CARBON BURIAL, AND ITS MICROSCALE VARIABILITY AND SOURCES IN A TROPICAL MANGROVE ECOSYSTEM IN INDIA

Mangroves have recently gathered the attention of the scientific community at large for their extraordinary sedimentary carbon storage. They store both autochthonous and allochthonous organic matter (OM) preserved due to the intertidal suboxic environment. However, as yet quantitative studies are still few. Moreover, little is known on the autochthonous vs. allochthonous portions of carbon buried in mangroves, which is relevant for the question whether the carbon buried is freshly fixed or just relocated carbon from another reservoir. Our results show a large microscale variability in the sediment TOC contents (< 0.1 % to 14 %) even within a small mangrove ecosystem like Pichavaram. The autochthonous production viz. mangrove and non-mangrove in the forested sites, in addition to the allochthonous contribution of the transported OM in the estuarine sites, is found to regulate the distribution of OC in mangrove sediments. The bulk CAR in Pichavaram (96.4 ± 99.8 g C m^-2 yr^-1) is spatially variable and comparatively small as compared to the regional estimates from the other studies. The carbon stock in Pichavaram (average of 80.7 ± 70.8 Mg C ha^-1 equating to 88.8 Gg C for the whole ecosystem) was much smaller than calculated for Indo-Pacific and other world mangroves. Our results indicate that sedimentary organic carbon stocks may vary substantially even within close proximities in a single mangrove ecosystem and between different mangrove systems. This study presents that mangroves ecosystems can also have low sedimentary carbon storage but surprisingly there are very few studies emphasizing this so far. There is need for more number of representative regional studies from both high and especially low carbon mangrove systems, in order to build a robust global mangrove carbon budget and predict their role in climate change mitigation.