Influence of the intensive mariculture on coastal sedimentary organic matter: Insight from size-fractionated particles

A portion of carbon produced from shellfish and kelp cultivation is buried in sedimentary environment, and mariculture carbon sequestration potential is an important part of marine carbon sink and has attracted worldwide attention. Total organic carbon (TOC), total nitrogen (TN) and their stable isotopes (delta C-13 and delta N-15), as well as the mass distribution of these size-fractionated particles were determined in order to study the distribution and sources of TOC in Sanggou Bay. Results showed that sediment organic matter has complex sources from kelp (30.4 %), marine phytoplankton (25.6 %), shellfish (23.7 %), terrestrial input (20.3 %), and mariculture activities of shellfish and kelp was the major component in surface sediment. Approximately 44-69 % of TOC was associated with the 16-32 mu m fraction. Low delta C-13 (-22.1 to -15.1%o) and high delta N-15 (5.0-5.7%o) were observed in fine particles (<16 mu m), indicating relatively high contribution of marine phytoplankton and mariculture derived organic carbon. On the contrary, relatively higher delta C-13 (-20.2 to -9.2%o) and lower values delta N-15 (-4.7 to 5.2%o) in coarse particles (>32 mu m) suggested that sedimentary organic carbon might be influenced by some additional sources from terrestrial input or seaweed. The mass distribution, delta C-13 and delta N-15 of sizefractionated particles in sediments indicated that sediment was obviously redistributed under the condition of mariculture, and further suggested that mariculture derived organic matter have modified the distribution and sources of sedimentary organic matter. This study provided great insight into distribution and source of sedimentary organic carbon from the perspective of size-fractionated particles in mariculture area.