Peter Hodson, of Queen’s University is an active scientist in the field of aquatic toxicology. In a recent conference held by the Society of Environmental Toxicology in Portland Oregon, Hodson made the claim that chemical dispersants used to clean up oil spills are more likely to cause damage than leaving the oil as is. He claimed that the dispersed oil will cause more damage to aquatic systems and the life pertaining to them. His reasoning behind this claim, was that when the oil, more specifically the toxic polycyclic aromatic hydrocarbons, is dispersed it is able to cover a greater volume of water rather than simply floating on the surface, thereby affecting a greater range of aquatic life. I feel like this claim made is a very broad exaggeration of the truth, and lacks hard evidence. His evidence he has to support his theory is research he has conducted on embryonic herrings. He claims to have found that, “Exposures as brief as an hour can have a negative effect on embryonic fish”.
The first point that I find weak about his claims is the fact that his study only focuses on the embryonic form of one species of fish in the entire oceanic sector of ecosystems. This poses two uncertainties in his theory, the first being that he only studies the effect in the embryos of a single species. Because the embryos could be much more sensitive to chemical and other external factors, like the PAH, it is unpractical to base the conclusion that dispersed oil is “worse” for the ecosystem the non-dispersed oil. The study on embryos does not take into account other, much more important pieces of the ecosystem, like the fish that must produce the eggs. If the fish of the ecosystem are not as sensitive to the dispersed oil compared to the embryos, and are more affected by the concentrated oil, than the oil dispersants should not be deemed “worse” for the ecosystem. Hodson claims that it is bad because “an entire hatch could be decimated”, but if there are no fish to lay the eggs and support the embryos then it is pointless to act in the interest of the embryos. The second reason for uncertainty is that only one species of fish was being experimented on. This creates uncertainty because other species of fish could have a different tolerance to PAH, or have unknown methods of preventing negative effects on themselves and their eggs. This difference could indeed be more devastating than the affect on herring, but without further research on the topic it is impossible to say. Hodson continues to claim that the health of embryonic fish in general is affected by the dispersed oil, when as I already stated, his study only consisted of herring embryo. Therefore, for the reasons listed above, to say that because the embryos of a certain fish are affected negatively by PAH, the ecosystem is affected more negatively by dispersed oil versus non-dispersed is unjust.
I feel that if Hodson could improve his evidence supporting his claim, his claim would be much sounder. To improve his evidence Hodson could do further research on the topic of his claim. He claims that the dispersed oil does more damage to the ecosystem than the floating surface slicks but has no supporting research on the effects of floating slicks on ecosystems or dispersed oil on the whole of the ecosystems. Therefore to improve this supporting evidence, he should research the effects of the slicks on factors such as the fish that the embryos rely on to exist, and the microbial activity that affects the water quality, of which all aquatic life depends on. If the slicks were found to do a significant amount of damage to such factors than Hodson’s claim would be somewhat falsified. Although on the other hand if there was no noticeable amount of damage comparable to that of the dispersed oil, than Hodson would have more supporting evidence to back-up his claim. Another way to strengthen his evidence would be to conduct research on other species embryonic forms that would be in harm’s way of the dispersed PAH. Determining whether it is just certain species embryos affected would help him to make his claim more reliable. A final way to increase the validity of his claim would be to test the effects of dispersed PAH on the fish themselves, whether that is herring or another species. If these tests showed that the fish were equally affected by the dispersion than his claim would be much sounder.
The lack of evidence Hodson had brought in support of his claim makes it impossible to make realistic condiserations on the topic of oil dispersants. Further research on this topic, whether that research is similar to that stated above or not, would greatly increase the external validity of his studies, and the soundness of his claim.
By: Matt Gillman
Reference:
Lovett, A.R. “Oil Spill’s Toxic Trade-off” Gulf of Mexico Oil Spill Blog Environmental Toxicology. November 10th 2010. http://gulfofmexicooilspillblog.com/2010/11/10/gulf-of-mexico-oil-spill-blog-environmental-toxicology/
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