Ocean Optics 2008

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OCEAN OPTICS 2007 CLASS PROJECT: IN SITU OPTICAL AND RADIOMETRIC AND DATA ACCURACY ASSESSMENT AND OPTICAL CLOSURE

Randolph, Kaylan ¹; Woods, Sarah ²; Cetinic, Ivona³; Gray, Amanda ⁴

¹University of Connecticut 1080 Shennecossett Road, Groton, CT, 06340, United States; ²University of Miami / 4600 Rickenbacker Causeway, Miami, Florida, 33149, United States; ³University of Southern California / 3616 Trousdale Pkwy, Los Angeles, California, 90089-0371, United States; ⁴University of Washington / 1013 NE 40th St., Seattle, Washington, 98105-6698, United States

Optical closure exercises are pivotal for evaluating the accuracy of water quality remote sensing techniques. Agreement between water-leaving radiance and inherent optical properties (IOPs) is necessary for resolving biogeochemical parameters from space. Relatively high errors have been reported for in situ instruments retrieving upwelling radiance in highly backscattering waters. Optically complex waters prove optimal for testing closure between apparent optical properties (AOPs), IOPs, and analytically measured biogeochemical parameters. A comprehensive suite of IOPs and AOPs were measured with depth for two sampling locations in the Damariscotta River Estuary, Maine on July 13, 2007. Ultimately, the largest percent difference (PD) between measured and modeled radiance reflectance was in the green portion of the spectrum at Station 2, where a 38% difference resulted. Stronger agreement was achieved for Station 1, where a maximum difference of 22% occurred at 660 nm. Neither closure routine meets the requirements of the SeaWIFS Project, for which the maximum acceptable uncertainty is 5%. Sources contributing to the resulting difference could be inaccuracies in radiometric measurements (i.e. sensor tilt) and in IOP measurements. Evaluation of those and other possible sources of error was assessed through instrument intercomparison and an appraisal of the assumptions applied in correction schemes.

INVERTING LIGHT WITH CONSTRAINTS

Rehm, Eric ¹; Mobley, Curtis D.²

¹University of Washington School of Oceanography 1013 NE 40th Street, Seattle, WA, 98105, United States; ²Sequoia Scientific, Inc., 2700 Richards Road, Suite 107, Bellevue, WA, 98005, United States

Long-term deployments of autonomous platforms present challenges for the direct measurement of the inherent optical properties (IOPs) of seawater due to weight and power considerations. However, measurement of hyperspectral radiometric data as well as a few IOPs fits within the weight and power budgets of some current platforms. Here we investigate the use of easily measured inherent optical properties such as beam attenuation c and backscattering b_b) at a small number of wavelengths to constrain the inversion of easily measured radiometric data E_d(l) and L_u(l) to order to obtain estimates of IOPs a(l), b(l) and c(l). We use Ecolight, the azimuthally-averaged version of the Hydrolight radiative transfer model as our forward model.First, we consider optimal methods for the constrained non-linear inverse problem.Next, assuming we can measure radiometric data throughout a homogeneous, well-mixed water column (e.g., such as a Lagrangian float in a N. Atlantic spring mixed layer), we investigate the quality of the inverted IOPs without IOP constraints.Finally, we investigate the quality of inverted IOPs when a small number of constraints, e.g., b_b(700) and c(600), are applied . We examine both the final goodness of fit as well as the rate of convergence. Results for water types with varying chlorophyll concentration and CDOM concentration are considered.

PARTICLE SIZE DISTRIBUTIONS OF COASTAL WATERS MEASURED WITH AN IN SITU LASER DIFFRACTOMETER.

Reynolds, Rick A.¹; Stramski, Dariusz¹; Wright, Vanessa M.¹; Wozniak, Slawomir B.²

¹Scripps Institution of Oceanography, UCSD 9500 Gilman Drive m/c 0238, La Jolla, CA, 92093-0238, United States; ²Institute of Oceanology, Polish Academy of Sciences, Powstancow Warszawy 55, 81-712, Sopot, Poland

The particle size distribution (PSD) plays a central role in understanding many facets of radiative transfer, yet it is rarely measured in situ. The LISST-100X (Laser In Situ Scattering and Transmissometry; Sequoia Scientific, Inc.) is a commercial instrument which estimates the PSD based upon the principle of optical diffraction, and can provide laboratory or in situ measurements of the PSD at high sampling rates. Particle suspensions of standard sized polystyrene microspheres, plankton cultures, and field samples were measured in the laboratory using the LISST, and directly compared with concomitant measurements of a standard electrical resistive particle sizer (Coulter Counter). For narrow size distributions, the dominant particle size is generally well identified by the LISST, but the shape of the PSD is not precisely reproduced because of the relatively low resolution of size measurement. For broad size distributions, a generally good agreement was found between the LISST and Coulter techniques over a large portion of the size spectrum above 3 micrometers, suggesting that LISST measurements can provide a reasonable estimate of in situ PSDs. Field measurements of the PSD from different coastal regions (San Diego waters, Monterey Bay, Baltic and North Seas) are examined within the context of commonly used parameterizations describing the distribution of particle size. The results for these coastal environments suggest an average value for the slope of the power law (Junge) distribution of -3.5, which is less steep than that generally assumed for open ocean waters. However, we also observed that the power law model frequently provides a poor description of the PSD due to the presence of significant particle peaks resulting from local dynamics in plankton populations. The potential implications of these departures from the idealized PSD to prediction of seawater optical properties are examined using Mie scattering calculations.

PHYTOPLANKTON DYNAMICS IN THE GULF OF MAINE: SECRETS REVEALED BY SEVEN YEARS OF HOURLY OPTICAL OBSERVATIONS ON A MOORED ARRAY

Roesler, Collin S.¹; Barnard, Andrew H.²; Pettigrew, Neal R.³

¹University of Maine Darling Marine Center, 193 Clark's Cove Road, Walpole, ME, 04573, United States; ²WET Labs, Philomath, Oregon, 97370, United States; ³University of Maine, 206 Libby Hall, Orono, Maine, 04469, United States

July 2008 represents the 7- year anniversary of the deployment of the buoy array known as the Gulf of Maine Ocean Observing System (GoMOOS). In addition to meteorologic and hydrographic sensors, these buoys have been instrumented with two flavors of optical sensing packages: the "small" packages consist of chlorophyll fluorometers and 4-channel irradiance sensors at one or two depths, the "large" packages include additionally ac9s, backscattering sensors, CDOM fluorometers, and 7-channel upwelling radiance sensors. This data set has provided an unparalleled view of phytoplankton dynamics in the Gulf of Maine. Seasonal springtime blooms propagate from the southwestern part of the gulf, along the coast to the northeast, following thermal stratification patterns. Seasonal autumn blooms propagate to the southwest following cooling, increased winds and mixing, although the pattern of destratification is highly variable and multiple fall blooms can be observed. This pattern is robust except in the presence of anomalous springtime precipitation events that coincide with high river discharge due to springtime melt water runoff. During these years, phytoplankton respond to the gulf-wide salinity-driven stratification and blooms occur synoptically along the shelf, months earlier than is typical. These freshwater anomaly years have also been associated with the development of anomalously strong blooms of the toxic dinoflagellate Alexandrium fundyense and subsequent paralytic shellfish-poisoning events. Our ability to optically discern phytoplankton functional types, in addition to phytoplankton biomass, may provide a method for providing early warning for such events. The pattern of phytoplankton bloom development observed by the GoMOOS array is fundamentally different from that represented by ocean color remote sensing because of the coherence of blooms to CDOM-rich river discharge, which confounds the remote assessment of chlorophyll. In situ observation of CDOM provide the capability for deconvolving the remotely sensed chlorophyll and CDOM patterns.

LIGHT ABSORPTION BY NATURAL AQUATIC PARTICLES IN THE NEAR-INFRARED (700 – 900 NM) SPECTRAL REGION.

Roettgers, Ruediger¹; Bracher, Astrid ²; Gehnke, Steffen¹; Schmitt, Bettina²; Wozniak, Slawomir³

¹Institute for Coastal Research, GKSS Max Planck Strasse 1, Geesthacht, --, D-21502, Germany; ²Alfred Wegener Institute for Polar and Marine Research, Bremerhaven, Europe, D-27570, Germany; ³Marine Optics Laboratory, Institute of Oceanology , , Sopot, Europe, 81-712, Poland

Light absorption by aquatic particle in the near-infrared spectral region is often assumed to be negligible. So, any observed attenuation in this spectral region was supposed to be due to errors induced by scattering, and a general practice to correct for this scattering error in absorption measurements is to subtract the attenuation of these NIR wavelengths from all other wavelengths. We used the sensitive quantitative filter technique to measure particulate absorption but placed the filter inside an integrating sphere. The positioning of the filter inside the sphere does strongly improve the precision of the whole measurement by making any scattering error negligible. This allowed us to perform very sensitive measurements in the NIR region of 700 to 900 nm. Samples from different environments (open ocean, coastal waters and a river) and geographical regions (North Sea, Baltic Sea and the Atlantic Ocean) were examined. In nearly all cases a significant NIR particulate absorption could be observed that was as well visible when the samples had been bleached. In many case the NIR particulate absorption was high, reaching even 40 % of the absorption at the red chlorophyll maximum (672 nm). A good correlation of NIR particulate absorption with back-scattering in the same spectral region and with the concentration of total suspended matter was observed. We conclude that near-infrared particulate absorption mainly by detritus and minerals is not negligible (but might sometimes be very low), and that a subtraction of the measured attenuation in this region might lead to a large underestimation of the real absorption at shorter wavelength.

REMOTE SENSING OF SUSPENDED PARTICULATE MATTER IN TURBID WATERS: STATE OF THE ART AND FUTURE PERSPECTIVES

Ruddick, Kevin¹; Nechad, Bouchra¹; Neukermans, Griet¹; Park, Youngje¹; Sirjacobs, Damien²; Beckers, Jean-Marie²

¹MUMM 100 Gulledelle, Brussels, --, B-1200, Belgium; ²GHER University of Liège, Liège, Liège, B-4000, Belgium

The state of the art and future perspectives for remote sensing of suspended particulate matter (SPM) in turbid waters will be assessed and illustrated with results from recent and ongoing research.

Interest in remote sensing of SPM in turbid waters is motivated by the environmental and economic importance of sediment transport in coastal waters. Applications include the optimisation of dredging/dumping operations, environmental impact of offshore construction activities, understanding of geomorphological change, etc. and are generally addressed by model studies supported by remote sensing data. While Total Suspended Matter (TSM) is a relatively easy parameter to detect optically even with the crudest of instruments, there is a need to continually improve the accuracy, the quality control and the spatio-temporal coverage of satellite-derived TSM maps. There is also a desire for more detailed information on particle size and composition.

Algorithms for TSM retrieval will be presented, including a hyperspectrally-calibrated algorithm which can be adapted to almost any remote sensor from AVHRR or SPOT to MODIS or MERIS. Spectral variation of the algorithms coefficients obtained by calibration from in situ measurements of water-leaving reflectance and TSM is shown to correspond, via optical closure, to spectral variation of the relevant inherent optical properties. Results for satellite data products from MODIS and MERIS are compared with other algorithms including the MERIS neural network algorithm. Methods for automatic quality control of satellite data products are described. Finally, some future perspectives are outlined including the use of spatio-temporal correlations to improve quality control and fill data fields for cloudy periods/regions and the use of geostationary sensors to give a dramatic improvement in temporal resolution.

The state of the art and future perspectives for remote sensing of suspended particulate matter (SPM) in turbid waters will be assessed and illustrated with results from recent and ongoing research.

RECONSTRUCTION OF MISSING SATELLITE TOTAL SUSPENDED MATTER DATA OVER THE SOUTHERN NORTH SEA AND ENGLISH CHANNEL USING EMPIRICAL ORTHOGONAL FUNCTION DECOMPOSITION OF SATELLITE IMAGERY AND HYDRODYNAMICAL MODELLING.

SIRJACOBS, Damien ¹; Alvera-Azcárate, Aïda ²; Barth, Alexander ²; Lacroix , Geneviève³; Nechad , Bouchra ³; Park , Youngje ³; Ruddick , Kevin ³; Beckers , Jean-Marie ²

¹GeoHydrodynamic and Environmental Research - University of Liège Allée de la Physique, B5 - Sart-Tilman, Liège, --, 4000, Belgium; ²Allée de la Physique, B5 - Sart-Tilman, Liège, --, 4000, Belgium; ³Management Unit of the North Sea Mathematical Models (MUMM), Royal Belgian Institute of Natural Sciences (RBINS), 100 Gulledelle , Bruxelles, Bruxelles, 1200, Belgium

Optical remote sensing data archives generally have many gaps caused by clouds or other retrieval problems. However, for the light forcing of ecosystem models continuous fields are required. For parameters exhibiting strong spatial and temporal correlations for regions of similar dynamics or from day to day, the missing data can be estimated by use of statistical techniques. In this context, the Data Interpolation with Empirical Orthogonal Functions (DINEOF) method is used for reconstruction of complete space-time information for surface total suspended matter (TSM) and chlorophyll a from a 5-year archive of MODIS and MERIS products over the Southern North Sea and English Channel.

The DINEOF univariate methodology has been previously demonstrated for Mediterranean sea surface temperature data (Alvera-Azcarate et al., 2005, Beckers et al., 2006). Alvera-Azcarate et al (2007) showed that SST reconstructions could be improved by using a multivariate approach in which SST, chlorophyll and wind fields are taken into account together for the analyses.

Here, TSM images will be used in combination with information from the COHERENS hydrodynamical model to provide a complete and continuous estimate of surface TSM for the Southern North Sea throughout the period 2003-2005. After normalisation of all parameters, an augmented state vector is submitted to DINEOF analysis by compiling wind fields, depth integrated currents, surface elevations and bottom stresses in addition to the remotely sensed TSM. Reconstucted images are compared with the original incomplete images. Validation of the method is achieved by estimation of information removed from the training data by exclusion of entire images and by addition of artificial clouds.

The data reconstruction technique has further applications in the processing and quality control of optical remote sensing data. Perspectives will be outlined for improving the quality control of retrieved parameters and for the improvement of retrievals by adding statistical information to the conventional spectral processing.

References:

Alvera-Azcarate, A., Barth, A., Rixen, M., and Beckers, J.-M.: Reconstruction of incomplete oceanographic data sets using Empirical Orthogonal Functions. Application to the Adriatic Sea, Ocean Modelling, 9, 325-346, 2005.

Alvera-Azcarate, A., Barth, A., Beckers, J. M., and Weisberg, R. H.: Multivariate Reconstruction of Missing Data in Sea Surface Temperature, Chlorophyll and Wind Satellite Fields, Journal of Geophysical Research, 112, C03008, doi:10.1029/2006JC003660, 2007.

Beckers J.-M., A. Barth & A. Alvera-Azcarate, DINEOF reconstruction of clouded images including error maps. Application to the Sea-Surface Temperature around Corsican Island, Ocean Sciences, 2: 183-199, 2006.

DETECTION OF ADJACENCY EFFECTS IN COASTAL AND INLAND WATERS: THE USE OF THE NEAR INFRARED SIMILARITY SPECTRUM.

STERCKX, SINDY¹; KNAEPS, ELS¹; RUDDICK, KEVIN²

¹VITO NV BOERETANG 200, MOL, --, 2400, Belgium; ²MANAGEMENT UNIT OF THE NORTH SEA - RBINS, BRUSSEL, BRUSSEL, 1200, Belgium

Since December 2000 the European Water Framework Directive (WFD) forms the legislative framework for the water management undertaken by the EU Member States. This directive requires the monitoring of biological and physico-chemical parameters within river basins, transitional and coastal waters. Remote sensing can support the implementation of the WFD by providing systematic observations to monitor and assess water status and trends. However before remote sensing can be used in a fully operational way, the correction for atmospheric scattering over waters close to land surfaces (i.e. nearshore coastal and inland waters) needs to be satisfactorily addressed. Such “adjacency effects” modify the spectral signature of the observed pixel, particularly in the near infrared. Artificially increased radiance values for the water pixels might easily be mistaken for bottom effects or suspended sediments. In this paper we first present a method for the detection of water pixels affected by adjacency effects. The approach is based on the near infrared (NIR) similarity spectrum defined by Ruddick et al. (2006). Pixels affected by adjacency effects, will have a water-leaving reflectance spectrum with different shape from the near infrared similarity spectrum at some specific wavelengths. This difference can be a measure of the magnitude of the adjacency effect. The methodology will be tested on hyperspectral airborne images acquired with various sensors (CASI, Hymap, AHS), at different altitudes and under varying atmospheric conditions. These datasets contain different types of non-uniform surfaces or high-contrast regions: water areas fully surrounded by land (eg. lakes) and land/sea borders. Secondly, a simple iterative adjacency correction algorithm is presented which retrieves information about the adjacency range from the image itself.

RESOLVING THE SPATIAL VARIABILITY OF OCEAN COLOR MATCH-UP SITES

Salama, Mhd.Suhyb¹; Su, Zhongbo¹

¹International Institute for Geo-Information Science and Earth Observation, ITC Hengelosestraat 99, Enschede, --, 7500 AA , Netherlands

In this paper an attempt to resolve the scale difference between observed and field-measured water leaving spectra in ocean color match-up sites is presented.

The results were function of measurement's position with respect to the population's median. Measurements at the edges of the population were most appropriate for reconstructing the sub-pixel spatial variability with RMS error values less than 12%.

Knowledge about the spatial variability of the match-up pixel will facilitate the planning of in-situ campaigns and the validation of ocean color data.

RETRIEVAL OF DEPTH AND COASTAL WATER OPTICAL PROPERTIES FROM AIR-BORNE HYPER-SPECTRAL IMAGERY

Salinas, Santo Valentin¹; Chang, Chew Wai¹; Liew, Soo Chin¹

¹Centre for Remote Imaging, Sensing and Processing BLK SOC1, Level 2, Lower Kent Ridge Rd, Singapore, --, 119260, Singapore

In a previous work [1], we explored the applicability of the Simulated Annealing algorithm (SA) as a non--linear global optimizer to solve the multi--parameter IOP retrieval problem. We combined the SA algorithm with widely known semi--analytical relations for coastal water's IOPs, to parameter--invert water properties from simulated and measured water leaving reflectance spectra. The new implementation was tested successfully against the simulated and in--situ data sets provided by the IOCCG working group as well as from our very own data measurements collected around Singapore's nearby islands. In this work, we investigate the applicability of this approach to the retrieval of water IOP's from air-borne hyper-spectral imagery. Three hyper-spectral images were acquired by our team during 2 fly-by's. Two images were acquired at a height of 914 m. approximately with a ground resolution of about 1.3 m. and another single image was acquired at a lower level (752 m.) with a ground resolution of about 0.75 m. Simultaneously to the plane fly-by, and for validation purposes, in--situ measurements of water depth and water leaving reflectance were collected at specific locations well inside the imager's field of view. Results and comparisons with present and previous results[1] will be presented.

References: [1] S.V. Salinas, C. W. Chang and S. C. Liew, Multi--parameter retrieval of water optical properties from above-water remote sensing reflectance using the simulated annealing algorithm. Appl. Opt., Vol. 46, 2727--2742 (2007).

DIFFERENCES IN THE FLUORESCENCE OF DISSOLVED ORGANIC MATTER IN SEAWATER INDUCED BY UV AND GREEN RADIATION

Salyuk, Pavel¹; Oleg, Bukin²; Alexander, Mayor²; Aleksey, Il'in³; Aleksey, Bulanov³

¹Pacific Oceanological Institute by V.I. Il'ichev FEB RAS 43, Baltiyskaya street, Vladivostok, --, 690041, Russian Federation; ²Institute for Automation and Control Processes FEB RAS, 5, Radio street, Vladivostok, Primorye, 690041, Russian Federation; ³43, Baltiyskaya street, Vladivostok, --, 690041, Russian Federation

The investigations were carried out in the sea expeditions and in laboratory conditions. There were used methods of laser induced fluorescence with 355 nm and 532 nm excitation wavelengths, dissolved organic matter measurements by WETStar fluorometer (370 nm excitation) and laser induced breakdown spectroscopy method for measurement of chemical elements in seawater. In the sea expedition were obtained in depth and along-track data in various waters cases including waters with anthropogenic pollution and River estuaries. Also laboratory experiments of dissolved organic matter degradation were conducted. Relationships between dissolved organic matter fluorescence intensities induced by radiation with different wavelengths, chlorophyll-a concentrations and total carbon concentrations were analyzed. It was shown that in the case of green excitation complex DOM molecules has more significant contribution to the total fluorescence signal as compared with UV excitation case.

MEASUREMENT UNCERTAINTIES ON INHERENT OPTICAL PROPERTIES AND THEIR IMPACT ON DERIVED OPTICAL PARAMETERS AND BIO-OPTICAL MODELS

Sanjuan Calzado, Violeta¹; McKee, David²

¹National Oceanography Centre Southampton European Way, Southampton, --, SO14 3ZH, United Kingdom; ²University of Strathclyde, Glasgow, Glasgow, G4 0NG, United Kingdom

Initial exercises coupling bio-optical models in ecosystem models have proved to provide a more accurate description of the underwater light field, which improves the performance of the ecosystem model. Generating remote sensing reflectance within the model is also extremely valuable when satellite data are used as a comparison interface for model outputs. Using remote sensing reflectance data from satellite instead of satellite products, such as chlorophyll, reduces the uncertainty associated with the data assimilation process. Some issues still present on the use of optical data in bio-optical models that this study intends to address.

Inherent optical properties (IOPs) are a key factor towards the generation of remote sensing reflectance on bio-optical models, but there are measurement uncertainties associated to them. We intend to examine the IOP’s uncertainty associated both from constituents and from optical parameters by using statistical methods. We present as well a new method to determine specific IOP’s (SIOP’s) from IOP’s taking into account the effect of measurement uncertainties and compare it with traditional calculations. Previous parameterizations of IOP’s from constituents in the literature will be also compared for suitability in our study area and bio-optical modelling purposes. We will compare error uncertainties on IOP’s both from in-situ optical data and from parameterizations. Finally, a radiative transfer model, (Hydrolight) and bio-optical models from literature will be used for sensitivity studies to address the impact of these uncertainties on the remote sensing reflectance spectra. Uncertainties on the final remote sensing reflectance are expected to be less than uncertainties associated with satellite products. This will provide a more reliable comparison interface ecosystem model – satellite data.

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

Bignami, Francesco¹; Pisano, Andrea ¹; Santoleri, Rosalia¹; Evans, Robert²

¹Via 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.

PICOPHYTOPLANKTON DISTRIBUTION IN THE ATLANTIC – IN-SITU MEASUREMENTS FOR GLOBAL OBSERVATION OF PHYTOPLANKTON FUNCTIONAL GROUPS

Schmitt, Bettina¹; Bracher, Astrid ¹; Röttgers, Rüdiger²; Gehnke, Steffen²

¹Alfred-Wegener-Institute for Polar and Marine Research Bussestrasse 24, Bremerhaven, --, D-27570, Germany; ²Institute for Coastal Research, GKSS, Geesthacht, Schleswig-Holstein, D-21502, Germany

Marine picophytoplankton, in particular cyanobacteria and prochlorophytes are ubiquitously distributed in the world’s oceans and are often – especially in the more oligotrophic regions –among the most important primary producers. The present work shows the results of in-situ measurements taken on three meridional transects across the Atlantic Ocean. Data for phytoplankton pigment composition and particulate absorption give information about the functional groups found in the study area. Flow cytometry and an analysis of phycobilins were employed to encompass genera of cyanobacteria such as Synechococcus and Trichodesmium. The aim is to improve 1) estimates of global marine primary production and 2) determinations of the distribution of major phytoplankton functional groups, by using hyper-spectral remote sensing data in combination with those in-situ measurements.

MARINE MAMMAL OBSERVATIONS USING MULTI-CHANNEL IMAGING SYSTEM

Schoonmaker, Jon¹; Contarino, Vincent M²; Gilbert, Gary¹; Podobna, Yuliya¹; Oakley, Daniel¹; Boucher, Cynthia¹

¹Advanced Coherent Technologies, LLC 4022 Liggett dr, San Diego, --, 92106, United States; ²Naval Air Systems Command, Patuxent River , MD, 20670, United States

The Advanced Coherent Technologies Mission Adaptable Narrowband Tunable Imaging Spectrometer (MANTIS) was used to detect and monitor marine mammals in the St Lawrence Seaway and in Maui Hawai’i. Both NADIR and grazing angle view angles were used. The system was configured with both narrowband spectral filters and polarization analyzers to reduce glint from the sea surface and multiple field of views in a foveal arrangement to explore both detection and classification in a single system. In addition optical models were combined with the diving profiles of various marine mammals to estimate the probability of detecting mammals as a function of water clarity and multi-channel system performance. Airborne and groundbased imagery of marine mammals are shown at various ranges and modeling results are presented.

REMOTE SENSING OF APPARENT AND INHERENT OPTICAL PROPERTIES OF TASMANIAN COASTAL WATERS: APPLICATION TO MODIS DATA

Schroeder, Thomas¹; Brando, Vittorio¹; Cherukuru, Nagur¹; Clementson, Lesley²; Blondeau-Patissier, David¹; Dekker, Arnold¹; Fischer, Juergen³

¹CSIRO Land & Water GPO Box 1666, Canberra, --, ACT 2601, Australia; ²CSIRO Marine Research, Castray Esplanade, Hobart, Tasmania, 7001, Australia; ³Free University Berlin, Carl-Heinrich Becker Weg 6-10, Berlin, -, D-12165, Germany

Global ocean colour algorithms significantly overestimate chlorophyll concentrations for the CDOM dominated coastal waters around Tasmania. In this work we describe the development, application and validation of the coupling of two physics-based inversion algorithms with the objective to improve the accuracy of chlorophyll estimates from remote sensing data in Tasmanian coastal waters. In this application, the proposed coupled algorithms derive apparent and inherent optical properties from spectral radiance measurement of the Moderate Resolution Imaging Spectrometer (MODIS) on-board of the NASA Earth Observation Systems (EOS) Terra and Aqua spacecrafts. The proposed coupled algorithms are generic in nature and can be applied to any other ocean colour sensor, like MERIS, SeaWiFS or OCM. The retrieval of optical properties is composed of two steps. First, an atmospheric correction algorithm based on inverse modelling of radiative transfer simulations and artificial neural network (ANN) inversion, derives the remote sensing reflectance at mean sea level on a pixel-by-pixel basis. Second, the inherent optical properties and the concentrations of the optically active constituents are retrieved from atmospherically corrected spectra by inverting a semi-analytical model with a variable specific inherent optical properties (SIOP) parameterization. The underlying SIOP sets of the semi-analytical model were derived from in-situ optical measurements in Tasmanian coastal waters. A validation of the algorithm outputs is performed with an independent data set of chlorophyll measurements. First results will be presented.

PRIMARY PRODUCTION IN THE SUBTROPICAL CONVERGENCE ZONE: COMPARISON OF IN-SITU MEASUREMENT METHODS AND REMOTE ESTIMATES

Schwarz, Jill¹; Gall, Mark²; Pinkerton, Matt¹; Kennan, Sean¹

¹National Institute for Water & Atmospheric Research NIWA, Private Bag 14901, Kilbirnie, Wellington, --, 6031, New Zealand; ²NIWA, PO Box 8602 Riccarton, Christchurch, Canterbury, 8011, New Zealand

The Subtropical Front (STF) is a 25,000 km-long convergence zone of subtropical and subantarctic waters that encircles the globe at around 45 degrees south. High phytoplankton abundance in the STF to the east of New Zealand is a conspicuous feature of ocean colour imagery, attributable to the front being bathymetrically locked to a broad submarine ridge extending eastwards from the New Zealand landmass.

The current understanding of optical, hydrodynamic, and biogeochemical factors setting the conditions for phytoplankton productivity in this region are summarised. A decade of ocean colour measurements were analysed by Objective Analysis to describe the seasonal climatology, time and space scales of covariance, and dominant modes of variability in the region. Much of the variability in the ocean colour climatology of the STF is explained by the seasonal and semiannual cycles (major austral spring and minor austral fall bloom), but there remains a large portion of unexplained variance suggesting that mesoscale eddies and transient fronts are important.

A range of at-sea approaches for estimating primary production in the STF over Chatham Rise are compared. Measurements include size-fractionated carbon-14 incubations, sun-induced fluorescence profiles, above-surface water-leaving radiance measurements, absorption-based estimates, and finally satellite-derived values from the MODIS fluorescence line-height evaluation product and the Vertical Generalized Production Model (VGPM). The compatibility and comparability of the different measurement techniques is presented. Knowledge of the physiological parameters PBmax and alphaK remains the major constraint on accurate derivation of daily production values from remote measurements.

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

Sciandra, Antoine¹; Stramski, Dariusz²; Marcel, Babin¹; Twardowski, Michael S.³; Carolina, Grob¹

¹Laboratoire 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.

VARIATIONS OF SURFACE PHYTOPLANKTON AND CDOM ABSORPTION COEFFICIENTS OF CLEAR NATURAL WATERS: AN EXTENDED OBSERVATION FROM SEAWIFS

Shang, Shaoling¹; Lee, Zhongping ²; Wei, Geomei¹

¹Xiamen University State Key Laboratory of Marine Environmental Science, Xiamen, --, 361005, China; ²Naval Research Lab, Stennis Space Center, MS, 39529, United States

The variations of phytoplankton in subtropical gyres were well studied recently using measurements of SeaWiFS along with other observational and/or modeled data. In those studies, as a standard practice, it is the chlorophyll-a concentration derived from the operational ocean-color algorithm used, in which there was no correction or separation of the effects from colored dissolved organic matter (CDOM). Here, for five locations in the North/South Pacific, North/South Atlantic, and the Gulf of Mexico where water is very clear (euphotic depth is about or greater than 80 m), and using the quasi-analytical algorithm (QAA), a time series (1998 – 2006) of absorption coefficients of phytoplankton (a_ph) and CDOM (a_CDOM) were obtained from SeaWiFS measurements. Not surprisingly, the temporal variations of a_ph and a_CDOM are different, and such variations are different among the five locations. More importantly, it is found that a_ph (a surrogate for phytoplankton biomass) is not necessarily having a strong seasonality while a_CDOM is always showing a strong seasonal variation. Such observations demonstrate a complex control of CDOM by photosynthesis and photo-bleaching, and suggest that, even for such clear natural waters, it is important to explicitly and accurately separate or correct CDOM effects in ocean-color remote sensing if we want to achieve rigorous evaluation of the phytoplankton dynamics. Further, to help understand the dynamics of these optical properties, the inter-relationships between them and sea-surface temperature are discussed.

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

Siegel, Herbert¹; Gerth, Monika¹; Stottmeister, Iris¹; Alling, Vanja²

¹Leibniz 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.

SOLVING THE BIAS AGAINST CYANOBACTERIA IN FLUORESCENCE MEASUREMENTS

Simis, Stefan¹; Babin, Marcel²; Huot, Yannick²; Leymarie, Edouard²; Seppälä, Jukka¹

¹Finnish Institute of Marine Research Erik Palménin Aukio 1, Helsinki, --, 00560, Finland; ²Laboratoire d'Océanographie de Villefranche, BP 8 , Villefranche-sur-mer, -, 06238, France

Fluorescence excitation/emission pairs are used to assess phytoplankton community biomass and photosynthesis capacity. Unfortunately, many instruments targeting chlorophyll-a fluorescence use excitation/emission pairs that elicit a strong fluorescence response in eukaryotic algae but low response in cyanobacteria. Cyanobacteria are therefore underrepresented in measurements of mixed phytoplankton communities. Light harvesting for photosystem II (PSII) in cyanobacteria takes mainly place in the phycobilisomes. These light harvesting complexes contain pigments sensitive to light in the 550-650 nm range which is hardly used by other phytoplankton groups. The important role of the phycobilipigments for energy supply to PSII and simultaneous small functional optical cross section of PSII in the blue cause the mismatch with fluorescence instruments that use blue/red excitation/emission pairs.

Multiple excitation wavelengths or white light can be used to excite the pigments supplying PSII in both algae and cyanobacteria. When exciting cyanobacterial phycobilipigments, however, there is a risk of overlap of their red fluorescence with fluorescence from chlorophyll-a. This contribution is variable, depending on phycobilisome pigment composition. It is desirable to interpret the fluorescence around 685-nm only in terms of chlorophyll-a so that photosynthetic kinetics can be modelled from the observed signal. Fluorescence from other pigments should thus be corrected for. We present a method to correct the observed fluorescence at 685 nm, based on deconvolution of fluorescence signatures of various cyanobacterial species into Gaussian shapes. The method is easily carried forward to the interpretation of variable fluorescence (the relative increase of fluorescence under continued light exposure). Traditional instruments measure low variable fluorescence for cyanobacteria compared to eukaryotic algae. With the use of amber excitation and correcting for phycobilipigment fluorescence we find that they act in the same range. Implementation of this method in oceanographic equipment would render it sensitive to the photosynthetic activity by both algae and cyanobacteria.

OPTICAL AND PHYSICAL PROPERTIES OF COASTAL WATER AND THEIR RELATIONS TO RADAR (ASAR) DATA – A CASE STUDY OF MUUGA BAY, GULF OF FINLAND

Sipelgas, Liis¹; Uiboupin, Rivo¹

¹Tallinn University of Technology Akadeemia tee 21B, Tallinn, --, 12618, Estonia

A field study of optical and physical properties in Muuga Bay, Gulf of Finland was performed on 30 May, 2007. In one of the studied stations traces of ballast water were visible on the water surface. An Advanced Synthetic Aperture Radar (ASAR) image was received and analysed from the same area. The vertical profiles of the absorption and attenuation coefficient together with the temperature and salinity profiles were measured in 13 stations. The concentrations of oil products, chlorophyll a, coloured dissolved organic matter, and suspended particulate matter were determined from water samples. The spatial distribution of temperature, salinity, and optically active substances indicated four distinct areas: the southern coastal area with saline, cold and chlorophyll a poor upwelling water, western coast of the bay with warmer and chlorophyll a richer surface water and open water dominated by higher concentrations of coloured dissolved organic matter, and Muuga harbour where the water had a high concentration of suspended particulate matter and chlorophyll a which caused stronger light attenuation and a thinner euphotic layer compared to the other parts of the bay. Regression analysis showed that the absorption coefficient at 676 nm correlated well with the chlorophyll a concentration and the scattering coefficient at 555 nm correlated with the suspended matter concentration in Muuga Bay. The correlation coefficient between ASAR data and oil products was 0.71 although the concentration of oil products was relatively low (0.01–1.72 ppm).

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-Marie³

¹Mare 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.

SIGNIFICANCE OF PARTICLE AGGREGATION ON OPTICAL PROPERTIES

Slade, Wayne Homer¹; Boss, Emmanuel¹

¹University of Maine 360 Aubert Hall, University of Maine, Orono, ME, 04469, United States

The scattering of light in aquatic environments is dominated by the effects of particulate material. The intensity and spectral characteristics of scattering depend strongly on the concentration, composition, and size distribution of suspended particles. In many environments a large portion of suspended particulate material is contained in aggregated particles, and the overall size distribution is a result of resuspension, settling, aggregation, and disaggregation. However, there is no accepted framework to describe the effects of aggregation on the scattering properties of suspended particulate material. Such understanding is necessary to constrain relationships between optical properties and suspended material. To increase understanding of the effects of aggregation on optical properties, measurements of particle size distribution and beam attenuation of in situ particle populations were made with two laser diffraction particle sizing instruments (LISST-100), one equipped with a pump to subject the sample to enhanced shear. The LISST observations (made at 1m above bottom in the Damariscotta River Estuary, Walpole, ME) reveal destruction of large particles by the pump and creation of smaller particles consistent with disaggregation. Beam attenuation for the sheared treatment is ~30% higher than the un-pumped control, suggesting that packaging of mass into aggregates compared with single grains has a significant effect on optical properties. To further investigate the effects of packaging of particles into and out of aggregates, laboratory aggregation experiments were performed. In these experiments clays were flocculated using salt and observed over time by a LISST instrument, in order to examine the effects of increasing aggregate size on beam attenuation.

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

Slivkoff, Matthew¹; Mckinna, Lachlan²; Furnas, Miles³

¹Curtin 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).

UV LIGHT PENETRATION OF THE OCEANS: MEASUREMENTS AND MODELLING USING A COUPLED ATMOSPHERIC IN-WATER UV RADIATIVE TRANSFER APPROACH

Smyth, Tim¹

¹Plymouth Marine Laboratory Prospect Place, Plymouth, --, PL1 3DH, United Kingdom

A hydrological model has been developed which uses as input the measured visible range inherent optical properties of the water column to determine the downwelling irradiance in the UV (range 300 - 400 nm). The required inputs to the model are: the Coloured Dissolved Organic Matter (CDOM) absorption at 440 nm together with associated slope (S); the absorption due to phytoplankton at 440 nm; and the total scatter at 510 nm together with its associated spectral slope (m). The model was coupled to a UV atmospheric radiative transfer model; both the atmospheric and hydrological models were validated using data obtained from a research cruise in the sub-tropical North Atlantic. During the cruise, the measured diffuse attenuation coefficient (K_d) varied between 0.2 and 0.3 m^-1 at 305 nm; 0.13 - 0.22 m^-1 at 325 nm; 0.09 - 0.16 m^-1 at 340 nm and 0.05 - 0.1 m^-1 at 380 nm. The lowest values at each wavelength were encountered in the most oligotrophic waters and the range and magnitude are in agreement with the literature. The closest agreement between the modelled and measured atmospheric UV light field was at 325, 340 and 380 nm where the modelled clear sky spectral light field was within +17%, +14% and +6% of the measured fields respectively. The resulting in-water downwelling irradiance (E_d) was modelled most successfully at 325 and 340 nm, where the mean log RMS difference with the measurements were 0.139 and 0.143 respectively.

REMOTE DETERMINATION OF OPTICAL BACKSCATTERING IN OCEANOGRAPHIC WATERS

Snyder, William¹; Bowles, Jeffrey¹; Weidemann, Alan²

¹Naval Research Laboratory Code 7231, Washington, DC, 20375, United States; ²Naval Research Laboratory Code 7333, Stennis Space Center, MS, 39529, United States

Remote sensing optical imagery is routinely used to estimate the absorption and scattering properties of water.This is typically done using models that relate the observed visible to near-IR remote sensing reflectance (Rrs) signal to these inherent optical properties of the water column.However, Rrs is related to the ratio of backscatter to absorption and the accurate retrieval of absorption and scattering depends on an accurate choice of backscattering ratio.The angular distribution of light leaving the water surface is directly related to the scattering phase function.Radiative transfer modeling of light through the water and to an airborne sensor shows that variations of up to 10% can be expected in Rrs over a 60^o off-nadir angular range, with the shape of these variations dependent upon the phase function.These angular changes are larger than the systematic errors in carefully executed measurements made from an aircraft.Thus, by measuring the angular distribution of water leaving radiance with an airborne remote sensing system it may be possible to recover information about the optical backscattering properties of the water column.A method for making these aircraft measurements and the results expected are described.

DETERMINATION OF DIFFUSE ATTENUATION COEFFICIENT IN THE CHESAPEAKE BAY FOR THE OCEAN COLOR SATELLITE APPLICATION

Son, SeungHyun¹; Wang, Menghua¹

¹NOAA/NESDIS/STAR NOAA/NESDIS/STAR E/RA3, Room 102, 5200 Auth Road, Camp Springs, MD, 20746, United States

It is important to accurately estimate the ocean diffusion attenuation coefficient for understanding not only physical processes such as the heat and light transfer processes, but also biological processes such as phytoplankton photosynthesis in the upper layer of the ocean. Satellite observation of the diffuse attenuation coefficient, K_d(490), is the only effective method to provide the large scale maps of K_d(490) over basin and global scale ocean waters. Several empirical and semi-analytical models of K_d(490) are commonly used to derive the K_d(490) maps from the ocean color satellite sensors. However, these models are applicable only for the clear open ocean waters, e.g., standard SeaWiFS/MODIS K_d(490) data. Therefore, it is highly required to derive a new method of K_d(490) for the turbid coastal waters.

In this study, we examine the standard models for the turbid coastal waters and derive new empirical methods of K_d(490) for the Chesapeake Bay waters using the in situ data set. Satellite-derived K_d(490) products using the new models as well as data from various standard (Case-1 clear ocean) models are compared with the in situ data in the main stream of the Chesapeake Bay. Results show that the satellite K_d(490) values from the new local models are well correlated with the in situ K_d(490) data, while those from the existing standard models are significantly underestimated.

PHYTOPLANKTON COMMUNITY REGULATION ON THE NEW ENGLAND SHELF: INSIGHTS FROM AUTOMATED SUBMERSIBLE FLOW CYTOMETRY

Sosik, Heidi M.¹; Olson, Robert J.¹

¹Woods Hole Oceanographic Institution MS 32, Woods Hole, MA, 02543, United States

Phytoplankton communities typically exhibit dramatic seasonal variations in temperate continental shelf systems. We are taking advantage of the Martha’s Vineyard Coastal Observatory (MVCO), a cabled facility on the New England inner shelf, as a model system to better understand the physical and biological processes that interact to produce this variability. Our approach depends on high resolution (~hourly) multi-year time series of taxonomically resolved phytoplankton acquired with FlowCytobot and Imaging FlowCytobot, custom-built automated submersible flow cytometers optimized for measurement of picoplankton and microplankton, respectively. These observational capabilities enable new approaches to understanding classical problems in plankton ecology. Annually at MVCO, chlorophyll concentrations are highest during bloom events in fall and winter, which Imaging FlowCytobot measurements show are dominated by microplankton, especially large (often chain-forming) diatoms. As water temperatures warm in spring, the community shifts to one dominated by pico- and small nanophytoplankton. Notably, this transition is associated not only with a decline in abundance of large diatoms, but also with a dramatic increase (100- to 1000-fold for picoplankton) in small cells. From FlowCytobot-based growth rate estimates, we show that the seasonal picoplankton variability is linked to effects of temperature and light limitation. On-going work is focused on exploring the hypothesis that fall and winter diatom blooms are linked to processes that control the availability of macronutrients.

OPTIMIZATION OF NEXT GENERATION OCEAN BIOLOGY REMOTE SENSORS USING A UNIFIED APPROACH TO FORWARD AND INVERSE MODELING

Stamnes, Knut¹; Li, Wei¹; Spurr, Robert²; Hamre, Boerge³; Stamnes, Jakob J.³

¹Stevens Institute of Technology Castle Point on Hudson, Hoboken, NJ, 07030, United States; ²RT Solutions, 9 Channing Street, Cambridge, Massachusuetts, 02138, United States; ³Department of Physics and Technology, Bergen, Hordaland, 5008, Norway

For SeaWiFS, MERIS and MODIS, ocean color retrievals rely on simplified two-step algorithms based on an atmospheric correction followed by two- or three-channel regression to deliver chlorophyll concentrations. We have already shown that a one-step simultaneous retrieval of aerosol and marine properties based on linearized coupled atmosphere-ocean radiative transfer and optimized bio-optical modeling yields a considerable improvement in retrieval accuracy [Li et al., IJRS, in press, 2008]. Next generation ocean biology remote sensors should be optimized to retrieve the maximum amount of information from the radiances measured in space. Current ocean color sensors have channels in the visible and near infrared. Spatial resolutions are quite good, but spectral variability is limited, and they do not measure polarized light. Aerosol information obtained from space is greatly enhanced with polarized backscatter measurements and multi-angle observations of the same scene, which is important for ocean color, because most of the satellite signal comes from the atmosphere. We discuss how to apply systematic error analysis and information budgeting to determine the importance of both polarization and multi-angle measurements for ocean color retrieval, and thus find the best choice of state-vector aerosol and marine parameters to be included in a simultaneous least-squares inversion procedure. Error budgeting requires extensive and accurate simulations of backscatter measurements and associated sensitivities (weighting functions). For this purpose we use a suite of fully coupled atmosphere-ocean multiple scattering radiative transfer models with scalar (intensity only) and vector (with polarization) capabilities, and the linearization facility to deliver analytic weighting functions. Exploring the wavelength range from the ultraviolet (300 nm) through the visible and the infrared to 2,500 nm, we discuss how to optimize the wavelength channels, channel widths, and viewing angle capability for a dedicated multi-angle ocean color polarimeter.

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

Stavn, Robert Hans¹; Richter, Scott²

¹University 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.

CDOM IN TROPICAL COASTAL WATERS OF THE GREAT BARRIER REEF: POTENTIAL AS A TRACER OF TERRESTRIAL DISCHARGE AND IMPLICATIONS FOR REMOTE SENSING

Steven, Andrew David Lesley¹

¹CSIRO 120 Meiers Rd, Indooroopilly, Brisbane, --, 4068, Australia

Andy Steven, Vittorio Brando, Phillip Ford, Thomas Schroeder, Lesley Clementson

CSIRO Land and Water, Australia

andy.steven@csiro.au

Understanding the patterns and variability in CDOM is important to trace the terrestrial discharge in the Great Barrier Reef lagoon and in developing regional algorithms for remote sensing of these optically complex coastal waters.

We surveyed the coastal waters of the Great Barrier Reef, Australia, between Cairns (~16.8 ^oS ) and Townsville (~18.8 ^oS) during the austral dry (October 2007) and wet (April 2008) seasons. At 48 stations, 16 of which were common to wet and dry season cruises, we measured CDOM fluorescence, absorption and composition (isotopic and NMR).

During both seasons CDOM concentrations were greatest as sites close to river mouths and decreased with distance from the coast. CDOM concentrations were also greater in the mangrove-dominated Hinchinbrook channel which is also subject to freshwater input from numerous creeks.

Wet season sampling followed several weeks after significant monsoonal activity that had resulted in flood plumes overlaying GBR coastal waters. Consequently, salinities were found to be significantly less than in the dry season sampling. Concentrations of CDOM were also greatest during the wet season and sites close to some rivers showed the greatest difference from dry season conditions.

In situ CDOM fluorescence varied significantly as a function of alkalinity but there were no discernible relationship with either suspended matter, Total Carbon or Total Organic Carbon. At inshore sites the composition was dominated by terrestrial sources while a greater proportion of marine sources were apparent at offshore sites.

CDOM fluorescence efficiency was estimated by comparing the in situ CDOM fluorescence measurements with spectrophotometric measurements of collected water samples. CDOM fluorescence efficiency varied significantly across the region in function of the DOC composition.

Given this cross-shelf and seasonal variability in CDOM concentration and composition algorithms will need to be developed to account for this variability.

Andy Steven, Vittorio Brando, Phillip Ford, Thomas Schroeder, Lesley Clementson

CSIRO Land and Water, Australia

andy.steven@csiro.au

Given this cross-shelf and seasonal variability in CDOM concentration and composition algorithms will need to be developed to account for this variability.

PARTICULATE ORGANIC CARBON (POC) IN THE NORTH ATLANTIC: SPATIAL AND TEMPORAL VARIABILITY

Stramska, Malgorzata¹

¹San Diego State University 6505 Alvarado Rd., Ste. 206, San Diego, --, CA 92120, United States

We have used the recently derived remote sensing algorithm (Stramski et al., 2008) to estimate surface concentration of POC in the North Atlantic. Our estimates are based on Level 3 standard mapped images (SMI) of daily normalized water leaving radiances at 443, 490, and 555 nm with a nominal 9 km x 9 km resolution from the ten years of SeaWiFS ocean color. In this presentation we discuss characteristic patterns of seasonal and geographic POC variability. We demonstrate that the large scale interannual trends in POC concentration are relatively small. POC variability is compared with patterns in primary productivity (PP) and export (PE). Mixed layer depth (MLD) climatology and optical depth estimates are used to derive estimates of POC reservoir in the North Atlantic surface waters.

SOUTHERN BAIKAL: REGIONAL OCEAN COLOR ALGORITHM

Suslin, Vyacheslav¹; Belykh, Ol'ga²; Sherstyankin, Pavel²

¹Marine Hydrophysical Institute 2 Kapitanskaya str., Sevastopol, --, 99000, Ukraine; ²Limnological Institute SB RAS/3 Ulan-Batorskaya str., Irkutsk, Eastern Siberia, 664033, Russian Federation

The relationships between SeaWiFS/MODIS-Aqua level 2 products and in situ chlorophyll concentration measured in the southern part of Lake Baikal during 2004 - 2006 were investigated. In most cases, as it had been expected the satellite standard product overestimated in situ chlorophyll a concentration in Baikal's gelbstoff-rich waters. On a log scale coordinate plane of in situ chlorophyll concentration versus band ratio, all points have been divided on two clusters. These clusters correspond two time periods: May-July during which optical properties of the upper layer of water are characterized by a low value of backscattering coefficient, and July-November during which optical properties of the upper layer of water are significantly affected by the Selenga river input and characterized by a high value of backscattering coefficient. For both clusters, the empirical equations describing dependence of chlorophyll concentration versus band ratio in the visible spectrum from 480-560 nm have been derived. These equations were used to plot the satellite-retrieved chlorophyll concentration time series. Both clusters have the same slope as for SeaWiFS and for MODIS-Aqua data, respectively. This fact could be explained by the different value of phytoplankton specific absorption coefficient in spectral domain of 550-560 nm caused by species composition of phytoplankton community.

REMOTE SENSING OF CHLOROPHYLL A CONCENTRATION AND COLOR DETRITAL MATTER ABSORPTION IN THE BLACK SEA: A SEMI-EMPIRICAL APPROACH FOR THE SEA-VIEWING WIDE FIELD-OF-VIEW SENSOR (SEAWIFS)

Suslin, Vyacheslav¹; Sosik, Heidi²; Churilova, Tatyana ³; Korolev, Sergei¹

¹Marine Hydrophysical Institute 2 Kapitanskaya str., Sevastopol, --, 99000, Ukraine; ²Woods Hole Oceanographic Institution, Woods Hole, MA, 02543-1049, United States; ³Institute of Biology of the Southern Seas, National Academy of Science, Sevastopol, Crimea, 99011, Ukraine

We describe an algorithm for retrieval of chlorophyll a concentration and colored detrital matter absorption in the Black Sea from SeaWiFS-derived normalized water-leaving radiances. A specialized approach is needed for the Black Sea, because of the optical complexity of the waters and overlying atmosphere. The algorithm is based on a simple physical model of seawater optical properties formulated in terms of two spectral ratios of normalized water-leaving radiance in SeaWiFS bands 3-5. Parameters of the model are selected empirically with a regional tuning procedure that presumes distinct water types for shelf and deep water regions of the Black Sea. In situ observations of chlorophyll a concentration and to a lesser extent of colored detrital matter absorption are used parameterize and evaluate the algorithm. We provide some preliminary assessments of sensitivity to critical parameters. In comparison to chlorophyll a concentration retrievals from the standard global empirical algorithm for SeaWiFS (OC4), our approach provides unbiased estimates across 100-fold range in values and produces much more realistic seasonality. In situ observations in the Black Sea remain sparse and more data is required for further evaluation. Our approach may be valuable for a variety of optically complex waters and we demonstrate this with preliminary application to other shelf and semi-enclosed seas.

EVALUATING TWO APPROACHES TO THE BIO-OPTICAL MODEL FOR COASTAL WATERS

Szeto, Mimi¹; Moore, Timothy¹; Campbell, Janet¹

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

The performance of two bio-optical models that describe remote-sensing reflectance (Rrs) in terms of inherent optical properties (IOPs) will be compared using several regional data sets. A model proposed recently by Sydor (2007) will be compared with the popular Gordon model (Gordon et al. 1988), which has served as the basis for several semi-analytic algorithms (GSM01, Garver and Siegel,1997; Maritorena et al. 2002; QAA, Lee et al. 2002). The Gordon et al. model, originally proposed for case-1 waters, expresses Rrs as a function of bb/(a+bb), whereas the Sydor model relates Rrs to the ratio of the total scattering coefficient to the total absorption coefficient. The ratio b/a is the average number of scatterings of a photon in the medium. Data sets used in the study are from the western Gulf of Maine (from COOA, UNH), the California Coast (from CalCoFI, SeaBASS), and Bermuda (from BBOP, SeaBASS) as a case-1 comparison. We parameterize both models for the regional data sets, and ask how well they perform in the forward direction to predict Rrs from IOPs, and when inverted to derive the IOPs given Rrs.

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

Sirjacobs, Damien¹; Tempera, Fernando²; Cardigos, Frederico²; Serrão Santos, Ricardo²; Bouquegneau, Jean-Marie³

¹(1) MARE Center, GeoHydrodynamics and Environmental Research (GHER), University of Liège (ULG), Allée de la Physique, B5, Sart-Tilman, Liège, Liège, B4000, Belgium; ²University of the Azores DOP/UAç, Cais de Santa Cruz, Horta, --, 9901-862, Portugal; ³(3) MARE Center, Laboratory of Oceanology (GHER), University of Liège (ULG), Allée de la Chimie, B6c, Sart-Tilman, Liège, Liège, B4000, Belgium

Benthic habitat mapping studies have been increasingly exploiting the use of underwater images to collect information on substrate nature and biological coverage. Concurrently, research has been ongoing to develop methods that use the imagery collected to conduct regular quantitative monitoring studies of biological resources distributed over large areas.

This study provides the first multi-annual monitoring information on the dynamics of a benthic macroalgae population derived from underwater imagery collected by scuba divers in the Monte da Guia Site of Community Importance /Natura 2000 network (Faial isl. Azores, NE Atlantic). The green alga Codium elisabethae - a long-living green alga that represents a potential good indicator of coastal environmental change - was chosen for the study. The analyses focus on using the underwater imagery to quantify seasonal fluctuations of density, percentage cover, biomass, growth rate and primary production of the species. Two study sites were investigated: one was located in a sheltered no-go reserve exhibiting a dense C. elisabethae population, and the other in a location experiencing more exposed conditions and holding a sparser population.

Between August 2003 and November 2005, fifteen (15) photo coverages were collected by scuba-divers. Subsequent processing consisted of producing image mosaics and using automated and interactive change detection methods that recognized, measured and counted individuals present in photos of fixed quadrats and yielded dynamical parameters such as population structures, growth, recruitment, and mortality. Chi-square tests of image-derived estimates and in situ measurements confirmed the validity of a centimeter precision estimation of population structure for individuals above 4 cm diameter. Important variability of population structure and density were observed at small spatial scales. Population density showed a sharp reduction in autumn 2003 and did not show a full recovery 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.

The production of information based on observations of thousands of individuals is mandatory in biological population statistics. The presented imagery approach made it possible, avoiding the need to collect all the measurements and quantitative information during time-constrained SCUBA diving operations.

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, Sam¹

¹City 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.

SEDIMENT RESUSPENSION IN CORAL REEFS MEASURED WITH IN-SITU OPTICAL MEASUREMENTS AND SATELLITE SENSORS

Toro-Farmer, Gerardo¹; Jones, Burton¹; Kiefer, Dale¹; Murdoch, Thaddeus²

¹University of Southern California 3616 Trousdale Pkway AHF 107, Los Angeles, CA, 90089, United States; ²Bermuda Zoological Society, Flatts, Flatts, P.O. Box FL 145, Bermuda

Coral reefs are evolutionarily optimized to thrive in tropical “clear” waters. Water column optical properties above coral reefs depend on the location along the reef, internal biogeochemical processes, biological activities, amount and composition of suspended or resuspended particles, as well as local to global anthropogenic influences. Resuspension of bottom sediments in these shallow ecosystems can be caused naturally by extreme episodic events such as winter storms or hurricanes. Human activities including navigation traffic can also dramatically change the optical properties of the water column, when materials from the bottom are resuspended to the water column more frequently, causing a rapid change from a clear to turbid water. In order to study how the spectral quality of light is affected by these resuspension events, in-situ variations in inherent optical properties and particle size distribution and concentration were measured above the reefs at different distances from navigation activities in the Bermuda Islands. Seasonal variations were considered by sampling during winter and summer, low and high traffic periods of ships, respectively. Additionally, in-situ measurements were compared with data retrieved for the same dates from satellite sensor at their higher spatial resolution. This study plus detailed characterization of the optical properties of the highly diverse bottom types in coral reef systems will improve our algorithms for modeling the very complex water column optical properties of these ecosystems.

IDENTIFICATION OF PHYTOPLANKTON PIGMENT ASSEMBLAGES USING SPECTRAL SHAPE ANALYSIS OF HYPERSPECTRAL REMOTE-SENSING REFLECTANCES

Torrecilla, Elena¹; Stramski, Dariusz²; Reynolds, Rick A²; Piera, Jaume¹; Millán Núñez, Eduardo³

¹Mediterranean Marine and Environmental Research Centre, Marine Technology Unit, UTM-CSIC Passeig Marítim de la Barceloneta 37, Barcelona, --, 08003, Spain; ²Marine Physical Laboratory, Scripps Institution of Oceanography, University of California San Diego, La Jolla, CA, 92093-0238, United States; ³CICESE, Oceanografia Biologica, Apdo. Postal 2732, Ensenada, B.C., 22860, Mexico

High spectral resolution measurements of the remote-sensing reflectance, Rrs, can potentially yield more information about the presence of diverse phytoplankton groups than can be gleaned from traditional analyses of single band-ratios. We explore this approach using a data set of measured and modeled optical properties collected along a north-to-south transect in the eastern Atlantic Ocean. Multispectral measurements of surface inherent optical properties (e.g. absorption, backscattering) and appropriate boundary conditions were used as inputs to the Hydrolight radiative transfer model to estimate Rrs over the range 375-725 nm with high (1 nm) spectral resolution. Simulated values of Rrs compared reasonably well with in situ measurements obtained in discrete spectral bands. Stations were classified into differing phytoplankton assemblages based upon the ratios of dominant accessory pigments to chlorophyll a. Distinct differences in the spectral shape of Rrs were observed between these classes, and were further examined using tools such as derivative and multiscale analysis (wavelet analysis). We discuss the potential provided by such shape analysis techniques to classify different open ocean environments in terms of biodiversity of phytoplankton populations.

EVALUATION OF A SUBMERGED REMOTE SENSING (SRS) TECHNIQUE

Trees, Charles C.¹; Pennucci, Giuliana¹; Austin, Ros²; Petzold (Deceased), Ted³

¹NATO 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.

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

Twardowski, Michael¹; Freeman, Scott¹; Vagle, Svein ²; Zhang, Xiadong³; Zaneveld, Ronald⁴

¹WET 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.

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 ²

¹Scripps 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.

INITIAL RESULTS FROM RADCAM, A HIGH DYNAMIC RANGE RADIANCE CAMERA

Van Dommelen, Ronnie¹; Wei, Jianwei²; Voss, Kenneth³; McLean, Scott¹; Lewis, Marlon²

¹Satlantic 3481 North Marginal Rd., Halifax, NS, B3K 5X8, Canada; ²Dalhousie University, Department of oceanography, Halifax, Nova Scotia, B3H 4J1, Canada; ³University of Miami, Physics Department, Coral Gables, Florida, 33124, United States

A high dynamic range camera has been developed as part of the Radiance in a Dynamic Ocean (RaDyO) program. The camera uses a CMOS array to achieve a scene dynamic range of 6 decades and a system dynamic range of more than 9 decades while maintaining an absolute radiometric accuracy of 10%. Three versions of the camera have been built including an in-air reference camera, a data logging version for ROV/AUV deployment and a profiler with both an upwelling and a downwelling camera. The high dynamic range allows the radiance field to be measured, including the sun, at the ocean surface. The spatial resolution is between half and one degree and the frame rate varies from 1-15 frames per second depending on the exposure time. Initial field data was collected off Scripps pier, under various surface wave conditions, using the first two cameras. Some initial results from this data will be presented.

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, Steef²

¹Plymouth 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.

VARIABILITY AND TRENDS IN 10-YEAR GLOBAL SEAWIFS TIME SERIES OF PHYTOPLANKTON CHLOROPHYLL A CONCENTRATION

Vantrepotte, Vincent¹; Melin, Frederic¹

¹JRC-European Commission Via Fermi, TP272, Ispra, --, 21027, Italy

The SeaWiFS global data set now offers a 10-year time series of consistent, well calibrated, ocean colour record that is suitable for temporal analysis. First, trends in the chlorophyll a (Chla) signal have been assessed using a classical linear regression analysis. From October 1997 to December 2007, a decline of the Chla concentration (ranging from <-1 to -5 %/yr) is observed in the various subtropical gyres but also in the North Atlantic Drift region. Conversely, an increase in Chla loads is detected in diverse coastal and upwelling areas (i.e. the Tasman Sea, the Arabian Sea, the Patagonian Shelf and the eastern Pacific and Californian upwelling). Increasing trends are also observed in large regions of the Southern Atlantic and Pacific oceans which are strongly contrasting with the situation reported for the gyres area in the latter oceanic domains. Moreover, the Chla monthly time series have been decomposed into seasonal, irregular and trend components using the Census X-11 decomposition approach that considers a nonlinear description of the long term changes and allows a varying amplitude for the seasonal fluctuations. This yields a classification of the biogeographic provinces of the ocean on the basis of their temporal variability. In particular, mid-latitudes regions are determined by their very high seasonality (> 60 % of the variance of the series) while a relevant contribution of the trend term to the Chla temporal variability is detected in various areas strongly affected, for instance, by the influence of ENSO (> 50% in the equatorial Pacific). The relevance of the Census X-11 procedure for analyzing Chla time series is demonstrated by the additional information provided on the nature of the long term changes detected by the simple linear approach.

ABSORPTION PROPERTIES OF PARTICULATE MATTER IN THE WESTERN MEDITERRANEAN SEA

Vellucci, Vincenzo¹; Ribera d'Alcalà, Maurizio²; Antoine, David¹

¹CNRS-LOV LOV, Villefranche sur mer, --, 06230, France; ²Stazione Zoologica Anton Dohrn, Naples, NA, 80121, Italy

Particulate matter is an optically significant constituent of marine waters playing a major role in absorbing environmental light in case I waters and modifying the radiant field. Compared to the global ocean, the Mediterranean Sea has been shown to be characterized by an anomalous blue to green reflectance ratio (B/G) for a given chlorophyll (Chl) concentration. In this region few in situ observations have been reported for the absorption properties of particulate matter, and its role in modulating the B/G has not yet been thoroughly assessed.

Here the characteristics of the absorption spectra of particulate matter in the Western Mediterranean Sea are described. Data were collected during seven cruises between 2001 and 2004. Absorption spectra were measured, in the visible domain, with filter pad technique and are representative of the oligo- and meso-trophic regimes generally encountered in the basin (measured Chl concentration spanning between 0.05 and 6.00 µg/l) and cover all seasons.

Spectra are divided into their algal and non-algal components, and regional models based on Chl content are derived to fit the observations. The obtained regional models are compared to the most representative homologous models for the global ocean. Differences between the proposed regional and the global models for absorption and specific absorption coefficients are pointed out and discussed. The absorption coefficients for the Mediterranean are introduced into a simple reflectance model to evaluate the impact of the algal and non-algal absorption components on the B/G. Finally the relationship between the underwater radiant field and the mean charachteristics of absorption spectra of phytoplankton is investigated.

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

Volpe, Gianluca¹; Buongiorno Nardelli, Bruno¹; Santoleri, Rosalia¹

¹GOS - 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.

A NEW SPECTRAL POLARIZED RADIANCE DISTRIBUTION CAMERA SYSTEM, DPOL

Voss, Kenneth J¹; Bhandari, Purushottam¹; Logan, Luke Andrew¹

¹Univ. of Miami 1320 Campo Sano Dr., Coral Gables, FL, 33146, United States

The polarized spectral radiance distribution is the most complete description of the lightfield at a single point. A fisheye system, with an electronic camera and filter changer, provides a useful way to collect the radiance distribution, and we have exploited this in several in-water and in-air camera systems. Adding polarization requires an additional complication of combining images, with different polarization states, each taken of the same light field. In the atmosphere this can be realized by sequential images, however in the ocean it requires simultaneous images. We have developed a new instrument that is a fisheye based system with 4 lens systems which are imaged onto a single camera sensor with a coherent fiber bundle. Each lens system has its own polarizer, so each image from the camera contains the information to determine the Stokes vector of the light field, the most complete, measurable description of the polarization state of the light field. This paper will describe the instrument in detail, the calibration procedure, and give examples of data collected with this instrument.

DETECTION OF ICE AND ICE-WATER MIXING PIXELS FOR THE MODIS OCEAN COLOR DATA PROCESSING

Wang, Menghua¹; Shi, Wei¹

¹NOAA/NESDIS/STAR E/RA3, Room 102, 5200 Auth Road, Camp Springs, MD, 20746, United States

Currently, the data processing for deriving ocean color products from the Moderate Resolution Imaging Spectroradiometer (MODIS) has no specific ice and ice-water detection procedure. The near-infrared (NIR) reflectance threshold at the MODIS 869 nm band, which has been used to discriminate clear sky from clouds (cloud masking) for the standard ocean color data processing, can eliminate most of the ice pixels. However, there are still many cases for which the ice and ice-water mixing pixels have been misidentified as ocean waters in the current ocean color data processing, leading to errors in the MODIS-derived ocean color product (e.g., chlorophyll-a concentration). This is particularly true for most of the ice-water mixing cases. For atmospheric correction using the shortwave infrared (SWIR) method, which also uses the SWIR reflectance for the cloud masking, the problem of ice misidentification is getting even worse. In this presentation, we describe a method for detection of ice and ice-water mixing pixels for the MODIS ocean color data processing. Using the MODIS-derived normalized water-leaving radiances at 412, 555, and 859 nm, a scheme for ice and ice-water detection has been developed and tested for producing MODIS global ocean color products. With the new ice detection scheme, pixels with ice and/or ice-water mixing can be discriminated, flagged and masked out. The detection results are compared with the MODIS ice mask product produced from the MODIS Land team, as well as ice product data obtained from the NOAA National Ice Center. We show improved results from the new masking algorithm for the purpose of the MODIS ocean color data processing, in particular, for the detection of ice-water mixing pixels.

REMOTE SENSING OF INHERENT OPTICAL PROPERTIES: UNCERTAINTIES AND SATELLITE APPLICATIONS (RESULTS FROM A WORKSHOP, 3-4 OCT 2008, BARGA, ITALY)

Werdell, Jeremy¹; Participants, IOP Algorithm Workshop¹

¹NASA Goddard Space Flight Center NASA-GSFC Mail Code 614.8, Greenbelt, MD, 20771, United States

Semi-analytical (SA) ocean color algorithms provide a mechanism for estimating marine inherent optical properties (IOP), such as spectral absorption and backscattering coefficients, from satellite radiometric measurements. While SA algorithms include empirical components, they improve upon purely statistical approaches through their foundation in radiative transfer theory and their ability to simultaneously retrieve multiple, often uncorrelated, optical parameters. Recently, the U.S. and international ocean color communities have shown considerable interest and invested significant effort in improving the regional and global quality of satellite-derived SA data products (see, e.g., IOCCG Report 5). As such, we hosted an international IOP algorithm workshop to extend the recent IOCCG IOP effort by explicitly defining the state-of-the-art with regards to the application of these algorithms to satellite radiometry. In particular, we reviewed algorithm: (a) parameterization, inversion, and optimization; (2) associated uncertainties; (3) spectral requirements; (4) applicable spatial and geophysical ranges; and (5) satellite inversion failure conditions (and their remediation). The workshop, held the weekend prior to Ocean Optics XIX, was the culmination of shared analyses conducted from June to September 2008 by the 25 workshop participants. Here, we present results from the workshop, specifically highlighting progress towards our underlying goal of achieving community consensus on an effective algorithmic approach for producing global-scale, remotely sensed IOP products.

DIAPHANOUS: OR DAYS OF FLY FISHING IN A SHORT CONVERSATION. WITH SOME ACCOUNT OF THE HABITS OF WHITE SUBMERSIBLE OBJECT OPERATORS BELONGING TO THE GENUS CAPTAIN OR SCIENTIST

Wernand, Marcel Robert¹

¹Royal Netherlands Institute for Sea Research Landsdiep 4, Den Hoorn, Texel, --, 1797 SZ, Netherlands

A standardized method to determine the water clarity (transparency) was adopted at the end of the nineteenth century. This method, lowering a white painted disc into the water until it disappeared out of sight, was described in 1865 by Alessandra Cialdi and Angelo Secchi . However, before 1865 there were several others who experimented, like Cialdi and Secchi, with white and coloured submersible objects to quantify water transparency. Why was it then that this method became known as the Secchi depth method?

BIO-OPTICAL OBSERVATIONS OF THE NORTH ATLANTIC SPRING BLOOM

Westberry, Toby K.¹; Dall'Olmo, Giorgio¹; Behrenfeld, Michael J.¹; Boss, Emmanuel²

¹Oregon 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.

RELATIONSHIPS BETWEEN MARINE MICROBIAL ECOLOGY AND THE UNDERWATER LIGHT FIELD IN A PERSISTENT OXYGEN MINIMUM ZONE

Whitmire, Amanda¹; Letelier, Ricardo¹; Ulloa, Osvaldo²

¹Oregon State University 104 COAS Admin Bldg, Corvallis, OR, 97331, United States; ²Universidad de Concepción, Cabina 7 -Barrio Universitario, Casilla 160-C, Concepcion, Octava Región, Casilla 160-C, Chile

The Eastern South Pacific (ESP) oxygen minimum zone (OMZ) is a permanent hydrographic feature located directly off the coasts of northern Chile and Peru. The ESP OMZ reaches from coastal waters out to several kilometers offshore, and can extend from the surface to depths greater than 700 meters. Anoxic waters often intrude into the euphotic zone in the ESP OMZ, and as a result, novel communities of uncultivated marine bacteria and archaea with diverse metabolic pathways are found there. Strong subsurface fluorescence maxima are often observed within anoxic waters, and initial results indicate that aerobic anoxygenic phototrophs and Prochlorococcus dominate the prokaryotic community at these depths. Low-light adapted Prochlorococcus strains have been observed in high concentrations below 1% of surface light levels in anoxic conditions.

We present results from ship-based profiles of hyperspectral upwelling and downwelling plane irradiance, CDOM and chlorophyll-a fluorescence, and backscattering at 440 nm in the ESP OMZ during June 2008. We characterize the underwater light field with respect to the quality and quantity of light available to novel populations of marine bacteria found above, within, and below the strong oxycline (dissolved oxygen reduction of up to 21 micro-Molar O₂ per meter). We also relate the spectral aspects of the downwelling light field to the presence of unique bacterial assemblages (including non-photosynthetic chemoautotrophs) in regions where anoxic waters do and do not penetrate the euphotic layer.

PHYCOERYTHRIN SPECTRAL SIGNATURES IN THE COASTAL OCEAN

Wood, Michelle¹; Everroad, C.¹; Gould, R. ²; Arnone, R. ²; Pegau, S.³

¹University of Oregon Dept. of Biology, University of Oregon, OR, 97403, United States; ²Office of Naval Research, Stennis Space Center, MS, 39529, United States; ³Oil Spill Recovery Institute, Cordova, Ak, 99574, United States

Phycoerythrin (PE), refers to a family of distinctive and highly fluorescent light harvesting pigments that are responsible for photosynthetic harvesting pigment in many marine picocyanobacteria, cryptomonads, Trichodesmium, red algae, and a few other taxa of marine phytoplankton. In this work we combine fluorescence data on PE spectral signature in bulk seawater, cell counts, and data on inherent and apparent optical properties to examine the degree to which PE spectral signature provides oceanographically useful information about the water column. Data were collected in the Arabian Sea, and in coastal waters off the coast of North America in the Pacific Ocean, Atlantic Ocean, Gulf of Mexico, and the Gulf of California. A key finding of the research is that the PE spectral signature associated with a relatively low ratio of phycourobilin (PUB) to phycoerythrobilin (PEB) chromophores (the so-called low PUB phycoerythrin), is a consistent marker for nutrient enrichment of oceanic waters. This form of PE consistently replaces the high PUB form of PE if phytoplankton growth is stimulated as a result of turbulent mixing or upwelling. Our data also show that the PE-containing picoplankton reach their highest concentrations in warm waters with high concentrations of colored dissolved organic matter (CDOM) and high Rrs(550):Rrs(450) ratios. In these environments, the small PE-containing picocyanobacteria routinely reach their highest concentrations (>10⁶ ml^-1) and are usually characterized by a PE spectral signature associated with the PUB-lacking form of PE. Thus, the results of this study contradict two prevailing ideas about PE-containing picocyanobacteria – first, that the low PUB form of PE is rare in the ocean and, second, that the preferred habitat of these organisms is the open ocean. Further, they demonstrate the utility of PE spectral signature in diagnosing the relative contribution of chlorophyll and CDOM to ocean color in optically complex coastal waters.

EFFECTS OF LARGE PARTICLE AND TURBULENT SCATTERING ON WAVEFRONT SENSOR MEASUREMENTS OF THE VOLUME SCATTERING FUNCTION

Woods, Sarah¹; Bogucki, Darek¹; Freda, Wlodek²

¹Division of Applied Marine Physics, RSMAS, University of Miami 4600 Rickenbacker Causeway, Miami, FL, 33149, United States; ²Physics Department, Gdynia Mar