Climate variations and the state of zooplankton in the Barents Sea

Abstract

We present data on zooplankton biomass distribution in August-September 2005-2006 obtained in the integrated ecosystem system survey for the Barents Sea performed by Russian and Norwegian vessels. In order to establish the general regularities of plankton biomass, data collected in the central latitudinal zone of the Barents Sea in individual years (cold 1987, moderate warm 1989, anomalous warm 2002, 2004, 2005) were analysed. Considerable annual differences in the species and age structure of plankton community in water masses of different origin depending on dynamics of the ice cover in that part of the sea were found. In 2002, owing to the northerly position of the ice edge in summer, the plankton community was characterized by its mixed composition (Atlantic and Arctic species) and high abundance. In 2005 when the advective processes were weak and the eastern areas became free from ice later, a considerable reduction in the abundance of warm-water species was observed. When the position of the ice edge was most southerly in 2004, the bulk of the plankton community was made up of Arctic species and a lack of warm-water species was recorded. In 1987 and 1989, high horizontal gradients of water temperature in the areas of Atlantic and interactions of Arctic water masses were, together with anomalous ice distribution, the main factors influencing the state of zooplankton.