Microplastics Aggravate an Important Viral Fish Disease

Microplastics, which are tiny particles produced when plastics weather and fragment, pose an increasing threat to ecosystems and human health.

A new laboratory study reveals that the presence of microplastics increases the severity of an important viral fish disease, going beyond direct physical or chemical impacts.

Virus plus microplastics equal a double whammy for fish health

(Photo : OLIVIER MORIN/AFP via Getty Images)

Dr. Meredith Evans Seeley, who conducted the research as part of her Ph.D. program at William & Mary's Virginia Institute of Marine Science, is the lead author of the study, which was published in Science of the Total Environment, as per ScienceDaily.

VIMS professors Rob Hale, Andrew Wargo, and Wolfgang Vogelbein joined her as co-authors, as did W&M professor Patty Zwollo and VIMS laboratory technician Gaelan Verry.

According to Seeley, microplastics and pathogens are present everywhere, but they are often present in the highest concentrations in densely populated aquatic environments such as fish farms.

They wanted to see if microplastics had any impact on the severity of IHNV infections in aquaculture.

IHNV is a highly pathogenic pathogen in salmonid aquaculture, affecting rainbow trout, steelhead trout, chinook salmon, and sockeye salmon.

The researchers wanted to see if there was a "cause-and-effect" relationship between microplastics, viruses, and fish mortality.

Seeley and colleagues exposed rainbow trout kept in aquariums to low, medium, and high concentrations of three different types of microparticles before adding the IHN virus to half of the tanks.

They chose plastics that are both widely used in aquaculture and commonly found in nature as breakdown products: polystyrene foam (commonly used in floats, buoys, home insulation, and food containers); and nylon fibers (lost from fishing nets, fishing lines, and clothing).

Infected and healthy fish were also exposed to tiny fragments of the common saltmarsh cordgrass Spartina alterniflora.

There were no viruses or microparticles in the control tanks.

According to their laboratory findings, the researchers believe that microparticle exposure worsens disease severity by physically damaging the delicate tissues of the gills and gut lining, making it easier for the virus to colonize its host.

Natural microparticles derived from Spartina had a greater impact than synthetic microplastics such as nylon and polystyrene.

Exposure to nylon-derived microfibers had the greatest impact.

The researchers believed this is due to their larger size, extended length, or the plastic's higher hardness when compared to plant matter.

The team's research has far-reaching implications beyond fish farming. "Our research question is very relevant in aquaculture," Seeley says, but it also applies to natural environments.

Because microplastics are found all over the world, they may be co-occurring with a variety of natural pathogens at any given time.

According to Hale, disease and microplastics may interact to produce worse outcomes in a variety of aquatic and terrestrial systems, including wild fish, corals, and birds.

If you just test microplastics and call it a day, you might not see any effects, but in the real world, those microplastics may interact with pathogens, rising temperatures, decreasing pH, increasing water turbidity, and other variables.

Also read: Microplastics Found in 75% of Fish Meant for Human Consumption: Is It Still Healthy to Eat Seafood?

Plastic Pollution Affects Sea Life

According to research, half of all sea turtles in the world have consumed plastic.

Some people starve as a result, believing they have eaten enough because their stomachs are full, as per PEW.

Plastic pollution is so prevalent on many beaches that it is affecting turtle reproduction rates by altering the temperatures of the sand where incubation occurs.

According to a recent study, sea turtles that consume just 14 pieces of plastic are more likely to die.

The young are especially vulnerable because they are less selective about what they eat than their elders and, like plastic, tend to drift with currents.

Every year, up to a million seabirds are killed by plastic waste.

When seabirds ingest plastic, it takes up space in their stomachs, sometimes causing starvation.

Many dead seabirds have been discovered with this waste in their stomachs.

Scientists estimate that 60% of all seabird species have consumed plastic, with the figure expected to rise to 99% by 2050.

While dolphins are highly intelligent and thus unlikely to consume plastic, they are vulnerable to contamination from synthetic compounds ingested by prey.

Plastic in our oceans has an impact on both large and small creatures, from seabirds, whales, and dolphins to tiny coral reef seahorses.

Plastic waste can promote pathogen growth in the ocean.

A recent study found that corals that come into contact with plastic have an 89% chance of contracting disease, compared to a 4% chance for corals that do not.

Scientists predicted that the weight of ocean plastics will exceed the combined weight of all fish in the seas by 2050 unless action is taken quickly to address this urgent problem.

Related article: 4 Million Pounds of Microplastics Found in Corals, Causing Tissue Necrosis in Fishes