ARCUS | Arctic Research Consortium of the United States

6th Annual ARCUS Award for Arctic Research Excellence


Submitted by   Janne Elin Søreide
Authors   Janne Elin Søreide
Category   Life Science
Title   Winter and spring distribution of macrozooplankton in the Marginal Ice Zone of the Barents Sea.
Affiliation   Institute of Aquatic Resources and Environmental , The Norwegian College of Fishery Science, Tromsø, Norway

Abstract

Macro-zooplankton was collected in the Marginal Ice Zone (MIZ) of the Barents Sea during two cruises in May 1999 and March 2000. Three north –south transects across MIZ were performed, two of them were also crossing the Polar Front. The largest fraction of the zooplankton community (> 3 mm) was sampled in a large and coarse plankton net (mouth opening ~ 2 m2, mesh size 1.55 mm) vertically from the bottom to the surface.
The water masses strongly influenced the macro-zooplankton distribution. In spring, different developmental stages of algal blooms were encountered from pre-bloom to late-bloom situations. However, the phytoplankton development stage and biomass seemed to have little effect on the total macro-zooplankton abundance and biomass in May, compared to the hydrography. Winter conditions, with very low phytoplankton biomass, were only recorded in March. Herbivorous macro-zooplankton dominated in numbers, but carnivorous macro-zooplankton made up most of the biomass. From May 1999 to March 2000 differences in specie composition, abundance and biomass were found. In Arctic waters, the abundance and biomass of carnivorous zooplankton increased from May to March, whereas in Atlantic waters, there was found a decrease in the abundance and biomass of herbivorous zooplankton from May to March.
In Arctic waters, the herbivores Calanus glacialis and C. hyperboreus dominated both in May and March. In Atlantic waters, euphausiids dominated both May and March, but Calanus hyperboreus exceeded euphausiids in abundance in May. In Atlantic waters in March, C. hyperboreus was found in low numbers. In highly transformed Atlantic and Arctic water masses a low total macro-zooplankton abundance was found, which was dominated of Calanus glacialis numerically. Carnivorous macro-zooplankton i.e. the siphonophore Dimophyes arctica, the hydromedusa Aeginopsis laurentii and the copepode Pareuchaetha spp. showed higher abundance in Arctic waters in March than in May.