The sources and burial fluxes of sedimentary organic carbon from the intensive mariculture zone in Haizhou Bay, China

Abstract

The rapid development of mariculture would cause a considerable impact on the coastal carbon cycle. For investigating the source and contribution of mariculture to sedimentary organic matter, the composition of sediment cores in Haizhou Bay were analyzed, including ²¹⁰Pb_ex activity, sedimentary total organic carbon (TOC), total nitrogen (TN), the stable carbon (δ¹³C) and nitrogen (δ¹⁵N) isotopic composition. The sediment accumulation rate in mariculture area varied between 1.7 and 2.8 cm·a⁻¹, which is significantly higher than in control site. The results of the MixSIAR isotope mixing model indicated that shellfish biodeposits and soil organic matter are the primary contributors of sedimentary organic matter (SOM), while marine phytoplankton and seaweeds played a lesser role in the study area. The contribution of shellfish biodeposits to SOM in SF-1, SF-2 and BS were 4.1–36.65 %, 4.7–50.31 % and 5.2–19.0 %, respectively. The terrestrial source were the main contributors in the early years, have been affected by the impact of mariculture activities, and their contribution has gradually declined. The OC burial fluxes from shellfish biodeposits (BF_biodepositis) in SF-1 (6.17–23.82 g·m⁻²·a^-1), SF-2 (7.62–79.71 g·m⁻²·a⁻¹) and BS (2.9–15.25 g·m⁻²·a⁻¹) tended to increase with the increasing scale of mariculture. Intensive shellfish mariculture influenced the sediment carbon sources and burial fluxes in coastal organic carbon cycles.