[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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