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Coastal bays, situated within Earth’s critical zone, play important ecological and socioeconomic roles. This study developed an integrated ecosystem health assessment framework based on ecosystem services specific to coastal bays, particularly exploring approaches to determine critical indicators and establish a reference benchmark. The framework was applied to two typical coastal bays (Jiaozhou Bay and Daya Bay) to ascertain significant health differences, subsequent challenges and prospective management. Comparatively, Daya Bay was healthier. Daya Bay received an overall comprehensive index ecosystem health score of 69.42 (good); however, its ecosystem services scores differed significantly (supporting services = 71.34, regulating services = 87.29, provisioning services = 3.59, cultural services = 74.30), indicating severe degradation in its ecosystem food provisioning function. Jiaozhou Bay received corresponding score of 55.79 (moderate), and its ecosystem services scores were relatively lower (supporting services = 63.31, regulating service = 54.30, provisioning services = 6.18, and cultural services = 54.74), indicating widespread ecosystem degradation. The health status of coastal bays is closely associated with both natural characteristics and human interventions. The narrow bay mouth of Jiaozhou Bay, its limited enclosed seawater area, and the intensive land reclamation that has taken place since the 1950s have directly or indirectly led to the low score of most of its indicators, particularly regarding the significant reductions in its water area and shoreline. The geological advantages of Daya Bay is its large area of water and that it is open to the outer sea, which have contributed to its comparatively healthier status, wherein scores of only a few indicators were bad (i.e., biological indicators of sensitive organisms in the upper food chain). Results from this study provide important information for prospective bay management. For Jiaozhou Bay, more effort should be paid to improving ecosystem health in a comprehensive way, particularly fishing control, land reclamation control and habitat restoration. For Daya Bay, overfishing should be better controlled, while more emphasis should be paid to protecting and restoring certain moderately specific habitats and species. For effective management, we highlight that ecosystem management strategies needs to be differentiated among different bays based on their significant natural and social features. Our approach provides a practical ecosystem health assessment tool that can be applied to other coastal bays to better inform sustainable management and conservation initiatives.

Long-term habitat shifts in marine fishes under climate change have been discussed over the last few decades. However, there is still a limited understanding of how fish distribution and biodiversity patterns will change in the offshore areas of China over time. In the present study, the potential distributions of 21 important marine fishes under current conditions and two climate change scenarios up to the 2050 s were projected using the maximum entropy (MaxEnt) model. The predicted habitat shifts were further used to observe how future environmental changes would affect communities. By the 2050 s, nine out of 21 fish species may have reduced habitats, which were considered as potential loser species in adapting to climate change, while the other 12 fish species were considered as winner species. The habitats of 20 species were predicted to move northward, with a mean habitat centroid shifting distance from 110 to 206.5 km. A novel discovery is that the Yangtze River Estuary is probably a geographical barrier for the northward migration of some species. An asymmetry in the habitat range shift was observed within the study region, wherein the leading edge moved 1° faster than the trailing edge. The Beibu Gulf, Pearl River Estuary, Southwest Taiwan Strait, and Yangtze River Estuary were identified as fish refuges, indicating that large river estuaries and upwelling systems may have positive effects on reducing the vulnerability of biological communities to climate change. At the community level, species richness would be reduced at lower latitudes, while it would be increased at higher latitudes, and species turnover was the main component of temporal beta diversity. Our study provides an informative outlook on the impact of climate change on the distribution and biodiversity of marine fish species in China, supporting the adaptive conservation and management of fish habitats.

Seagrass meadows provide important ecosystem services, but are among the least conserved marine ecosystems. The Southern bioregion of China has the nation’s largest seagrass distribution. However, lack of information on the distribution of seagrasses and the threats they face pose a significant obstacle to their conservation and restoration. Accordingly, a framework for prioritizing conservation and restoration objectives was proposed in the present study. First, we modeled the suitable habitats with MaxEnt, random forest (RF), and ensemble models to obtain a reliable basis map of seagrass distribution. A potentially suitable area of approximately 3,536–4,852 km2 was mapped in the coastal sea of South China, with the greatest area occurring between 18 °N and 22 °N. The anthropogenic pressures on the seagrass habitat were then estimated using an integrated exposure index consisting of four indicators, namely, population density, fishery economy, aquaculture, and shipping. The results indicated 48% of the coastal seas were under intensive anthropogenic pressures, with a higher exposure in the north than the south. The current conservation status suggests that there is a large seagrass conservation gap. By coupling the two dimensions of habitat suitability and integrated exposure, priority sites for seagrass management in South China were identified for the first time. Our work will not only provide basic information for coastal ecosystem management, but also serve as a tool to support the conservation and restoration planning of seagrass, thus, ultimately promoting the sustainability of seagrasses habitats.