Distribution patterns of zooplankton communities around Iceland in spring

This paper presents an analysis of zooplankton composition and abundance based on sampling over the depth range 0-50 m at nine transects (61 stations) during a hydrobiological survey of Icelandic waters in May-June 1992. Zooplankton abundance and species distribution is considered in relation to water masses and topography. The biomass of zooplankton was highest in the oceanic areas northeast of Iceland [∼⃒8-20 g dry weight (dw) m −2 ], whereas the lowest values were generally observed in the offshore areas southeast, south and southwest of Iceland (<2 g dw m −2 ). Over the shelves, the values tended to be intermediate (∼⃒2-5 g dw m −2 ). In total, 93 species and identification groups were identified in the samples. Calanus finmarchicus was by far the most abundant species [about half of the total numbers of zooplankton if Calanus spp. nauplii (∼⃒20%) are included]. Less numerous groups were Oithona spp., cirripede larvae, euphausiid larvae (nauplii, calyptopis and furcilia stages), larvaceans, Pseudocalanus spp., C. hyperboreus , Acartia spp., and Temora longicornis . A cluster analysis was carried out in order to reveal relationships among stations in zooplankton abundance and species composition. The analysis classified stations into four groups, mainly defined by bathymetry and hydrographic conditions. In the coastal water south and west of Iceland, cirripede larvae were by far the most abundant group, followed by C . finmarchicus and euphausiid larvae (group A), while in the coastal water north of the country, C . finmarchicus , euphausiid larvae and larvaceans were most abundant (group B). In the offshore waters south of the island, C . finmarchicus , Oithona spp. and echinoderm larvae were most abundant (group C), whereas in the offshore area north of Iceland C . finmarchicus , Oithona spp. and C. hyperboreus were most abundant (group D).