Oil, sand, and microbes

I’ve posted some references on the possibilities and the issues of oil-eating bacteria in the Gulf Coast clean-up attempts, but these were essentially focused on oil in the ocean (see this post and the links within it). But what goes on in the sand, in what is normally a thriving microcosm of critters in the spaces between the grains on the beach? A few days ago, Sean (who writes as “F”) pointed out a link to a press release from Florida Sate University on a new study of how fast microbes can break down oil in the beach sands of the Gulf of Mexico. The topic is far too interesting and important to be left stranded within a comment, so I thought that I would highlight it here.

The study began, on something of an emergency basis, in June, and is being headed up by oceanography professors Markus Huettel and Joel E. Kostka. As the introduction to the article describes:

A new Florida State University study is investigating how quickly the Deepwater Horizon oil carried into Gulf of Mexico beach sands is being degraded by the sands' natural microbial communities, and whether native oil-eating bacteria that wash ashore with the crude are helping or hindering that process.

What oceanography professors Markus Huettel and Joel E. Kostka learn will enable them to predict when most of the oil in the beaches will be gone. Their findings may also reveal ways to accelerate the oil degradation rate — and speed matters, because toxic crude components that remain buried on Gulf Coast beaches may seep into the groundwater below.

In many respects, the already degraded oil in the form of mats, pancakes, and tar-balls is relatively easy to clean up when it lands on the beach. Much more difficult and longer-lasting is liquid oil that seeps down into to the sand – and its effects are not very well known. In fact, the entire world between the grains of a beach is not very well known. One of the (many) great surprises that I encountered while researching my book was the incredible biodiversity of microscopic creatures that inhabit what Rachel Carson described as the “underground city” of the beach. Meiofauna (“lesser animals”) is the general term for this microscopic subsurface zoo, and I wrote a little about these extraordinary creatures in a post a year ago. In that piece I described how we should be grateful to these wondrous creatures because they keep our beaches clean, consuming undesirable bacteria. But, in the great scheme of things and the startling panoply of nature, we shouldn’t indulge in sweeping denigrations of bacteria – as we know from the oil-eating ones that live naturally in the ocean, there are many things that we should be grateful to them for.

But what happens when oily water, together with marine bacteria munching away, arrives on a sandy beach? How is the entire zoo affected? What happens as the oil percolates deeper and deeper into the sand, through the oxygen-rich layers where aerobic life thrives down into the anaerobic realms where there is no oxygen? The Florida State study will help answer these questions and, hopefully, provide some ideas on remediation methods. But it’s going to be a complex challenge:

Kostka said oil accumulations deposited on the beach surface are easily removed by, for example, scraping off the top layer of sand. However, the oil components that penetrate into the sand can only be removed by microbial degradation.

"If oxygen is present — as it is in the water and in the upper layers of the beach sand — the microbes decompose the oil aerobically (by using oxygen)," Kostka said. "This degradation process is much faster than the degradation under anaerobic conditions (when no oxygen is available), such as those found in deeper sediment layers of the beach. That's why at the site of the Exxon Valdez oil spill in Alaska, oil can still be found deeply buried in the gravel beach sediments, because anaerobic microbial degradation is slow and, in Alaska, slower still because of the cold climate."

"Unfortunately," said Huettel, "crude oil contains such harmful substances that even small amounts can kill fish larvae — which means that oil stored in deep layers of beach sediment presents a potential source of toxins to near-shore waters and groundwater."

Heavily oiled sand samples from a Louisiana barrier island (from the Florida State article)

Meanwhile, out in the ocean, there are reports of much increased bacterial activity. The Miami Herald recently carried an article in which Samantha Joye, a marine sciences professor at the University of Georgia at Athens, is quoted as saying "That's really, really surprising. Clearly the microbial community is responding rapidly and rigorously to the input of oil and gas." Let’s hear it for the microbes!

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And, while I’m at it, to return briefly to the vexing topic of the sand berms, the “Great Wall of Louisiana”. Discovery News recently carried a piece, borrowed from Len Bahr’s LACoastPost blog, with some interesting photographs of bulldozing the Chandeleur Islands. Well worth taking a look – I was reminded of the story of King Cnut…….

[header images from the US Coast Guard site]

 

Comments

[F]

Those images of the Chandeleur islands are quite telling. It is rather sad to see this operation of "destroy to protect", in which no actual protection occurs at all, anyway.

King Cnut, indeed. He would have known better.

The studies done by Samantha Joye are very interesting, especially because she is accounting for sub-surface oil, the existence of which some people are apparently denying.

I rather enjoyed your take on the FSU article. The subject matter is so interesting, but it is terrible that we learn of these things or get funding for studies only due to this ghastly eruption of crude oil. here's hoping the latest "fix' is more successful than the last.

[Perrykidposts.wordpress.com]

Thanks for summarizing this! I'm really curious to find out what happens with biodegradation on shore and in the ocean. I wonder if the dispersant will be found to be harmful or helpful to degradation - harmful because it may be toxic to microbes but potentially helpful because it increases the surface area available to microbes.

[Sandglass]

Good question! There seems to be a considerable range of views on the effects of the dispersants. Their toxicity is a matter of some debate (see, for example, http://www.reuters.com/article/idUSTRE6701KV20100802); perhaps their influence on bacterial activity is yet another aspect that we don't fully understand.....