IMIS

Day/night vertical distribution of zooplankton was studied in the central part and MIZ of the Barents Sea. Stratified vertical tows (50-0m, 100-50m and bottom – 100m) were done with a WP-2 net (0.5 m2 mouth area, 180 µm mesh) at 3 stations in March 1998, 4 stations in May 1998, and 5 stations in July 1999. The ship was R/V Jan Mayen; geo-referencing of stations was done with a GPS using latitude and longitude with two decimals. These cruises produced a database with 1500 rows consisting of 20 species. The zooplankton vertical distribution reflected both seasonal changes in the productive cycle and a latitudinal shift in the onset of events. No diel vertical migrations were found. Bearing in mind the fact that the total biomass was dominated by Calanus finmarchicus and/or Calanus glacialis we can consider seasonal and regional dynamics in zooplankton depth distribution as a result of ontogenetic vertical migrations of these two species.