Influence of shellfish biodeposition on coastal sedimentary organic matter: A case study from Sanggou Bay, China

Abstract

The environmental impacts of mariculture in large scale have attracted worldwide attention. Identifying the sources of sedimentary organic matter plays a key role in elucidating the environmental impacts of the mariculture. In this study, surface sediments of the Sanggou Bay were sampled in October 2014, as well as March, May and August 2015 for grain size, total organic carbon, total nitrogen and stable carbon and nitrogen isotope (δ13C and δ15N) analyses. Results showed that silt was the primary fraction in mariculture areas, and the grain size distribution was closely related with mariculture and hydrodynamic conditions. A significant positive correlation (r = 0.97, p < 0.001) between total organic carbon and total nitrogen indicated that they were homologous. According to the combined analysis of δ13C and C/N, the main source of sedimentary organic matter was shellfish deposition, kelp and soil organic matter. Using a three-end-member mixed model, the contribution rates of shellfish biodeposition, soil organic matter and kelp were found to be 48.53% > 37.44% > 14.03%, respectively. These results highlighted the significant impact of shellfish biodeposition on the benthic environments.