New research posits that microplastics could also be a vector for pathogens, spreading antimicrobial-resistant genes. Shutterstock image.
What threat do microplastics, a.k.a. ‘ocean hitchhikers’, pose to aquaculture?
Wednesday, October 28, 2020, 09:00 (GMT + 9)
The following is an excerpt from an article published by The Global Aquaculture Advocate:
Trends in Microbiology: Microplastic ‘ocean hitchhikers’ could be a vector for pathogens, putting bivalve shellfish at risk
Microplastics might be small but their impact on aquatic life looms large.
The plastic particles, shed from textiles or created when larger pieces of plastic waste break down, are the most prevalent marine debris found in the ocean. Up to 51 trillion plastic particles, weighing between 93,000 to 236,000 metric tons, are estimated to be floating on the surface of the oceans.
Microplastics from primary and secondary sources enter the food chain by direct ingestion at all trophic levels, but are also acquired in prey items and hence may bioaccumulate in larger organisms, causing negative health effects that may impact population persistence. Ultimately microplastics and associated additives or sorbed pollutants may threaten the safety of seafood ingested by humans (Image: courtesy https://doi.org/10.1002/lol2.10122 Citations: 5) | Click image to enlarge
That seems like a lot, but it’s only about 1 percent of the plastic waste estimated to have entered the ocean in 2010 alone.
“Plastic pollution is overwhelming [and] almost unavoidable to some degree,” Maria Sepulveda, DVM, Ph.D., professor in the aquaculture research lab at Purdue University, told the Advocate.
Microplastics, which technically measure less than five millimeters in diameter, have been found in myriad aquatic life, ranging from plankton to whales. Research shows that microplastics affect growth rates, increase stress and contribute to higher mortality rates. A new paper published in the journal Trends in Microbiology posits that microplastics could also be a vector for pathogens, spreading antimicrobial-resistant genes.
The concentration of antimicrobial-resistant bacteria is up to 5,000 times higher on microplastic surfaces than in the surrounding seawater, which could allow the sesame seed-sized plastic particles to transmit harmful microorganisms and trigger disease outbreaks.
Mussels, oysters, clams and other filter feeders are potential hosts for the so-called “ocean hitchhikers” and microplastic is often detected in the edible bivalves, raising concerns about pathogen transfer and potential economic losses in aquaculture, according to study co-author Ceri Lewis Ph.D., marine biologist and associate professor at the University of Exeter.
“When [plastics] become smaller they will pass through guts quite slowly and they take up space that should be full of food,” explained Lewis. “Most of the mussels and oysters and other species at the bottom of the food chain have to grow and reproduce pretty quickly [and] anything that reduces their ability to take up energy from their food can slow down their growth and have more consequences for their reproduction.”
Sepulveda of Purdue Univ. worries that trout and other fish-eating species might also be exposed to toxic microplastics because the particles floating around in marine environments could end up in their guts – and the guts of the fish they eat – leading to sublethal or lethal exposures.
“There are a lot of chemicals that stick to the plastic from the environment. So now we’re talking about an inert particle that’s not inert anymore because it has all these bioactive chemicals surrounding it,” she explains. “The fish acts like a carrier.”
Data is limited
So far, little work has been done to assess the impacts of microplastics (or their potential to transmit pathogens) in aquaculture. Lewis admits that questions remain about whether the pathogens on the microplastics will transfer to marine species or increase the number of times producers have to shut down to recover from outbreaks.
Research on microplastics is still new but the risks are not, Lewis added. The pathogens that could be transmitted on microplastics are already found naturally in oysters and mussels and producers monitor for them in aquaculture operations.(continued...)
Author: Jodi Helmer / The Global Aquaculture Advocate | Read the rest of the story by clicking the link here