The potential of waste items in aquatic environments to act as fomites for viral haemorrhagic septicaemia virus

Bacterial community profiling associated with pearl culture facilities of Liusha Bay, the largest marine pearl culture base on the western Guangdong coast, South China

A large number of aquaculture facilities produced during the farming process are made of plastics. These plastics can be a distinct habitat for bacteria due to their unique materials. Therefore, this paper focuses on plastic aquaculture facilities and investigates the impact of bacterial accumulation on plastic surfaces. In this study, the high-throughput sequencing of 16S rRNA was conducted to investigate bacterial community profiling associated with the pearl culture facilities (cultured net cages and foam buoys) and surrounding water of Liusha Bay. Alpha diversity analysis showed that the richness and diversity indexes of bacterial communities in pearl culture facilities were higher than those in the aquatic environment. The richness and diversity indexes of bacterial communities were different between cultured net cages and foam buoys. Spatially influenced bacterial communities attached to pearl culture facilities varied between aquaculture areas. Thus, plastic has become a habitat for bacteria, floating in the marine environment and providing a favorable living environment for marine microorganisms and specific preferences for different substrate types. The relative abundance of certain functions on the attached bacterial community of the culture facility was high, which suggested that plastics did not only alter community structure but also influenced bacterial function. In addition, we detected small amounts of pathogenic bacteria, such as Vibrio and Bruegeria, in pearl culture facilities and surrounding seawater, suggesting that plastics can act as vectors for potentially pathogenic bacteria that may have an impact on the development of aquaculture. Our understanding of plastic ecology has been enriched by the discovery of the various microbial assemblages that can occur in aquaculture facilities.

Ecological risks in a 'plastic' world: A threat to biological diversity?

Microplastics pollution is predicted to increase in the coming decades, raising concerns about its effects on living organisms. Although the effects of microplastics on individual organisms have been extensively studied, the effects on communities, biological diversity, and ecosystems remain underexplored. This paper reviews the published literature concerning how microplastics affect communities, biological diversity, and ecosystem processes. Microplastics increase the abundance of some taxa but decrease the abundance of some other taxa, indicating trade-offs among taxa and altered microbial community composition in both the natural environment and animals' gut. The alteration of community composition by microplastics is highly conserved across taxonomic ranks, while the alpha diversity of microbiota is often reduced or increased, depending on the microplastics dose and environmental conditions, suggesting potential threats to biodiversity. Biogeochemical cycles, greenhouse gas fluxes, and atmospheric chemistry, can also be altered by microplastics pollution. These findings suggest that microplastics may impact the U.N. Sustainability Development Goals (SDGs) to improve atmospheric, soil, and water quality and sustaining biodiversity.

Experimental Evidence of Epizootic Epitheliotropic Disease Virus (Salmoid Herpesvirus-3, Alloherpesviridae) Transmission via Contaminated Fomites and Subsequent Prevention Using a Disinfectant

Epizootic epitheliotropic disease virus (EEDV) has caused considerable mortality in hatchery-reared lake trout Salvelinus namaycush in the Great Lakes Basin, and yet the routes of transmission and efficacious means of prevention remain poorly understood. To determine whether EEDV can be transmitted via contaminated fomites and clarify whether such transmission could be prevented via fomite disinfection, juvenile lake trout (n = 20 per treatment) were handled in nets previously soaked in an EEDV suspension (7.29 × 10⁴–2.25 × 10⁵ virus copies/mL of water) that were further immersed in either 1% Virkon^® Aquatic (“disinfected” treatment, in triplicate) or in sample diluent (“EEDV-contaminated” treatment). Negative control nets were soaked in sterile sample diluent only. Characteristic gross signs of EED developed in the “EEDV-contaminated” treatment group, which was followed by 80% mortality, whereas no gross signs of disease and 0–5% mortality occurred in the negative control and “disinfected” treatment groups, respectively. EEDV was detected via qPCR in 90% of the “EEDV-contaminated” treatment fish, however, it was not detected in any fish within the negative control or “disinfected” treatment groups. Study findings not only demonstrate that EEDV can be readily transmitted via contaminated fomites, but importantly suggest that Virkon^® Aquatic is an efficacious option for preventing EEDV contagion via the disinfection of hatchery tools, thereby highlighting a promising tool for improving lake trout hatchery biosecurity and minimizing EEDV-linked losses.

Spatial Environmental Heterogeneity Determines Young Biofilm Assemblages on Microplastics in Baltic Sea Mesocosms

Microplastics in aquatic environments provide novel habitats for surface-colonizing microorganisms. Given the continuing debate on whether substrate-specific properties or environmental factors prevail in shaping biofilm assemblages on microplastics, we examined the influence of substrate vs. spatial factors in the development of bacterial assemblages on polyethylene (PE), polystyrene (PS), wood, and seston and in the free-living fraction. Further, the selective colonization of microplastics by potential pathogens was investigated because among the bacterial species found in microplastic-associated biofilms are potentially pathogenic Vibrio spp. Due to their persistence and great dispersal potential, microplastics could act as vectors for these potential pathogens and for biofilm assemblages in general. Incubation experiments with these substrates were conducted for 7 days during a summer cruise along the eastern Baltic Sea coastline in waters covering a salinity gradient of 4.5-9 PSU. Bacterial assemblages were analyzed using 16S rRNA-gene amplicon sequencing, distance-based redundancy analyses, and the linear discriminant analysis effect size method to identify taxa that were significantly more abundant on the plastics. The results showed that the sample type was the most important factor structuring bacterial assemblages overall. Surface properties were less significant in differentiating attached biofilms on PE, PS, and wood; instead, environmental factors, mainly salinity, prevailed. A potential role for inorganic-nutrient limitations in surface-specific attachment was identified as well. Alphaproteobacteria (Sphingomonadaceae, Devosiaceae, and Rhodobacteraceae) and Gammaproteobacteria (Alteromonadaceae and Pseudomonas) were distinctive for the PE- and PS-associated biofilms. Vibrio was more abundant on the PE and PS biofilms than on seston, but its abundances were highest on wood and positively correlated with salinity. These results corroborate earlier findings that microplastics constitute a habitat for biofilm-forming microorganisms distinct from seston, but less from wood. In contrast to earlier reports of low Vibrio numbers on microplastics, these results also suggest that vibrios are early colonizers of surfaces in general. Spatial as well as temporal dynamics should therefore be considered when assessing the potential of microplastics to serve as vectors for bacterial assemblages and putative pathogens, as these parameters are major drivers of biofilm diversity.

Microplastic-associated bacterial assemblages in the intertidal zone of the Yangtze Estuary

Plastic trash is common in oceans. Terrestrial and marine ecosystem interactions occur in the intertidal zone where accumulation of plastic frequently occurs. However, knowledge of the plastic-associated microbial community (the plastisphere) in the intertidal zone is scanty. We used high-throughput sequencing to profile the bacterial communities attached to microplastic samples from intertidal locations around the Yangtze estuary in China. The structure and composition of plastisphere communities varied significantly among the locations. We found the taxonomic composition on microplastic samples was related to their sedimentary and aquatic origins. Correlation network analysis was used to identify keystone bacterial genera (e.g. Rhodobacterales, Sphingomonadales and Rhizobiales), which represented important microbial associations within the plastisphere community. Other species (i.e. potential pathogens) were considered as hitchhikers in the plastic attached microbial communities. Metabolic pathway analysis suggested adaptations of these bacterial assemblages to the plastic surface-colonization lifestyle. These adaptations included reduced "cell motility" and greater "xenobiotics biodegradation and metabolism." The findings illustrate the diverse microbial assemblages that occur on microplastic and increase our understanding of plastisphere ecology.

Potential Reservoirs and Risk Factors for VHSV IVb in an Enzootic System: Budd Lake, Michigan

Viral hemorrhagic septicemia virus genotype IVb (VHSV IVb) has caused major, sporadic fish die-offs in the Laurentian Great Lakes region of North America since 2005. Presently, factors affecting VHSV IVb persistence in enzootic systems are not well understood. Even with annual surveillance, the virus can go undetected for several years after an outbreak before again re-emerging, which suggests that the virus is maintained in the system either below detectable levels or in untested reservoirs. The aim of this study was to identify potential reservoirs of VHSV IVb in Budd Lake, Michigan; VHSV IVb was first detected in Budd Lake in 2007 but remained undetected until 2011. Additionally, we explored the susceptibility of naive fish introduced into a water body enzootic for VHSV IVb by stocking age-0 Largemouth Bass Micropterus salmoides at varying densities into enclosures in the lake. The virus was not detected among samples of the fishes Notropis spp. and Lepomis spp., cylindrical papershell mussels Anodontoides ferussacianus, leeches (subclass Hirudinea), sediment, or water. However, the virus was successfully isolated from amphipods (family Hyalellidae) and Largemouth Bass held in the enclosures. Our finding of VHSV IVb in Hyalellidae amphipods in combination with other research that has detected the virus in Diporeia spp., a large benthic amphipod important as a food resource to Great Lake fishes, suggests that benthic macroinvertebrates are a reservoir for VHSV IVb in infected systems. If there are environmental reservoirs for VHSV IVb in infected systems, they are likely unevenly distributed. Findings of this study add to our understanding of the seemingly complex ecology of this deadly and economically detrimental virus. Received February 22, 2016; accepted October 16, 2016.

Millimeter-sized marine plastics: a new pelagic habitat for microorganisms and invertebrates

Millimeter-sized plastics are abundant in most marine surface waters, and known to carry fouling organisms that potentially play key roles in the fate and ecological impacts of plastic pollution. In this study we used scanning electron microscopy to characterize biodiversity of organisms on the surface of 68 small floating plastics (length range = 1.7–24.3 mm, median = 3.2 mm) from Australia-wide coastal and oceanic, tropical to temperate sample collections. Diatoms were the most diverse group of plastic colonizers, represented by 14 genera. We also recorded ‘epiplastic’ coccolithophores (7 genera), bryozoans, barnacles (Lepas spp.), a dinoflagellate (Ceratium), an isopod (Asellota), a marine worm, marine insect eggs (Halobates sp.), as well as rounded, elongated, and spiral cells putatively identified as bacteria, cyanobacteria, and fungi. Furthermore, we observed a variety of plastic surface microtextures, including pits and grooves conforming to the shape of microorganisms, suggesting that biota may play an important role in plastic degradation. This study highlights how anthropogenic millimeter-sized polymers have created a new pelagic habitat for microorganisms and invertebrates. The ecological ramifications of this phenomenon for marine organism dispersal, ocean productivity, and biotransfer of plastic-associated pollutants, remains to be elucidated.