Impacts of Oil Spills on Marine Biodiversity

Its estimated that most oil spills occur because of daily operations, mostly in oil or port terminals. However, there are still occasions where oil spills occur due to oil exploration, extraction and production or through transporting oil by sea and these vessels crashing or running aground (Fingas, 2019). These tend to have great impacts on the local marine biodiversity. An example of an oil spill that occurred due to oil extraction is the BP Deepwater Horizon blowout in the Gulf of Mexico in 2010. An example of the latter occasion is the recent MV Wakashio oil spill near Mauritius. This essay aims to address the impacts of oil spills on marine biodiversity, in relation to goal 14, “Life Below Water”, of the Sustainable Development Goals (SDGs).

Causes of Oil Spills

From 1970 to 2019, half of the large oil spills occurred in open seas, of which more than half were because a ship hit another vessel, ran aground or hit something in the water. These spills were even more frequent when the vessel was navigating inland waterways or ports and harbours. A small amount of these spills also occurred during loading and discharging of the vessel, hull or equipment failure, fire or explosions or any weather-related damage. The size of oil spills has been split into three categories: less than 7 tonnes, between 7 tonnes and 700 tonnes, and more than 700 tonnes. Since 2014, the number of spills greater than 7 tonnes due to collisions of some sorts has been greater than in previous decades at around 44% (Singh Khadka, 2020).

Damage from Oil Spills

The extent of the damage from an oil spill depends on various factors, including the location of the spill, the prevailing weather conditions, the response time to help with controlling the oil spill and the volume of the oil spilt (Fingas, 2013). Many of the impacts on marine life will depend on what species there are at the location as well as the amount of oil spilt. However, as oil is less dense than seawater, it will create a thin film on the water surface and float. The floating oil will stick to the fur and feathers of marine mammals and birds causing them to lose their insulating and water-repelling properties, exposing them to the cold. In addition, marine species will often ingest the oil residue, causing them to die or have health problems (Singh Khadka, 2020).

Oil Spill Occurrence

Fortunately, the number of oil spills occurring annually is decreasing (see figure 1). This may be due to tighter regulations and improvements in safety standards, for example the introduction of double hull vessels (ITOPF, 2020). The International Maritime Organisation (IMO) has also introduced a new fuel oil to be used from January 2020. This is a low sulphur oil to help reduce air pollution (Alfalaval, 2018).Deepwater Horizon

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The BP Deepwater Horizon oil rig exploded on the 20th April 2010, due to a failed blowout protector. This caused nearly 400,000 tonnes of oil to spill into the Gulf of Mexico, of which 800,000 barrels of oil were collected with booms (Kaiser et al., 2011), over 87 days and contaminate about 1,300 miles of coastline (Borunda, 2020).

Impacts of the oil spill

It killed thousands of species, ranging from plankton to dolphins. Fish absorbed some of the oil-sourced contaminants, while a recorded 1000 dolphins died in the following month due to ingesting toxins from the oil. The long-term impact of the oil on longer lived species like dolphins, whales and turtles is still unknown, but the dolphins who didn’t die due to toxin ingestion, have been ill ever since. Some of the hardest hit animals were birds, which may have led to a population explosion for fish of species like the Gulf Menhaden. However, many species, like deep-sea coral, common loons and spotted sea trout are still struggling, their populations being partly lower than they have been before (Meiners, 2020). Other severe impacts are impaired reproduction and reduced growth as well as disease and lesions. The Red Snapper was found to have skin lesions until 2012 when they became less severe and frequent (Borunda, 2020). The impacts on the local wildlife can still be seen today and recovery may take another few decades (Meiners, 2020).

MV Wakashio Oil Spill

On the 25th July 2020, the MV Wakashio, a large bulk carrier vessel, ran aground coral reef near Pointe d’Esny, on the southern coastline of Mauritius (Lewis, 2020). On the 6th August, the hull broke into two which was when the majority of the oil onboard leaked into the ocean. The vessel had around 4,000 tonnes of oil abroad – 200 tonnes of marine gas oil and 3,900 tonnes of fuel oil. Of the 4,000 tonnes of oil, only about 1,000 tonnes were spilt as the local government was able to pump the majority of the oil elsewhere (ITOPF, 2020). Due to the new IMO regulations, the vessel was carrying low sulphur fuel oil. This oil spill was the first of its kind under these regulations, and thus the long-term effects of the low-sulphur oil are unknown (Lewis, 2020).

Impacts of the Oil Spill

Although only 15 km of coastline was smeared with oil, Pointe d’esny is near wetlands that are designated as a site of international importance under the Ramsar Convention on Wetlands and a known sanctuary for wildlife unique to Mauritius (Lewis, 2020). The area is home to about 1,700 different species including 786 types of fish, 17 marine mammals and two turtles (UN Convention on Biological Diversity). Because of the oil, these animals are at risk of drowning which has direct consequences on Mauritius’ already weakened economy (Greenpeace Africa, 2020). This decline is caused by the lack of tourism due to the ongoing pandemic. In addition, the toxic hydrocarbons released from the oil bleaches the coral which is bad as the coral become vulnerable which in turn affects other species that depend on them (Singh Khadka, 2020).

Conclusion

In conclusion, oil spills tend to have similar impacts on marine biodiversity, the extent of which depends on factors including location, prevailing weather conditions and response time. Usually, the spills end with health problems in marine species, possibly even death. Often the effects are still seen years later, as in the case of the Deepwater Horizon explosion. The long-term effects of the new low sulphur fuel oil that the MV Wakashio was carrying, are still unknown.