EPAA Reports High Levels of Marine Debris in Four Species of Sea Turtles in Sharjah

In the past few decades, we observed an ever increasing interest by the scientific community, policy makers and the wider public on the creeping and growing threat of plastics and other anthropogenic waste in the marine environment. It was estimated that approximately 275 million metric tons of plastic waste were produced in around 200 coastal countries, and that roughly 4.8 to 12.7 million tons of that waste are entering the ocean. A later estimate suggested that, in 2015 alone, 144 million tons of single-use plastic products were produced (approximate equivalent to the weight of 20.5 million African elephants), while a mere 9% of global plastic waste has been recycled. When exposed to natural environments, plastics undergo weathering and degradation into fragments or microplastics, increasing their dispersal into different marine environments. Today, plastics and other forms of anthropogenic marine debris occur in every reservoir of freshwater and marine habitat in the world. Consequently, sea turtles are exposed to harmful interactions with marine debris through all of their life stages. Beached marine debris, also known as beach litter, can act as a barrier for gravid (pregnant) sea turtles crawling onto nesting beaches. This forces these turtles to spend additional energy and time through the nesting process, thereby increasing their exposure and risk to predators. Hatchlings are also subject to entanglement or entrapment in beach litter. Marine debris also has significant impacts on the habitats that marine turtles depend on through the introduction of harmful non-native species which hitch-hike onto floating marine debris. Marine debris also causes direct damage to corals, sea grass and other marine habitats that turtles depend on. Still, through all of their life stages, marine turtles are primarily threatened by the risks associated with ingesting or being entangled by marine debris.

Loggerhead sea turtles.

In two recent studies published in the Marine Pollution Bulletin titled“Junk Food:Interspecific and Intraspecific Distinctions in Marine Debris Ingestion by Marine Turtles” and “Junk Food: A Preliminary Analysis of Ingested Marine Debris by Hawksbill Eretmochelys imbricata and Olive Ridley Lepidochelys olivacea Sea Turtles (Testudines: Cheloniidae) from the eastern coast of the United Arab Emirates”, the Environment and Protected Areas Authority (EPAA) investigate the ingestion of marine debris by four species of sea turtles from the Gulf of Oman coast of the UAE. This was done through the investigation of the gut contents of the dead, stranded sea turtles as part of the activities of the EPAA’s Sharjah Strandings Response Programme (SSRP). This included the sampling of 36 green, 14 loggerhead, 7 olive ridley and 6 hawksbill sea turtles from the coasts of Kalba and Khor Fakkan. Marine debris were detected in 83.3% of hawksbills, 75% of greens, 57.1% of loggerheads and 28.6% of olive ridley sea turtles. To put these numbers into context, a previous similar study from the same area conducted in the late 1970s by Dr John Perran Ross found no evidence of marine debris ingestion in green sea turtles from Oman. This suggests a drastic and rapid increase in debris ingestion by marine turtles in the region. The reported high frequency of marine debris ingestion by hawksbill sea turtles examined in these studies is consistent with the literature which suggests that the omnivorous hawksbill sea turtles most frequently ingest marine debris, followed by the herbivorous green sea turtles, while carnivorous species (which includes olive ridley and loggerhead sea turtles) were the least likely to ingest marine debris.

Ingested by loggerhead sea turtles.

Ingested by green sea turtles.

In terms of quantities of ingested marine debris, we observed that green and loggerhead sea turtles do ingest the highest quantities of marine debris, particularly plastics. The results convey that green sea turtles are likely to ingest soft items such as threads (ropes, fishing lines and fishing nets) and sheets (plastic bags and plastic wrappers) because of their similarity to algae, seagrass, cuttlefish and jellyfish. On the other hand, loggerhead sea turtles appear more likely to favour hard items such as bottle caps and other hard plastics because of their similarity to gastropods and bivalves. Overall, when considering the amount, frequency and type of ingested marine debris, green sea turtles, particularly younger specimens, carry the highest risk of ingesting marine debris. The reason young green sea turtles may be ingesting so much marine debris is because young green sea turtles are opportunistic feeders with a very flexible diet consisting of both plants and animals. This flexible feeding habit may cause them to be less capable of discriminating their natural food from marine debris. Overall, plastics were observed to be the most predominant debris ingested in all species. While, non-plastic rubbish, particularly metallic fishing gear (fish hooks and gargour fish traps) were observed to present significant and lethal hazards by puncturing the digestive tract. In light of this, and previous studies, the evidence strongly suggests that marine debris as well as other pollutants are an important threat to marine turtles in the region.

Protection of marine turtles from ingesting marine debris cannot be separated from broader actions intended to prevent waste from escaping from waste management streams into the marine environment. Further work is needed on a policy level to halt the global stream of plastics and other waste products from entering the environment. Individuals from the general public have an important role to play as well. The high consumer demand for single-use plastics and other single-use products is a key factor behind the increasing levels of marine debris. Readers are encouraged to reconsider the unnecessary use of single use items, learn how to correctly recycle in their area and most importantly avoid littering behaviour.

EPAA researchers responding to stranded turtle.

ABOUT SSRP:

Sharjah Strandings Response Program

Through the examination of stranded marine reptiles, marine mammals and sea birds, this programme, led by the Environment and Protected Areas Authority (EPAA), aims to expand the existing knowledge on the biodiversity, ecology and threats of marine fauna in the Emirate of Sharjah, UAE.

This knowledge would support the development of evidence-based conservation action and policy in the region as well as educate the wider public on the importance of conserving species and other emerging issues. Additionally, this programme acts as an important tool for the response and rescue of live strandings.