Micro- and mesozooplankton in Southwest Greenland waters in relation to environmental factors

Abstract

Plankton samples and oceanographic data were obtained during transect studies across fishing banks over the Southwest Greenland shelf in June 1999, May, and July 2000. The study gives a detailed description of micro- and mesozooplankton distributions and community structures during spring bloom and post bloom periods. Plankton distributions were related to the physical environment described by a hydrodynamic ocean circulation model. More than 30 species and a larger number of taxonomic categories were identified in the zooplankton samples. Large copepodites of Calanus finmarchicus, Calanus glacialis, and Calanus hyperboreus generally dominated the micro- and mesozooplankton biomass, with Pseudocalanus spp., Metridia longa, and Oithona spp. comprising most of the remaining biomass. By number, bivalves larvae and relatively large copepod nauplii (>200 μm) dominated the zooplankton community (>50 μm) in May, whereas smaller copepod nauplii (<200 μm) were dominating in June and July. In May during a spring bloom period, diatoms, Thalassiosira spp. and Chaetoceros spp., generally dominated the biomass of the plankton community of the upper 100 m followed by heterotrophic flagellates, copepods, other invertebrates, and ciliates. Conversely in June (and July) during post bloom, large copepods were dominating. Hydrodynamic model simulations of ocean currents and trajectories of potential plankton transports showed differences in potential advection of plankton across shelf banks. The circulation around the banks seems to create retention areas entrapping plankton for periods. Model simulations predict that upwelling occurs west of the shelf banks and to a lesser extent in the deep channels separating the banks. This upwelling, caused by wind and tidal motions, probably increases productivity and carbon cycling over the shelf areas.