Profiling of bacterial assemblages in the marine cage farm environment, with implications on fish, human and ecosystem health

This research presents a comprehensive study of bacterial assemblages within the water column and in the surface sediments in the zone of two European sea bass cage farms. By the application of the high-throughput amplicon sequencing of 16S rRNA gene, and further implementing microbial ecology tools, a bacterial segment from cage culturing systems and their respective controls were analyzed, with special reference to potential impact on animal, human and environmental health. Samples of seawater and sediments were collected seasonally, at locations situated in the central and southern Adriatic Sea. Bacterial composition was significantly different in the seawater vs. sediment. No significant differences in alpha diversity in sediments were indicated between aquaculture and control sites, and it appears that it is not affected by farming practices. Control sediments have higher relative abundance of aerobic and facultative anaerobic bacteria, while aquaculture sediments are markedly anaerobic. Sediments largely contain functional groups for respiration of sulfate and sulfur compounds, though doubly more in aquaculture sites. Seasonal groupings of bacterial assemblages were confirmed in the seawater, with higher relative abundance of known aquaculture pathogens (except Photobacterium in the winter samples) detected in the winter and summer, opposed to other two seasons. Rare taxa were analyzed in the sediment and in the water column in the search for known fish pathogens, with five genera detected: Vibrio, Pseudomonas, Photobacterium, Tenacibaculum and Mycobacterium. Biomarkers important for the impact of aquaculture on the environment were identified, e.g. Blastopirullela, Sva0081, Suflurovum, Spirochaeta 2, etc., as well as human and fish potential pathogens: Vibrio ichtyoentery, V. harvey, Acinetobacter lwoffi, A. johnsonii, Clostridium perfringens, etc. Chemoheterotrophy has emerged as the dominant functional group in both environments. Regarding priorities for aquaculture microbial management, seawater seems to contain a higher percentage of taxa connected to health-related functional groups

Profiling of bacterial assemblages in the marine cage farm environment, with implications on fish, human and ecosystem health

This research presents a comprehensive study of bacterial assemblages within the water column and in the surface sediments in the zone of two European sea bass cage farms. By the application of the high-throughput amplicon sequencing of 16S rRNA gene, and further implementing microbial ecology tools, a bacterial segment from cage culturing systems and their respective controls were analyzed, with special reference to potential impact on animal, human and environmental health. Samples of seawater and sediments were collected seasonally, at locations situated in the central and southern Adriatic Sea. Bacterial composition was significantly different in the seawater vs. sediment. No significant differences in alpha diversity in sediments were indicated between aquaculture and control sites, and it appears that it is not affected by farming practices. Control sediments have higher relative abundance of aerobic and facultative anaerobic bacteria, while aquaculture sediments are markedly anaerobic. Sediments largely contain functional groups for respiration of sulfate and sulfur compounds, though doubly more in aquaculture sites. Seasonal groupings of bacterial assemblages were confirmed in the seawater, with higher relative abundance of known aquaculture pathogens (except Photobacterium in the winter samples) detected in the winter and summer, opposed to other two seasons. Rare taxa were analyzed in the sediment and in the water column in the search for known fish pathogens, with five genera detected: Vibrio, Pseudomonas, Photobacterium, Tenacibaculum and Mycobacterium. Biomarkers important for the impact of aquaculture on the environment were identified, e.g. Blastopirullela, Sva0081, Suflurovum, Spirochaeta 2, etc., as well as human and fish potential pathogens: Vibrio ichtyoentery, V. harvey, Acinetobacter lwoffi, A. johnsonii, Clostridium perfringens, etc. Chemoheterotrophy has emerged as the dominant functional group in both environments. Regarding priorities for aquaculture microbial management, seawater seems to contain a higher percentage of taxa connected to health-related functional groups

AQUAHEALTH: Physiochemical parameters and Vibrio spp. abundance in water samples gathered in the Adriatic Sea

The genus Vibrio includes > 60 species that are autochthonous and ubiquitous aquatic microorganisms, members of the bacterial community in marine environments worldwide. Given their impact on human and animal health and the relative ease of their cultivation, Vibrio species have been well studied: the genus includes human and animal pathogens that have caused major diseases around the world (e.g. cholera or vibriosis). The dataset contains Vibrio spp. abundance and measurements of environmental parameters (temperature, salinity, total dissolved solids, pH, dissolved oxygen, total nitrogen, total phosphorus, total particulate matter, particulate organic matter and particulate inorganic matter), gathered at Mali Ston Bay in the Adriatic Sea. Water sampling was conducted at two locations: a floating cage fish farm (located near small island Maslinovac) and a control site (near island Pučenjak) at different depths (0.5 m, 5 m, 10 m and 18 m). The sampling period covers seasonal measurements between 2016 and 2019

Characterization of Vibrio Populations from Cultured European Seabass and the Surrounding Marine Environment with Emphasis on V. anguillarum

Vibrio species are widely distributed and can be potentially pathogenic to aquatic organisms. In this study, we isolated Vibrio spp. from environmental samples (seawater, sediment, and fish swabs) collected over a three-year period from a fish farm in Mali Ston Bay in the Adriatic Sea, Croatia, and assess their distribution. A total of 48 seawater samples and 12 sediment samples, as well as gill and skin swabs from 110 farmed European seabass, were analysed for the presence of Vibrio. Vibrio strains were identified to the species level by MALDI TOF MS. The analysis revealed that V. alginolyticus was the predominant species in European seabass, followed by V. anguillarum. V. alginolyticus was isolated from the sediments, along with V. gigantis and V. pomeroyi, while V. chagasii, V. cyclitrophicus, V. fortis, V. gigantis, V. harveyi, V. pelagius, and V. pomeroyi were isolated from seawater. V. anguillarum was isolated only twice during two different spring seasons, once from a diseased sea bass and the second time from a healthy sea bass. We analysed these two isolates and found that they differ both genetically and in terms of resistance to antibiotics. Our results confirm the seasonality of vibriosis incidence and the presence of the pathogenic V. anguillarum, which increases the risk of vibriosis

Assessment of Vibrio spp. abundance as a water quality indicator: Insights from Mali Ston Bay in the Adriatic Sea

Due to high anthropogenic pressures, science-based coastal management required to ensure the sustainable use of coastal areas highly depends on environmental indicators used for decision-making. In this paper, we argue for the inclusion of Vibrio spp. abundance as a supplemental indicator of water quality for science-based coastal management by examining the environmental and bacterial indicators at a fish farm and a control site in Mali Ston Bay in the Adriatic Sea. Unexpectedly, heterotrophic bacteria, enterococci and Vibrio spp. were more abundant in the cold season, while E. coli and total coliforms, following a more traditional pattern, were more abundant in the warm season. Each of the currently used indicators has a specific purpose: heterotrophic bacteria indicate the presence of both nonpathogenic and pathogenic bacteria, while enterococci are pathogenic bacteria indicating fecal pollution. Vibrio spp. abundance additionally represents a non-fecal bacteria that can cause vibriosis in humans and aquatic organisms. Since vibriosis is the leading cause of disease-related fish mortality in aquaculture, pathogenic Vibrio spp. have large health and economic implications. These implications, as well as the added interpretative value when compared to other bacterial indicators, make Vibrio spp. abundance a good candidate as a water quality indicator. Significant dependence of the abundance on depth further differentiates Vibrio spp. from other indicators, thus bolstering the candidacy - especially in aquaculture areas. Before inclusion of any Vibrio spp. indicators into legislature, further research is needed particularly into (i) abundance thresholds characterizing water quality, and (ii) identification of species whose abundance should be monitored for best estimate of the disease risks

Characterization of Vibrio Populations from Cultured European Seabass and the Surrounding Marine Environment with Emphasis on V. anguillarum

Vibrio species are widely distributed and can be potentially pathogenic to aquatic organisms. In this study, we isolated Vibrio spp. from environmental samples (seawater, sediment, and fish swabs) collected over a three-year period from a fish farm in Mali Ston Bay in the Adriatic Sea, Croatia, and assess their distribution. A total of 48 seawater samples and 12 sediment samples, as well as gill and skin swabs from 110 farmed European seabass, were analysed for the presence of Vibrio. Vibrio strains were identified to the species level by MALDI TOF MS. The analysis revealed that V. alginolyticus was the predominant species in European seabass, followed by V. anguillarum. V. alginolyticus was isolated from the sediments, along with V. gigantis and V. pomeroyi, while V. chagasii, V. cyclitrophicus, V. fortis, V. gigantis, V. harveyi, V. pelagius, and V. pomeroyi were isolated from seawater. V. anguillarum was isolated only twice during two different spring seasons, once from a diseased sea bass and the second time from a healthy sea bass. We analysed these two isolates and found that they differ both genetically and in terms of resistance to antibiotics. Our results confirm the seasonality of vibriosis incidence and the presence of the pathogenic V. anguillarum, which increases the risk of vibriosis