[Coral-List] Does oil stick to coral mucus

Gene Shinn eshinn at marine.usf.edu
Fri Aug 18 10:59:12 EDT 2006

Chris Hind wrote: Does anyone happen to know how well exposed coral 
at low tide can repel oil with its mucus? I will attempt an answer 
that may be more than you wanted to know.
      First, I know you are aware that this is an emotion-loaded 
subject conjuring up visions of oil coated seabirds and dead fish. 
Many will take issue with my response to this question but I think 
some of this ancient history is in order. In the 1970s I wrote the 
section on spills and corals reefs in the API oil spill handbook. It 
basically said do not do anything. My chapter was based on some 
simple experiments and observations conducted on the effects of crude 
oil in the summer of 1972. I did the experiment because I was being 
sent to Australia to be a witness representing the industry at the 
Great Barrier Reef hearings that took place in the wake of the crown 
of thorns episode. I felt a little uneasy because no one knew what 
oil did to corals in those days. The 2 year + series of hearings 
focused on the potential effects of oil drilling on or near coral 
reefs. This two years before I left the industry in 1974. to do coral 
reef geological research in Florida, and elsewhere. I continue to 
monitor the literature on oil spills. To my dismay little has been 
learned or attempted to be learned regarding the effects of untreated 
crude oil on corals. There has been some research on oil toxicity 
using the more toxic refined products, such as diesel oil. The needed 
studies on toxicity of various crude oilsm however, has to my 
knowledge never been conducted and I remain confident that no 
government agency will ever fund the controlled experimental work 
that is needed. Oil companies will not conduct the work because they 
pretty much know the results already and also that their results 
would not have credibility. In addition, young biologists will not 
become involved with the subject due mainly to peer pressure and 
problems with tenure. It would be a career-ending move for a young 
biologist. With all that said here is some information that may 
provide some guidance. I can confidently state that crude oil does 
not stick to coral mucus even if you can get the floating oil on the 
coral in the first place.
      Before going to Australia to present my previously published 
data on Acropora growth rates I obtained 5-gallons of Louisiana crude 
and headed for the Florida Keys on holiday. I already knew that the 
Great barrier reef corals are exposed to the air at low tide for up 
to 1.5 hours. That is when corals can come in direct contact with 
floating oil. In my simple experiments Acropora cervicornis was 
attached to rods driven into the bottom off Key Largo. Clear 
5-gallon-sized plastic bags were placed over the corals and tied to 
the rod below the coral colonies. One bag contained about one gallon 
of crude oil and half of the coral colony protruded into the oil that 
floated at the top of the bag. In another bag the coral was only in 
contact with the water below the oil that floated at the top of the 
attached bag. Another was a control with no oil. Yet another 
experiment involved small Montastrea sp heads placed under 2 Lucite 
plastic domes. One was in direct contact with the oil under the dome 
and another was a control. Both experiments lasted 1.5 hrs to 
simulate the exposure time on the Australian barrier reef. A. 
cervicornis immediately retracted its polyps in the bags containing 
crude. When I removed the bags it was obvious that the oil would not 
adhere to the coral. That was the first surprise. The second was 
that, 14 days later I returned to the site and found the corals 
alive. They appeared healthy, the polyps were extended but I had no 
way of knowing their true condition. Montastrea also did not appear 
to be harmed. Photos of the experiment were published in a Sea 
Frontiers article in 1989. With this information in hand I went to 
the Barrier Reef Hearings feeling a little more relieved and 
confident. At the hearing I read testimony about an Australian who 
had had done a related experiment. Using a back-pack sprayer this 
person had repeatedly sprayed a 10 by 10 m area of the reef at low 
tide. His results were similar to mine. I believe these simple, 
mainly anecdotal, experiments answer the basic question of whether or 
not oil sticks to coral mucus.
     Later after leaving the industry I did a similar experiment with 
a student off Miami. We totally immersed A. cervicornis in crude for 
an hour in the laboratory and then transplanted the colonies out to 
the reef. They remained alive for several weeks until the student 
decided this was not the result she was seeking.
     Over the years it has been interesting to note that when there is 
a  crude oil spill on or near a coral reef the media predicts 
disaster yet none have reported death of corals or reef fish. I think 
because the media never presents the facts the public, including many 
coral reef researchers, have become very polarized. What we do know 
for sure is that the damaging effects occur when the oil reaches 
shore, often due mainly to the clean-up methods.
     The most devastating spill, (reported in Science) was the one 
near Goleta Point in Panama in the early 1980s mentioned by John 
Cubit. This was a case of onshore tanks spilling into the ocean and 
passing over the Goleta Point coral reef adjacent to the Smithsonian 
Institution field station. That oil was treated with dispersants, 
according to my information, and yes, corals began to die on the 
adjacent reef, (I don't recall that  there were intertidal corals on 
this reef when I visited the reef in 1974). Many respected scientists 
were witness to this event and Minerals Management Service funded the 
subsequent study published in Science. In retrospect what we know 
now, but did not know then, was that this was also the beginning of 
the Caribbean-wide coral demise that continues today. The years 
1983-1984 (also el Nino years) were the most devastating for Acropora 
corals throughout the Caribbean including those on reefs around 
sparsely populated islands.
     If one conducted the same simple exposure experiments I did in 
1972 under todays conditions it is very likely the even the controls 
would die. Something changed radically beginning in the late 1970s 
and began peaking in the early 1980s. Bleaching appeared in the late 
1980s. Ongoing coral diseases whose source has not been 
scientifically determine has been well documented and continues even 
around Caribbean islands isolated from the usual pollutants. Corals, 
even in isolated places like Dry Tortugas have declined and lack 
their former resilience. E. A. Shinn


No Rocks, No Water, No Ecosystem (EAS)
------------------------------------ -----------------------------------
E. A. Shinn, Courtesy Professor
University of South Florida
Marine Science Center (room 204)
140 Seventh Avenue South
St. Petersburg, FL 33701
<eshinn at marine.usf.edu>
Tel 727 553-1158---------------------------------- 

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