Orcas and Oil: Repost


ResearchBlogging.orgWhen a scientist is writing a scientific paper we look for that one quintessential figure that tells the whole story. Other figures are ancillary to fill in the specifics but the ‘cardinal figure’ is where all the meat of the paper is distilled to one remarkable graph. A senior scientist once told me that deciding on and constructing this figure is the hardest part of writing the paper. After the “cardinal figure” everything else writes itself.

Think of the “cardinal figure” as manuscript feng shui. An off-balance figure with improperly aligned objects lead to paper disharmony. Bad figure…bad paper moojoo.

I mention this because the paper I will expound on here presents a cardinal figure that truly exemplifies a “picture is worth a thousand words”. It does so well at conveying the message little more commentary is needed. I merely, and humbly, fill in the details.


So the details not on the graphs… Whales here is killer whales. The AB Pod is a resident pod in Prince William Sound. You can clearly see both in terms of number and reproductive value they are not doing so well. You might also notice that 1989 starts the downtrend. What happened in 1989 you might ask? On March 24, 1989, the supertanker ‘Exxon Valdez’ ran aground on Bligh Reef in northeastern Prince William Sound, Alaska, spilling 42 million liters of crude oil, the largest oil spill in USA history.

The oil was most volatile and produced the most aromatics in the weeks immediately following the spill (Spies et al. 1996), and inhalation of oil or concentrated aromatics is extremely toxic (Griffiths et al. 1987, Geraci 1990, Neff 1990). Cetaceans are obligatory surface breathers and the large quantities of monoaromatic hydrocarbons evaporating out of the oil slick would have been most concentrated immediately above the water’s surface. Monoaromatics easily cross membranes in the lungs, and will be taken up rapidly, resulting in a narcosis response well documented in humans (Ainsworth 1960, Bass 1986). The fumes themselves may not have been directly lethal, but they could easily have caused marine mammals to lose consciousness and drown (St. Aubin & Geraci 1994). The acute response could have happened in minutes if monoaromatic concentrations were high. We believe that the 7 animals missing when AB Pod was thoroughly photographed 6 d after the spill likely died as a result of inhaling oil or its vapors. The effects of vapor or oil inhalation may range from instant death to sub-lethal damage to mild irritation, depending on concentration and length of exposure (Geraci 1990). If there were acute mortalities, then sub-lethal damage should have been prevalent as well. Inhaled hydrocarbons may inflame mucous membranes, cause lung congestion, lead to pneumonia and cause neurological damage and liver disorders (Geraci 1990, Neff 1990, Lipscomb et al. 1994).

Matkin, C., Saulitis, E., Ellis, G., Olesiuk, P., Rice, S. (2008). Ongoing population-level impacts on killer whales Orcinus orca following the ‘Exxon Valdez’ oil spill in Prince William Sound, Alaska. Marine Ecology Progress Series, 356, 269-281. DOI: 10.3354/meps07273

Dr. M (1730 Posts)

Craig McClain is the Assistant Director of Science for the National Evolutionary Synthesis Center, a National Science Foundation supported initiative. He has conducted deep-sea research for 20 years and published over 50 papers in the area. He has participated in and led dozens of oceanographic expeditions taken him to the Antarctic and the most remote regions of the Pacific and Atlantic. Craig’s research focuses on how energy drives the biology of marine invertebrates from individuals to ecosystems, specifically, seeking to uncover how organisms are adapted to different levels of carbon availability, i.e. food, and how this determines the kinds and number of species in different parts of the oceans. Craig’s research has been featured on National Public Radio, Discovery Channel, Fox News, National Geographic and ABC News. In addition to his scientific research, Craig also advocates the need for scientists to connect with the public and is the founder and chief editor of the acclaimed Deep-Sea News (http://deepseanews.com/), a popular ocean-themed blog that has won numerous awards. His writing has been featured in Cosmos, Science Illustrated, American Scientist, Wired, Mental Floss, and the Open Lab: The Best Science Writing on the Web. His forthcoming book, Science of the South (http://www.scienceofthesouth.com/), connects cultural icons of South such as pecan pie with the science behind them.

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