Impacts of unprecedented loss of sea ice on multiple trophic levels and ecosystem structure in the Chukchi and Beaufort Seas

Arctic warming in recent years has surpassed historical measurements, prompting an evaluation of the effects of changes in sea ice extent, and the timing of ice formation and retreat, on ecosystem structure. Here we present the impacts of warming on physical processes, productivity, phytoplankton, and fish from ecosystem research surveys in the Alaskan Chukchi and Beaufort Seas during 2018 and 2019, two back-to-back years of record low winter sea ice extent. Recent results from a suite of physical measurements (satellite data, moorings including Prawler profiling devices, and ship-based water column profiles) and biological surveys (plankton and fish collections) suggest that warmer temperatures and loss of sea ice affected stratification, nutrient production, and the timing of phytoplankton. These in turn, had cascading impacts across trophic levels. Zooplankton were less abundant and plankton communities were dominated by small, lipid poor, copepods that serve as lower quality food for young fish and higher trophic levels. Abundances of Arctic ichthyoplankton species (Boreogadus saida and Eleginus gracilis) that are prey for sea birds and marine mammals were low in comparison to less extreme years. Catches of older fishes included salmon, walleye pollock, Arctic cod, and saffron cod. Seabird mortalities were observed at sea. The record low winter sea ice occurring in the Arctic is having cascading impacts on the Arctic ecosystem as a whole, changing physical oceanographic conditions, reshaping biological communities, affecting food webs, and altering trophic connections.