Springtime Renewal of Chukchi Sea Plankton by Northwards Advection from the Bering Sea

Chukchi Sea plankton are primarily comprised of populations that have been advected northwards from the Northern Bering Sea through Bering Strait. Whether populations persist in-situ in the Chukchi Sea or are renewed annually following harsh, overwintering conditions remains un-described. Here we use data from two bio-physical surveys of the Chukchi Sea -- one in early-winter 2011 and the other in late-spring 2104 -- to describe the planktonic distributions and relate them to the seasonal hydrographic conditions. The zooplankton populations in early-winter showed differences in population structure, species abundances, and species occurrence between locations characterized by Canada Basin water types versus Chukchi Sea Winter Water and Bering Sea water. A similar situation existed during the first part of the late-spring cruise, with population structure, species abundance and occurrence being fairly uniform across the middle-northern Chukchi Sea, in Chukchi Sea Winter Water. However, conditions were distinctly different at stations near the shelfbreak that are influenced by Arctic waters. During the latter portion of the late-spring cruise, high abundances of meroplankton, including the previously absent younger copepodid stages of the copepod Calanus glacialis, were observed in the mid-Chukchi Sea. We investigate how the boundary between these different community types is related to the seasonally varying hydrography, and how this Arctic-Subarctic interface progresses northward in time through the Chukchi Sea. Such movement substantially impacts both the planktonic and, through settlement of meroplankton, benthic communities, as well as the prey available for a range of seabirds and marine mammals.