Biomass size spectra of mesozooplankton in the Chukchi Sea during the summers of 1991/1992 and 2007/2008: an analysis using optical plankton counter data

To evaluate regional characteristics, zooplankton communities were analyzed by an Optical Plankton Counter (OPC) in the Chukchi Sea during summers of 1991, 1992, 2007 and 2008. Zooplankton abundance and biomass ranged from 5000 to 1 170 000 ind. m^[-2] and 0.2 to 10.9 g dry dry-mass m^[-2], respectively. Based on the zooplankton biovolume at 48 bins every 0.1 mm between 0.25-5.0 mm equivalent spherical diameters (ESD), Bray-Curtis cluster analysis classified zooplankton communities into four groups (A-D). There was no observed change in zooplankton communities in the south of Lisburne Peninsula (group A) throughout the four years, while there observed change in zooplankton communities north of Lisburne Peninsula: group B (normal) in 1991/ 1992, group D (low biomass) in 2007, and group C (predominance of barnacle larvae) in 2008. Analysis of Normalized Biomass Size Spectra (NBSS) with groups revealed that the groups A and C were highly productive. Thus, the zooplankton community in the south of Lisburne Peninsula was constantly highly productive, which may be caused by the continuous inflow of Pacific Water containing high nutrients. The zooplankton community in the north of Lisburne Peninsula varied greatly by year, which may be related to the inter-annual changes in sea ice extension