An Integrative, Multiparametric Approach for the Comprehensive Assessment of Microbial Quality and Pollution in Aquaculture Systems

Fulvic acid modulates mucosal immunity in fish skin: Sustainable aquaculture solution or environmental risk factor?

This is the first study determining the effects of bath exposure to fulvic acid, a humic substance, on the skin mucosal immunity of rainbow trout (Oncorhynchus mykiss). Humic substances have recently been gaining attention for their increasing concentrations in aquatic ecosystems and their use as supplements in sustainable aquaculture. This study demonstrated that water exposure to fulvic acid at concentrations of 5 mg C/L and 50 mg C/L increased lysozyme and alkaline phosphatase activities in the mucus by approximately 2-fold and 2.5 to 3.2-fold, respectively. Furthermore, exposure to 50 mg C/L resulted in a 77.0% increase in mucosal immunoglobulin concentrations compared to the other groups. Importantly, all mucus samples demonstrated significant antibacterial activity against Yersinia ruckeri, with control mucus reducing bacterial growth by 44.5% and exposure to fulvic acid increasing this effect to 26.3%. Although these modulations show promise for application in aquaculture, alterations of the beneficial microbiota from long-term exposure in natural waters can be expected. Monitoring the rising concentrations of humic substances in natural water bodies is therefore urgently needed. Overall, this study represents the first investigation revealing the ability of humic substances to modulate skin mucosal immunity and the capacity to combat microorganisms.

Environmental and ichthyofaunistic characteristics of Amazonian streams with and without fish farm

The environmental impacts caused by fish farming can lead to changes in aquatic ecosystems, especially in fish communities. In this study, we investigated possible changes in water quality, in the number of species and individuals of the same species caused by the construction of fish nurseries in dammed Amazonian streams. For this purpose, four streams located in the municipalities of Novo Airão and Presidente Figueiredo were selected. Samples were collected in streams without fish farming and in streams with stretches used for fish farming, where collections took place both downstream and upstream. The fish were captured, identified, quantified and the water was collected for physical and chemical analyses, in addition to the environmental characterization that was carried out. Comparisons were made using fish richness and abundance indices between the sampled points and correspondence analysis of the species identified at the collection sites, using the Mantel test and principal component analysis (PCA) for the environmental characteristics of the water and variables physical and chemical, and permutational multivariate analysis of variance (PERMANOVA) to verify the possible effects of species composition on the sampled conditions and on the analyzed environmental variables. In total, 2,302 fish belonging to 53 species, 15 families and six orders were found. We conclude that the Amazonian streams dammed for fish farming, under the analyzed conditions, can be characterized as environments with different and specific levels of richness and abundance, however, the data set analyzed in this study did not show that these characteristics are directly related to productive activity. We recommend that further studies be carried out following the current research.

Tools to Enumerate and Predict Distribution Patterns of Environmental Vibrio vulnificus and Vibrio parahaemolyticus

Vibrio vulnificus (Vv) and Vibrio parahaemolyticus (Vp) are water- and foodborne bacteria that can cause several distinct human diseases, collectively called vibriosis. The success of oyster aquaculture is negatively impacted by high Vibrio abundances. Myriad environmental factors affect the distribution of pathogenic Vibrio, including temperature, salinity, eutrophication, extreme weather events, and plankton loads, including harmful algal blooms. In this paper, we synthesize the current understanding of ecological drivers of Vv and Vp and provide a summary of various tools used to enumerate Vv and Vp in a variety of environments and environmental samples. We also highlight the limitations and benefits of each of the measurement tools and propose example alternative tools for more specific enumeration of pathogenic Vv and Vp. Improvement of molecular methods can tighten better predictive models that are potentially important for mitigation in more controlled environments such as aquaculture.

Aquaculture bacterial pathogen database: Pathogen monitoring and screening in coastal waters using environmental DNA

Increasingly diverse pathogen occurrence in coastal and mariculture areas demands improved monitoring platforms to prevent economic and public health implications. Accessible databases with up-to-date knowledge and taxonomy are critical for detecting and screening environmental pathogens. Condensed from over 3000 relevant reports in peer reviewed articles, we constructed an aquaculture bacterial pathogen database that provides specialized curation of over 210 bacterial pathogenic species impacting aquaculture. Application of the aquaculture bacterial pathogen database to environmental DNA metabarcoding monitoring data in Hong Kong coastal and mariculture waters effectively characterized regional pathogen profiles over a one-year period and improved identification of new potential pathogen targets. The results highlighted the increase in potential pathogen abundance related to aquaculture activity and the associated inorganic nitrogen load, which was chiefly due to the enrichment of Vibrio during the atypical dry winter season. The value of the aquaculture bacterial pathogen database for empowering environmental DNA-based approaches in coastal marine pathogen surveillance benefits water resource management and aquaculture development on a global scale.

Cyanobacterial Harmful Algal Bloom Toxin Microcystin and Increased Vibrio Occurrence as Climate-Change-Induced Biological Co-Stressors: Exposure and Disease Outcomes via Their Interaction with Gut-Liver-Brain Axis

The effects of global warming are not limited to rising global temperatures and have set in motion a complex chain of events contributing to climate change. A consequence of global warming and the resultant climate change is the rise in cyanobacterial harmful algal blooms (cyano-HABs) across the world, which pose a threat to public health, aquatic biodiversity, and the livelihood of communities that depend on these water systems, such as farmers and fishers. An increase in cyano-HABs and their intensity is associated with an increase in the leakage of cyanotoxins. Microcystins (MCs) are hepatotoxins produced by some cyanobacterial species, and their organ toxicology has been extensively studied. Recent mouse studies suggest that MCs can induce gut resistome changes. Opportunistic pathogens such as Vibrios are abundantly found in the same habitat as phytoplankton, such as cyanobacteria. Further, MCs can complicate human disorders such as heat stress, cardiovascular diseases, type II diabetes, and non-alcoholic fatty liver disease. Firstly, this review describes how climate change mediates the rise in cyanobacterial harmful algal blooms in freshwater, causing increased levels of MCs. In the later sections, we aim to untangle the ways in which MCs can impact various public health concerns, either solely or in combination with other factors resulting from climate change. In conclusion, this review helps researchers understand the multiple challenges brought forth by a changing climate and the complex relationships between microcystin, Vibrios, and various environmental factors and their effect on human health and disease.

Aquaculture—Production System and Waste Management for Agriculture Fertilization—A Review

Aquaculture is the fastest growing animal food production sector worldwide and is becoming the main source of aquatic animal foodstuff for human consumption. However, the aquaculture sector has been strongly criticized for its environmental impacts. It can cause discharge and accumulation of residual nutrients in the areas surrounding the production farms. This is because, of the total nutrients supplied to production ponds, only 30% are converted into product, while the rest is usually discharged into the environment to maintain water quality in aquaculture culture systems, thereby altering the physic-chemical characteristics of the receiving water. In contrast, this same accumulation of nutrients is gaining importance within the agricultural sector, as it has been reported that the main nutrients required by plants for their development are found in this aquaculture waste. The purpose of this review article is to indicate the different aquaculture production systems, the waste they generate, as well as the negative effects of their discharge into the environment. Biofiltration and bioremediation processes are mentioned as alternatives for aquaculture waste management. Furthermore, the state of the art in the treatment and utilization of aquaculture waste as a mineral source for agricultural nutrition through biodigestion and biomineralization processes is described. Finally, aquaponics is referred to as a biological production approach that, through efficient use of water and recycling of accumulated organic nutrients in aquaculture systems, can contribute to addressing the goals of sustainable aquaculture development.

Vibrio spp.: Life Strategies, Ecology, and Risks in a Changing Environment

Vibrios are ubiquitous bacteria in aquatic systems, especially marine ones, and belong to the Gammaproteobacteria class, the most diverse class of Gram-negative bacteria. The main objective of this review is to update the information regarding the ecology of Vibrio species, and contribute to the discussion of their potential risk in a changing environment. As heterotrophic organisms, Vibrio spp. live freely in aquatic environments, from marine depths to the surface of the water column, and frequently may be associated with micro- and macroalgae, invertebrates, and vertebrates such as fish, or live in symbiosis. Some Vibrio spp. are pathogenic to humans and animals, and there is evidence that infections caused by vibrios are increasing in the world. This rise may be related to global changes in human behavior (increases in tourism, maritime traffic, consumption of seafood, aquaculture production, water demand, pollution), and temperature. Most likely in the future, Vibrio spp. in water and in seafood will be monitored in order to safeguard human and animal health. Regulators of the microbiological quality of water (marine and freshwater) and food for human and animal consumption, professionals involved in marine and freshwater production chains, consumers and users of aquatic resources, and health professionals will be challenged to anticipate and mitigate new risks.