Blue carbon stock of the seagrass meadows of Gulf of Mannar and Palk Bay off Coromandel Coast, south India

Abstract

Blue carbon stock of the seagrass meadows of Gulf of Mannar and Palk Bay, off Coromandel Coast, south India, were computed from the organic carbon content and dry bulk densities of sediment core taken from the seagrass meadows of these two ecosystems. The Gulf of Mannar (GoM) and Palk Bay (PB) harbour 13 seagrass species dominated by Cymodocea serrulata and Syringodium isoetifolium. The soil carbon density of both GoM and PB were higher in subsurface cores. The blue carbon stock of seagrass meadows of the GoM was estimated as 0.001782 Tg and that of PB as 0.043996 Tg. The estimated value of blue carbon stored in seagrass meadows of GoM was 17820 US$ and that of PB was 43,99,682 US$. The results of this study are discussed in the light of climate change mitigation, emphasising the need to conserve these underwater meadows.

Ecological connectivity of seagrasses with mangroves increases the carbon storage of tropical seagrass meadows of an island ecosystem

“…The sediment Corg in our present study is significantly higher (~9-13 times) than other studies of seagrass meadows from the east coast of India (Ghosh et al 2016;Ganguly et al 2017a;Kaladharan et al 2020Kaladharan et al , 2021. The sediment Corg in our study is also higher than the global average (5.7 ± 0.3 % C DW) but was within the range (0-100 %C DW) reported for various seagrass ecosystems (Fourqurean et al, 2012).…”

“…This suggests that seagrass meadow size plays an important role in determining the total carbon storage in the ecosystem. A similar impact of meadow size affecting seagrass carbon storage has been observed for seagrass ecosystems of India at Chilika lake of Odisha, Pulicat lake, Gulf of Mannar and Palk Bay of Tamil Naidu (Ghosh et al 2016;Ganguly et al 2017a;Kaladharan et al 2020Kaladharan et al , 2021.…”

“…Similarly, from the seagrass meadow perspective, we estimated the carbon stock in a total of 292 ha for both MG and WMG sites and have avoided the extrapolation to the total seagrass area of ANI. Avoiding the extrapolation was necessary because, in India, previous seagrass carbons storage research has measured carbon storage in a single species and have extrapolated that data to the total seagrass coverage, which have mixed species of seagrass (Kaladharan et al 2020(Kaladharan et al , 2021Ghosh et al 2018). This has resulted in biased carbon storage values because seagrass carbon storage capacity is species-specific, and the local abiotic factors such as hydrodynamics, land run-off, anthropogenic pollution and habitat disturbances play an important role in determining this capacity (Howard et al, 2014;Duarte and Krause-Jensen, 2017;Macreadie et al, 2019 (Nurdianto and Resosudarmo, 2016) for ASEAN countries, where the price of one ton of CO2 was priced at US$10.…”

“…Seagrass ecosystems of India consist of 16 seagrass species that covers an area of 517 km2 along the east and the west coast of India, including the islands of Andaman and Nicobar and Lakshadweep up to a depth limit of 21 m (Geevarghese et al 2018;Bayyana et al 2020). As mentioned above, the carbon storage potential of these seagrass ecosystems is limited to only a few studies and five species, i.e., Halophila ovalis and Halodule uninervis from the Chilika lagoon, Cymodocea serrulata, Syringodium isoetifolium, and Thalassia hemprichii from Palk Bay and Gulf of Mannar region and H. ovalis and T. hemprichii from the Andaman and Nicobar Islands (Ghosh et al 2016;Ganguly et al 2018;Kaladharan et al 2020;. Interestingly, Stankovic et al (2021) observed that an area of 200 hectares of H. ovalis and T. hemprichii meadows from the Andaman and Nicobar Islands could reduce around 3% of the carbon emissions of India, suggesting the massive potential of the seagrass ecosystems of India as a natural carbon sink and its role in offsetting carbon emissions.…”

Sediment blue carbon stock of Avicennia officinalis in Vembanad Lake ecosystem, Kerala, India

“…The carbon sequestration potential of various ecosystems is of concern as the atmospheric CO 2 concentration goes on increasing steadily. But in India, studies on carbon sequestration potential were mainly on agriculture and forest ecosystems, barring a few from seaweed (Kaladharan et al, 2009), seagrass (Kaladharan et al, 2020(Kaladharan et al, , 2021 and mangrove ecosystems (Kathiresan et al, 2021).…”