Marine wildlife is endangered by plastic pollution. Plastic straws, bottles, and bags that litter beaches have long been recognized as a threat. However, microplastics—plastic fragments smaller than 5 millimeters in size—are also a significant contributor.
Up to 91 percent of the microplastics that float around our oceans are made of microfibers, which are the most common type of microplastic. These minuscule fibers are shed from textiles when clothes are worn and washed, as well as when marine equipment is weathered and abrashed.
These microplastics will be encountered by and even consumed by marine animals. Shellfish, which filter the water to get their food, are particularly vulnerable. According to one study, shellfish consume significantly more microplastics than most other marine creatures.
My coworkers and I conducted research at the Plymouth Marine Laboratory over a three-month period to examine how exposure to microfibers affected tiny young blue mussels. Animals younger than adults are typically more susceptible to environmental changes. For instance, predation is primarily to blame for the higher mortality rates of young mussels in the wild. As a result, the microplastic contamination of young mussels is likely to have a significant impact.
In our paper, presently distributed in micro- and nanoplastics, we found that drawn-out openness to polyester microfibers prompted more modest mussels that developed at a slower rate.
Because they reveal broader ecosystem trends, blue mussels are an important species for scientists to use as indicators. Blue mussels are a good indicator of water quality because they are exposed to pollutants because they filter water constantly. Mussels, as members of the bivalves family of shellfish, play an important role in marine food security.As a result, the marine ecosystem and the bivalve aquaculture industry could be shaken if reduced growth is also occurring in the wild.
More modest mussels
In a controlled-temperature lab, we presented the mussels to polyester microfibers (somewhere in the range of 0.01mm and 0.5mm in size) at two fixations: Eighty-eight microfibers per liter Additionally, we gave the mussels 80 microfibers per liter of cotton.
Marine microplastic concentrations of 10 particles per liter of seawater are common, according to scientists. Therefore, our study’s concentrations are typical of natural environments.
Compared to blue mussels that were not exposed to any microfibers, those that were exposed to the higher concentration of polyester microfibers were noticeably smaller and had an average growth rate that was 36% lower. Only the mussels that were exposed to the highest concentration of polyester microfibers showed this result. Young mussels’ growth rates did not significantly decrease when they were exposed to cotton microfibers.
Spending energy wisely Microplastics can harm adult mussels on a molecular and cellular level, according to toxicology studies. After six hours of exposure to polyethylene microplastic particles, mussel cells showed a significant inflammatory response, according to one study.
The decrease in mussel development in light of plastic microfiber openness could originate from a change in their vigorous financial plan (the harmony between the energy taken in and the energy utilized). These alterations could be the result of the mussels altering their feeding habits to avoid ingesting microfibers, focusing energy on processing ingested microfibers instead of growing, or focusing on repairing damage caused by microfibers.
Diminished development rates in mussels could thusly influence the more extensive biological system.
Young mussels grow quickly and reach a size that can be sold in 12 to 24 months. However, they must compete with other species and each other for food and space. Younger mussels that are unable to grow as quickly may be outcompeted by other species and more preyed upon.
Additionally, smaller mussels have a lower nutritional value. Crabs, whelks, starfish, and a number of bird species may have to consume more of these smaller mussels. Both the populations of the mussels and their prey could be affected by this.
People, as buyers of fish, will likewise be impacted by more modest mussels. Over 8 million tons of oysters, mussels, and scallops alone provide the world’s population with food each year. However, mussels with slower growth rates will take longer to reach harvestable size. More modest creatures and a longer time to market might lessen the benefit of bivalve hydroponics later on.
Contaminated waters
Microplastics plainly affect the development of young blue mussels. However, the actual impact may be even more significant.
Microplastic concentrations as high as 182 particles per liter have been found in some more polluted marine environments, which is more than twice the concentration used in our experiment. Because many of the microplastics in our oceans are too small to be counted, separate research suggests that their concentrations may be even higher than they are currently.
When assessing the effects of microplastics on marine life, our research demonstrates the significance of carrying out long-term experiments. When an organism is exposed to microplastics, the effects on its cells and tissues can be felt quickly.
However, much longer observation times are needed to observe the effects of environmental-relevant concentrations of microplastics on growth, reproduction, and survival, which are most important for entire populations.
Overfishing and climate change are already threatening marine environments. The harmful effects that microfibers and other microplastics have on the animals that live in our oceans are starting to become more apparent thanks to studies like ours.
More information: Christopher Walkinshaw et al, Impact of polyester and cotton microfibers on growth and sublethal biomarkers in juvenile mussels, Microplastics and Nanoplastics (2023). DOI: 10.1186/s43591-023-00052-8
