Annual in situ carbon dioxide and oxygen flux across a subtidal marine sediment

Abstract

Dissolved carbon dioxide release (445 l CO2 m−2 year−1) measured with chambers placed in situ over subtidal sediments at Eastern Passage, N.S. exceeded oxygen uptake by 2·5 times. Patterns of seasonal changes in flux were similar for both gases with maximum rates at times of highest temperature between May and July. Estimates of algal pigments in surface sediments were not correlated with seasonal changes in gas flux. If concentrations of organic carbon in surface sediment layers vary around steady-state levels, and if mineralization of organic carbon decreases exponentially over time, the ratio of carbon dioxide loss to average concentrations of organic carbon in the upper 1 cm of sediment implies that decomposition is 95% complete in less than 2 years. If carbon dioxide is derived from the upper 10-cm sediment layer, estimates of turnover time increase to 15 years.