A 5-year study of seasonal patterns in mesozooplankton community structure in a sub-Arctic fjord reveals dominance of Microsetella norvegica (Crustacea, Copepoda)

The study presents data from a multi-year zooplankton sampling programme with year-round monthly sampling in a sub-Arctic fjord in Greenland (Godthabsfjord). A total of 56 zooplankton groups were identified over 5 years, with the copepod Microsetella norvegica dominating the mesozooplankton community. Microsetella norvegica was found to be very abundant (maximum abundance: 408 125 plus or minus 161 387 nauplii m super(-3) and 91 995 plus or minus 6 864 copepodites m super(-3)) and to make up, on average, 87% of the annual copepod assemblage. There was a seasonal zooplankton succession whereby Cirripedia nauplii dominated the biomass in March and April, and Calanus spp. dominated in May and June, followed by M. norvegica from July to September. The total copepod biomass peaked in August (71 plus or minus 10 mg C m super(-3)), mainly (68% on average) due to biomass of M. norvegica, indicating that small copepods are important in this system. This multi-year study describes inter-annual variation in species abundance and seasonal succession. Fjord-ocean interactions, tidal mixing and the extensive freshwater run-off from the Greenland Ice Sheet are characteristic features of fjords in Greenland that could be a principle driver behind the present findings.