Contrasting intra-annual inorganic carbon dynamics and air–water CO2 exchange in Dhamra and Mahanadi Estuaries of northern Bay of Bengal, India

• Published in: Limnology 2020-01, Vol.21 (1), p.129-138
• Main Authors: Pattanaik, Suchismita, Chanda, Abhra, Sahoo, Rajesh Kumar, Swain, Sanhita, Satapathy, Deepty Ranjan, Panda, Chitta Ranjan, Choudhury, Saroj Bandhu, Mohapatra, Pradipta Kumar
• Format: Article
• Language: English
• Subjects: Air; Alkalinity; Annual variations; Biomedical and Life Sciences; Blue carbon; Carbon dioxide; Dissolved inorganic carbon; Ecology; Environment; Estuaries; Estuarine dynamics; Fluxes; Freshwater; Freshwater & Marine Ecology; Inland water environment; Life Sciences; Monsoons; Net Primary Productivity; Organic carbon; Partial pressure; Primary production; Remineralization; Research Paper; Summer; Surface water; Turbidity; Water circulation; Water column; Wind
• ISSN: 1439-8621; 1439-863X
• DOI: 10.1007/s10201-019-00592-0

Surface water partial pressure of carbon dioxide [pCO 2 (water)], total alkalinity (TA), dissolved inorganic carbon (DIC), and air–water CO 2 flux were measured in two estuaries of the Bay of Bengal namely Mahanadi and Dhamra. Though the annual average air–water CO 2 fluxes at the Mahanadi and the Dhamra Estuaries were − 3.9 ± 21.4 (mean ± standard deviation) µmol m −2  h −1  and − 2.9 ± 11.6 µmol m −2  h −1 , respectively, the intra-annual variation of air–water CO 2 fluxes in the two estuaries was contrasting. Nonetheless, from the perspective of net primary productivity, the surface water of both the estuaries were found autotrophic throughout the study period with varying rates at different seasons and highest during summer months. Mahanadi Estuary acted as a CO 2 source toward atmosphere during monsoon months, whereas, Dhamra Estuary acted as a source during pre-monsoon months. On the contrary, Mahanadi and Dhamra Estuaries acted as CO 2 sink during pre-monsoon months and monsoon months, respectively. The salinity in Mahanadi Estuary was much lower compared to Dhamra, which indicated significant freshwater discharge rich in organic carbon, and the remineralization of this carbon to DIC during summer and monsoon months explained the CO 2 source character. Whereas, in Dhamra, reduced freshwater flow and high turbidity were held accountable for net heterotrophic character of the water column during the post-monsoon months. The annual data set of air–water CO 2 fluxes from these two estuaries produced from this study could be utilized in future to fill the data gap and upscale the Indian estuaries scenario from the perspective of blue carbon budgeting.