Air-Sea CO sub(2) dynamics from tropical estuarine system Mahanadi, India

Abstract

The biogeochemical characteristics of Mahanadi estuarine system in eastern India were investigated to understand the seasonality in carbon parameters and their influence on sea-air CO sub(2) gradient. In general, the stations close to the estuary had higher salinity and total alkalinity; and lower pCO sub(2)(water) relative to the inner most stations. In contrast, the riverine stations had low pH and high pCO sub(2(water)) and lower total alkalinity. The chlorophyll a values ranged between 0.27 to 11.22 mg m sup(?3) during this investigation. We found that the seasonal oscillations in sea-air CO sub(2) gradient (delta pCO sub(2) = pCO sub(2(water))-pCO sub(2(air))) were negative during winter and positive during summer, wherein the estuary acted as a weak source. The average air-water CO sub(2) flux density values varied between -5.65 to 13.11 micro mol m sup(?2) h sup(-1) throughout the study period. Two-way ANOVA showed strong seasonal control on environmental variables. The relationships observed between pH and salinity with pCO sub(2) suggest that fluvial inputs of nutrients and the accompanying heterotrophic processes may possibly control the sea-air CO sub(2) gradient in the surface waters of the Mahanadi estuary.