Cross-shelf variation in habitat characteristics of arctic whales in Baffin Bay measured using ocean gliders

Abstract

Zooplankton distribution and abundance play a crucial role in shaping the foraging behavior of bowhead whales, Balaena mysticetus, in Arctic marine ecosystems. Understanding how physical oceanographic conditions influence the vertical and horizontal zooplankton abundance is essential for assessing critical foraging habitats. In this study, we analyzed depth-integrated zooplankton abundance and maximum zooplankton abundance across distinct water masses on and off the West Greenland continental shelf using Cabot 198 ocean glider. The glider transited along six transects that travelled cross-shelf, collecting 176 vertical profiles of zooplankton abundance and environmental variables including temperature, salinity, and bathymetric depth. Zooplankton were primarily concentrated within the upper 300m of the water column, with diel vertical migration (DVM) observed, as aggregations shifted from the top 100 m at night to depths below 200 m during the day. Bathymetric depth was a significant predictor of total depth-integrated zooplankton abundance (individuals/m², p < 0.001). The highest zooplankton densities were recorded in association with Arctic and Atlantic Waters. These findings suggest that Arctic and Atlantic-influenced waters provide key foraging grounds for bowhead whales by supporting prey densities exceeding previously established foraging thresholds.