Cross-shelf gradients of epipelagic zooplankton communities of the Beaufort Sea and the influence of localized hydrographic features

Abstract

Biological, chemical and physical oceanographic data were collected in the Beaufort Sea between Point Barrow, Alaska and the Mackenzie River during August and September from 2010 to 2014 in order to provide baseline information for the Beaufort Sea's poorly characterized zooplankton communities. Mean holozooplankton abundance and biomass across the survey years ranged from 1110 to 3380 ind. m-3 and 23.8 to 76.9 mgDWm-3, respectively. The zooplankton community was predominantly Arctic in faunal character during all surveys, although Pacific and Atlantic expatriates were observed. The community was dominated by Calanus glacialis, Calanus hyperboreus, Metridia longa, Oithona similis, Triconia borealis, Microcalanus pygmaeus, and the Pseudocalanus species complex; this group composed 44-81% of abundance and 52-71% of biomass across survey years. Despite the dominance of these taxa, seven distinct faunal groups were identified. These faunal groups reflect a transition from neritic to oceanic communities and the influence of more localized hydrographic features, such as Pacific-origin Alaska Coastal Water and Mackenzie River-derived Water. Community structure was most strongly related to temperature and salinity averaged over the upper 200 m, suggesting that future changes in the physical environment will be manifested by concurrent shifts in the distribution of Beaufort Sea zooplankton communities.