Variation in zooplankton biomass with hydrological regime beneath the seasonal ice, mcmurdo sound, Antarctica

Abstract

Variations in zooplankton biomass are correlated with major hydrological features of south‐eastern McMurdo Sound (77° 50'S, 166° 30’ E). Biomass values fluctuate proportionally with tidal height and tide‐influenced current speed. There is a reversal in vertical distribution of zooplankton from open to sub‐ice waters: zooplankton is most abundant near the surface in open water areas, but in sub‐ice areas the greatest abundance is in the deepest water. A sub‐ice area of high zooplankton content is explained in terms of zooplankton productivity. High biomass associated with high tide in the south‐western part of the area studied is presumed to be due to the transport of enriched open‐sea water under the ice. There is marked depletion of the sub‐ice fauna in all water layers close to Ross Island, which is apparently correlated with the presence in this area of a warmer surface current. The deeper water layers are the emergent stream of a sub‐ice circulatory current.