Researchers supported by the EMBRC-coordinated, EU-funded ASSEMBLE Plus project and the EvoCELL project have discovered that the chemicals in plastic (and not just the plastic itself) is harmful for aquatic life.
In their study, the results of which were published in the journal ‘Environmental Pollution’, the researchers soaked different plastic samples in seawater. After removing the plastic, they raised sea urchin embryos in the water to study its effect on embryo development. They found that the chemicals in the leached water caused various abnormalities, including delayed development, deformed skeletons, and nervous and immune system malformations. 'We are learning more and more about how ingesting plastic affects marine animals', stated lead author Flora Rendell-Bhatti of EvoCELL project partner University of Exeter in a news item posted on the ‘ScienceDaily’ website. 'However, little is known about the effects of exposure to chemicals that leach into the water from plastic particles. This study provides evidence that contamination of the marine environment with plastic could have direct implications for the development of larvae, with potential impacts on wider ecosystems'.
The scientists used three types of plastic pellets in their experiment: new pre-production plastic nurdles (used to make most plastic products) and nurdles and biobeads (floating filters used in wastewater treatment plants) washed up on beaches. An estimated 60 ml of each plastic type was soaked in 240 ml of seawater for 72 hours at 18 °C. The water was then filtered and tested for chemicals known to affect animal development.
The effects of chemicals, and their absence
According to co-author Eva Jimenez-Guri, also of the University of Exeter, '[M]any plastics are treated with chemicals for a variety of purposes, such as making them mouldable or flame retardant. If such plastics find their way to the oceans, these chemicals can leach out into the water. Plastics can also pick up and transport chemicals and other environmental contaminants, potentially spreading them through the oceans'.
The analyses revealed the presence of detrimental chemicals such as polycyclic aromatic hydrocarbons and polychlorinated biphenyls in all the leached water samples. All sample types also led to serious developmental abnormalities in sea urchins both at the embryonic and larval stages. Conversely, normal development was observed in sea urchin embryos raised in water that had contained polyethylene particles with no additive chemicals or environmental contaminants. This suggests that, rather than being caused by the plastics themselves, the observed abnormalities were actually the result of the urchins’ exposure to pre-existing industrial additives or environmentally adsorbed contaminants. Although the plastic-to-water ratio used in the ASSEMBLE Plus and EvoCELL study would only be found in highly polluted waters, it nevertheless highlights the detrimental effects of plastic pollution on aquatic life. 'Our work contributes to the growing evidence that we all need to help reduce the amount of plastic contamination released into our natural environment, to ensure healthy and productive ecosystems for future generations', concluded Rendell-Bhatti.