Invited Speakers

Percy L. Donaghay

Percy Donaghay is a Senior Marine Research Scientist at the University of Rhode Island’s Graduate School of Oceanography. He received a B.A. degree in Biology from the University of Delaware and a M.S. and a Ph.D. in Biological Oceanography from Oregon State University. His research is focused on understanding how physical-biological, biological-biological and chemical-biological interactions operating at fine to meso-scales control the dynamics and impacts of plankton patches. He has been particularly interested in thin layers of phytoplankton and zooplankton. These layers range in thickness from 12 centimeters to a few meters, yet can extend horizontally for kilometers, persist for hours to months, and dramatically impact the dynamics of plankton populations and the performance of optical and acoustical sensors. His research has involved (1) the development of testable models of the underlying processes and interactions, (2) collaboration with engineers and optical, acoustical, and chemical oceanographers in the development of new instruments, calibration methods, and deployment techniques need to simultaneously sample physical, chemical and biological structures and processes at centimeter scales, and (3) an observational program designed to test thin layer models in the field and quantify their patterns of occurrence and persistence in a variety of coastal environments. These efforts have recently culminated in the ONR Layered Organization of the Coastal Ocean (LOCO) experiments conducted in Monterey Bay in 2005 and 2006. Dr. Donaghay also has served on a series of national and international committees involved in developing research programs such as LOCO, ECOHAB, GEOHAB and ORION. These efforts have involved helping develop the scientific framework for these programs and helping evaluate new technologies that are crucial to their success. He has recently been elected to the applied technology position on the TOS council.

ABSTRACT

EVOLUTION OF PROFILING SYSTEMS FOR UNDERSTANDING THE CHARACTERISTICS, DISTRIBUTIONS, DYNAMICS AND IMPACTS OF THIN PLANKTON LAYERS IN STRATIFIED WATERS

Percy L. Donaghay, Graduate School of Oceanography, University of Rhode Island, Narragansett, USA 02882

For many years, one of the central paradigms in oceanography was that small scale mixing processes in the upper ocean were sufficiently strong and equal in all directions that biological, chemical and optical layers less than a few meters thick would be rapidly dispersed and thus could be ignored in both sampling and modeling upper ocean biological, chemical and optical dynamics. Although it is extremely difficult to sample at these scales using standard oceanographic CTDs, bottles and nets, recent improvements in optical sensors and deployment techniques now allow both ship-deployed slow-drop and autonomous bottom-up profilers to simultaneously collect decimeter or better resolution profiles of physical, chemical, optical and acoustical structure in the coastal ocean.  The resulting data has challenged the generality of the paradigm by demonstrating that previously unresolved optical thin layers ranging in thickness from 12cm to a few meters can develop in stratified waters, persist for hours to days, extend horizontally for hundreds of meters to kilometers, and be sufficiently intense to alter the interpretation of optical measurements and impact a wide variety of biological and bio-geochemical processes. The detection of such thin layers raises five important questions: (1) what are their properties and patterns of occurrence;  (2) what are their temporal and spatial scales; (3) what are the mechanisms that control the formation, maintenance and dissipation; (4) what are their impacts, and (5) how do the above vary between coastal systems that differ in physical size, exposure to physical forcing, and susceptibility to advective inputs? Herein, we will first summarize the science drivers, then discuss how slow-drop and autonomous bottom-up profiling techniques have been developed to sample at the critical scales needed to address thin layer questions.  In the final section, we will discuss the limitations and potential future evolution of these techniques.