6. CO₂ Exchange Dynamics in the Household and Abandoned Ponds of the Indian Sundarbans from the Perspective of Climate Change

Lentic ecosystems though encompass a much smaller area compared to the lotic water bodies of the world, are found to emit substantial quantities of greenhouse gases like CO₂, towards the atmosphere. The Sundarbans Biosphere Reserve (SBR) of India, besides being the abode of the world’s largest mangrove forest, shelters almost 4.4 million people with a substantially high population density. The CO₂ dynamics from several compartments of this biosphere reserve is studied in the recent past; however, the ponds are yet to receive any attention as such. The present chapter reports the variability of the partial pressure of CO₂ in water [pCO₂(water)] and the air–water CO₂ flux from four different types of ponds situated within the SBR. One of these selected ponds is abandoned, and not used for any human purpose and another pond is well-maintained and not at all used for any human purpose. The rest of the two ponds are typical homestead ponds with varying degrees of anthropogenic disturbances. The results indicated that all four ponds acted as a source of CO₂ towards the atmosphere; however, the rate of emission varied across the ponds. The most well-maintained least anthropogenically disturbed pond emitted CO₂ at the lowest rate, whereas the dilapidated and abandoned pond, which exist in a hypereutrophic state emitted the most. The other two ponds showed an intermediate range of fluxes. Biological processes played a dominant role over physical processes in governing the CO₂ fluxes. Water temperature showed a strong, positive, and statistically significant relationship with pCO₂(water). Thus, given the ongoing climate-change-induced rise in temperature can effectively enhance the emission rate of these ponds.