We dump a lot of trash into the world’s oceans — so much that there’s a massive trash vortex swirling around in the North Pacific, as you’ve probably heard.
A lot of that trash is plastic. In a study published last year, researchers estimated that the world generated 275 million metric tons of plastic waste in 2010 alone, and that as much as 4.8 to 12.7 million metric tons of that entered the ocean.
With the amount of plastic waste produced every year expected to grow by an order of magnitude over the next decade, the impacts of microplastics on marine ecosystems is a cause of growing concern among scientists.
“Given their ubiquitous nature and small dimensions, the ingestion and impact of microplastics on marine life are a cause for concern, notably for filter feeders,” according to a study published in the Proceedings of the National Academy of Sciences this month.
Larger pieces of plastic break down in the ocean into what are called microplastics, while industrial processes and consumer products — especially the type with plastic microbeads, like toothpastes and cosmetics, that get washed down the drain and eventually end up out in the ocean — are direct sources of microplastics entering marine environments.
Scientists at the French Research Institute for Exploitation of the Sea studied how microplastics impact Pacific oysters (Crassostrea gigas) by feeding a group of them a mixture of polystyrene microspheres and microalgae, a more typical meal. A control group, meanwhile, was fed just microalgae.
After two months, the oysters being fed the microplastics were found to have also consumed more microalgae and to have digested it more efficiently, too, which the researchers say was most likely to compensate for all of the plastic they had eaten.
The more serious effect was that the additional expenditure of energy required to digest more microalgae compromised the oysters’ reproductive systems, the researchers discovered. Male oysters had slower sperm, and female oysters produced fewer and smaller oocytes, the cells that become eggs. That led to offspring that were 18 percent smaller and 41 percent fewer in number.
“This study provides evidence that [microplastics] cause feeding modifications and reproductive disruption in oysters, with significant impacts on offspring,” the researchers write in the PNAS paper.
Arnaud Huvet, a marine physiologist at the French Research Institute for Exploitation of the Sea and a co-author of the PNAS article, told the LA Times that much more research is needed to determine the full impacts of microplastic pollution in marine ecosystems.
But Huvet is not worried about the ability of “strong populations” of Pacific oysters to withstand the reduced reproductive capacities. Pacific oysters are native to Asia’s east coast but have been introduced the world over and become a “core constituent of many coastal ecosystems” as well as an important seafood item, Huvet and his co-authors write in the study.
For weaker populations of Pacific oysters that are less well established, as well as populations of less robust native species like the European flat oyster or North America’s Olympia and eastern oysters, Huvet said having fewer, smaller offspring could pose a significant problem.
A 2014 study estimated that there is a minimum of 5.25 trillion particles of plastic weighing as much as 268,940 tons polluting the world’s oceans.
- Eriksen M, Lebreton LCM, Carson HS, Thiel M, Moore CJ, Borerro JC, et al. (2014) Plastic Pollution in the World’s Oceans: More than 5 Trillion Plastic Pieces Weighing over 250,000 Tons Afloat at Sea. PLoS ONE 9(12): e111913.doi:10.1371/journal.pone.0111913
- Jambeck, J. R., Geyer, R., Wilcox, C., Siegler, T. R., Perryman, M., Andrady, A., … & Law, K. L. (2015). Plastic waste inputs from land into the ocean. Science 347(6223), 768-771. doi:10.1126/science.1260352
- Sussarellu, R., Suquet, M., Thomas, Y., Lambert, C., Fabioux, C., Pernet, M. E. J., … & Corporeau, C. (2016). Oyster reproduction is affected by exposure to polystyrene microplastics.Proceedings of the National Academy of Sciences, 201519019. doi:10.1073/pnas.1519019113
Article published by Mike Gaworecki, source: Mongabay