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.