By Roberta Attanasio, IEAM Blog Editor
Microplastics—the tiny bits of plastic that are now infamously and ubiquitously present in the world’s waterways—are polluting aquatic life and ending up in our food supply. As evidence of the damage that microplastics inflict on aquatic life accumulates, so does the amount of microplastics dispersed in oceans, seas, lakes, and rivers. Virtually indestructible in natural environments, these tiny bits of plastic contain a combination of very small particles—microparticles and nanoparticles—that derive from the breakdown of larger plastic items, for example plastic bags and bottles, and include, among others, pre-production plastic pellets (the so-called nurdles), microbeads from personal care products, and microfibers from textiles.
In 2015, researchers demonstrated that, off the coast of British Columbia, both copepods and euphausiids—the zooplankton at the bottom of the marine food web—contain microplastics. In other words, zooplankton are mistaking microplastics for food. Because copepods and euphausiids serve as a primary food source for juvenile salmon, the researchers estimated that a juvenile salmon off the British Columbia coast would consume two to seven microplastic particles per day in its prey, and returning adult salmon would ingest close to a hundred per day.
Not surprising, then, are the findings from a study showing that many species of fish and shellfish sold for human consumption in Makassar, Indonesia, and California, U.S., contain plastic debris. Six out of the 11 species tested in Indonesia, and 8 out of 12 species tested in California (including striped bass and Chinook salmon) contained plastic or other anthropogenic debris. Interestingly, all debris recovered from fish in Indonesia was plastic, whereas debris recovered from fish in California was primarily fibers, a likely reflection of differences in sources of plastics and waste management strategies between the two countries.
Thus, a little at a time, we’re starting to understand the magnitude of the problem. The latest discovery on the effects of plastic pollution on aquatic life comes from researchers at Uppsala University, Sweden: larval European perch exposed to microplastics during development not only show stunted growth and increased mortality rates but also changes in behavior. Exposed fish swim shorter distances and are more likely to spend time motionless. In addition, plastic microbeads affect their olfactory senses, which are used to detect predators and trigger anti-predator behaviors. Altogether, these changes endanger fish survival by making them more likely to be killed by predators.
Even more disconcerting is the finding that larval perch develop a taste for microplastics—when given access to the particles, they eat only microplastics and ignore free-swimming zooplankton, their natural source of food. Peter Eklöv, co-author of the study, said in a press release: “This is the first time an animal has been found to preferentially feed on plastic particles and is cause for concern.”
Other anthropogenic activities have caused massive fish die-offs recently, resulting in serious economic damage to regional and international fishing industries, not to mention long-lasting ecological changes. A few months ago, an estimated 40,000 tons of farmed salmon died in the Los Lagos region of Chile due to the so-called red tide—an algal bloom that turns the seawater red and makes seafood toxic. At the same time, millions of dead fish lined the beaches over 200 kilometers of central Vietnam, apparently as a result of toxic discharges from a Taiwanese-owned steel plant.
Microplastics pollution poses a much more insidious danger to aquatic life than algal blooms or toxic discharges—we are not aware of massive die-offs caused by it, because its effects are cumulative and sub-lethal rather than cause sudden, catastrophic events. However, given the enormous and continuously increasing amount of microplastics present in the world’s waterways, it is reasonable to expect the discovery of more long-lasting, negative impacts on fish survival and seafood quality. We may never know the full effects though. Californian oceanographer Captain Charles J. Moore, who first discovered the Great Pacific Garbage Patch and studies the impact of seaborne plastic, told CNN: “It is impossible to quantify death in the ocean as weak and dying creatures are so rapidly consumed.”
Plastic pollution is a recognized global threat, and this recognition has led to the launch of major initiatives, as for example the Global Partnership on Marine Litter, which brings together policymakers, conservationists, and business interests in order to develop solutions to reduce and manage marine litter. However, sustainable solutions for plastic pollution should include intervention that minimizes the disposable plastic culture and, moreover, the throwaway culture.