Gulf oil moving deeper, not disappearing

Aug 17 2010

The gulf oil is moving into "deeper waters," according to USF scientists where phytoplankton and other basal organisms will be threatened. I've been reading stories like this for a week, scientists concerned about the settling oil on the ocean floor and the potential toxic effect on the food chain.

This is in addition to GA scientists stating that 80 percent of the spilled oil lingers in the Gulf's waters, starkly contrasting the claims by the US gov that it's mostly gone.

7 responses so far

  • Bill K says:

    Why would the oil "settle"? I thought oil was lighter than water and hence floats. Also, phytoplankton do not live on the ocean bottom. By definition they are plants, requiring sunlight and thus living on the surface.

    • jeremy says:

      Clarity issue on my end Bob, just tossed up the links when I found them. They're concerned with the oil plumes moving into deeper columns, which threatens plankton further out from shore, as well as the heavier portions of the dispersed/separated oil sinking to the sea floor and poisoning organisms there. From what I understand, these can travel great distances. Jen's exactly right.

      Two separate but connected issues that I jumbled a bit. Thanks for pointing that out.

      • jeremy says:

        Another note I forgot to mention: since oil is actually an assemblage of a whole bunch of different hydrocarbons and other organic compounds, it's hard to determine just how the dispersants are affecting the spill, especially in concert with natural biological agents, currents and the seawater itself. Parts will float, some evaporates, some remains suspended in plumes and the heavier stuff sinks. It might be in dozens of different states at this point.

  • Jennifer says:

    It's my understanding the the dispersant they used caused the oil to settle on the ocean floor. The dispersant is really bad stuff.

  • ctenotrish says:

    Hi Bill K,

    Another thing that is not often known when it comes to phytoplankton is that many species are motile, and they undertake vertical migration as well. See below for a paper that models vertical migration of phytoplankton. Basically, the nutrients are in deep water, and the light is (of course) shallow. They need both . . . and they actively move through the water column to get to each. http://plankt.oxfordjournals.org/cgi/content/abstract/29/9/803

  • bowsprite says:

    BP contracted a few of our NYHarbor tugs to go down there to 'help skim' the oil, however because of the dispersants they applied (and seas and weather), it was impossible. It was days and days of ineffective activity, and friends return from their 2 week hitches, saying in disgust: "Some people are making a LOT of money down there..."

    Keep in mind:
    http://www.nytimes.com/2010/07/30/us/30gulf.html?_r=4

  • Gerald R. Campbell, Ph.D. says:

    The reason the oil is settling is that it is being separated into its various components. Some, like the VOCs and short- to medium-chain aliphatics, are lighter than water, by quite a bit. But others, including most of the more complex and more toxic stuff, is actually heavier than water - not by much, but a little. (Louisiana crude is "heavy", which refers to a density greater than 0.93; it is actually higher than that, but that is the minimum definition for heavy crude. That means it has a higher percentage of the more dense, more complex molecules compared to, for instance, Saudi crude, which is "light.")
    The addition of dispersants has allowed the various components to separate, and dispersant molecules intertwine (at a molecular level) with the various components, also making them more dense. There is also a weathering factor, chiefly by evapooration of light components, and UV irradiation. The UV causes molecular cross-linking, increasing density even more.

    the NOAA chief blithely made the assertion that "there is no evidence" for bioaccumulation of toxic oil components or dispersant. She also asserted that "the oil" will be broken down by "the fish." There is no evidence that it does because there is NO EVIDENCE. There isn't even a method for detecting Corexit in biological tissues, never mind one validated as reproducible and sensitive. Plus, the biodegradation process, as with evaporation, largely eliminates the lighter components, effectively concentrating the more toxic ones. Keeping them suspended as small particles ensures that filter feeders like clams and oysters will receive a huge dose. (I noted earlier that one report stated that clams and oysters "broke down" the oil least quickly - but that could also mean that they are continuing to receive exposure to suspended oil components & Corexit.) Fish may be able to avoid a lot of the pollution simply by changing depth or swimming away, but that alternative is not available for mollusks and crustaceans. I expect that, whatever assurances NOAA and the FDA give, Gulf oysters, clams, crawfish and shrimp will continue to be polluted for some time - the only questions are how much, and how large an effect they will have.

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