Wednesday, March 1, 2023

Just One Word - Plastics!

Bay Bulletin, Study Finds Microplastics Pollution Makes Fish Viruses More Lethal

Microplastic fragments are becoming an increasing environmental problem in our waterways. They are the tiny particles that weathering creates from Styrofoam cups and plastic bottles, particles that make their way into the Chesapeake Bay. But new research finds their impact on marine life goes even deeper than we thought.

Toxins like microplastics work slowly in fish. But when combined with something like a virus, they can be lethal. A new study published in the journal Science of the Total Environment by toxicologists at the Virginia Institute of Marine Science (VIMS) saw it happen up close. Their lab research showed that certain types of microplastic fragments can cause enough damage to delicate structures like gill membranes to allow viruses to enter more easily.

The lead author, Dr. Meredith Evans Seeley, and several co-authors from VIMS and the College of William & Mary, wondered if the IHN virus, common in salmon and trout farms, would cause more fish to die in water containing plastic fragments than in water containing fragments of natural material like decayed marsh grass.

The team exposed rainbow trout, a common species in Virginia farms, to low, medium, and high concentrations of three different common types of microparticles, and later infected half the tanks with the IHN virus.

The particles came from polystyrene foam, nylon fibers from clothing, and the common plant saltmarsh cordgrass. Control tanks held no virus or microparticles.

“We found that co-exposure to microplastics and virus increased disease severity,” said Dr. Seeley, “with nylon fibers having the greatest impact. This is the first time this interaction has been documented, and emphasizes the importance of testing multiple stressors, which is more environmentally realistic. Nylon microfibers are larger and may be more likely to become trapped in and damage the delicate tissues of the gills and gut lining. That could make it easier for the virus to enter and stress the host.”

While the research speaks directly to the aquaculture industry, it’s also applicable to natural environments like the Bay and its tributaries, VIMS researchers say.

“Disease and microplastics may interact to produce worse outcomes across a range of aquatic and terrestrial systems,” added collaborating VIMS professor Rob Hale, “including in wild fishes, corals, and birds, raising questions far beyond fish farms. If you just test microplastics alone, you might not see any impacts and call it a day, but in the real world those microplastics may interact with pathogens, rising temperatures, decreasing pH, increasing water turbidity, and other variables.”

This research is likely to prompt further study of microplastics and a variety of other contributing factors.

To my knowledge, this is the first study to show a significant (to use the word in it's commonplace usage, not its scientific/statistical sense) negative effect of microplastics  on aquatic life, and even then, they had to introduce a second factor, a lethal virus. I tried following the links to the study (I got to the abstract, not the body). Microplastics were not harmful in the absence of virus, and natural fibers from rotting seagrass, and microplastics increased mortality above the virus alone, with the microplastics having a greater effect.

I have a few questions. 

First, how realistic were the microplastic exposure? It's nowhere in the abstract how the microplastics exposure compared to those in the real world. I wouldn't be shocked if it were several times, or even orders of magnitude higher than what is commonly found. That wouldn't be unexpected in a first study.

Second, how were the microplastics created? 'Natural' microplastics result from the slow chemical, biological and physical breakdown of plastic in the environment. Were the test microplastics created by grinding solid plastics? They could have very different, and much harsher effects than naturally created microplastics.

Third, how were the microplastics treated prior to the test? 'Real world' microplastics would mostly have a long prior exposure to the water before interacting with the fish gills. The would almost certainly become coated with "biofilm", the slimy mix of bacteria, their exudates, as well as natural organic compounds from the water, making them much more similar to natural microparticles. 

1 comment:

  1. A few months ago i read an article in Down East a Maine Magazine that discussed Abby Barrows microplastics study as it affects oyster farming in downeast Maine. Brian Kevin wrote the article, I know who can trust someone with two first names. Abby had a big research career going which she quit to take over an oyster farm. The research included microplastic pollution. The microplastics come from many places, one interesting microplastic sources is toothpaste, I used to be concerned only about fluoride.

    This is a great article.