One of the principal forms of combatting climate change is through biological carbon sequestration. Biological carbon sequestration occurs when carbon dioxide (CO2) is drawn down from the atmosphere into photosynthesising organisms, such as plants and algae, where it is converted into organic carbon. For the organic carbon to be considered sequestered on time-scales relevant to humans and global climate change, it must avoid degradation for thousands of years. Coastal seagrass meadows have been identified as hotspots for carbon sequestration. This is because of the high productivity of seagrasses, which results in large amounts of CO2 being incorporated into their leaves and shoots as organic carbon. The dense flexible canopy of seagrass meadows attenuates flow and stabilises the seafloor, promoting the entrapment and accumulation of organic carbon from both the seagrasses themselves and other external sources of organic carbon throughout the coastal zone. This organic carbon accumulates on the seafloor where it eventually gets buried within the seafloor sediments, a place where degradation is slower due to low oxygen, anoxic conditions. Assessing the ability of coastal habitats to sequester carbon, and thus, their impact on the global carbon cycle, provides the opportunity to further promote carbon sequestration and minimise events that might result in the unintentional degradation of organic carbon and subsequent release of CO2.
Up to now, research has focussed on assessing the total organic carbon stocks within seagrass meadows and their associated sediments. Stock-type measurements, however, vary from site to site depending on local factors of water motion and organic carbon supply. To be able to reliably assess the carbon sequestration capacity of an ecosystem and gain the power to promote further carbon sequestration, there is a need to understand the processes governing organic carbon capture and burial in marine sediments. Combining expertise from biogeochemists and ecologists the SCaLED project’s overall objective was to quantify organic carbon transformation within the coastal zone under varying environmental factors. This involved measuring the productivity of the seagrasses and the rates of CO2 incorporation into their biomass across the temperate seasons, folllowed by quantifying the degradation processes of the organic carbon as it moves through the coastal zone and gets buried within the seafloor sediments. With these measurements, we aimed to provide the necessary data to highlight the overall impact that seagrass meadows have on the coastal carbon cycle and to detail the conditions required to promote carbon sequestration within the coastal zone. Furthermore, this data will be utilised by ocean modellers to examine varying scenarios of global change and its impact on the marine carbon cycle.
