Peter J. S. Franks (SIO), James M. Pringle (UNH), Jeffrey A. Runge (UNH), Changsheng Chen (UMassD),
Edward G. Durbin (URI), Wendy Gentleman (UW)

The goal Of the proposed work is to gain a mechanistic understanding of the influences of climate variation on the population dynamics and production of target zooplankton species on Georges Bank (Calanus finmarchicus, Pseudocalanus moultoni, P. newmani, and Oithona similis) through its effects on advective transport, temperature, food availability, and predator fields. Using data analysis and models as tools, results acquired during the first three phases of GLOBEC will be incorporated into a new synthesis of the physical and biological processes regulating zooplankton abundance on the Bank. Physical models will be forced with measured daily, interannually variable data, and coupled to biological models synthesizing the detailed observations collected during the GLOBEC program.

To understand the role of advection, and to disentangle the effects of physical and biological processes, a hierarchy of physical and biological models is proposed. These include 1-, 2-, and 3-D physical models, ecosystem models, and individual-based models (IBMS) for the target species. The IBMs will be coupled to 1-D physical models designed to represent the characteristic environments of the different Gulf of Maine and Georges Bank subregions. Ultimately, the IBMs will be coupled to the full 3D physical/ecosystem model through particle tracking. This will provide a physical and biological milieu in which to develop and probe hypotheses regarding the combined influences of physical and biological factors on the copepod population dynamics.

Although the population dynamics in all broadscale survey years will be studied, initial investigations will concentrate on 1995, 1998 and 1999. The data sets are the most complete for these years, and SeaWiFS data are available for 1998 and 1999. These years also represent a wide range of environmental conditions: an extensive winter bloom in the Gulf of Maine in 1999 related to Scotian Shelf inflow and increased stratification; a slightly warmer year in 1995; and stronger storm activity in 1998 than 1999. In addition 1998, and to a lesser extent 1999, give indication of being strong years for haddock recruitment but apparently not for cod.

Specific issues to be investigated include: wind control of the advective supply of the target zooplankton species to Georges Bank during January-April; interannual and/or event-level variations in the advective flux of Calanus finmarchicus to Gulf of Maine basin diapausing populations during June-April; interannual and/or event-level variations in advective losses of copepods from Georges Bank and bank subregions; the influence of stratification on the planktonic ecosystem, and how this affects the population dynamics of the target zooplankton species through food and predation. As a link to Phase IV synthesis studies on target ichthyoplankton, our investigation will provide mechanistic insight into the factors determining production of copepod prey for larval cod and haddock on the Bank.

The proposed work will educate a number of graduate students over the course of the Phase IV research. These students will represent the best of our ability to train broadly educated researchers adept at combining techniques from a variety of disciplines in their work. In addition, this will be the first major independent funding source since graduation for two young investigators (Pringle, Gentleman).