Mussels that clump together in reefs may ingest triple the plastic
The impact of plastic on the many species that call the ocean home is a huge unknown, but scientists are starting to piece together the kinds of risks this pollution poses to the marine ecosystem. The latest finding in this area concerns a common seafood in blue mussels, which researchers have found may ingest three times as much plastic when clumped together in the reef structures commonly seen in nature.
The research was carried out by scientists at Plymouth University, who conducted a set of experiments to investigate how the tendency of blue mussels to form reef structures might impact their uptake of plastic waste.
This involved placing aggregations of mussels in water flumes and subjecting them to waves of different speeds. The team experimented by adding microplastic particles to the water throughout the different experiments, observing how the varying water flows influenced ingestion risk for the mussels.
Through this series of experiments, the team found that when the mussels were clumped together to form the reef-like structures in the lab, they slowed down the water flowing over them, while also increasing the turbulence. The upshot of this was a three-fold increase in ingested plastic, with the researchers describing these reef structures as “natural sinks” for plastic and other pollutants, driven largely by the complexity and surface roughness of the structures.
"Often we look to protect reef-forming species based on who they are,” says Dr Antony Knights, Associate Professor in Marine Ecology at Plymouth University. “However, we are not aware of any research that has shown that the physical structure of reef itself – which we have shown can help these filter-feeding organisms to be more effective feeders – might also inadvertently increase their exposure to pollutants like microplastic. With no means of addressing this issue, due to our increasing awareness of the quantity of microplastic in the marine environment, this study offers the first evidence that forming a reef is a double-edged sword for individuals."
This isn’t the first we’ve heard of the ill effects plastic pollution can have on mussels. A study published last year found that exposure to microplastics could induce a strong immune response in the animals, which caused them to secrete less of the adhesive fibers they rely on for their famed ability to cling to rocks. While the risks of plastic pollutions for all marine species should be cause for concern, the popularity of mussels as a seafood snack, combined with their crucial role in a healthy marine ecosystem, may make them a priority for researchers in the field.
"Species such as the blue mussel are both commercially valuable as seafood but also environmentally important,” says Knights. “They form natural reefs within marine and coastal settings which enhance biodiversity to such a degree that they are commonly protected under conservation actions. If they are particularly susceptible to microplastic pollution, there are many potential knock-on effects that we need to be aware of.”
The research was published in the journal Environmental Research Letters.
Source: University of Plymouth via EurekAlert