Plastic Pollution and Small Juvenile Marine Turtles: A Potential Evolutionary Trap

Abstract

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.

Occurrence of Macro- and Micro-Plastics on Pasir Pandak Beach, Sarawak, Malaysia

“…Clear plastics seemed to be due to the breakdown process where the plastic wastes were exposed to the UV radiation and mechanical stress caused by the wave movement at the beach (Lechthaler et al, 2020). Duncan et al (2021) reported that clear (36 %), white (36 %), green (16 %), and blue (16 %) were the dominant colors found in turtle stomachs from the Pacific Ocean regions, with the most common polymers identified were PE (58 %) and PP (20.2 %). These ingested plastics were usually found as hard fragments (52 %), filaments (52 %), and plastic sheet (38 %) with sizes from about 5 mm to approximately 220 mm.…”

Overview of Effect of Plastic Waste Pollution on Marine Environment

“…Plastic reaches the turtles through random feeding, as turtles sometimes do not differentiate between food and plastic, especially that plastic, which is very similar to turtle food [21]. There are two ways for plastic to reach sea turtles direct and indirect road, direct ingestion of plastic parts and bags where this is observed in all types of sea turtles Figure 2 [22,23]. Ingestion sometimes occurs directly when plastic pieces are mixed with the food of choice for these sea turtles, for example, a study found that small green turtles (Chelonia mydas) inside their digestive system contain pieces of plastic because they feed on a type of macro algae that had plastic pieces attached to it Di Beneditto and Awabdi [24].…”

Public choice for payment vehicles of turtle conservation in Terengganu, Malaysia

“…WWF Malaysia (2020) discovered that if a turtle ate just one piece of plastic, it had a 22% chance of dying. The ingestion of plastics by sea turtles is found in all species (Duncan et al 2021). The plastics' sharp edges can damage their internal organs and can cause intestinal blockages, making them unable to feed which leading to starvation.…”