A microplastic-free case?

The presence of microplastics in marine organisms is a growing concern worldwide, as these materials can have harmful effects on animal health and the ecosystem as a whole. The selected study of this month focused on the analysis of microplastics’ presence in the adipose tissue of ringed seals (Pusa hispida) in the Arctic.

Between 2017 and 2019, samples from the adipose tissue of ringed seals captured by indigenous hunters from western Canada were examined. The technique used for the analysis has a capacity to detect microplastic particles as small as 10 microns. Surprisingly, the results indicated that none of the samples contained detectable microplastics. This differs from previous studies that found high levels of microplastics in the adipose tissue of other seal species, such as ribbon seals.

Fibers are usually the most common type of microplastics found in marine mammals, followed by fragments and films. Even though the researchers have found small plastic based fibers in the samples, it is believed that their origin is based on contamination during sample handling in the laboratory. Cohen’s D, or standardized mean difference, is a common way to test whether an effect size is significant, statistically speaking, which in this case related to the ingestion of microplastic particles. In this study, with a sample size of content from 10 seal individuals, the observed effect was 0.37. For that value to be sifnificant, the sample would have to be composed of 91 individuals, being that with the 10 individuals examined, the effect would only be significant with a Cohen’s D value of at least 1.16 (blue and red lines, respectively, Fig.1).

Fig.1 With an increase in sample size, the required effect size for statistical significance decreases.

According to the researchers, the absence of microplastics in ringed seals in this study may be related to a small ingestion of plastic particles, compared with other marine fauna. Their main food supply is composed by fish, which presents a far less probability of microplastic ingestion, contrary to a diet dominated by benthic invertebrates. However, it is also possible that the technique used for analysis may not have been the most sensible to detect plastic particles with smaller dimensions, or that the study region in Canada is not exposed to the same levels of microplastics as other areas.

Although this study provides us with good news on this microplastic free ringed seal population in western Canada, it is still important to remember that other studies of the same kind have found high levels of microplastics in other populations around the world. Therefore, it is crucial to continue researching the presence and effects of microplastics in marine ecosystems in order to better understand their impacts and take measures to protect marine life and human health.

Overall, this study highlights the need for continued research on microplastics and their effects on marine organisms. It also emphasizes the importance of taking action to reduce the amount of plastic pollution in the ocean, through measures such as reducing plastic use and improving waste management systems. By working together to address this global issue, we can help protect marine ecosystems and the animals that rely on them for survival! 

Source: Jardine, A.M., Provencher, J.F., Insley, S.J., Tauzer, L., Halliday, W.D., Bourdages, M.P.T., Houde, M., Muir, D., Vermaire, J.C. (2023). No accumulation of microplastics detected in western Canadian ringed seals (Pusa hispida). Mar Pollut Bull. 2023 Mar;188:114692

DOI: 10.1016/j.marpolbul.2023.114692

Author: Laura Lopes


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