Microzooplankton along a transect from northern continental Norway to Svalbard

In the framework of the Italian International Polar Year project entitled Evolution of a Glacial Arctic Continental Margin: the Southern Svalbard Ice Stream-dominated Sedimentary System, a study was carried out on microzooplankton distribution and biomass along a south-to-north transect extending from northern Norway to the Svalbard Archipelago, from 65° to 78°N. Tintinnids, heterotrophic dinoflagellates, aloricate cilates and micrometazoans were the main groups observed in the samples collected at 17 surface stations from 9 to 13 July 2008. Total microzooplankton abundance ranged from 17 to 438 ind l−1. Tintinnids and heterotrophic dinoflagellates were the most abundant organisms, ranging from 1.5 to 292.5 ind l−1 and from 0 to 232 ind l−1, respectively. Micrometazoans (mainly copepod nauplii) reached a maximum of 45.5 ind l−1, whereas aloricate ciliates were scarce at all stations. Microzooplankton carbon content ranged from 0.87 to 5.18 µg C l−1. In particular, tintinnids and micrometazoans made up the largest part of the microzooplankton biomass. Parafavella denticulata, Parafavella gigantea, Acanthostomella norvegica and Ptychocylis obtusa were the most common species among tintinnids, whereas Leprotintinnus pellucidus was recorded in only one station close to Svalbard. Protoperidinium was the most representative genus among heterotrophic dinoflagellates. The community of naked ciliates was dominated by Strombidiidae and Holotrichia. A clearly increasing gradient in both abundance and number of taxa was observed from south to north, with the temperature decreasing from 13.3 to 2.5°C