Carbon and nitrogen uptake dynamics during 1997 and 1998 anomalous conditions in the Bering Sea

Abstract

During 1997 and 1998, unusual physical conditions caused dramatic changes in the regional oceanic environment and function of the southeastern Bering Sea ecosystem. The changes in ecosystem function were examined using ¹³C and ¹⁵N tracer techniques. In 1997, unusually clear and calm conditions allowed an ice-related early bloom over the middle shelf of the southeastern Bering Sea and resulted in nitrate uptake below the pycnocline. In 1998, the duration of phytoplankton growth was extended by warm temperatures and frequent storms that resulted in slow growth of phytoplankton and prevented rapid utilization of nitrate over the shelf. In coccolithophorid bloom regions, ammonium concentrations were high (>3 uM), while nitrate concentrations had a larger range (O.1-10.8 uM). Nitrate utilization rates, which estimate 'new' production, were similar for both years and were somewhate greater (ca. 30%) than those observed during the 70's and 80's PROBES studies. The fate of primary production may have differed in 1997 and 1998.