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Oceans are vast, dynamic, and complex ecosystems characterized by fluctuations in environmental parameters like sea surface temperature (SST), salinity, oxygen availability, and productivity. Environmental variability acts as the driver of organismal evolution and speciation as organisms strive to cope with the challenges. We investigated the evolutionary consequences of heterogeneous environmental conditions on the mitogenome of a widely distributed small pelagic fish of Indian ocean, Indian oil sardine, Sardinella longiceps. Sardines were collected from different eco-regions of the Indian Ocean and selection patterns analyzed in coding and non-coding regions. Signals of diversifying selection were observed in key functional regions involved in OXPHOS indicating OXPHOS gene regulation as the critical factor to meet enhanced energetic demands. A characteristic control region with 38–40 bp tandem repeat units under strong selective pressure as evidenced by sequence conservation and low free energy values was also observed. These changes were prevalent in fishes from the South Eastern Arabian Sea (SEAS) followed by the Northern Arabian Sea (NAS) and rare in Bay of Bengal (BoB) populations. Fishes belonging to SEAS exhibited accelerated substitution rate mainly due to the selective pressures to survive in a highly variable oceanic environment characterized by seasonal hypoxia, variable SST, and food availability.

Mangroves are keystone ecosystems which provide numerous environmental services. Mangroves assume significance as standing stores of sequestered atmospheric carbon and are therefore, important in the light of climate change mitigation. In this study, we attempted to assess the biomass of mangroves in the Kadalundi wetland, south-west coast of India and evaluated the potential of these mangroves to sequester and store carbon. The C-stocks of above-ground and root biomass were 83.32±11.06 t C ha-1 and 34.96±4.30 t C ha-1 respectively, while the C-stock in sediment was estimated to be 63.87±8.67 t C ha-1. The estimates of mean combined C-stocks in the mangrove biomass and sediment of Kadalundi shows that this estuarine mangrove wetland stored 182.15 t C ha-1, which was equivalent to 668.48 t CO2 ha-1. The mangroves which cover an area of 13.23 ha in the Kadalundi wetland is assumed to have a potential to sequester and store a substantial quantity of 2,409.84 t C which is equivalent to 8,844.11 t CO2. The study underscores the importance of these intertidal forests for climate change mitigation and stresses the importance of protecting the mangroves which provide many other important ecosystem services that benefit communities.

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.

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