Chapter 11 Benthic Processes in Polynyas

Abstract

Abstract Polynyas are areas of open water in ice-covered seas, and are important sites for enhanced water column and benthic production in both the Arctic and Antarctic. Research on polynyas during the last twenty years has allowed multi-disciplinary evaluation of processes in various polynyas, including the Northeast Water (NEW) polynya, North Water (NOW) polynya, St. Lawrence Island polynya (SLIP), and the Bathurst (BATH) polynya in the Arctic, and the Ross Sea polynya (RSP), McMurdo Sound polynya (MSP), and Terra Nova Bay (TNB) polynya in the Antarctic. Several other coastal polynyas around Antarctica have received limited study. Studies of benthic patterns and processes in polynyas indicate that faunal biomass, productivity, and carbon cycling are dependent on depth, season, ice cover, carbon supply, and hydrographic forcing. Polynyas generally have high primary productivity, which typically supports rich benthic communities through enhanced vertical carbon flux. Short and long-term indicators can provide a “foot print” of water column processes within polynyas, such as sediment community oxygen consumption and benthic biomass. Although zooplankton production directly influences the retentive nature of carbon in the euphotic zone, depth is the critical factor for the impact of net carbon export to the underlying benthos. We use a simple modeling exercise of two polynya case studies, the SLIP in the Arctic and RSP in the Antarctic, to evaluate export efficiency and benthic carbon cycling. Depth ultimately influences whether a polynya is a “retentive” versus “export” ecosystem, impacting the underlying benthic populations and associated carbon cycling. Defining polynyas and marginal ice zones as retentive versus export systems is potentially a powerful tool for understanding polar shelf processes, particularly when primary production is not measured simultaneously with benthic parameters.