Deepwater Horizon: what will the future bring?

Disasters like Deepwater Horizon create long- and short-term effects. Our past two blogs have covered what happened immediately once the crude oil arrived on the shores of the Louisiana wetlands. This blog will look at how those wetlands recovered, and where things stand 10 years later. The good news is walking along the shoreline now, unless you were very familiar with the damaged area, most of the wetland life has sprung back up.

The previous blogs have dealt with immediate (up to 12 month) impacts on the coastal soils and wetlands and the discovery of oil deposits from the spill. This blog looks a few years to present, and how the area has recovered.

The biggest environmental impact was during this acute oil contamination period lasted during the summer and fall of 2010, and cleanup continued into 2011 and 2012 polishing up the removal effort along the coast. The coastal wetlands impacted by Deepwater Horizon began recovering.

In areas where the oil layer from Deepwater Horizon was light, the oil was soaked into the wetland soils. There, it was “eaten” by either plants or soil microbes. That’s a good thing. This could only happen in areas where the oil layer wasn’t too thick. Both plant roots and soil microbes need enough air to use hydrocarbons as a food source. This helped to reduce the amount of oil remaining in the soil over time.

Some plants that were partially covered with too much oil could still recover. If enough of the leaves and stalks were able to continue receiving sunlight and oxygen, the plants recovered. But, if plants were completely soaked by oil, then they died.

Erosion was also an issue in the effected areas. Soil microbes and plant roots both participate in controlling erosion – when they died, the soils were buffeted by tides and waves without protection. Many areas have been restored. But, some small wetland islands were completely lost.

Contamination also effected soil microbes and fauna that is soil-dwelling. Earthworms, nematodes, ants – all commonly present in sandy soils, would be deprived of oxygen and water if the oil was too thick. Healthy soils have pores between particles – and this is particularly true on beaches where most of the particles are sand. Further into the wetland areas, the soil would be a mixture of sand, silt and clay. Pore spaces were clogged in heavily contaminate areas. This could reduce soil aeration and water infiltration. Both contributed to erosion as well.

Many of us are familiar with the acute effect the oil spill had on larger animal life. We’ve seen commercials of detergents used to wash oil off bird feathers. Humans had to help in this case, because the birds or other animals with fur were unable to bathe themselves enough to remove the oil. Feathers and fur are important aspects to keep animals healthy.

There was a study on common loons in 2016 that showed some of their blood samples contained hydrocarbons. Loons spend the winters in the southern states, and the summers in northern US and Canada. The problem with testing for hydrocarbons in their blood is that loons are so mobile, and diesel exhaust, forest fires and more can cause high levels in bloodstreams. It’s hard to define where the loons – which live for an average of 25 years – picked up these contaminants in the last decade.

For aquatic animals, most that live near the wetlands have short life cycles. Fish, shrimp, oysters, and more live for only months to a few years. Ten years later, we are multiple generations beyond Deepwater Horizon. These seem to be mostly recovered.

There are still some small deposits of oil along the shore. They look a bit like asphalt lumps – because they are very similar in composition. The spilled oil spent time in the ocean, which is salty. Then it was exposed to oxygen in the air, as well as sunlight. As oil turned into jelly-like material, it also got bumped and bounced by tides and weather. All these effects create tar-like balls that remain.

Eventually, these remaining deposits will find their way back to the bottom of the ocean. In fact, most of the oil from the Deepwater Horizon spill was eaten by microbes or degraded by sunlight. Bacteria turn the oil into more bacteria and then these are eaten by other marine life, so that the oil eventually become part the animals that live in the Gulf. Some small amounts of  residue left from the oil spill ended up on the ocean bottom. The effects of this in deep waters is unknown.

What is known is that the oil that we drill and use in our daily lives to run machines, warm our homes, and power our cars, started out as decaying organic matter. This organic matter could come from zooplankton, algae, or plant material that fell to the ocean floor. Biological and geological processes turned this decaying organic matter into hydrocarbons millennia ago. Perhaps some of the remains of Deepwater Horizon are going through that process now, to be turned into future fuel.

Most of coastal Louisiana’s wetland is substantially recovered. It’s hard to find significant coastal long-term damage to nature. The effects of the spill disrupted many humans – whether through their jobs in fishing, their homes, or vacationers enjoying the Louisiana coast and all it offers. Chemical spills contaminate the environment and disrupt lives and economies. Disasters like Deepwater Horizon should always be avoided, to prevent acute contamination of our natural resources and the lived of our coastal communities.

By Ed Overton, Louisiana State University, retired

Read our other blogs about Deepwater Horizon here:

How did Deepwater Horizon’s spill affect the coastal soils and wetlands in the Gulf of Mexico?

Determining the impact of the Deepwater Horizon spill on soil

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