Zooplankton biodiversity and life histories of common copepods in an Antarctic nearshore habitat

Abstract Coastal Antarctic ecosystems feature long periods of sea ice cover, strong seasonality in primary production, and low biodiversity relative to marginal ice zone regions. There are few records of annual cycles of biodiversity and abundance of neritic Antarctic zooplankton, limiting the ability to predict how communities will respond to environmental change. Using a historical data set, we assess the annual cycle of primary production and zooplankton abundance in relation to the growth cycle of fast ice near Vestfold Hills, East Antarctica. Zooplankton abundance and biodiversity were high during the productive summer months, generally showing a lag behind peaks in chlorophyll a concentration. A total of 27 taxa were recorded from the water column, while only three species were recorded from the sea ice, apart from incidental occurrences. Copepods dominated the system throughout the year, especially in the non-productive season, with a small number of species contributing to overall abundance, including Paralabidocera antarctica, Oithona similis, and Oncaea curvata. The abundance of fauna living within the brine channel system was very high, although biodiversity was low relative to the water column. To survive the winter, the copepods employed a combination of life history strategies, including strong association with the fast ice habitat, synchronicity with the spring phytoplankton bloom, and dietary switching in winter. Complementary strategies, such as lipid storage and advection to and from deeper offshore waters, were also observed.