Four months on from our blog entitled 'Deepwater Horizon Oil Disaster: What Next?' we thought now would be a good opportunity to look at the potential impact that the world's largest accidental marine oil spill has had on the marine environment, so we've been doing some reading!

Apart from the obvious unsightly effects associated with the spill of 5 million barrels in the Gulf of Mexico leading to vast slicks in the ocean; the indirect effects and those that we can't physically 'see' could be the most damaging. The Mississippi River delta is one of the world's richest river deltas, home to economically important shrimp & oyster fisheries, turtles, birds and various other species. Consisting of a variety of environments such as open bays, canals, salt & brackish marshes and freshwater swamps, the Louisiana Wetlands are (were?!) one of the most productive ecosystems in North America.

Reported effects of the oil spill so far include fish eggs and larvae that are at risk of being coated in microscopic particles of oil, which will persist up the food chain with consequences that scientists are still not sure of. Fishing grounds were shut around the Macondo oil well, and many fishermen found themselves involved in the cleaning up process as they tried to save the environment that their livelihoods so depend on. Even some of the chemicals used in the clean up process have since been reported as being toxic. Such 'dispersants' work by breaking down the oil and making it less cohesive so therefore rather than sitting on the water's surface it sinks, but this only begs the question in my mind: out of sight, out of mind?

It is still difficult to asses with actual numbers the true extent of the damage caused, especially as the oil can differ so much in how it is deposited on the coast depending on weather patterns, but it's fair to say that the results do not create a pretty picture. Considering that scuba divers still report evidence of oil from the 23 year old Ixtoc I spill (600,000 barrels of oil) also in the Gulf of Mexico does not fill us with hope. The impact of Deepwater Horizon still needs to be assessed on a range of levels (coastal, oceanic, benthic (sea floor), and inland (knock on effects on humans) and also at a range of scales (long & short term; local & regional) and also on a species and ecosystem level.

Does this spill mark the end of deepwater oil drilling? The odds are not in our favour. Due to shrinking onshore oil reserves and technological advancements leading to discoveries of offshore oil, a rush was ignited towards drilling in deep water. Before the Deepwater Horizon disaster, big oil spills had become something of a rarity, with tankers considered to be the main threat to the marine environment. Even the American federal agency that regulated the offshore drilling environment in the Gulf of Mexico claimed that the chances of a blowout were less than 1%. As fate would have it, they were wrong.

After much finger pointing over the blame, many factors were attributed to the devastation that was caused. It would be fair though to argue, as many do, that we are all to blame due to our own appetite for oil in the age of "the hydrocarbon man". In this instance, the cost of oil is not just reflected in the price at the petrol station.

For all of us who love to scuba dive, the news of the Deepwater Horizon blow out was devastating. Sadly the question remains in many people's minds of when, not if, the next spill will occur. Hopefully we will have learnt from our mistakes and the clear up response will be much more coherent to prevent the oil from not only damaging the environment, but quite possibly becoming part of it.

Photo Credits: Oiled brown pelicans: IBRRC. Deepwater Horizon on fire: US Coast Guard.