Oceans, caught between devil and the deep blue sea… (Pun intended!) – XV

Oil spills are a byproduct of human activity in which oil is leaked “from ships, shore facilities, pipelines and offshore platforms” into oceans causing catastrophic situations. Despite popular belief, that the most significant contributors to oil spills are tankers and ships that carry large amounts of oil; most considerable contributors are automobiles, boats, industrial plants, and machinery. Urban run-offs into oceans also carry huge oils with them spilled on roads.  All this oil eventually reaches the sea where it harms marine ecosystems. The severity of oil spills, however, is influenced by many factors, including the type of spillage, the quantity of oil, and the effects of tidal waves.


It is clear that the impacts of an oil spill depend hugely on the circumstances. Spill volume is only one factor and not necessarily the most important. Oil source and type, wave action, water depth, the amount of sediment in the water, winds, and tides, temperature and how close the spill is to the shore can make the difference between no detectable impact and a severe impact on many resources. The combination of these physical and chemical factors will also determine which habitats are exposed to the oil and in what form. A slick of oil on the water surface, a cloud of oil droplets in the top few meters of the water column, a floc of oiled particles on the seabed, a plume of oil rising from a subsea release, a coating of oil on a shoreline – can be examples of various situations. 

According to the U.S. Fish and Wildlife Service, oil spills can be classified into five categories: very light oils, light oils, medium oils, heavy oils and very heavy oils.

Very light oils, such as gasoline and jet fuel, are extremely toxic to marine organisms, but evaporate rapidly in water, so cleaning of spills of this type is unnecessary.

Light oils, such as diesel, leave a residue in water and have long-term consequences on ocean life. Although light oils have fewer toxins than very light oils, they are still damaging. Nevertheless, light oil spills can be cleaned efficiently.

Fractional_distillationMedium oils, including crude oils like petroleum, do not evaporate quickly. As such, these oils can devastate marine communities residing in intertidal areas, or areas between high and low waters. Medium oils are especially threatening to birds and mammals as they can adhere to their feathers, hair, or fur. Cleaning up medium oils is most successful if done immediately following the spill.

Heavy oils, on the other hand, are less likely to evaporate in water and can be exceptionally detrimental to aquatic life. Heavy oils are known to injure birds and mammals that come in contact with the contaminated site. Decontaminating areas in which heavy oils have been spilled is also very challenging.

Very heavy oils, also known as Group V oils, are capable of hovering and diffusing into the water, affecting animals like lobster, which subsist on ocean floors. While Group V oils are not as toxic as the lighter oils, finding and pinpointing these oils is a difficult task (3).

In addition to killing many sea dwellers, oil spills can also impact the health of those that survive. Oil can modify invertebrate feeding habitats, disrupt their shell development, and cause slow suffocation. Bottom-dwelling invertebrates are especially at risk when oil accumulates at the shoreline. Many bottom-dwellers can survive oil contamination; however, they transmit these toxins to their predators, leading to increased concentration of the toxins in higher species. From oil spills, fish can experience impeded growth, respiratory and cardiac malfunction, and stunted larval development. As a result, survival rates for offspring are low.

Oil spills can similarly thwart plant development. They can also spur the growth of specific algae populations. When oil directly contacts birds, it can get in their feathers, which impedes their abilities to fly. As a result, many birds drown while others die of hypothermia. If oil is ingested, kidney, liver and lung damage often results, usually followed by death. Other side effects include an inability to reproduce, abnormal behaviors, a debilitated immune system, and skin irritability.

Humans can also be affected by oil spills. In Ogoniland, Nigeria, for example, the people have dealt with nearly 50 years of oil production and water contamination. Many communities are faced with dangerous levels of carcinogens, cancer-causing agents. In one such community, families are drinking water polluted with benzene, a type of carcinogen, at a concentration 900 times that considered to be safe. In other areas of Ogoniland, nearly eight centimeters of oil was found on top of the water. This horrific spill has so far killed tens of thousands of people, as well as livestock, and is predicted to take up to 30 years to reach its former clean state. Altogether, it will cost approximately $1 billion to rebuild the area. The Shell Oil Company, which was responsible for the spill, has neglected the impact this spill has had on the Nigerians. They have, however, taken responsibility for the recent 2008 and 2009 oil spills.

As of Ogoniland issue, I am also giving separately “United Nations Environment Program (UNEP) Ogoniland assessment” for your reading interest. 


  1. W. Farrington, J. E. MacDowell, Mixing Oil and Water (2004).
  2. Effects of Oil Spills on Wildlife and Habitat (2004). – US Fish & Wildlife Service
  3. Oil and Nature (October 1998). – US Fish & Wildlife Service
  4. Nigeria Ogoniland oil clean-up ‘could take 30 years’ (2011). On BBC, UK website

Milind Joshi


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