U.S. GLOBEC: Abundance and distribution of zooplankton on Georges Bank

E. Durbin

This proposal is in response to the Announcement of Opportunity for Phase 2 of the US GLOBEC directed towards the following Program Objective in the Announcement of Opportunity: (1) Quantification of the abundances of target species in time and space on Georges Bank over the winter/spring period. The present proposal is a request for the continuation of the zooplankton component of the broadscale survey for the 1997, 1998 and 1999 field seasons. There are a number of objectives of this survey and results will be used to answer basic scientific questions as to the processes controlling the population dynamics of these target species and of their life history strategies. Specific questions being addressed include: (1) What are the abundance levels of the target species in space and time on Georges Bank? (2) How is the bank repopulated in the winter, and when and where on the bank does this repopulation first occur? (3) How many generations of each of the target species occur on the bank? (4) What is the relationship between the abundance and spatial and temporal distribution of the target species and physical processes? This includes general circulation features, mesoscale advective features such as Scotian Shelf inflows, the presence and location of fronts, and the degree of vertical stratification? (5) Do the target species have life history strategies which, through an interaction with physical processes, serve to act as retentive mechanisms both on the seasonal and shorter time scales? (6) To what extent is there interannual variation in any of the above?

Zooplankton will be collected during six two week broadscale survey cruises between January and June of each year. Samples are collected using a 1 m**2 MOCNESS net equipped with 0.150 mm mesh nets. For enumeration the MOCNESS samples are split with a folsom splitter to provide a subsample of about 1000-1200 animals. The two target species (Calanus finmarchicus and Pseudocalanus spp) are enumerated to stage, while other copepods are identified to species and grouped as copepodites and adults. Other zooplankton are identified to the lowest possible taxa and counted. This survey is essential to the success of a number of components of the GLOBEC Georges Bank study and without it the different components could not be brought together to answer the more general goals of the overall program.