Impact of Biological and Physical Processes during the Mesoscale Transport of Zooplankton, especially Calanus finmarchicus, around Georges Bank: GLOBEC Phase II Results

K. Wishner, D. Outram, B. Sullivan, P. Donaghay, C. Gelfman,
D. Van Keuren, and J. Sullivan

Calanus finmarchicus does not overwinter on Georges Bank, and thus its advective input to the Bank, transport around the Bank, and removal from the Bank are critical processes for the population and ecosystem of that region. Representative sites and mesoscale advective features on and near the Bank were studied during 3 springtime cruises in 1997 as part of the US GLOBEC program. Vertically stratified day and night MOCNESS tows were taken to sample Calanus and associated predators. Water and zooplankton (including predators) were transported downstream along isopycnals from the northeast inflow region, clockwise around Georges Bank, and then out into a detrainment feature associated with a warm core ring. The Calanus population in May decreased by 77% from the northeast to the south flank and then by another 30% in the detrainment feature. Processes contributing to this loss include both physics (advection and dilution by mixing), as well as predation.