Alexandrium spp., globally recognized as harmful algal bloom (HAB) species, pose severe threats to marine ecosystems, fisheries, and public health. Based on 469 occurrence records and 24 marine environmental variables, this study employed the Biomod2 ensemble modeling framework to predict the potential distribution of Alexandrium spp. under current and future climate scenarios, and to assess the role of key environmental factors and the spatiotemporal dynamics of habitat centroid shifts. The results revealed that (1) the ensemble model outperformed single models (AUC = 0.998, TSS = 0.977, Kappa = 0.978), providing higher robustness and reliability in prediction; (2) salinity range (bio18, 19.1%) and mean salinity (bio16, 5.8%) were the dominant factors, while minimum temperature (bio23) also showed strong constraints, indicating that salinity determines “whether persistence is possible,” while temperature influences “whether blooms occur”; (3) under present conditions, high-suitability habitats are concentrated in Bohai Bay, the Yangtze River estuary to the Fujian coast, and parts of Guangdong; (4) climate change is predicted to drive a southward shift of suitable habitats, with the most pronounced expansion under the high-emission scenario (RCP8.5), leading to the emergence of new high-risk areas in the South China coast and adjacent South China Sea; (5) centroid analysis further indicated a pronounced southward migration under RCP8.5 by 2100, highlighting a regional reconfiguration of ecological risks. Collectively, salinity and temperature are identified as the core drivers shaping the ecological niche of Alexandrium spp., and future warming is likely to exacerbate HAB risks in southern China. This study delineates key prevention regions and proposes a shift from reactive to proactive management strategies, providing scientific support for HAB monitoring and marine ecological security in China’s coastal waters.

Carbon peaking and neutrality goals constitute the major strategic decisions in ecological civilization construction in China. The port industry is characterized by intense carbon emissions, strong regional aggregation, and large emissions of single-used equipment. Port is an important battlefield for the transportation industry to promote carbon peaking and neutrality. Against this backdrop, it needs to intensify clean energy application by facilitating harbor machinery and vehicles powered by clean energy, elevating the equipment energy efficiency, improving the level of port automation and specialization, and developing means of green transportation. These initiatives are all bolstered to cultivate new and competitive industrial advantages in achieving carbon peaking and neutrality, thereby contributing to China’s constructive solutions to the low-carbon transitions of global transportation.

Cryptophyta are ecologically important microalgae in marine and brackish ecosystems, but their future habitat suitability and ballast-water-associated surveillance priorities under climate change remain insufficiently understood. Based on 136 georeferenced occurrence records from China’s coastal waters and 24 marine environmental variables, this study applied the Biomod2 ensemble modeling framework to predict the current and future potential distribution of Cryptophyta in the Bohai Sea, Yellow Sea, East China Sea, and South China Sea. The ensemble model showed high predictive performance (Kappa = 0.94, TSS = 0.94, AUC = 0.997), outperforming most individual algorithms. Annual mean temperature (bio22) and maximum salinity (bio15) were identified as the dominant environmental constraints, indicating that thermal and salinity regimes jointly shape habitat suitability. Under present conditions, suitable habitats were broadly distributed across China’s coastal and shelf waters. Future projections indicated that suitable habitats generally remained extensive under most climate scenarios, suggesting that future environmental changes may maintain or reshape potential recipient environments for Cryptophyta. However, this response was not linear with increasing emission intensity; under the high-emission scenario, suitable habitats declined in some regions and showed stronger spatial reorganization, implying that excessive warming or altered salinity may reduce broad-scale suitability. These findings suggest that climate change may alter the spatial pattern of Cryptophyta habitat suitability under different emission pathways. Given the role of ship ballast water in transporting planktonic microalgae, persistent or newly suitable habitats, especially those located near ports, estuaries, semi-enclosed bays, and aquaculture areas, should be regarded as habitat-suitability-based surveillance priorities. This study provides a basis for climate-informed monitoring, ballast-water-associated screening, and adaptive management of coastal microalgae in the China Seas.