U.S. GLOBEC Northeast Pacific Study: Mesoscale zooplankton distribution and productivity
Meng Zhou [University of Minnesota], Mark E. Huntley [University of Hawaii]

This proposal addresses one of 3 central hypotheses of the U.S. GLOBEC Northeast Pacific (NEP) Study: "Spatial and temporal variability in mesoscale circulation constitutes the dominant physical forcing on zooplankton biomass, production, distribution, species interactions and retention and loss in coastal regions." (U.S. GLOBEC Northeast Pacific Implementation Plan, U.S. GLOBEC Report No. 17). We respond to specific components of the NOAA/NSF GLOBEC announcement which call for:

• 3-dimensional mesoscale surveys (in a 100-km-wide coastal region from Newport, Oregon to Eureka, California) aimed at determining the distribution and productivity of zooplankton in relation to their physical environment, and
• process studies focussed on understanding zooplankton in situ population dynamics processes and the interaction between physical and biological processes.

It is not well understood how mesoscale features in the California Current System impact zooplankton biomass, production, distribution, or retention and loss from coastal regions. No wonder. These interacting phenomena have been studied rarely off California, and even more rarely off Oregon. Mesoscale physical dynamics are relatively easy to measure, but require a high sampling frequency. Most standard methods of measuring zooplankton are simply not compatible with the sampling frequency required to resolve mesoscale features. This fundamental challenge must be met for GLOBEC to succeed.

Our group has invested a decade in the development and application of an integrated methodology for measuring zooplankton biomass, distribution and productivity at the high resolution required for mesoscale studies. We find significant mesoscale interactions between physical forcing and zooplankton productivity in the California Current System off northern California. In a 1993 pilot study, we found net decreasing productivity in the central jet of the California Current, and net increasing productivity in adjacent eddy systems. The mesoscale match of physical and biological processes was striking - but underlying causes remain obscure. The GLOBEC NEP study offers an unparalleled opportunity to understand these dynamics upstream - off Oregon - and so to shed light on fundamental processes.

We propose to study both physical and biological processes, and their spatio-temporal coupling, by measuring and mathematically deducing individual processes of advection, vertical migration, and rates of productivity. We will use the integrated Sea-Soar-Optical Plankton Counter (OPC) and ADCP in mesoscale surveys, coupled with critical net sampling, to resolve spatial and temporal distributions of size- and species-structured zooplankton at the mesoscale. Rates pertinent to population dynamics will be determined from the biomass spectral method (Zhou and Huntley, 1997) in conjunction with certain complementary and independent field measurements. We believe our approach will produce estimations of biomass and productivity - resolved at the same scale as mesoscale physics - and will clarify factors controlling variations in zooplankton productivity. These results are not only critical to defining the "food field" of juvenile salmon (a key GLOBEC NEP target species), but can improve our general understanding of interactions between zooplankton populations and their dynamic physical environment, which is the central goal of GLOBEC.

Statement of Work for Year One

We will have two mesoscale surveys in spring and fall, 2000. Prior to the first spring survey, we will need 5-6 months to calibrate our instruments and necessary modification of our Optical Plankton Counter (OPC) for better integration of SeaSoar and OPC to improve the data quality. In addition to the hardware preparation, we will continuously develop our OPC data processing software for the purpose of onboard data processing and computation of zooplankton distribution and productivity. After the first cruise, we will conduct the calibration between OPC measurements and net tow samples, data quality control, and further develop our data processing software (See the following table for details).

PERSONAL	10/01/99 -	Spring cruise	-	Fall cruise
M. Zhou (PI) 2 months (50%)	Organizing, OPC hardware/software development	OPC data process, zoopl. Sampling	Post OPC data process, calibration,	OPC data process, zoopl. Sampling
M. E. Huntley (PI) 1 month	Organizing, model development, sampling gears and lab prep.	OPC data/zoopl. Sampling	OPC-Zoopl. Sample comparison
X. Irigoien 12 months	Logistics, model development, sampling gears and lab prep.	OPC data/zoopl. Sampling	Lab exp., zoopl. sample processing	OPC data/zoopl. Sampling
Y. Zhu 4 months	OPC software preparation (filtering and interpolation)	Onboard data processing	OPC data process, software develop.	Onboard data processing
J. Peterson (Grad. Student)	OPC hardware, sampling gears, and lab preparation	OPC data acquisi. Zoopl. Sampling	Zoopl. sample/OPC data process	OPC data/zoopl. Sampling

This page was last updated on March 15, 2007.

Maintained by:
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College of Oceanic and Atmospheric Sciences
Oregon State University
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