Microplastics Ingested By All Sea Turtles

By current estimates, up to 12.7 million tons of plastic waste could be entering our seas and oceans annually. Typically, microplastics are categorized into two groups: primary – most commonly associated with exfoliators in cosmetic products, plastic pre-production “nurdles” and “microbeads” used in various industries, ranging from biomedical to air‐blasting technology and automotive tire wear or fibres from the breakdown of clothing; and secondary – from the disintegration of larger plastic items (macroplastics) via wave action, UV radiation and physical abrasion as the plastics are moved about and washed over shorelines.

As more and more incidences of plastic ingestion in animals are emerging, more research is being carried out to understand the possible physiological and ecological effects of their ingestion. For example, microfiber ingestion in crabs has been shown to affect food consumption and energy balance, while ingestion of microscopic PVC has been found to reduce growth and energy reserves in marine worms. Meanwhile, knowledge relating to ingestion of microplastics in marine turtles still remains very limited, even though previous research has shown that all seven species of marine turtles ingest macroplastics (pieces larger than 5 mm).

Despite ever-rising concerns over the environmental impacts of microplastics, knowledge of the incidence and levels of synthetic particles being ingested by large marine vertebrates is lacking. Quite simply, we know it’s a problem but we don’t have much of a concept of the scale got larger animals.

In this study, a group of scientists developed a method to explore whether synthetic micro-particles (smaller than 5 mm) could be isolated from marine turtles. The overall goals were to identify the extent of microplastic ingestion in all species of marine turtles and explore the polymer type of the ingested particles.

The findings are shocking – synthetic particles were present in every turtle subjected to investigation, which included individuals from all seven species of marine turtle, sampled from three ocean basins. The 100% incidence contrasts highly variable occurrence rates of recorded microplastic ingestion.

The non-fibrous microplastics included elastomers – flexible plastics. Here, the researchers highlight that a major contributor to their presence in the seas might be particles from tire wear, most of which reach marine ecosystems via road side run‐off. The scientists warn that since plastics are found in species occupying different trophic levels (omnivores and herbivores, predators and prey), multiple ingestion pathways are possible. These include exposure to polluted seawater and sediments, and additional trophic transfer from contaminated prey or forage.

In the future, the researchers hope to know whether microplastics affect aquatic organisms more subtly, too, for example, via exposure to associated contaminants such as heavy metals, persistent organic pollutants, PCBs and pathogens. The researchers argue that further research is necessary to answer which ingestion pathways are significant, and whether there are species and site‐specific variability.

Although the researchers suggest that microplastics are unlikely to present a significant conservation problem at current levels, animal advocates will surely see these warning bells as a need for action. A potential 100% exposure to ingested plastics is surely a welfare issue, in addition to the great threats that turtles are exposed to through fishery by-catch, the ingestion of macroplastics and entanglement in anthropogenic debris.