[ACG56-10] Evaluation of carbon export from blue carbon ecosystems and allochthonous sequestration using eDNA techniques
Keywords:Carbon sequestration, Seagrass meadow, Mangrove, Sediment, Environmental DNA, Blue carbon
The purpose of this study is to demonstrate by using environmental DNA techniques that OC derived from the blue carbon ecosystems can be transported to and stored in open ocean sediments. As a case study, coastal area off the west coast of Busuanga Island, Philippines, was set as study site, where natural coral reefs, seagrass beds, and mangroves are relatively well preserved. DNA probes for MatK sequences (part of chloroplast DNA) of two mangrove species (Rhizophora mucronata, Sonneratia alba) and two seagrass species (Enhalus acoroides, Thalassia hemprichii) as well as ITS sequence (part of nuclear DNA) of R. mucronata were designed. Then, the DNA copy numbers of respective sequences contained in extracts from surface sediment samples were quantified by the qPCR method. In addition, the organic and inorganic carbon concentrations and the specific surface area of the surface sediment samples were determined, and the origin of the sediment OC was assessed using a carbon stable isotope mixing model. During sample collection, seismic profiling with a sub-bottom profiler was also conducted to evaluate thickness of sediment accumulated in the studied area.
In this presentation, we summarize the results of these surveys to evaluate the areal extent to which seagrass- and mangrove-derived OC is transported and stored in relatively intact state, and identify environmental conditions that influence the accumulation in open ocean sediments of OC derived from blue carbon ecosystems. Difficulties in converting the data of DNA copy numbers into the amount of OC derived from specific plant species in the sediment will be also discussed.