We analyzed the seasonal and interannual variability of the planktonic communities in a densely sampled
region of the northeastern Chukchi Sea as part of a multidisciplinary ecosystem study from 2008 to 2010.
Observations of chlorophyll-a, inorganic macronutrients, and zooplankton (using both 150-mm and 505-mm
mesh nets) were made within two 900-NM 2 grids (Klondike and Burger) at high spatial resolution three times
each in 2008 and 2009, with a third grid (Statoil) sampled twice in 2010. Sea-ice conditions prior to sampling
varied notably during the study: seasonal sea ice retreat was earlier and sea-surface temperatures (SSTs) were
warmer in 2009 than in 2008, whereas SSTs for 2010 were intermediate between the 2008 and 2009 values.
Eighty taxonomic categories of zooplankton, including 11 meroplanktonic categories, were recorded, with the
greatest diversity found within the copepods (25 species), followed by the cnidarians (11 species). All species
are typical for the region and most are seeded from the Bering Sea. A seasonal progression of the community
structure was apparent over each survey area and was likely influenced by temperature. Cold oceanographic
conditions in 2008 likely slowed growth and development of the zooplankton, such that holozooplankton
abundance averaged 2389 and 106 individuals m–3 and biomass averaged 10.5 and 8.3 mg DW m–3 in the
150- and 505-mm nets, respectively. An early phytoplankton bloom in 2009 apparently supported a
zooplankton community of greater abundance, but moderate biomass, averaging 6842 and 189 individuals
m–3, and 16.3 and 7.0 mg DW m–3 in the 150- and 505-mm nets, respectively. Highest zooplankton
abundance and biomass values among the three years occurred in 2010: 7396 and 198 individuals m–3 and
102.9 and 33.5 mg DW m–3 in the 150- and 505-mm nets, respectively. Holozooplankton biomass changes
were driven by increases in large-bodied, lipid-rich copepods. The contribution of meroplankton was
substantial in this shallow-water ecosystem: numerically, they contributed 28% in 2008, 8% in 2009 and
56% in 2010 to the total zooplankton community and 43%, 27%, and 11%, respectively, terms of biomass for
the 150-mm nets. Interannual differences in ice-melt timing, water temperatures, northward transport of
water masses, and nutrients and chlorophyll concentrations resulted in highly variable pelagic productivity.