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Plastic Pollution and Small Juvenile Marine Turtles: A Potential Evolutionary Trap
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This study investigated microplastic ingestion by commercially harvested Pacific oysters from aquaculture sites at varying proximity to a major urban estuary, finding body burden correlated with site proximity to urban inputs. The study estimated the average consumer microplastic intake from regular oyster consumption and found values that exceeded estimates from other dietary sources for frequent consumers.
The ingestion of plastic by marine turtles is now reported for all species. Small juvenile turtles (including post-hatchling and oceanic juveniles) are thought to be most at risk, due to feeding preferences and overlap with areas of high plastic abundance. Their remote and dispersed life stage, however, results in limited access and assessments. Here, stranded and bycaught specimens from Queensland Australia, Pacific Ocean (PO; n = 65; 1993–2019) and Western Australia, Indian Ocean (IO; n = 56; 2015–2019) provide a unique opportunity to assess the extent of plastic (> 1mm) ingestion in five species [green ( Chelonia mydas ), loggerhead ( Caretta caretta ), hawksbill ( Eretmochelys imbricata ), olive ridley ( Lepidochelys olivacea ), and flatback turtles ( Natator depressus )]. In the Pacific Ocean, high incidence of ingestion occurred in green (83%; n = 36), loggerhead (86%; n = 7), flatback (80%; n = 10) and olive ridley turtles (29%; n = 7). There was an overall lower incidence in IO; highest being in the flatback (28%; n = 18), the loggerhead (21%; n = 14) and green (9%; n = 22). No macroplastic debris ingestion was documented for hawksbill turtles in either site although sample sizes were smaller for this species (PO n = 5; IO n = 2). In the Pacific Ocean, the majority of ingested debris was made up of hard fragments (mean of all species 52%; species averages 46–97%), whereas for the Indian Ocean these were filamentous plastics (52%; 43–77%). The most abundant colour for both sites across all species was clear (PO: 36%; IO: 39%), followed by white for PO (36%) then green and blue for IO (16%; 16%). The polymers most commonly ingested by turtles in both oceans were polyethylene (PE; PO-58%; IO-39%) and polypropylene (PP; PO-20.2%; IO-23.5%). We frame the high occurrence of ingested plastic present in this marine turtle life stage as a potential evolutionary trap as they undertake their development in what are now some of the most polluted areas of the global oceans.
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Plastic and marine turtles: a review and call for research
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This review examined evidence for plastic debris effects on all seven marine turtle species, finding they all experience ingestion or entanglement, with documented consequences including intestinal blockage, dietary dilution, malnutrition, and death. The authors also highlight how plastic pollution on nesting beaches can alter nest temperature and sediment permeability, potentially affecting sex ratios and reproductive success.
Plastic Ingestion in Post-hatchling Sea Turtles: Assessing a Major Threat in Florida Near Shore Waters
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Plastic fragments were found in the digestive tracts of 93% of stranded juvenile loggerhead sea turtles examined in Florida, with up to 287 fragments and a plastic-to-body weight ratio as high as 1.23%. The high ingestion rates in animals this young suggest that plastic pollution poses a serious threat to sea turtle survival from the earliest life stages.
Differential impact of marine debris ingestion during ontogenetic dietary shift of green turtles in Uruguayan waters
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Researchers analyzed gut contents of 96 stranded green turtles from Uruguay and found debris in 70% of individuals, with hard plastics most abundant by weight; smaller (juvenile) turtles had significantly more debris ingestion, identifying the early juvenile life stage as particularly vulnerable to plastic pollution in the southwestern Atlantic.
Association of ocean macroplastic debris with stranded sea turtles in the Central Gulf of Thailand
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Researchers retrospectively analyzed records of 388 stranded sea turtles in the Central Gulf of Thailand from 2017-2020 and examined macroplastics from the gastrointestinal tracts of 30 dead turtles and 13 beaches, finding that green turtles (Chelonia mydas) comprised the majority of strandings and that plastic ingestion and entanglement were significant mortality factors.
A Preliminary Report of Plastic Ingestion by Hawksbill and Green Turtles in the Saudi Arabian Red Sea
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This preliminary study examined plastic ingestion in ten deceased sea turtles collected along the Saudi Arabian Red Sea coast. Forty percent of the turtles had ingested plastics, predominantly thread-like fragments, underscoring the need for long-term monitoring of plastic pollution impacts on marine megafauna near major coastal development projects.
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When a large batch of papers lands in the Atlas, we read through it and send a short write-up of what stood out.