Carbon balance of a sewage-fed aquaculture wetland

Abstract

Wetlands are considered as one of the most effective carbon (C) sink among various ecosystems. To substantiate this view, the present investigation was conducted in one of the units of sewage fed East Kolkata wetlands (EKW), a Ramsar site, over a period of 3 years. The result revealed that because of high primary productivity due to abundance of primary producers and other sources of C input primarily through sewage influx, there is net positive balance of C in the system. The rate of C accumulation estimated through C budget was 1245.27–2490.55 kg C ha−1 year−1 while the rate estimated through sediment core analysis came out to be 1584 kg C ha−1 year−1. The amount of total C deposited up to 15 cm depth in sediment was 29.37 Mg ha−1, quite higher than the C deposited up to 15 cm depth of reference upland soil which was measured at 23.79 Mg ha−1. If C burial from this experiment in 55 ha is up-scaled for entire EKW of 12,500 ha area, then it empirically corresponds to 56.97–113.94 Gg CO2 captured from atmosphere per annum. EKW is not only used for aquaculture production thereby harvesting blue carbon but also has great potential to accumulate C in its sediments and thus helping mitigate climate change.