Microplastic pollution poses a significant threat to filter-feeding marine megafauna — including manta rays, whale sharks and baleen whales — according to new research.
The study, published in the journal Trends in Ecology & Evolution, determined that filter-feeders are at risk because they swallow hundreds of cubic metres of water each day in an effort to capture plankton. They can ingest microplastics directly from the water or via contaminated prey.
These species also tend to congregate in microplastic pollution hotspots such as the Gulf of Mexico, the Mediterranean Sea and the Bay of Bengal. While a definitive connection between microplastic ingestion and toxin exposure still needs to be established, studies into fish and sea birds have found a link.
Despite growing concern about the effects of plastic pollution on the marine environment, there has been little research into the impact on filter feeders. This is because conventional methods for assessing plastic concentrations, including stomach analysis, aren’t suitable for threatened species like whale sharks.
The study’s authors therefore used non-lethal tissue sampling methods to test for chemical tracers.
Filtering of indigestible plastic particles can block nutrient absorption and cause damage to the digestive tracts of marine animals. Pollutants can also accumulate within wildlife over the course of several decades and alter biological processes, leading to altered growth, development and reproduction.
The study’s lead author, Elitza Germanov of Murdoch University, Australia, believes that further research is needed to evaluate the long-term impacts of microplastic ingestion.
“As plastic production is projected to increase globally, the establishment of long-term monitoring programs is needed in the feeding grounds of these ocean giants, so we can check on toxicity levels in these creatures over a period of time,” she said.
“The microplastics issue potentially places the viability of nature based tourism involving these creatures under threat also. This kind of tourism is a significant source of income in the regions where filter feeders congregate.
“Raising awareness of this issue in communities, among governing bodies and industries could help to change behaviours around the production, management and use of plastics.”