The reduced abundances of all taxa during winter
relative to fall may have been caused by the vertical
redistribution to depth or sub-ice, as discussed above.
Alternatively, seasonal changes in abundance or, for
marine snow, decreased particle production, may have
resulted in plankton and particles being present in too low
an abundance during winter to be effectively imaged, or
detected, by the VPR. However,
dramatic reductions in plankton abundance during winter
also were documented using other instruments. A reduction in plankton abundance during
winter relative to fall has been observed previously for the
region, although not to such a
great magnitude as observed during 2001.