A comparison of CO₂ dynamics and air‐water fluxes in a river‐dominated estuary and a mangrove‐dominated marine estuary

Abstract

Abstract The fugacity of CO 2 ( f CO 2 (water)) and air‐water CO 2 flux were compared between a river‐dominated anthropogenically disturbed open estuary, the Hugli, and a comparatively pristine mangrove‐dominated semiclosed marine estuary, the Matla, on the east coast of India. Annual mean salinity of the Hugli Estuary (≈7.1) was much less compared to the Matla Estuary (≈20.0). All the stations of the Hugli Estuary were highly supersaturated with CO 2 (annual mean ~ 2200 µatm), whereas the Matla was marginally oversaturated (annual mean ~ 530 µatm). During the postmonsoon season, the outer station of the Matla Estuary was under saturated with respect to CO 2 and acted as a sink. The annual mean CO 2 emission from the Hugli Estuary (32.4 mol C m −2 yr −1 ) was 14 times higher than the Matla Estuary (2.3 mol C m −2 yr −1 ). CO 2 efflux rate from the Hugli Estuary has increased drastically in the last decade, which is attributed to increased runoff from the river‐dominated estuary.