The Role of Freshwater Bodies in Carbon Cycling and Climate Change Mitigation

The various freshwater bodies, comprising rivers, lakes, wetlands, and reservoirs, are very dynamic yet undervalued parts of the global carbon cycle. Despite occupying less than one percent of the total surface area of the Earth, they play a very significant role in governing terrestrial carbon release into the oceans, controlling greenhouse gas fluxes, and modifying local climate feedbacks. The present work aims to understand the role of freshwater systems in the carbon cycle, focusing specifically on DOC, DIC, and POC at selected freshwater bodies in the Western Ghats and Deccan Plateau regions of South India. Samples were collected seasonally from five different freshwater body types. Data on water chemistry, carbon flux parameters, and pCO₂ levels was obtained over a period of one year. This shows that the highest carbon concentration and 8.7 ± 1.1 mg C L⁻¹ and CO₂ evasion rates occur during the monsoon season, where DOC concentration attains the value 8.7 ± 1.1 mg C L⁻¹ and CO₂ flux is estimated at 22.6 ± 3.4 mmol m⁻² d⁻¹. Human activities such as agricultural and industrial effluents have greatly increased carbon content in the waters. Wetlands were identified to have the highest carbon sequestration capacity, which ranged from 0.22 to 0.45 Tg C yr⁻¹. Various climate mitigation measures were evaluated in terms of their climate benefits.