Scientists fed European sea bass different amounts of rayon microfibers—tiny plastic-like particles found in ocean water—and watched how it affected the bacteria living in and around the fish. They discovered that these fibers changed which bacteria lived in the fish’s gut, on its skin, and in the water around it. Interestingly, at very high doses, the fish’s bacteria communities bounced back to look similar to fish that ate no fibers at all, suggesting the fish’s body may have protective mechanisms. This research helps us understand how microplastics in our oceans might affect fish and other marine life.

The Quick Take

  • What they studied: How tiny rayon fibers (a type of microplastic) in fish food affect the bacteria living inside fish and in the water around them
  • Who participated: European sea bass (a type of farmed fish) divided into groups eating different amounts of rayon fibers—from none to high levels
  • Key finding: Medium doses of rayon fibers changed the bacterial communities the most, but at the highest dose, the bacteria patterns returned to look similar to fish eating no fibers, suggesting the fish’s body adapted to the stress
  • What it means for you: This research suggests that microplastics in seafood may affect the health of farmed fish through changes in their gut bacteria. While this study focused on fish, it raises questions about whether similar effects could happen in other animals. More research is needed before drawing conclusions about human health.

The Research Details

Researchers created four groups of European sea bass and fed each group fish food containing different amounts of rayon microfibers. One group ate normal food with no fibers (the control group), while the other three groups ate food with increasing amounts of fibers. The scientists then used advanced DNA testing to identify and count all the different bacteria living in three places: the fish’s gut (digestive system), the fish’s skin, and the water in the fish tanks. They used a special technology called Nanopore sequencing, which can identify thousands of different bacterial species. By comparing the bacterial communities across all groups, they could see how the rayon fibers changed which bacteria thrived and which ones declined.

This research approach is important because it looks at bacteria in multiple locations (gut, skin, and water) rather than just one place. This gives a complete picture of how microplastics affect the entire ecosystem around the fish. The study also measured the actual amount of fibers that accumulated in the fish’s body and water, which helps prove that the bacteria changes were actually caused by the fibers themselves.

The study used modern DNA sequencing technology that can identify nearly 2,800 different bacterial species, making it very thorough. However, the paper doesn’t clearly state how many individual fish were tested in each group, which makes it harder to judge how reliable the results are. The research builds on previous work that already showed these fibers accumulate in fish tissue, which strengthens the findings.

What the Results Show

The rayon fibers caused significant changes in which bacteria lived in the fish and their water. The water microbiome (bacteria in the water) showed the biggest changes, with 691 different bacterial types affected. The fish’s skin bacteria changed less dramatically (253 types affected), and the gut bacteria showed the smallest changes (99 types affected). As the dose of fibers increased, the overall diversity of bacteria decreased—meaning fewer different types of bacteria were present. This happened in a dose-dependent way, meaning more fibers caused more bacterial loss, up to a point. Interestingly, at the highest fiber dose, some bacterial diversity bounced back, and the bacterial communities started looking more like the control fish again, suggesting the fish’s body may have activated protective mechanisms.

The researchers identified specific bacteria that increased or decreased with fiber exposure. Certain bacteria that can break down starches and hydrocarbons became more common, while other bacteria like Synechococcus decreased. In the fish’s skin, bacteria associated with vitamin B6 production and muscle repair became more abundant at high fiber doses. In the gut, bacteria linked to breaking down complex carbohydrates increased, but these same bacteria were also associated with inflammatory responses in the fish’s body. This suggests the fish was mounting an immune response to the fiber exposure.

This study extends previous research on the same fish species that showed rayon fibers accumulate in fish tissue and cause fatty liver and inflammatory responses. This new research confirms those findings by showing that the bacterial changes align with the inflammatory markers previously observed. The bacterial shifts toward starch and hydrocarbon-degrading bacteria may represent the fish’s attempt to process or manage the foreign material in its system.

The study doesn’t clearly report the exact number of fish tested in each group, making it difficult to assess statistical reliability. The research was conducted in controlled farm conditions, which may not reflect how wild fish would respond to microplastics in natural ocean environments. The study only looked at one fish species, so results may not apply to other types of fish or marine animals. The mechanism by which the bacterial communities recover at the highest dose isn’t fully explained and needs further investigation.

The Bottom Line

Based on this research, there is moderate evidence that rayon microfibers can significantly alter the bacterial communities in farmed fish. Fish farmers should be aware of potential microplastic contamination in feed sources and water. However, this is preliminary research, and more studies are needed before making major changes to farming practices. The finding that bacteria partially recover at very high doses suggests the fish’s body has some adaptive capacity, but this doesn’t mean exposure is safe.

Fish farmers and aquaculture companies should pay attention to this research as it may affect fish health and product quality. Environmental scientists and policymakers concerned about microplastic pollution should note these findings. Seafood consumers may want to stay informed as more research emerges, though this single study doesn’t warrant changing eating habits. People working in textile manufacturing should be aware of how synthetic fibers enter aquatic environments.

The bacterial changes observed in this study occurred during the feeding period, suggesting effects happen relatively quickly. However, the long-term consequences for fish health and whether these changes persist after exposure stops are unknown and require additional research.

Want to Apply This Research?

  • If tracking seafood consumption, users could note the source of fish (farmed vs. wild) and type of fish consumed, then monitor any digestive symptoms or changes in how they feel after eating seafood from different sources. This personal tracking could help identify individual patterns over time.
  • Users interested in reducing microplastic exposure could use the app to track purchases of seafood from farms known to have strict quality controls or choose wild-caught fish from regulated sources. They could also track consumption of other foods potentially exposed to microplastics and monitor their overall microplastic exposure from various sources.
  • Create a long-term tracking system that monitors digestive health, energy levels, and overall wellness in relation to seafood consumption patterns. Users could set reminders to note any changes in digestion or health markers weekly, then review trends monthly to see if patterns emerge related to their seafood choices.

This research describes changes in fish bacteria caused by rayon microfibers in controlled laboratory conditions. While interesting, this study was conducted on farmed fish and does not directly measure effects on human health. The presence of rayon fibers in seafood has not been proven to cause illness in people. If you have concerns about microplastics in your diet, consult with a healthcare provider. This summary is for educational purposes and should not replace professional medical or nutritional advice. More research is needed to understand the full implications of microplastic exposure for both fish and human health.