CO2 fluxes from aquaculture ponds of a tropical wetland: Potential of multiple lime treatment in reduction of CO2 emission

Abhra Chanda; Sourav Das; Sourav Bhattacharyya; Isha Das; Sandip Giri; Anirban Mukhopadhyay; Sourav Samanta; Dibyendu Dutta; Anirban Akhand; S B Choudhury; Sugata Hazra

doi:10.1016/j.scitotenv.2018.11.332

CO₂ fluxes from aquaculture ponds of a tropical wetland: Potential of multiple lime treatment in reduction of CO₂ emission

Sci Total Environ. 2019 Mar 10:655:1321-1333. doi: 10.1016/j.scitotenv.2018.11.332. Epub 2018 Nov 23.

Authors

Affiliations

¹ School of Oceanographic Studies, Jadavpur University, Kolkata 700032, West Bengal, India. Electronic address: abhrachanda.sos.rs@jadavpuruniversity.in.
² School of Oceanographic Studies, Jadavpur University, Kolkata 700032, West Bengal, India.
³ School of Oceanographic Studies, Jadavpur University, Kolkata 700032, West Bengal, India; Institute of Environmental Studies and Wetland Management, Department of Environment, Govt. of West Bengal, Salt Lake, Kolkata 700 064, India.
⁴ National Remote Sensing Centre, Department of Space, Government of India, Hyderabad 500042, Telengana, India.
⁵ Coastal and Estuarine Environment Research Group, Port and Airport Research Institute, 3-1-1, Nagase, Yokosuka 239-0826, Kanagawa, Japan.

PMID: 30577124
DOI: 10.1016/j.scitotenv.2018.11.332

Abstract

Partial pressure of CO₂ in water [pCO₂(water)] and air-water CO₂ flux were estimated in two aquaculture ponds (one received no lime treatment (NTP) and in the other lime treatment was performed (LTP) four times a year) every month throughout an annual cycle, situated in East Kolkata Wetlands, a Ramsar Site in eastern India. It was hypothesized that lime treatment can potentially lower the pCO₂(water) in aquaculture ponds and hence make these aquatic bodies sinks for CO₂. The results portrayed that NTP acted as a source of CO₂ throughout the year (annual mean: 1929 ± 1397 μmol m^-2 h^-1), whereas, LTP acted as CO₂ sinks post lime addition (monthly mean ranged from -366 ± 16 to -449 ± 32 μmol m^-2 h^-1), though the effect of lime addition was found to diminish by the next month and it acted as source for CO₂ in the months when no lime treatment was done (LTP annual mean: 1010 ± 1617 μmol m^-2 h^-1). Lime treatment increased the pH level and reduced the turbidity which facilitated optimum photosynthesis and the productivity increased rapidly. Beyond the critical pH value of 8.9-9.0, the pCO₂(water) values became under-saturated with respect to atmospheric CO₂ concentration. The effect of lime treatment was not found to prevail in the following months as a steady source of sewage from the Kolkata metropolis which feeds these aquaculture constantly bring in a huge carbon source both in inorganic and organic form. As soon as the flocculation effect of the lime dies off, the water column starts becoming turbid again which aids in converting the system into a net heterotrophic one from a net autotrophic. Based on the results we could successfully accept our hypothesis that lime treatment can not only reduce the CO₂ emission but also make the system a CO₂ sink.

Keywords: Aquaculture ponds; CO(2) emission; East Kolkata Wetlands; India; Lime treatment.