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News article7 December 2022Directorate-General for Environment

Green turtles in remote Azores feeding grounds are ingesting plastic, reveals new study

Issue 591: Analysing two decades of data on stranded turtles in the North East Atlantic, researchers have found that 14% of turtles were entangled in litter and 86% of those examined after death had ingested plastic. 

Green turtles in remote Azores feeding grounds are ingesting plastic, reveals new study
Photo by Willyam Bradberry, Shutterstock

This study indicates the effect of litter on turtles that feed near oceanic islands. Coordinated stranding networks which report marine mammals washed ashore either because they are sick or injured or have died, provide a crucial tool for studying species in remote locations, say the researchers.

Green turtles (Chelonia mydas), found near coastal areas in temperate, subtropical and tropical waters around the world, are on the IUCN Red List of Threatened Species. They are challenging to study in their juvenile stage, when they rapidly move from nesting beaches to the open ocean. In particular, there is scarce information on green turtles that feed in the open north-east Atlantic.

To improve the understanding of this species and how it interacts with marine litter, researchers analysed data on turtles stranded in the Azores archipelago between 2000 and 2020, collected by the Regional Stranding Network in the Azores (Rede de Arrojamento de Cetáceos dos Açores RACA)1. Entanglement in marine litter and marine litter ingestion (detected through stomach and intestine content of dead animals or by stool analysis in rehabilitated animals) were noted.

In total, 21 juvenile green turtles were found stranded in the region between 2000 and 2020, mostly on the islands of Faial and São Miguel. Three turtles were entangled in plastic fishing gear. Nine of the turtles were found dead and five of those found alive subsequently died. Of these 14 dead turtles, seven were given autopsies. A further seven were found alive, rehabilitated and released.

Most of the necropsied turtles were found to have ingested marine litter, and all litter items recovered from guts were made of plastic materials. The most common type of plastic ingested was hard white or transparent fragments, 1–25mm in diameter, contrary to other studies that have reported to have found plastic bags ingested by other species. This reflects the most abundant marine litter found on the coastline, say the researchers, who carried out 10 beach surveys in 2019 to estimate the composition of litter present in the marine environment in this area. It also reflects findings on plastic ingestion in other species, such as loggerhead turtles, in the Atlantic2. Hard plastic fragments may damage the gastro-intestinal tract, note the researchers.

When the researchers analysed the plastic using pyrolysis-gas chromatography/mass spectrometry (a sample is heated to decomposition to create smaller molecules that are separated by gas chromatography and detected using mass spectrometry), they found most ingested items were found to be polyethylene – the most commonly manufactured plastic globally, used in plastic bags, films and bottles, for example. They suggest that green turtles in the Azores may not be selecting specific litter items, but unintentionally consume floating litter while feeding.

This study provides the first baseline assessment of the interaction of juvenile green turtles and plastic litter on the east edge of the North Atlantic subtropical gyre (part of a large system of rotating ocean currents). Results indicate that migratory species such as these turtles, that use remote oceanic islands as feeding grounds, are exposed to anthropogenic litter, especially plastic, despite the distance from dense human populations or urban centres. Other animals that may be affected by plastic ingestion in remote locations include whales, albatrosses and penguins.

The researchers acknowledge that the small sample number in the study is a limitation for drawing robust conclusions, however, findings indicate the susceptibility of green turtles to feeding on plastic litter, with potentially major ecological consequences.

Footnotes:

  1. The Regional Stranding Network in the Azores, (Rede de Arrojamento de Cetáceos dos Açores) (RACA), was established in 1999. RACA is coordinated by the Regional Coordination Centre of the Direção Regional dos Assuntos do Mar (DRAM). It further relies on a network of institutional partners, including Maritime Authorities (National Guard – GNR/SEPNA and Maritime Guard –Policia Maritima), which organise operational centres on each island and the island natural parks. In addition, this network also cooperates with a wide variety of stakeholders, including veterinarians, tourist operators, professional fishers, volunteers and scientists.
  2. Pham, C.K., Rodríguez, Y., Dauphin, A., Carriço, R., Frias, J.P., Vandeperre, F., Otero, V., Santos, M.R., Martins, H.R., Bolten, A.B. and Bjorndal, K.A. (2017) Plastic ingestion in oceanic-stage loggerhead sea turtles (Caretta caretta) off the North Atlantic subtropical gyre. Marine Pollution Bulletin, 121(1–2): 222–229.

Source:

Rodríguez, Y., Vandeperre, F., Santos, M.R., Herrera, L., Parra, H., Deshpande, A., Bjorndal, K.A. and Pham, C.K. (2022) Litter ingestion and entanglement in green turtles: An analysis of two decades of stranding events in the NE Atlantic. Environmental Pollution, 298: 118796. Available from: https://doi.org/10.1016/j.envpol.2022.118796

To cite this article/service:

Science for Environment Policy”: European Commission DG Environment News Alert Service, edited by the Science Communication Unit, The University of the West of England, Bristol.

Notes on content:

The contents and views included in Science for Environment Policy are based on independent, peer reviewed research and do not necessarily reflect the position of the European Commission. Please note that this article is a summary of only one study. Other studies may come to other conclusions.

Details

Publication date
7 December 2022
Author
Directorate-General for Environment

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