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Effects of BP spill on Gulf corals deeper and broader than previously thought

Two coral communities in the Gulf that show patchy brown growth rather than a healthy golden glow
Two coral communities in the Gulf that show patchy brown growth rather than a healthy golden glow
Fisher Lab, Penn State

In a scientific paper published in the Proceedings of the National Academy of Sciences (PNAS) July 28, Gulf researchers showed how extensive and broad the impacts of the 2010 BP oil spill have been on coral reefs, a species that can last thousands of years.

Namely, multiple coral communities up to 22 km. from the spill site and at depths over 1800 meters, were harmed by the effects of the Deepwater Horizon 87-day "spill" off the Louisiana coast in 2010. Adding to the effects was the abundant dousal of Corexit, a dispersant banned in the UK, even though researchers were unable to parse out its direct impact.

Dr. Charles Fisher with the Department of Biology at Penn State, who headed up the research and who spoke with us back in 2012, agreed to answer some questions. He has been studying the coral communities and other deep sea life in the Gulf of Mexico for many years, including prior to the Apr. 20, 2010 spill.

Fisher states on his university bio that,

My research interests include the physiology of the animals and the ecology of the communities that inhabit cold seeps and hydrothermal vents in the deep sea. Much of this research focuses on the functioning of the major players in these communities: animals harboring autotrophic symbionts. These types of symbiotic associations are extremely important in the world’s oceans, where symbiont-dependent species are often the primary ecosystem-structuring organisms in both shallow tropical environments, such as coral reefs, and in the deep sea where biomass may be limiting.

Fisher was one of a handful of prominent scientists plucked to speak at the Jan. 2011 University of Georgia "Building Bridges in Crisis" symposium, where this examiner spoke as part of a media panel. Since then, he's kept up his studies on the toxicity of the spill on coral reefs, saying that his team tries to get out there (for a dive) at least once a year.

The Nov. 2011 dive, the one from which data was drawn for this particular paper, was performed at 29 sites using the autonomous underwater vehicle Sentry.

Following is a transcript of our online conversation:

1. What were your most significant findings on the most recent dive and expedition, and since we spoke in 2012 (see my story in the Examiner.)

This is about the paper which is based on the 2011 expedition. It is premature to talk about the most recent dives last month.

2. Why should people care about corals? In your paper you talk about fish using corals as spawning grounds and corals’ importance in biodiversity, nitrogen and decomposition processes.

In addition to providing habitat and spawning grounds, think of the corals as an indicator species. (check out the first paragraph in the Corals as Biomonitors section of the paper.) They give evidence of where there was impact; things like fish and crabs that were there at the time are not now.

3. How are you able to differentiate damage caused by oil versus damage from Corexit/dispersants or did you not separate those out? For example, on page 4 of your paper you mention you talk about the possibility of “microdroplets or particles” or “oil containing marine snow”, and the fact that these were not evenly dispersed throughout the area.

We cannot. We do not know exactly what caused the impact to the corals, only that it was connected to the spill.

4. I realize you used a certain site as a benchmark from which to measure other corals’ damage, but were you also able to tease out how much worse damage is because of the additional hit from Corexit to the corals? And if so, did you have a benchmark for that?

See answer to #3

5. Did you see any conflict of interest in using BP sonar data (as is noted in the paper) to locate five additional areas to study around the Macondo wellhead? For example, how is one able to trust this data given BP’s obvious interest in downplaying damage to the Gulf from the spill?

No conflict. They supplied side scan sonar maps that we confirmed were accurate at the meter scale.

6. What are the predominate type of corals found in the Gulf – the Octocoral or the Stony Coral, the Scleractinia, and is one type more susceptible to damage from an oil spill than another?

Octocorals are more abundant below 1000 m depth. We don’t really know the answer to the question about which is more susceptible.

7. The numbers in Table 1 are jarring for MC294 and MC297 (location sites on the seafloor), which had 49 coral colonies showing spill-related damage. MC294 is some 3.7 miles from the wellhead. Generally, the closer the proximity of the corals to Macondo the worse the damage? Or not necessarily?

Check out Table 1 for all the numbers. We really do not have enough data to generalize about proximity to the spill and worse damage. Direction and depth are also important and not all sites within 22km were impacted.

8. In your paper, you say that “Although early National Oceanic and Atmospheric Administration models and empirical studies suggested that the deepwater plume of hydrocarbons from the blowout moved predominantly to the southwest, later models suggest a more dynamic pattern of swirling flow from the wellhead that could readily transport hydrocarbon rich fluids to the east in the direction of MC344.” It would seem to the layperson, perhaps, that the “swirling” you talk about resulted from the extensive spraying of Corexit. Is that a fair assumption?

No . The swirling is due to ocean currents. Corexit would have no effect on the ocean currents.

9. Finally, when will you next be studying the damage to the corals? What will that expedition involve in terms of underwater vehicles used, duration of study, etc.? Do you plan to write another paper at that time?

We just returned from an expedition on the EV Nautilus and will be working up the hundreds of images we took on this cruise over this year. We hope to get out again next summer as well. I expect that we will have a couple additional papers out within the year. One on the effects on animals associated with corals and another on details of the effects of hydroids (secondary colonists on damaged areas) on the corals. The long term survival story is taking a long time to play out.

To read the scientific paper, "Footprint of Deepwater Horizon blowout impact to deep-water coral communities" by Charles R. Fisher and several other scientists/researchers, please visit the PNAS website and for a small fee, one can obtain short-term access to the site. To read the abstract for the paper, please click here.

Photo: Two colonies of coral from a coral community discovered in late 2011 with attached anemone and brittle stars from a site 6 km. from the Deepwater Horizon spill site. The "patchy brown" growth on the coral is a sign that it's unhealthy: it's usually a nice gold. This, according to Fisher, is "diagnostic for corals impacted during the spill."

Bold marks and hyperlinks are those of the examiner's.

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