 vertical POC profiles.

A LIGHT ABSORPTION BUDGET FOR SOUTH PACIFIC WATERS

BRICAUD, Annick¹; BABIN, Marcel¹; CLAUSTRE, Hervé¹; RAS, Joséphine¹; TIECHE, Fanny<sup>1

1</sup>Laboratoire d'Océanographie de Villefranche BP 08, Villefranche-sur-Mer, --, 06238, France

The relative contributions of phytoplankton, non-algal particles and colored dissolved organic matter (CDOM) to total light absorption, and their variability, are essential information for bio-optical and biogeochemical models. They remain, however, poorly documented in the open ocean, particularly in clear waters because of the difficulty in measuring very low absorption coefficients. The BIOSOPE cruise (October-December 2004), from Marquesas Islands to Concepcion (Chile), investigated a large range of oceanic regimes from hyper-oligotrophic waters in the sub-tropical gyre, to eutrophic waters in the upwelling area off Chile. The spectral absorption coefficients of phytoplankton and non-algal particles were determined using the classical filter technique, while the CDOM absorption coefficients were measured using a spectrophotometer equipped with a 2-m capillary waveguide (UltraPath, WPI Inc.). Over the whole transect, the absorption coefficients of both dissolved and particulate components covered approximately two orders of magnitude, and in the gyre, they were among the lowest ever reported for open ocean waters. In the oligotrophic and mesotrophic waters, absorption coefficients of phytoplankton were notably lower than those measured in other oceanic areas with similar chlorophyll contents, indicating some deviation from the standard chlorophyll-absorption relationships. The contribution of absorption by non-algal particles to total particulate absorption showed large variations, not only along the vertical but also horizontally, ranging in the surface layer from 10-15% (at 440 nm) in the upwelling area to around 50% in the clearest waters. The slopes of absorption spectra of non-algal particles revealed structured spatial variability. The contribution of CDOM to total absorption showed also structured variations both along the vertical and along the transect, ranging within the surface layer from 25-40% (at 440 nm) in the upwelling area to more than 70% in the gyre. Finally, some features on absorption spectra of phytoplankton and CDOM were observed and will be discussed.

AERONET-OC: STRENGTHS AND WEAKNESSES OF A NETWORK FOR THE VALIDATION OF SATELLITE COASTAL RADIOMETRIC PRODUCTS

Zibordi, Giuseppe¹; Holben, Brent²; Slutsker, Ilya²; Giles, David²; D'Alimonte, Davide³; Melin, Frederic¹; Berthon, Jean-Francois¹; Vandemark, Doug⁴; Feng, Hui⁴; Schuster, Gregory⁵; Fabbri, Bryan ⁵; Kaitala, Seppo ⁶; Seppala, Jukka<sup>6

1</sup>Joint Research Centre Via E. Fermi 1, Ispra, --, 21027, Italy; ²NASA Goddard Space Flight Center, Greenbelt, MD, 20771, United States; ³Centro de Inteligencia Artificial / Universitade Nova de Lisboa, Caparica, Lisboa, 2819-516, Portugal; ⁴University of New Hampshire / OPAL, Durham, NH, 03824, United States; ⁵NASA Langley Research Center , Hampton, VA, 23681, United States; ⁶Finnish Institute of Marine Research , Helsinki , Helsinki, 00561, Sweden

The Ocean Color component of the Aerosol Robotic Network (AERONET-OC) has been implemented to support long-term satellite ocean color investigations through cross-site consistent and accurate measurements form above-water autonomous radiometer systems deployed on offshore fixed platforms. The ultimate purpose of AERONET-OC is the production of standardized measurements performed at different sites with identical measuring systems and protocols, calibrated using a single reference source and method, and processed with the same code.

The AERONET-OC primary data product is the normalized water leaving radiance determined at center-wavelengths of interest for satellite ocean color applications with uncertainties lower than 5% in the blue-green spectral regions and higher than 8% in the red.

Measurements from 6 sites counting the northern Adriatic Sea, the Baltic Proper, the Gulf of Finland, the Persian Gulf, and, the northern and southern margins of the Middle Atlantic Bay, have shown the capability of producing quality assured data over a wide range of bio-optical conditions including Case-2 yellow substance- and sediment-dominated waters.

This work briefly introduces network elements like: deployment sites, measurement method, instrument calibration, processing scheme, quality-assurance, uncertainties, data archive and products accessibility. Emphases is given to those elements which underline the network strengths (i.e., mostly standardization of any network element) and its weaknesses (i.e., the use of consolidated, but old-fashioned technology). The work also addresses the application of AERONET-OC data to the validation of primary satellite radiometric products over a variety of complex coastal waters and finally provides elements for the identification of new deployment sites most suitable to support satellite ocean color missions.

LOOKING AT “DENSE WATER” AND "FLUID SAND”. A CASE STUDY IN THE WADDEN SEA.

Hommersom, Annelies¹; Peters, Steef¹; Wernand, Marcel R.<sup>2

1</sup>Institute for Environmental Studies (IVM), Free University Amsterdam De Boelelaan 1085, Amsterdam, --, 1081 HV, Netherlands; ²Royal Netherlands Institute for Sea Research (NIOZ), Den Burg (Texel), P.O. Box 59, 1790 AB, Netherlands

The Wadden Sea is a shallow sea with mudflats and high concentrations of sand, chlorophyll and CDOM. In a period of two years 150 samples were taken to study the optical behaviour of the Wadden Sea. Total absorption and beam attenuation were measured with an AC9, CDOM absorption was measured in a cuvette, reflectance was measured with a TriOS system and concentrations of suspended particulate material, organic matter, and Chlorophyll-a were determined. Additional measurements included secchi depths, salinity, wind speed and - at some stations - filterpad measurements of chlorophyll-a specific pigment absorption and specific particle absorption.

These measurements are used to study the spatial and temporal variability of the optical properties of the Wadden Sea area. Temporal changes in concentrations, absorption and reflectance due to tides and between seasons are examined. Concentration ranges (Chlorophyll 5-50 ug/l, SPM 5-400 mg/l, CDOM(440) 2.5 1/m) and optical differences were large, mainly due to shallowness which leads to constant resuspension of bottom material, but also due to mixing of water from the North Sea with water from various rivers (Ems, Jade, Weser). Spatial patterns in absorption and reflectance have not been studied before in this area. The measurements will increase the calibration accuracy of optical remote sensing models of this area and contribute to the general knowledge of optical properties of tidal areas. First results will be presented of the comparison between processed MERIS images (using the Hydropt algorithm (Van der Woerd and Pasterkamp, 2008) calibrated with measured specific optical properties) and in-situ observed concentrations and spectra. From space the large heterogeneity of the area becomes visible.

DIEL AND SPATIAL VARIABILITY OF PARTICLE SIZE DISTRIBUTION IN THE EASTERN SOUTH PACIFIC

Sciandra, Antoine¹; Stramski, Dariusz²; Marcel, Babin¹; Twardowski, Michael S.³; Carolina, Grob<sup>1

1</sup>Laboratoire d'Océanographie de Villefranche sur mer - CNRS Station Zoologique - BP28 - Chemin du Lazaret, Villefranche sur mer, --, 06234, France; ²Marine Physical Laboratory, Scripps Institution of Oceanography, University of California San Diego, La Jolla, California, 92093-0238 , United States; ³Department of Research, WET Labs, Inc., 165 Dean Knauss Dr., Narragansett, Rhode Island, 02882, United States

The particle size distributions (PSDs) were measured on discrete water samples with an electrical resistive particle sizer (Multisizer 3, Beckman Coulter) and an optical particle sizer (Hiac, Pacific Scientific) during the French BIOSOPE cruise along a 7500 km transect in the eastern South Pacific from the Marquesas Islands to the Chilean coast. The PSDs of small particles (less than about 10 µm) obtained with the Multisizer 3 and the PSDs for larger particles (> 4 µm) from Hiac were merged to obtain continuous PSDs within the size range 0.7 - 100 µm. A good agreement was generally observed between the two instruments within the overlapping size range, which provided a basis for merging the data at a particle diameter of about 5 mm. A total of 160 PSDs representing samples from the euphotic oceanic layer allowed us to analyze the spatial and diurnal variability of PSD across different trophic regions explored during the cruise. A common feature for a majority of PSDs is that they can be partitioned into three segments. In the range of submicrometer particles (SMP), the slope of PSD was typically significantly steeper (from -9 to -5) compared to that for larger particles (about -4). The SMP displayed diel variations, especially well-pronounced in the deep chlorophyll maximum layer within the South Pacific Subtropical Gyre. In the 1-4 µm size range, the PSDs showed distinct features associated with plankton populations, which appear clearly as maxima in the particle volume distributions. These features also exhibited diel variations. Flow cytometer measurements and PSD data obtained for isolated species upon sorting suggest that the diel variations in the PSD slope in the submicrometer range and the 1 - 4 µm range can be attributed to cyanobacteria and small-sized eukaryotic phytoplankton populations, respectively. For particles larger than 4 µm, the PSDs were generally more regular in shape, but also displayed diel variations. Our data suggest that the general parameterization of PSD in terms of a single slope over a broad size can be often inadequate for marine environments, including open ocean waters dominated by biological particles. The observed diel variations in PSDs are expected to have ramifications for variability in seawater optical properties.

VARIATION IN ABSORPTION PROPERTIES OF THE EUROPEAN COASTAL WATERS: APPLICATION TO OCEAN COLOR SATELLITE ALGORITHMS.

Tilstone, Gavin¹; Van der Woerd, Hendrik Jan²; Eleveld, Marieke²; Peters, Steef<sup>2

1</sup>Plymouth Marine Laboratory (PML), Prospect Place, West Hoe, Plymouth, Devon, PL1 3DH, United Kingdom; ²Vrije Universiteit Amsterdam De Boelelaan 1087, Amsterdam, --, 1081 HV, Netherlands

We aim to improve the quality of Chlorophyll a (Chla) retrieval in European coastal waters by proper characterization of an optimal IOP set to describe various water types. The absorption properties of phytoplankton (a_ph), non-algal particles (a_NAP) and colored dissolved organic material (a_CDOM) and concentrations of Chla and Total Suspended Material (TSM) were measured at 468 stations in the North Sea from April 2002 to September 2003. Chla varied from 0.2 to 35 mg m^-3, TSM from 0.2 to 75 g m^-3 and a_CDOM(442) varied from 0.02 to 0.26 m^-1. In European coastal areas, Chla was significantly higher along the Dutch coast, TSM along the German Bight and East Anglia, UK coast and a_CDOM was significantly higher in Norwegian waters. A budget was constructed using Chla, TSM and a_CDOM data which indicated that approximately 75% of the stations sampled were Case 2, of which 25 % dominated by a_CDOM, 8% dominated by TSM.Approximately 40% stations had similar proportions of Chla, TSM and a_CDOM(442). We present multiple approaches to categorize the inherent optical properties based on geography, an absorption budget and absorption signatures associated with dominant water masses in the North Sea. For the water masses,a_CDOM(442) and a_NAP(442) regressed against salinity exhibited four distinctive relationships which are associated with the hydrography of the North Sea; a_CDOM dominated waters in the Skagerak originating from Baltic Sea outflow, TSM dominated waters typical of the Continental European Coast, Chla dominated waters associated with the inflow of Atlantic water and Chla-TSM- aCDOM waters representing the mixing of Atlantic, Continental Coastal and Skagerak waters.

Each approach was used to parameterize the semi-analytical remote sensing algorithm HYDROPT. Differences in Chla, TSM, CDOM concentrations between each approach will be presented and compared to products available from standard MERIS, MODIS and SeaWiFS algorithms.

EOF ON CHL, SST AND SEA LEVEL OVER THE MEDITERRANEAN SEA: A CORRELATION ANALYSIS

Volpe, Gianluca¹; Buongiorno Nardelli, Bruno¹; Santoleri, Rosalia<sup>1

1</sup>GOS - ISAC - CNR Via Fosso del Cavaliere 100, Rome, --, 00133, Italy

Different EOF analyses have been performed over chlorophyll-a (CHL), sea surface temperetaure (SST) and Mediterranean Absolute Dynamic Topography (MADT) weekly maps from 1998 to 2006, covering the Mediterranean Sea. EOF analyses require data to be continous in space and time; therefore a Data INterpolating Empirical Orthogonal Functions (DINEOF) analysis was performed over gappy fields to fill in missing data, due to clouds and/or low sampling rates. Standard EOF analysis main results are that seasonality can explain up to 57%, 97% and 70% of the variance of CHL, SST and MADT, respectively. To explain the eventual dependence of one process upon the other, spatial and lagged correlations between different variable EOF modes were computed. As seasonality drives most of the variance in all of the three datasets, first modes from the three variables were highly correlated in time with different time lags. Second modes of variability explain only 7%, 1% and 3% of total variance of CHL, SST and MADT time series, respectively. Nonetheless, especially for CHL and SST, those second modes are unequivocally referred to the joint Gulf of Lions-Ligurian Sea spring bloom, and to the deep water formation dynamics of the Gulf of Lions. Those modes present a maximum correlation at lag of 6 months (r=-0.6). The analysis was repeated using a low-pass filter on climatology-removed data to remove the seasonality and the higher frequency signals. Interannual components were successfully detected. Biological space-time variability was found to be sensitive to circulation changes which were thought to have had a minor or negligible impact.

FIELD CHARACTERIZATION OF THE DAILY VARIABILITY OF THE PARTICULATE BEAM ATTENUATION COEFFICIENT

GERNEZ, Pierre¹; ANTOINE, David²; HUOT, Yannick<sup>2

1</sup>ACRI-st and CNRS-LOV LOV, Villefranche sur mer, --, 06230, France; ²CNRS-LOV, Villefranche sur, mer, 06230, France

The particulate beam attenuation coefficient at 660 nm (cp) is a descriptor of the particulate matter load. In the open ocean, over large spatial scales, cp varies at first order with the phytoplankton biomass. A second order variability in cp is also observed in response to local changes, such as wind events, cloud cover and changes in the bulk particle composition. Furthermore, a daily cycle in cp is associated the daily changes in irradiance.

In situ investigation of the cp daily variability is, however, generally limited to a few days. The development of instrumented moorings allows in situ measurements to be performed at high frequency, over long periods (years) and under varying environmental conditions (trophic state, vertical distribution of the water properties, cloudiness, sea state).

A time series of inherent and apparent optical properties (cp, chlorophyll fluorescence, backscattering coefficient, downward and upward irradiances ) has been collected at an open ocean mooring (BOUSSOLE project) in the North western Mediterranean Sea (60 km offshore Nice, France). All data are simultaneously recorded every 15 minutes at 4 and 9 m depth. This database allows us to characterize the daily variability in cp, with consideration of the physical forcing and the phytoplankton population composition (as described by monthly HPLC analyses). We show seasonal changes linked to the physical and trophic state of the water.

IMAGE-DERIVED AUTOMATED ATMOSPHERIC CORRECTION FOR COASTAL REMOTE SENSING APPLICATIONS

Hou, Weilin ¹; Lee, Zhongping¹; Martinolich, Paul¹; Gould, Rick¹; Arnone, Robert<sup>1

1</sup>Naval Research Laboratory 1009 Balch Blvd, Stennis Space Center, MS, 39529, United States

Coastal oceanic and estuarine environments are important areas for ecological studies, pollution monitor and control, as well as defense and homeland security applications. Research in such areas is complicated by more factors compared to open oceans, not only because of the dynamic nature associated with interactions between land runoff, river discharge, and bottom impacts, but also complications caused by cloud coverage as a result of land-sea aerosol interactions. However, this added challenge can be beneficial under certain conditions and can be used to improve atmospheric correction (Lee et al, 2007). This study presents the initial results of an automated approach to find the proper pairs of in/out shadow pixels for atmospheric correction, and further the derived subsurface properties from the corrected image. Hyperion images from different scenes around Florida are used for the testing of the automated cloud-shadow correction algorithm and retrieval of subsurface properties. Specifically, remote sensing reflectance derived from Hyperion imagery after cloud-shadow correction is compared to in situ measurements. Further, bathymetry data retrieved using Hyperion remote sensing reflectance is shown to match calibrated bathymetry data, which is provided by SHOALS. Retrieved absorption values at selected wavelengths are also in general agreement with field measurements. These results suggest validity as well as portability of this automated cloud-shadow approach when sparse cloud coverage is available. This approach helps to eliminate artificial requirements imposed by other correction methods.

ASSIMILATION OF REMOTELY SENSED OBSERVATIONS IN A SEDIMENT TRANSPORT MODEL

Eleveld, Marieke A.¹; van der Woerd, Hans ¹; El Serafy, Ghada²; Blaas, Meinte¹; van Kessel, Thijs ¹; de Boer, Gerben<sup>1

1</sup>VU-IVM De Boelelaan 1087, Amsterdam, --, NL-!081 HV, Netherlands; ²Deltares (former Delft Hydualics), Rotterdamseweg 185, Delft, (Zuid-Holland), NL-2629 HD , Netherlands

Since 2003, VU-IVM has been developing HYDROPT, a case-2 algorithm based on HYDROLIGHT solutions, which allows derivation of amongst others SPM and CHL concentrations and their associated error products, and also generates KD output. MERIS-derived suspended particulate matter concentrations and their associated error products were assimilated into the Delft3D-WAQ numerical transport model of the southern North Sea. In this dynamic region, a case study was carried out aiming at a better understanding of the Dutch coastal sediment transport system and characterising the baseline SPM situation before extension of Rotterdam Harbour. Independent in situ data were used for validation. The results show that assimilation of SPM remote sensing products into the model is feasible, and that Ensemble Kalman filtering indeed improved the skill of the sediment model. Time-series showing remote sensing observations, original model output and the assimilation results provide insight into the behaviour of the SPM retrieval under different hydrodynamic conditions. We will demonstrate effects of tide, wind, and freshwater inflow and stratification. Interestingly, the hydro-optical algorithm HYDROPT works well even close to the coast (1-2 km offshore) where high sediment fluxes occur. The methods developed in this test case are promising for application to other sensors, water bodies, and parameters. The HYDROPT algorithm is physically based and was recently also adapted for MODIS. The hydrodynamic and sediment transport model also contains various components that are not North Sea specific, and the tools developed for the Ensemble Kalman filtering are also generic. For the North Sea, we would like to better characterize SPM (particle size, organic / inorganic) and associate the optics with settling velocities in the hydrodynamic and sediment transport models. Finally, assimilation in ecological models, using also KD, CHL and our first case-2 primary production estimates is foreseen.

VALIDATION OF HYPERSPECTRAL IMAGE-DERIVED BENTHIC COVER USING TOWED UNDERWATER VIDEO TRANSECTS

Klonowski, Wojciech¹; Lynch, Mervyn¹; Gray, Mark¹; Fearns, Peter<sup>1

1</sup>Curtin University of Technology Kent st, Bentley, --, 6102, Australia

Inversion-based approaches for mapping benthic cover from hyperspectral imagery are becoming increasingly popular, as a result of the promising results they have shown to date. Subsequently these approaches are now being applied to highly diverse and complex ecosystems, however, often without validation of the benthic cover products. In this study, we apply a shallow water reflectance model to hyperspectral imagery captured over the Ningaloo Marine Park, Australia. The model incorporates a bottom reflectance term, which is parameterised by a combination of 3 key benthic habitat classes (sediment, vegetation and coral). A benthic cover map is derived from the retrieved model parameters and is validated with towed underwater video footage. We present the comparison results and discuss the issues involved with validating benthic cover.

RADIATIVE TRANSFER CLOSURE IN THE ST-LAWRENCE GULF AND ESTUARY : ESTIMATION OF THE SPECTRAL BACKSCATTERING FRACTION

Çizmeli, Servet¹; O'Neill, Norman¹; Roy, Suzanne²; Larouche, Pierre³; Yayla, Mehmet<sup>1

1</sup>University of Sherbrooke 2500 Blvd. Université, Sherbrooke, QC, J1K2R1, Canada; ²Institut des Sciences de la Mer de Rimouski / 310 Allée des Ursulines, Rimouski, Québec, G5L3A1, Canada; ³Institut Maurice Lamontagne / 850, route de la Mer C.P. 1000, Mont-Joli, Québec, G5H3Z4, Canada

In order to help solve the problems associated with the estimation of the marine chlorophyll-a concentration from space, assumptions have to be made regarding the magnitude and spectral characteristics of all in-water IOPs (Inhrent Optical Properties) and their relationship with the AOPs (Apparent Optical Properties) measured by the satellite. The AOPs are functions of the IOPs and the IOPs are primarily functions of both the concentration and the optical nature of chlorophyll-a, SPM (Suspended Particulare Matter) and CDOM (Chromophoric Dissolved Organic Matter) in the water column. Radiative transfer simulations offer valuable information when dealing with the remote sensing problem in the optically complex waters of the St. Lawrence gulf and estuary as they reveal the dependency of the AOPs to each optically active IOP. During the bio-optical cruises that were performed in the St. Lawrence gulf and estuary in May 2000 and April 2001, the in-water multispectral reflectance, absorption and attenuation coefficients were measured at 44 stations in total. A radiative transfer closure study was performed using measured absorption and attenuation coefficient spectra and trial families of parameterized backscattering coefficient spectra as inputs. For eachstation visited, 111 simulated reflectance curves were produced where each curve corresponds to a different set of assum