Present estimation and future prediction of seagrass distribution and carbon storage in andaman coast of Thailand

Abstract

Seagrass meadows have one of the largest carbon sink capacities in coastal ecosystems, trapping more than 18% of marine carbon sequestration. Their role in mitigation of climate change is vital, as they are responsible for assimilation of 2% of CO2 from anthropogenic sources, which remains trapped in the ecosystem for millennia and centuries. The aim of this study was to estimate carbon storage of these ecosystems in present time, to determine important variables influencing the carbon storage, to develop the predictions of the seagrass distribution and to estimate gains and losses of carbon within these meadows in the future climates. The study was conducted in diversely characterized (disturbed vs undisturbed, exposed vs sheltered, high density vs low density) seagrass ecosystems, in uniform (Enhalus acoroides) and mixed species (E. acoroides and Thalassia hemprichii or Cymodocea serrulata) meadows, along the Andaman coast of Thailand, in Phuket, Krabi and Trang provinces. The results suggested that higher amounts of organic carbon were stored in uniform meadows than in mixed, in undisturbed comparing to disturbed, while exposed and sheltered seagrass meadows had similar amounts. Organic carbon storage was highly influenced by meadow type and disturbance, suggesting that undisturbed, uniform and high density meadows store the highest amount of organic carbon. In the future climates, mixed meadows were constantly expanding their areas, while uniform meadows expanded their distributions by 2025 and then underwent decrease until several of meadows completely disappeared. The increase of the mixed meadows in the future climates had important influence on the climate, as the newly occupied areas assimilated large amounts of carbon from the ocean and atmosphere, consequently mitigating the climate change. However, uniform meadows had the opposite trend, loss of the areas, which released large amounts of carbon back to the ocean, and via direct ocean-atmosphere exchange the concentrations of CO2 in atmosphere were affected. Our results presented the essential knowledge required to understand and set the baseline for proper management and conservation in the present time, and to more effectively address the importance of the natural carbon sinks in the mitigation of climate change.