Ecological carrying capacity and carbon sequestration potential of Ruditapes philippinarum : A case study in Dashentang National Marine Ranch in TianJin Bohai Bay,China

Yue Zhang¹Debin Zheng²Yongjun Guo³Shuang Liang³Biao Guo^2*Muhan LI^1*

• ¹College of Economics and Management, Tianjin Agricultural University, Tianjin, China
• ²Tianjin Fisheries Research Institute, Tianjin, China
• ³Key Laboratory of Aquatic Ecology and Aquaculture, College of Fisheries, Tianjin Agricultural University, Tianjin, China

As an ecologically and economically significant bivalve species,the Ruditapes philippinarum plays a vital role in carbon sequestration and marine ecosystem restoration. However,its ecological carrying capacity and carbon sequestration potential remain relatively underexplored.In this study, we further incorporated carbon budget estimation, Mixed Trophic Impact (MTI) analysis, and pedigree analysis to provide a comprehensive system-wide evaluation. Methods:The Dashentang Marine Ranch in Tianjin, China, covering 23.6 km² (13.6 km² artificial reefs), served as the study area. We constructed an EwE food-web model based on two seasonal surveys (May and August 2023), including 20 functional groups such as Oratosquilla oratoria, Dorippe japonica, Sebastes schlegelii, Lateolabrax japonicus, Apostichopus japonicus, and Ruditapes philippinarum. Biomass, production/consumption parameters, and diet compositions were used to simulate ECC and carbon dynamics. The carbon budget of R. philippinarum was quantified, MTI analysis was conducted to assess its trophic interactions, and a pedigree index was applied to evaluate model reliability. Results and Discussion:The EwE model estimated the ECC of R. philippinarum at 208.1 t/km², far above its current biomass of 6.3 t/km², indicating substantial aquaculture potential. Carbon sequestration assessment showed that at ECC, R. philippinarum contributes 21,500 tonnes of carbon uptake, 10,300 tonnes of benthic deposition, 280,000 tonnes of harvestable biomass, and 870,000 tonnes of carbon release via respiration.MTI analysis revealed that increasing R. philippinarum biomass exerts strong positive impacts on demersal fish (e.g., Lateolabrax japonicus) and benthic habitat quality, but negative impacts on benthic predators (e.g., Sebastes schlegelii, Decapoda), reflecting trade-offs in trophic competition.Pedigree analysis yielded an index of 0.716, suggesting a moderate-to-high level of model reliability, supporting confidence in the results.Overall, ecological network analysis demonstrated that higher clam biomass enhances ecosystem maturity and stability while providing significant carbon sink and economic benefits. Conclusion:Therefore,this study suggests that increasing the cultivation of Ruditapes philippinarum within its ecological carrying capacity can enhance the carbon sequestration potential of marine ranch ecosystems.The integration of carbon budget estimation, MTI analysis, and pedigree validation highlights both the ecological trade-offs and reliability of these findings, providing robust evidence that effective management of R. philippinarum can simultaneously improve carbon sink function and economic efficiency in marine ranches.