Distribution of zooplankton in the Northeast Water Polynya during summer 1992

Abstract

Abstract The distribution and abundances of zooplankton in the Northeast Water (NEW) Polynya during the summer of 1992 have been determined from samples collected with Bongo (this study) and MOCNESS (earlier analysis) plankton net tows. The initial hypothesis was that the troughts of the Greenland Shelf in the region of the NEW polynya would be conduits for the infusion of zooplankton species of Arctic and North Atlantic origin on to the shelf. Analysis of MOCNESS tows indicated instead that advection of zooplankton onto the shelf in the polynya region was limited, resulting in low abundances of the large herbivores in the polynya. The distribution of zooplankton determined from the 43 Bongo tows reported here strengthen this finding. Low abundances of the large herbivorous copepods and of other primarily herbivorous zooplankton taxa were observed throughout the ice-free region, in contrast to higher abundances observed further to the east in Westwind Trough or in the south in Belgica Trough. Cluster analysis was used to identify groups of co-occurring zooplankton taxa and groups of stations with similar relative compositions of zooplankton taxa. The community composition of the Belgica Trough was distinctly different from that observed in northern regions, with high abundances of open ocean copepods ( Calanus finmarchicus and C. hyperboreus ). Two types of communities were identified in the northern regions: one typical of the eastern basin (Westwind Trough) and one typical of the western basin (Norske Trough) of the northern trough. The relationship between the different zooplankton communities and the water mass characteristics was not conclusive; however, it did appear that zooplankton populations had been advected in the upper water column into the Westwind Trough from north of the study area. The low abundances of herbivorous taxa in the ice free region supported previous estimates that meso-macro zooplankton may not be significant consumers of primary production in the polynya.