Temporal changes in the inorganic carbon system of the southeastern Bering Sea during spring 1980

Abstract

Previous studies of the inorganic carbon system in the southeastern Bering Sea¹ demonstrated the occurrence of extremely low partial pressures of carbon dioxide ($P_{\text{C}{\text{O}}_{\text{2}}}$) and depressed total carbon dioxide concentrations (∑CO₂) during late spring. To test the hypothesis that these conditions develop during the spring phytoplankton bloom, and to provide biological production data that would be independent of the carbon-14 technique², we monitored the inorganic system in this region intensively during spring 1980. We demonstrate here that there is a clear relationship between the changes in the inorganic carbon system and the spring phytoplankton bloom. Initially (March–early April), $P_{\text{C}{\text{O}}_{\text{2}}}$ values in the surface waters were near or above the mean atmospheric content of 339 p.p.m., and ∑CO₂ concentrations were ∼2 mmol l⁻¹. By the end of the bloom, these variables were sometimes below 125 p.p.m. and 1.75 mmol l⁻¹ respectively, and the changes were correlated with nutrient decreases and dissolved oxygen and chlorophyll increases. At a mid-shelf station, it was possible to calculate net community organic carbon production from our data. The average rate between 23 April and 23 May was 3.6 g C m⁻² day⁻¹, in fair agreement with carbon-14-based primary production estimates.