China has recently launched extensive marine ranching projects, highlighting the need for scientific evaluation of ecosystem structure and function to guide their development. This study established two energy flow models and an evaluation index system to assess the structure, function, carrying capacity, and ecological status of both a marine ranching ecosystem and a nearby control site in the Beibu Gulf. The results show that the ranching ecosystem outperformed the control ecosystem in terms of food chain length, system size, and ecological carrying capacity of economically important species. The ranching ecosystem was classified as “relatively good”, while the control ecosystem was deemed “relatively poor”, which may confirm the success of the ranching efforts. Mussels, large crabs, and scorpaenidae were identified as key species for stock enhancement based on their biomass potential. Scenario simulations using Ecosim, driven by biomass and fishing factors, indicate that stock enhancement strategies targeting MOB (mussels, oysters, and barnacles) significantly improved the ranching ecosystem, raising its status to “good”. However, the simulations also revealed that stock enhancement had limited effects on optimizing food web structure, system organization, and energy transfer efficiency, suggesting that a combination of strategies is necessary for further improvement.

Pacific oysters (Crassostrea gigas) are widely cultured in Chinese marine ranching with high economic value. However, mass death of farmed oysters has occurred frequently in recent years because of diseases and environmental disturbance (e.g., high temperatures). In order to analyze the potential relationships between microorganisms and the death of farmed oysters, we compared the dynamics of bacterial and protist communities in oysters at different growth phases using high-throughput sequencing. The results showed that the microbial communities in farmed oysters significantly changed and were markedly different from microbes in natural oysters and the surrounding environments. The number of biomarker taxa among farmed oysters and their surrounding environments decreased gradually with the growth of oysters. During the mass death of farmed oysters, the microbial communities’ abundance of ecological function genes changed, and the correlations among microorganisms disappeared. These results enrich our understanding of the dynamics of microbial communities in farmed oysters at different growth phases, illustrating the characteristics of interactions among microorganisms during the mass death of farmed oysters. Our study is beneficial to promote the healthy aquaculture of oysters.

The ecological ‘attraction’ and ‘production’ functions of reef areas have been the subject of ongoing debate requiring further clarification. The present study focused on the black rockfish (Sebastes schlegelii), an economically dominant species in reef areas of Dabuquan Bay. Comparisons of stable carbon (C) isotopes between the muscle and liver tissues of black rockfish were conducted to identify residency and potential sources of non-resident individuals in the coastal Yellow Sea, China. Subsequently, isoscape values, derived from C isotopes of zooplankton gathered from inshore and offshore areas surrounding the reef, were compared to determine potential sources of the non-resident black rockfish individuals. According to the results, (1) the isotopic values between the muscle and liver tissues of black rockfish remained consistently aligned across both reef and control areas but showcased significant seasonal variations, and (2) the residency ratios of individuals within the reef area exceeded 84% across all seasons, highlighting the prolonged stays of this species. The findings are consistent with previous studies on rockfish residency and could facilitate the formulation of strategies for local stock enhancement and management.

China has recently launched extensive marine ranching projects, highlighting the need for scien-tific evaluation of ecosystem structure and function to guide their development. This study estab-lished two energy flow models and an evaluation index system to assess the structure, function, carrying capacity, and ecological status of both a marine ranching ecosystem and a nearby control site in the Beibu Gulf. The results showed that the ranching ecosystem outperformed the control ecosystem in terms of food chain length, system size, and the ecological carrying capacity of eco-nomically important species. The ranching ecosystem was classified as "relatively good," while the control ecosystem was deemed "relatively poor," confirming the success of the ranching efforts. Mussels, large crabs, and Scorpaenidae were identified as key species for stock enhancement based on their biomass potential. Scenario simulations using Ecosim, driven by biomass and fishing factors, indicated that stock enhancement strategies targeting MOB (mussels, oysters, and barna-cles) significantly improved the ranching ecosystem, raising its status to "good." However, the simulations also revealed that stock enhancement had limited effects on optimizing food web structure, system organization, and energy transfer efficiency, suggesting that a combination of strategies is necessary for further improvement.

Macrobenthic fauna are vital to the ecological health of the Yellow River Estuary, yet their long-term population drivers are poorly understood. This study used Boosted Regression Tree models to analyze the spatio-temporal distribution of five dominant species: Glycinde gurjanovae, Sternaspis scutata, Moerella jedoensis, Theora fragilis, and Raphidopus ciliatus. Key environmental drivers included ammonia nitrogen, water depth, sand content of sediment, and water temperature. Specifically, S. scutata and R. ciliatus preferred deeper waters, M. jedoensis favored habitats with moderate sand content of sediment, T. fragilis primarily occurred at water temperatures lower than 25 °C, and G. gurjanovae distribution was most influenced by ammonia nitrogen. All species exhibited a preference for lower ammonia nitrogen concentrations. Inorganic nitrogen and freshwater discharge from the Yellow River significantly influenced the distribution of G. gurjanovae, whereas river discharge alone was positively correlated with areas exhibiting a high occurrence probability (>0.5) for M. jedoensis. Future studies that integrate comprehensive seasonal monitoring data, hydrodynamic conditions, and food availability could further enhance predictive accuracy, providing stronger theoretical and technical support for ecological conservation and management in the Yellow River Estuary.