Plastic additives in muscle tissue of Western Mediterranean Sea turtles

Institute of Environmental Assessment and Water Research (IDAEA)
  • Chemical additives associated with plastics are detected for the first time accumulated in the muscles of loggerhead turtles in the Catalan and Balearic coasts.
  • The concentration levels of chemical additives found in the turtles are higher than in other species of marine animals, such as dolphins and whales.
  • This study shows that plastic pollution goes beyond the physical problem of big-size plastic litter, such as fishing nets or plastic bags, to be present on a chemical level.

 

In the area of plastic production, plasticisers or plastic additives are chemical compounds added to modify polymers, providing greater flexibility, strength, durability or other desirable characteristics. Some commonly used plasticisers include phthalates, organophosphate or aliphatic esters, among others. The applications of plasticisers are relevant in areas such as the production of consumer goods, coated fabrics, cables, film coverings, etc. The global demand for plasticisers follows an upward trend, and is estimated to become a market sized over $18,500 million by 2022, according to published reports.

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An individual of the species Caretta caretta after laying eggs on the beach.

In connection with the widespread use of plasticisers, the Institute of Environmental Assessment and Water Research (IDAEA-CSIC) and the University of Barcelona led a study that shows for the first time the accumulation of chemical additives associated with plastics in the muscle tissues of Mediterranean Sea turtles. Loggerhead turtles (Caretta caretta) is a species of turtle that may ingest floating plastic debris voluntarily, confusing them with prey. As a result, this species is chronically exposed to plastic additives. Alas, little is known about how this reflects in the levels of these compounds in the tissues of turtles.

 

Organophosphate esters in loggerhead turtles

Samples of the loggerhead turtle (Caretta caretta) were taken between 2014 and 2017 in the Catalan and Balearic Islands coasts (Spain). Organophosphate esters (OPEs) were the chemical compounds studied because some of them are known endocrine disruptors, exhibit neurotoxicity and/or have carcinogenic activity. Plasticisers were found in all of the turtles studied, ranging from 6 to 100 nanograms of OPEs per gram of muscle. Higher values were found in the Balearic turtles, which may be explained by these turtles coming from the Algerian basin, where a greater amount of plastic garbage is found in the sea.

To identify the possible sources of pollution, the diet of the turtles was analysed (jellyfish, squid and sardines), as well as samples of marine garbage that turtles ingest, such as bags, bottle caps and floating plastic fragments. OPE plasticisers were found in all samples. Although most of the compounds were present in the diet, the turtles and the garbage, some of them were only found in the turtles and in the garbage, showing that plastic intake is responsible for the presence of these pollutants in the muscle tissue.

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Contribution, in %, of detected organophosphate esters to the total levels in turtles, diet and plastics from Balearic Islands.

Although most compounds were present in both the turtles’ prey and in plastic debris, the distribution of plasticisers in loggerhead turtles if compared with these sources was different. Some organophosphate esters (T2IPPP, TPP and TBOEP), were detected in plastic debris and turtle muscle but not in their prey. This suggests that ingestion of plastic debris was the main source for these particular OPEs.

Contrarily, the levels of other OPEs (TEP, DCP, 2IPPDPP or 4IPPDPP) in turtle muscle were much higher than in jellyfish, their main prey, indicating a potential for biomagnification of these particular substances. Biomagnification is taking place if the concentration of the chemical in the animal exceeds the concentration present in its food source (as long as the major exposure route to the substance is the diet of the animal).

 

The invisible impact of plasticisers

Even though the overall impact of plasticisers in turtles is not well known, what is certain is that these chemical compounds are cause to oxidative stress on any type of cell (including human cells), according to a previous study from IDAEA. The cellular damage OPEs cause accelerates aging and may contribute to the development of diseases such as cancer, Parkinson's or Alzheimer's.

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Loggerhead turtles may ingest plastic matter voluntarily, confusing it with prey, such as these Aurelia aurita jellyfish.

Comparing with studies conducted on different marine species, such as whales or dolphins, some differences can be found regarding plasticiser accumulation. For instance, one can find that the levels of chemical additives associated with plastics are higher in loggerhead turtles. As points out the leader of the study Dr. Ethel Eljarrat, "turtles are more exposed to plastic garbage because they ingest macroplastics such as bags, which they confuse with jellyfish, while the ingestion of floating microplastics is more common in other species".

Eljarrat concludes indicating that "this study shows that plastic pollution not only has an impact at a physical level, when turtles get trapped and choke, but it is also present at a chemical level via the accumulation of pollutants, even though this is not visible to the naked eye”.

 

 

Image Credits:

Picture of loggerhead turtle by Luis Cardona provided by IDAEA and re-used with permission.

Figure with detected organophosphate plasticisers provided by IDAEA from the original research article, and re-used with permission.

Aurelia aurita jellyfish picture was downloaded from Flickr and licensed via a Creative Commons Attribution-NonCommercial-ShareAlike 2.0 Generic (CC BY-NC-SA 2.0) license.

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