Remineralization and preservation of sedimentary organic carbon, and authigenic mineral formation in Alian Bay and its adjacent areas, China: Implication for the influence of abalone (Haliotis discus hannai Ino) and kelp (Saccharina japonica) mariculture

Although mariculture activities play a significant role in coastal carbon cycling, there is a lack of research on sedimentary organic carbon (SOC) in mariculture areas. In this study, remineralization of SOC in Ailian Bay, China, and an adjacent offshore control area was analyzed by combining sediment and pore water analyses, to investigate the effects of mariculture on the preservation of SOC and the related mechanisms. The significant higher total organic carbon (TOC) to sediment surface area in abalone culture area (0.74 ± 0.10 mg·m−2) than those in control area (0.59 ± 0.06 mg·m−2) suggested the maricultural activities may increase the preservation efficiency of SOC. During anaerobic incubations, higher vertical profiles and production rates of ΣCO2 in pore water of sediments in the abalone culture area than those in the control area indicated that maricultural activities may increase the rate of organic carbon remineralization. Furthermore, similar findings in dissolved organic carbon (DOC) suggested maricultural activities may increase the release of DOC in the sedimentary environment, which is an important supplement to the marine DOC pool. Additionally, the higher vertical concentrations and fluxes of the three major cations (i.e., K+, Ca2+, and Mg2+) coupled with the increased rate of SOC remineralization in the abalone culture area demonstrated that the maricultural activities strongly strengthened the formation of authigenic mineral. In conclusion, these findings suggested that maricultural activities play an important role in the coastal carbon cycle, significantly affecting the remineralization, preservation of SOC and the biogeochemical cycling of other important biogenic elements.