Controls on zooplankton assemblages in the northeastern Chukchi Sea

Abstract

The Chukchi Sea is a broad and shallow marginal sea of the western Arctic Ocean that lies between the Bering Sea and the deeper Amerasian basin. It plays a pivotal role as the only gateway for transporting heat, carbon, nutrients, and plankton from the North Pacific into the Arctic Ocean. I examined the seasonal and inter-annual variability of the zooplankton communities in the northeastern region of the Chukchi Sea as part of a high-resolution multidisciplinary ecosystem study. Specifically, I examined how the physical onset of each open water season influenced the composition, abundance, and biomass of zooplankton assemblages from the 2008 to 2010 field seasons. Copepods in the genus Pseudocalanus are key members of the Chukchi community, and may be undergoing species-level biogeographic shift in response to climate change. I determined the degree of gene flow and population connectivity in the Chukchi Sea through comparative phylogeographic analysis of the Pseudocalanus species complex to the northern Gulf of Alaska and Beaufort Sea. I then investigated the extent to which biogeochemical factors influence these zooplankton assemblages by relating a portion of the seasonal production to concurrent changes in herbivorous mesozooplankton biomass during 2010 and 2011. This work demonstrates just how complex and variable marine ecosystems of the western Arctic are, where multidisciplinary and analytical approaches will become essential in detecting change, especially with the rate of present-day climate perturbations.