The inf luence of advection on Calanus near Svalbard: statistical relations between salinity, temperature and copepod abundance

We quantify statistical relationships between hydrography and abundance of Calanus spp. in the Arctic–Atlantic transition zone around Svalbard (78–82°N) during early autumn. The Atlantic species C. finmarchicus was more abundant in warmer and more saline waters, as expected from its distributional core area. Conversely, the Arctic species C. hyperboreus was more abundant in colder and fresher waters. However, the Arctic species C. glacialis showed opposing relationships with hydrography in shallow compared with deep regions. In shallow waters, the numbers of C. glacialis decreased with temperature and salinity as expected, while somewhat surprisingly the opposite trend was found in deep locations. Sub-surface hydrography between 50–150 m was in most cases a better predictor for Calanus spp. abundance than near-surface conditions, the former generally explaining up to ∼50% of the variability in abundance of each species. Despite finding significant relationships between hydrographic properties and the abundance of each of the three Calanus species, we did not detect significant relationships between the total Calanus biomass and temperature.