Oil Spill Linked with Mass Mortality of Sea Snakes

FROM THE GULF OF OMAN, COAST OF SHARJAH

BY FADI YAGHMOUR

Marine biodiversity has suffered significantly from the impacts of anthropogenic activities including unsustainable exploitation of marine resources, development of coastal habitats, climate change and the release of pollutants into the marine environment. In the United Arab Emirates (UAE), plastics and other forms of marine debris have enjoyed a great deal of well deserved attention by researchers, policy makers and the wider public over the past few years. Yet other forms of marine pollution remain persistent in a region that depends heavily on fossil fuels. The lethal impacts that oil spills have on marine fauna has been extensively documented in the scientific literature. Heavy surface oil can mire and kill organisms that dwell near the surface. As such, seabirds were frequently documented to be affected by poisoning or suffocation in oil. Sea turtles are also documented to suffer greatly from the impacts of oil spills as they may ingest oil, inhale toxic fumes or get coated in sticky viscous oils that restricts their mobility. Oil spills also cause widespread contamination of food items leading animals to become malnourished or chronically poisoned. A great deal of our knowledge regarding these impacts was derived from studies conducted during large and catastrophic oil spills such as Exxon Valdez and Deepwater Horizon. However, as these spills were restricted to the Pacific Ocean, our knowledge on spill related impacts is also restricted to the species that occur there. The global distribution of sea snakes, the most biodiverse group of marine reptiles, is largely limited to the Indo-West Pacific. In a recent study, published in the scientific journal Science of The Total Environment, titled “Oil spill causes mass mortality of sea snakes in the Gulf of Oman”, the Environment and Protected Areas Authority of Sharjah (EPAA) reported the first ever assessment of sea snake mortalities caused by an oil spill.

On the evening of the 12th of November 2021 the EPAA received reports from local fishermen of seagulls drenched in oil found afloat in the coastal waters of Kalba.The injured birds were rescued and transported to the EPAA’s Breeding Centre of Endangered Arabian Wildlife (BCEAW) where they were provided with veterinary support and treatment. Over the next two days viscous oil and tar balls were observed washed ashore along the coast of Kalba. It is not known whether the pollution source was accidental crude oil spillage or intentional, illegal bilge discharge. During this time, monitoring efforts by the EPAA’s Sharjah Strandings Response Program (SSRP) were intensified to where beach surveys were conducted twice daily along the entire Kalba coastline.This escalation continued until the 19th of November when the die-off related to the spill appeared to have ended.

Live strandings observed and rescued during this period underwent veterinary treatment and rehabilitation until they were healthy and fit for release. EPAA veterinarians and scientific researchers examined dead strandings to determine the cause of death and collect biological and toxicological data. Overall, 48 strandings were reported from the 13th to the 19th of November 2021, of which 39 (81.3%) were sea snakes. Of the 39 stranded sea snakes reported, 37 were collected and underwent post-mortem examinations. The investigated sea snakes belong to four different species: yellow-bellied sea snakes, Arabian Gulf coral reef sea snakes, Yellow sea snakes and ornate sea snakes. The majority (84.6%) of sea snakes were observed to have oil covering 75-100% of their bodies. This level of external oiling is enough to immobilise the sea snakes causing them to drown, overheat or starve. Sea snakes are also capable of transcutaneous oxygen uptake, meaning they rely on their skin to breath which makes external oiling even more hazardous to them. Furthermore, the majority (91.4%) of sea snakes were also observed with oil covering their snouts and eyes, further compromising their ability to breath. Finally, a large proportion of sea snakes were observed with oil in their mouth (25.8%), esophagus (41.4%) and stomach (34.5%).

It is likely that sea snakes are significantly more susceptible to the hazards of oil inundation in marine environments than previously considered. Furthermore, the abrupt increase in sea snake strandings observed by the SSRP coinciding with the oil spill suggests that these events, even at small scales, may be a significant factor in the morbidity and mortality of sea snakes in the Gulf of Oman. The EPAA is conducting further work to better understand the acute and chronic risks that oil spills and other marine pollutants pose to sea snakes.