Massive amount of Deepwater Horizon oil transported to the seafloor as marine oil snow

Massive amount of Deepwater Horizon oil transported to the seafloor as marine oil snow
An example of a funnel-shaped sediment trap, used to collect marine oil snow particles. (c) ECOGIG

October 04, 2016

A recent paper by ECOGIG researchers Dr. Uta Passow and Dr. Kai Ziervogel, published in the GoMRI special issue of Oceanography, describes in detail the formation of marine oil snow (MOS). The formation of marine oil snow is caused by the interaction of mucus created by microscopic animals floating in the water and oil- creating particles that are heavy enough to sink from the surface of the water to the seafloor. During and after the Deepwater Horizon accident in 2010, marine oil snow deposition rates were 4 times higher than before the spill, meaning a significant amount of the spilled oil made its way to the seafloor as marine oil snow. This was a surprising and unexpected event- it was assummed that the oil, which is less dense than water, would stay at the surface. 

Passow and Ziervogel used a combination of field and lab work to understand the mechanisms of oil incoporation into marine snow particles. Their field work included placing funnel shaped sediment traps that captured settling particles at their research sites in the Gulf of Mexico, marine snow cameras that took underwater photographs of marine snow concentration and abundance, and sampling sediment cores collected on research cruises to investigate the layering of material on the seafloor. Experimental lab work was used to investigate the mechanisms of marine snow formation in the prescence of oil under controlled, laboratory conditions. 

Their finding that oil can accumulate on the seafloor as marine snow after an oil spill has occurred has major implications for the animals that live at the seafloor, such as deepwater corals and bottom feeding animals (crabs, fish, shrimp, sea stars). These animals were heavily impacted by the oil from the Deepwater Horizon accident. 

These findings are also important for planning future responses to oil spills, as the response depends on the distribution of oil- skimming, burning and dispersing spilled oil at the surface of the water will not work to effectively recover all of the oil if a significant portion of it sinks to the seafloor as marine oil snow. 

To read more, you can access the entire paper "Marine snow sedimented oil released during the Deepwater Horizon spill" here.

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