Sea oysters: another victim of plastic pollution
The occurrence of small plastic particles on beaches and in coastal waters was first reported in the 1970s. It has become evident that distribution of particles is global, including isolated mid-ocean islands, the open ocean and at high latitude.
Researchers have estimated that in the year 2010, world generated 275 million metric tons of plastic waste and 4.8 to 12.7 million metric tons of these plastics entered the ocean. It is likely that the amount of plastic waste in the ocean will continue to increase, driven primarily by the inexorable rise in plastics consumption and the continued inadequacy of re-use, recycling and waste management practices in many parts of the world.
Larger pieces of plastic break down in the ocean into microplastics, generally smaller than 1 mm down to micrometer range. Various sources are cosmetics, clothing, and industrial processes. As plastics do not break down, they persist in the environment at high levels, particularly in aquatic and marine ecosystems and thus they are ingested and incorporated into and accumulated in the bodies and tissues of many organisms. Because of this, the effects of microplastics on marine ecosystem are a cause of growing concern among scientists.
Scientists at the French Research Institute for Exploitation of the Sea have shed light on this area. To evaluate this, they fed the Pacific oysters (Crassostrea gigas) a meal of polystyrene microspheres and microalgae for two months. A control group, meanwhile, was fed just microalgae. As a result it was found that microplastics fed oysters consumed more microalgae and digested more efficiently when compared with the control group. The researchers say that this is most likely to compensate the plastic they had eaten. However, the more serious effect was that the additional expenditure of energy required to digest more microalgae compromised the oysters’ reproductive systems. Male oysters had slower sperm, and female oysters produced fewer, smaller oocytes leading to 18% smaller and 41% fewer in number of offspring.
This study shows that microplastics cause feeding modifications and reproductive disruption in oysters, with significant impacts on offspring. However the researchers think that more research is required to determine the full impacts of microplastic pollution in marine ecosystems, posing a significant problem to nature.
Sussarellu R et al. (2016). Oyster reproduction is affected by exposure to polystyrene microplastics. PNAS; 201519019.
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