While floating waste of biological origin is spontaneously biodegraded, an enormous amount of non-biodegradable materials such as plastics and marine debris are accumulating in this ocean area. Instead of biodegrading, plastic photodegrades, that is, it disintegrates into smaller and smaller pieces up to the size of the polymers that compose it; nevertheless, the latter remain plastic and their biodegradation is still very difficult.
The effects on the environment have not yet been studied in depth and appear difficult to assess given the extent of the phenomenon and the associated time scales, but they are probably important. Above all of the high concentrations of PCBs that can enter the food chain since the plastic filaments are difficult to distinguish from plankton and therefore ingested by marine organisms, but also to the ability of microplastics to provide support for proliferation of microbial colonies of pathogens.
More generally, the presence of pervasive and toxic waste in a fundamental ecosystem during periods of tens or hundreds of years is worrying. Researchers from the Plastics in our water: Fish microbiomes at risk? said in their research published on the Comparative biochemistry and physiology: "Water contaminated with plastic debris and leached plasticizers can be ingested or taken up by aquatic invertebrates and vertebrates alike, exerting adverse effects on multiple tissues including the gastrointestinal tract.
As such, gut microbiomes of aquatic animals are susceptible targets for toxicity. Recent studies conducted in teleost fishes report that microplastics and plasticizers (e.g., phthalates, bisphenol A) induce gastrointestinal dysbiosis and alter microbial diversity in the gastrointestinal system.
Here we synthesize the current state of the science regarding plastics, plasticizers, and their effects on microbiomes of fish. Literature suggests that microplastics and plasticizers increase the abundance of opportunistic pathogenic microorganisms (e.g.
Actinobacillus, Mycoplasma and Stenotrophomonas) in fish and reveal that gamma-proteobacteria are sensitive to microplastics. Recommendations moving forward for the research field include (1) environmentally relevant exposur es to improve understanding of the long-term impacts of microplastic and plasticizer contamination on the fish gastrointestinal microbiome; (2) investigation into the potential impacts of understudied polymers such as polypropylene, polyamide and polyester, and (3) studies with elastomers such as rubbers that are components of tire materials, as these chemicals often dominate plastic debris.
Focus on both microplastics and the gut microbiota is intensifying in environmental toxicology, and herein lies an opportunity to improve evaluation of global ecological impacts associated with plastic contamination. This is important as the microbiota is intimately tied to an individual's health and fragmentation of microbial community networks and gut dysbiosis can result in disease susceptibility and early mortality events."