Coastal Blue Carbon Storage, Sources and Accumulation in Gautami-Godavari (Coringa) Mangrove sediments

The mangrove ecosystem is an important natural sink of carbon owing to its potential to accumulate and store large amounts of organic carbon, in particular in its anaerobic sediments. To better understand the role of and quantify this carbon sink, the present study measured organic carbon stocks, carbon accumulation rates, and organic matter sources in the sediments of the Gautami-Godavari (Coringa) mangrove ecosystem, Andhra Pradesh, India. The carbon and nitrogen stable isotopic composition and elemental ratios of total organic carbon (TOC) to total nitrogen (TN) have been used to detect the sedimentary organic matter sources in the Coringa mangrove complex. ²¹⁰Pb isotopes have been used to determine the sedimentation rates and carbon accumulation rates. The value of ∂¹³C ranges from -17.8‰ and -26.1‰ with an average value of -23.3‰ and TOC/TN ranges from 9-27 with an average value of 15. The spatial variation of all sedimentary parameters i.e., TOC, TN, ∂¹³C, and ∂¹⁵N is found to be significant at various sites. Both Sedimentary Carbon Stock and Carbon Accumulation Rates also have significant spatial variation among different sites and their values are maximum in an area where mangroves are directly affected by aquaculture effluents. The lowest carbon stock has been observed in an area where mangroves are degraded. The scatter plot between δ¹³C and TOC/TN ratio reveals that most of the sedimentary organic matter originated from non-mangrove sources like algae, phytobenthos, and suspended particulate matter.