Epiplankton in the Barents sea: Summer variations of mesozooplankton biomass, community structure and diversity

Zooplankton link primary producers (phytoplankton) and higher trophic levels (fish, marine mammals, and seabirds) and are considered to be an important component in pelagic marine systems. In this paper we analyze a mesozooplankton data set obtained in the Barents Sea from 2003 to 2009 to test for climatic influences on some important parameters of the epi-zooplankton community in summer. The maxima of both mean water temperature in the upper 100 m layer and averaged chlorophyll a concentration in the surface strata were recorded in 2006, which may be considered as an anomalously-warm year. Total mesozooplankton biomass ranged from 743 +/- 106 mg C m(-2) in the southern region to 3716 +/- 664 mg C m(-2) in the northern region. The proportions of herbivores and large zooplankters (animals with total length of 2.7-7.0 mm) were highest in 2006 and tended to increase with temperature. Diversity, evaluated as the Shannon index of the mesozooplankton communities, was weakly correlated in time with environmental variables, and the mean and total number of taxa increased with water temperature in the southern and central Barents Sea. Most of the biological characteristics of the mesozooplankton community were only weakly correlated in time with the NAO and AO indices; however, the proportion of animals in 1.0-2.7 mm and 2.7-7.0 mm size classes tended to increase with increases in the monthly PC-based NAO index for August. Our data suggest that the complex zooplankton parameters (biomass, trophic and size structure, and diversity) can be useful in studying climatic impacts on marine ecosystems. (c) 2012 Elsevier Ltd. All rights reserved.