The mangrove and seagrass meadow ecosystems demonstrate high productivity and are highly susceptible to both natural processes and anthropogenic activities. To evaluate the impact of human activity on these ecosystems, three sediment cores were collected from mangroves, seagrass meadows, and mud flats located in Maowei Sea within the Beibu Gulf region of China. We measured ²¹⁰Pb activities, grain size distribution, total organic carbon (TOC), total nitrogen (TN), and stable carbon isotopes (δ¹³C). Our findings reveal that the Qinzhou mangrove area exhibits the highest carbon burial rate at 90.43 g C m^-2yr^-1, followed by the seagrass meadow at 27.21 g C m^-2yr^-1; whereas the mud flat displays the lowest rate at 13.16 g C m^-2yr^-1. A significant decline in TOC content as well as the calculated contribution of mangrove-derived organic carbon (OC) has been observed since 1980 in both mangrove and mud flat ecosystems; conversely, an increase in TOC content along with the contribution of seagrass-derived OC has been documented in seagrass meadows. This study suggests that human activities such as land reclamation for agriculture or shrimp ponds may be associated with mangrove degradation.

historical change;,carbon burial flux,source of organic carbon