To determine the potential of the recreational marine environment as a dissemination vector of antibiotic-resistant microorganisms, the dissemination of antibiotic-resistant E. coli strains isolated from an urban coastal beach was studied. Sixty-nine and thirteen E. coli strains were isolated from the seawater and sand, respectively, in Fujiazhuang bathing beach, China. The average Antibacterial Resistance Index (ARI) value detected in the seawater is approximately three times that in beach sand. All the isolates from the sand were grouped into one cluster and only the isolates from the municipal sewage outlet were classified into three antibiogram clusters that were observed in the hetero-sites of the E. coli isolates. The E. coli strains with multiple antibiotic resistance (58% of total) were prevalent in the seawater, whereas the isolates from the sand were not detected with multiple antibiotic resistance. A significant association (p < 0.05) between all phenotypic and relative genotypic resistance profiles was observed in the isolates, except in the quinolones resistance genotype. The presence of a class 1 integron was significantly correlated with the resistance of E. coli to sulfonamides, streptomycin, and levofloxacin (p < 0.01). This study revealed that the municipal sewage discharge may impact the dissemination of antibiotic-resistant strains in the urban coastal beach, and that the class 1 integrons play an important role in mediating the resistance of E. coli to sulfonamide antibiotics.

Dalian Jinshitan beach was chosen to evaluate the impact of a typhoon on the bacterial community structure and water quality of a marine bathing beach. The concentration of enterococci was determined by the cultivation method. The bacterial community structure and abundance were analyzed using the 16S rDNA next-generation sequencing and qPCR methods. Results showed that the abundance of cultivable enterococci both in alongshore and offshore seawater increased, while it decreased in dry, wet and submerged sand. The water quality deteriorated immediately after the typhoon, and nearly recovered one month after the typhoon. The typhoon event also decreased the bacterial abundance and changed the bacterial community of the beach. Sphingomonadaceae and Rhodobacteraceae significantly increased in seawater and decreased in dry sand immediately after the typhoon. Human and other fecal taxa increased in water and sand. One month after the typhoon, the diversity and many dominant bacterial taxa nearly recovered in seawater and wet sand. Our work shows that the typhoon changed the bacterial dynamics, deteriorated the water quality and proved the transportation of bacterial taxa and input of fecal pollution between water and beach sand or land. Apart from the impact of the typhoon, the geographical location was another important factor in the changed bacterial community.

Marine organisms that episodically aggregate near coastal nuclear power plant water intakes pose a substantial risk to cooling water security. Predicting the spatial distribution of such high-risk species remains challenging because their occurrence is shaped not only by environmental conditions but also by complex trophic interactions. In this study, we model the habitat distribution of three high-risk nektonic species, Dotted gizzard shad (Konosirus punctatus), Japanese swimming crab (Charybdis japonica) and squid (Loligo sp.), in the cooling water intake area of a coastal nuclear power plant in eastern Liaodong Bay using generalized linear models (GLMs) and joint species distribution models (JSDMs). Based on summer surveys conducted in 2024–2025, we explicitly incorporated trophic linkages among target species, their prey, and predators within JSDMs. Model performance was evaluated using cross-validation based on AUC, RMSE, and coefficient of determination (R²). Our results indicate that water depth was the dominant environmental driver for all three species, while chlorophyll-a concentration and distance to the intake exerted species-specific effects. By incorporating interspecific trophic associations and environmental responses, JSDMs showed consistently improved predictive performance relative to GLMs, with approximately 1.5-fold higher R² values and 10–30% lower RMSE, while offering enhanced ecological interpretability. The models revealed strong positive associations between target species and both lower-trophic prey and higher-trophic predators, suggesting that top–down and bottom–up processes jointly regulate aggregation dynamics. This study demonstrates that integrating trophic interactions into species distribution modeling substantially improves predictions of high-risk marine species near coastal infrastructure and provides an ecological basis for proactive management of cooling water intake systems.