The origin of the suspended particulate matter in the seagrass meadow of tropical waters, an evidence of the stable isotope signatures

摘要

Suspended particulate matter(SPM) has been known as an important variable in the organic matter flow of coastal ecosystem. Half of burial carbon in seagrass meadows is contributed by allochthonous sources that compose the SPM such as phytoplankton, seagrass detritus, marine snow aggregates and terrestrially derived particles. Each composition of the SPM contributes different roles and is important to be identified, for instance,the exact contribution of seagrass detritus will be useful for determination of carbon export through the detritus form in seagrass meadows. Here, the SPM of seagrass meadows is studied in Bintan Island and the Selayar Archipelago. The aim of this research is to determine the source origin of the SPM using a stable isotope signature.In order to fulfill this aim, the objectives are defined as:(1) to specify the stable isotope signature(δ13C and δ15N)of the SPM, and(2) to determine the proportional distribution of the SPM's prospectus sources. The result shows that the possibility of the source origin of the SPM includes a seagrass fraction(Enhalus acoroides and Thalassia hemprichii), terrestrial C4 plant, macroalgae, and terrestrial C3 plant. The SPM lies between the marine-and terrigenous-end members. However, it seems that the SPM is more to be terrigenous-end and allochthonous.According to a Bayesian mixing model, the terrestrial C4 has the highest contribution of the SPM at all sites except Barugaia and Pasi Island in Selayar(i.e., the highest contribution of the SPM is from the detritus of E. acoroides).The second contribution has been contributed by either seagrass detritus(E. acoroides or Th. hemprichii) or terrestrial C3 plant. The finding of this study indicates that there is a strong influence of the terrigenous sources in the SPM of the seagrass meadows.