Oil Found Deep in Gulf Is Toxic to Tiny Marine Life

Gulf oil
Oil droplets become visible when displayed under an ultraviolet light
ST. PETERSBURG (2010-8-17) -

The capping of BP's Deepwater Horizon well hasn't stopped oil from affecting marine life in the Gulf. Oil is now being found on the ocean bottom far from the well site.

A 10-day expedition to the northern Gulf by USF scientists has found oil in microscopic plankton that makes up the base of the marine food chain. Marine geochemist David Hollander says this could affect the entire ecosystem of the Gulf.

"The idea that this could have an impact on the food web and on the biological system is certainly a reality," says Hollander. "This is not addressing the question of turtles or of sharks or of birds, which are at the top of the food web, but rather the organisms that are at the base of the food web."

That means that oil ingested by plankton will likely be eaten by fish - and eventually consumed by land-based animals.

These preliminary results came from the research vessel Weatherbird Two, which is based at the Florida Institute of Oceanography in St. Petersburg. Hollander says bacteria at the Gulf's surface seem to be particularly sensitive to oil, while plankton on the ocean bottom are affected more by the dispersants used by BP.

"The smaller organisms seem to be affected more quickly. So things like fish larvae, which could see small droplets, could consume them," he says. "And that's 100 percent oil. Fish eggs - if they're in that environment - they may not be consuming it, but it's like paint in the air. You breathe it at low concentrations for a long enough time, you're still going to have that response."

And oil has been found on the Gulf's bottom - the furthest east it's been found. The expedition found oil in the DeSoto Canyon, a fissure that leads from the Deepwater Horizon site to just 40 miles from Panama City Beach. Hollander says that could mean Florida's panhandle could see more oil if large storms or hurricanes pass through the area.

"The conduit aspect," says Hollander, "that there may be a mechanism to bring subsurface oils with dispersants potentially to the continental margin seems to be potentially reality."

The DeSoto Canyon is one of the major spawning grounds for fish species off the Florida Coast. USF marine microbiologist John Paul says their findings should concern fishermen.

"Hopefully, this will be a short-term blip," Paul says, "and not a long-term disaster in commercial and recreational fishing."

The news comes as Escambia County officials say levels of oil in their waters are within safe standards. Just two weeks ago, the head of the National Oceanic and Atmospheric Administration said three-quarters of the spilled oil had essentially disappeared.

But the USF researchers and another research team from the University of Georgia beg to differ. Hollander estimates only 25 to 30 percent of the oil has been skimmed, burned or collected.

"That leaves about 70-75 percent that is not accountable," Hollander says. "The question is, is all unaccountable oil not dangerous, is all unccountable subsurface or sedimentary oils or oils on the beaches not dangerous? Those are good questions. So considerations of budgets of where the oil is dispersed does not mean "gone," and it certainly doesn't mean that it's healthy water."

Paul says USF researchers are looking at how much oil is present in larger organisms, such as fish larvae. That analysis isn't expected for several weeks. The Weatherbird II is set for another trip into the Gulf in September.

More detail of the research results is presented below, courtesy of USF:

Water and sediment samples from east of the Deepwater Horizon wellhead (stations DSH 8, DSH9, DSH10) and at the edge of the DeSoto Canyon (station PCB-03) on the outer continental shelf are emitting visible fluorescence when examined under UV light, resulting in signals that match BP’s MC252 oil.

Excitation Emission Matrix Fluorescence Spectroscopy (EEMS) of these water samples also indicated the presence of oil-like hydrocarbons. The UV-induced fluorescence, which has been digitally photographed, resembles a dense constellation of microscopic blue stars on the sediment surface and in the filter pads.

Fluorescence continued after five hours of freezing, suggesting that the fluorescence was not caused by living organisms. Minerals or other non-oil materials may also fluoresce in this manner, requiring the samples undergo further testing through molecular organic geochemical and compound-specific isotope analyses. Those tests will allow scientists to verify whether the fluorescence was due to the presence of petroleum hydrocarbons and whether the hydrocarbons are associated with BP’s oil.

Biosensor assays indicate that marine organisms, phytoplankton and bacteria, express a strong toxic response in subsurface and surface waters that show positive indicators of petroleum hydrocarbons. Two toxicity tests were employed: the Microtox Assay (SDI) and the QwikLite 200 Biosensor System (Assure Controls, Inc.) Both assays detect a toxic response as suppression of bioluminescence induced by the sample.

For Gulf samples, the dinoflagellate (QwikLite) assay indicated that the subsurface samples (the DHS08 sample taken at 275 meters depth and the PCB03 sample taken at 50 meters depth) had the greatest toxic responses followed by samples from DHS08 at 215 meters depth, PCB03 at 35 meters depth, and DHS10 at 60 meters depth.

These samples have not yet been statistically verified, yet 39 percent of the samples tested showed some degree of toxicity. DCMU/fluorometry, an indicator of phytoplankton health, confirmed that phytoplankton photosynthesis was stressed at the same stations that were determined to be toxic.

The bacterial (Microtox) assay indicated that the samples of surface waters of DHS08, DHS09, and FT1 were toxic - or 3 of the 14 stations (21.4 percent) had positive results. These field-based results are consistent with shore-based laboratory studies that showed that the dinoflagellate assay was more sensitive to dispersant than the bacterial assay which was more sensitive to oil.

These results indicate that a further, coordinated, comprehensive study and survey is needed to determine how extensive the contamination.

The August 6-16 Weatherbird II research cruise was funded by USF’s Research Foundation and led by chemical oceanographer David Hollander, biological oceanographers John Paul and Kendra Daly and geological oceanographer David Naar.

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