Distribution of larval krill and zooplankton in association with hydrography in Marguerite Bay, Antarctic Peninsula, in austral fall and winter 2001 described using the Video Plankton Recorder

Abstract

The Western Antarctic Peninsula is a critical locus of Antarctic krill Euphausia superba abundance and thought to be a site of successful overwintering, particularly for the larval stages. A primary goal of the Southern Ocean GLOBEC program was to describe factors that contribute to the overwintering success of krill in this region. As part of this effort we conducted Video Plankton Recorder (VPR) surveys during austral fall and winter, 2001. The VPR survey yielded high-resolution distributions of larval krill, other plankton, and marine snow in relation to hydrography from a series of transect lines orthogonal to the coast on the continental shelf of the Western Antarctic Peninsula. Four taxa (larval krill, copepods, polychaetes, pteropods) and marine snow were numerous during fall; much lower abundances of all categories were present during winter, with only larval krill, copepods, and polychaetes present in any abundance. Distributions of plankton and marine snow were associated with water-mass types and the vertical structure of the environment, particularly for larval krill that were primarily associated with the pycnocline. During fall, larval krill were present across the entire shelf, with high abundances at the shelf break. Copepods were most numerous at depth during fall, consistent with ontogenetic migration to depth at the onset of winter.