Spatial occurrence and abundance of marine zooplankton in Northeast Greenland

Abstract

We present a large-scale survey of mesozooplankton (size range 0.2–20 mm) across coastal, shelf, and slope locations in Northeast Greenland (latitudes 74–79° N, August 2015 and September 2017). Our study is centred on the Video Plankton Recorder (VPR) for non-invasive in situ observations of taxa distribution and abundance while simultaneously recording oceanographic profiles. A modified WP-2 plankton net (85-μm mesh size) was used primarily not only to verify taxa detected by the VPR but also to make a preliminary comparison of abundance estimates by the two gears. A total of 35 zooplankton taxa were identified with 10 genera alone among copepods (Hexanauplia). Selected taxa from the VPR (N=16) were associated with the temperature-salinity spaces and the chlorophyll a-depth profiles in the study area. From surface to > 900 m depth, the overall temperature and salinity ranged between −1.9 and 6.8 °C and 26.6 and 35.3, respectively. Two copepod genera dominated, i.e. Pseudocalanus prevailed in the upper sub-zero layers in coastal waters whereas Calanus was omnipresent, but mainly abundant in the warmer Atlantic waters at the shelf break. Chlorophyll a levels were in general very low (< 2 mg m-3) and peaked at 30–50 m depth, suggesting post-bloom conditions. Overall, zooplankton abundances tended to increase from the coast towards the slope (9–344×103 individuals m-2). Biodiversity in terms of taxon richness, on the other hand, showed the opposite trend and decreased from 16 taxa at the coast to 5 taxa further offshore.