Energy Budget and Carrying Capacity of the Surf Clam, Mactra veneriformis and the Estuarine Clam, Potamocorbula laevis in Geligang, Liaodong Bay

China is the largest aquaculture country in the world, with mariculture production accounting for more than 50% of the total production in the world. In 2021, the production of shellfish in China increased to 1.546 × 107 tons, accounting for approximately 70% of the mariculture production. Filter-feeding bivalves such as oysters and clams are the main species of mariculture in China. In addition to the important economic values, filter-feeding bivalves influence ecosystem nutrient cycling through feeding, metabolism, and biodeposition and play roles in increasing the water transparency, preventing harmful algal blooms, controlling eutrophication, and promoting carbon storage. The physiological activities of filter-feeding bivalves, especially ingestion and metabolism, form the link between planktonic and benthic ecosystems, and their physiological indicators are the basic parameters for evaluating the energy budget and carrying capacity. However, although researchers have conducted a series of studies on the physiological activities of filter-feeding bivalves, some limitations in monitoring and the subsequent data processing remain. Therefore, it is urgent to improve the measurement of the physiological activities of filter-feeding bivalves, including the accuracy of data collection and the rigorousness of data processing, to ensure the accuracy of the experimental results.Mudflats are located in the interaction zone between the land and sea and are important areas for the habitat, growth, and reproduction of several macrobenthic organisms. As the dominant species of macrobenthic communities, mudflat-buried shellfish play a crucial role in the material and energy flows of a mudflat ecosystem. However, recently, with the expansion of shellfish aquaculture, the mudflat environment has been deteriorating accompanied by a series of ecological problems, such as high mortality and slow growth rates and alteration in the structure of phytoplankton community, which has led to significant losses to the shellfish aquaculture industry. Therefore, the ability of the ecosystem to support shellfish production must be evaluated, and its carrying capacity must be estimated. Generally, numerical methods for estimating the carrying capacity of shellfish based on food limiting indicators include physical-biological ecosystem modelling, trophodynamic modeling, and energy balance modeling. Current methodologies for estimating shellfish carrying capacity are divided into two main categories: dynamic and static modellings. Compared with the dynamic estimation model, static estimation methods are based on the environment of the target area and the key physiological parameters of shellfish and have been widely applied in some aquaculture areas such as Sanggou Bay, Jiaozhou Bay, and Zhangzidao in China.Here, to explore the energy budget and carrying capacity of the surf clam, Mactra veneriformis, and the estuarine clam, Potamocorbula laevis, in Geligang, Liaodong Bay, a portable particle counter and a continuous oxygen monitoring system were used in combination with flow-through chambers to detect the feeding and metabolic parameters of M. veneriformis and P. laevis. Furthermore, the carrying capacity of two mudflat-buried bivalves in Liaodong Bay was estimated based on the organic carbon supply-demand balance model. The results indicated that 1) the clearance rates of M. veneriformis and P. laevis were (4.87±0.85) L/(h·g) and (6.46±2.25) L/(h·g), respectively, and the oxygen consumption rates were (0.94±0.45) mg/(h·g) and (0.22±0.14) mg/(h·g), respectively. The energy absorption of M. veneriformis and P. laevis ranged from 748.97 to 1 333.52 J/(h·g), and 931.55 to 1 647.08 J/(h·g), respectively. 2) Using organic carbon supply-demand balance model combined with the primary productivity and shellfish clearance rate, we found that the carrying capacity of M. veneriformis in Geligang, Liaodong Bay, was 57, 47, and 34 ind./m2 for age-1 (total wet weight 6.7 g), age-2 (total wet weight 9.3 g) and age-3 (total wet weight 14.6 g), respectively; and the carrying capacity of P. laevis was 346, 143, and 99 ind./m2 for age-1 (total wet weight 0.14 g), age-2 (total wet weight 0.69 g), and age-3 (total wet weight 1.25 g), respectively. These results provide basic data for the rational exploitation and utilization of shellfish resources and the conservation of biodiversity in a mudflat ecosystem.