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Abstract:
Mangroves are known for exchanging organic and inorganic carbon with estuaries and oceans but studies that
have estimated their contribution to the global budget are limited to a fewmangrove ecosystems which exclude
world's largest the Sundarbans. Here, we worked in the Indian Sundarbans and in the Hooghly river/estuary in
May (pre-monsoon) and December (post-monsoon), 2014. Aims were, i) to quantify the riverine export of particulate
organic carbon (POC) and dissolved organic and inorganic carbon (DOC, DIC)) of the Hooghly into the Bay
of Bengal (BoB), ii) to estimate the C export (DOC, DIC, POC) from the Sundarbans into the BoB by using a simple
mixingmodel, aswell as iii) to revise the existing C budget constructed for themangroves. The riverine exports of
POC, DOC and DIC account for 0.07 Tg C yr−1, 0.34 Tg C yr−1 and 4.14 Tg C yr−1, respectively, and were largest
during the monsoon period. Results revealed that mangrove plant derived organic matter and its subsequent
degradation is the primary source of DIC and DOC in the Hooghly estuary whereas POC is linked to soil erosion.
Mangroves are identified as amajor source of carbon (POC, DOC, DIC) transported from the Sundarbans into the
BoB, with export rates of 0.58 Tg C yr−1, 3.03 TgC yr−1, and 3.69 Tg C yr−1 respectively, altogether amounting to
7.3 Tg C yr−1. This C export from the Indian Sundarbans exceeds the ‘missing C’ of the previous budget, thus necessitating
further research to finally resolve themangrove C budget. However, these first baseline data on C exports
fromthe world's largest deltaicmangrove improves limited global data inventory and signifies the need of
acquiring more data from different mangrove settings to reduce uncertainties.
