This is the first study to make comparisons between marine species on how they interact with and respond to microplastics at concentrations found within the field. Sea urchins live on the sea bed and are omnivorous meaning that they eat a range of small animals as well as algae. Algae are generally soft in texture while smaller organisms can comprise of hard parts, such as small shells, tubes of worms, bone fragments. Some sea urchin species have stronger food preferences for softer food or towards food materials with more hard particles. We know that ingesting microplastics can potentially induce some physical damage along the gut, so this paper focusses on and identifies that those with experience of ingesting hard particles as part of their normal diet have a stronger resilience to ingesting microplastics compared to those ingesting mostly softer food materials. While more work is needed, this highlights the potential for feeding habit as a sensitivity indicator to microplastic ingestion which would be useful for waste management decision making organizations.
Here’s some information about the study:
Suckling, CC, (2020). Responses to environmentally relevant microplastics are species-specific with dietary habit as a potential sensitivity indicator. Science of the Total Environment. 751: 142341
Abstract: There is a lack of information on understanding how marine organisms respond to environmentally relevant microplastics (MP) which hampers decision making for waste management strategies. This study addresses this information gap by determining whether responses to MPs are species specific within a functional group. Benthic residing sea urchins, Psammechinus miliaris and Paracentrotus lividus were used as a case study. Psammechinus miliaris are strong omnivores with dietary intake including hard components (e.g. shell, tubeworms) and therefore likely to cope with the ingestion of MPs, while P. lividus are strong herbivores consuming softer dietary items (e.g. biofilms, algae) and therefore more likely sensitive. Responses to environmentally relevant MPs were conducted across two trials. Trial one determined the impact of short term (24 hours) external exposure to storm-like sediment resuspension of MP concentrations (53 μm polyvinyl chloride (PVC) 25,000 MP L-1) compared to a control without MPs. No significant impacts were observed for both P. lividus and P. miliaris on metabolic rate or righting time, and urchins were able to remove MPs from the body surface using pedicellariae and cilia. Trial two determined the impact of medium term (3 months) ingestion of a diet laced with PVC MPs (59 μm) at an inclusion rate of 0.5% mass and a control diet (without MPs) on somatic growth and animal condition. The ingestion of MPs did not significantly impact P. miliaris but significantly reduced the alimentary index within P. lividus, indicating a compromised nutritional state. This study shows that responses to microplastics are species-specific and therefore cannot be generalized. Furthermore, feeding habit could act as a potential indicator for sensitivity to MP ingestion which will be important for impact assessments of plastic pollution and management strategies.