Exploring carbon dynamics in connected mangrove forests and seagrass beds: How important is it?

Summary: Carbon sequestration is one of the most important ecosystem services provided by mangrove forests and seagrass beds that help with climate change adaptation. Mangrove forests and seagrass beds are important ecosystems in tropical and subtropical locations that sequester significantly greater amounts of carbon within their living biomass as well as in their sediments compared to terrestrial ecosystems. Although mangrove forests and seagrass beds usually occur adjacent to each other they are frequently evaluated independently without taking into account how connectivity between these coastal vegetated ecosystems can influence carbon accumulation. Therefore, a comparison of connected with isolated mangrove forests and seagrass beds will help to understand the effect of connectivity on carbon accumulation at the seascape scale. Five field studies in Singapore (Asia), Adelaide (Oceania), Zanzibar (Africa), Florida and Bonaire (Americas), were chosen to evaluate the influence of connectivity between mangrove forests and seagrass beds. Other aspects such as connectivity with other ecosystems (i.e. salt marsh, macroalgal beds), community characteristics, sediment nutrient concentration and geomorphic settings were tested and compared separately in each place. Isolated seagrass beds had up to double sediment carbon content compared with connected mangrove forests and seagrass beds. This was mainly driven by higher amounts of inorganic carbon in isolated beds since sediment organic carbon quantity was similar across the sampled beds. Factors such as mangrove forests cover area, community composition and health state of mangrove communities influence both the sediment carbon accumulation in mangrove forests and their exportation of carbon to adjacent ecosystems. Connectivity between mangrove forests and seagrass beds is affected by different localized factors and that degrees of connectedness between those two ecosystems and other adjacent ecosystems should be further study.