[Coral-List] coral and crude oil
Eugene Shinn
eshinn at marine.usf.edu
Sun May 2 11:39:07 EDT 2010
Dear listers here is some information re the effects of crude oil on
coral that may be of use at this crucial time.
With the developing oil disaster in the Gulf I thought a few
comments regarding the effects of crude oil on coral reefs might be
healthful. Some of you know my background in the industry and work
with API committees before 1974. In 1972 I was sent to Australia to
testify before the Great Barrier Reef Commission regarding effects of
drilling on coral reefs. I was concerned so in preparation for the
trip I obtained 5 gallons of Louisiana sweet crude (the kind
presently blowing out off the Mississippi Delta) and traveled to the
Keys to do some personal in-situ experimenting. Corals on the Barrier
reef flats (including various species of staghorn coral) are exposed
to the air at low tide each day for more than one hour. Since that is
the length of time that corals there are likely to be exposed
directly to floating oil I performed some crude experiments where I
exposed Florida staghorn and star coral directly to oil for one and a
half hours. In these experiments I placed large clear plastic bags
containing crude oil over live staghorn that was fixed to rods driven
into the bottom. At the same time I placed plastic domes (skylights)
containing oil over the tops of small star coral heads for the same
length of time. The experiment was conducted in about 15 ft of water
off Tavernier Key. What I found, and described pictorially in the
1989 issue of Sea Frontiers, was truly surprising. Corals retracted
their polyps but the oil would not stick to the coral because of its
mucus. When I removed the oil there was no oil on the coral. Fifteen
days later the corals were living and appeared normal. While at the
hearings in Australia I learned that another researcher wearing a
backpack garden sprayer had sprayed crude oil on the same exposed
corals at low tide every day for several days. His results were
similar to mine.
After joining the USGS a Masters candidate approached me to do
similar experiments for a thesis project. In the laboratory at Fisher
Island Station we totally submerged ten fragments of living Acropora
cervicornis in Louisiana crude for 2 hrs. We then transported them
(in sea water) to the reef line off Virginia Key, Florida and placed
them in concrete holders in 20 ft of water. When we returned a week
later the corals were alive and appeared healthy. The disappointed
student decided not to continue that project.
In yet another experiment students of Tom Bright from Texas A
and M University conducted an oil experiment on Carysfort reef
lighthouse off Key Largo. A 20-gallon aquarium was filled with
aerated seawater. The aquarium contained two butterfly fish and some
live A. cervicornis branches. A layer of crude oil about one inch
thick was then floated over the coral and fish. Butterfly fish are
known to feed on live polyps so the purpose of the experiment was to
see if various fractions of the oil would contaminate the coral and
then be transferred to the flesh of the fish. The fish did pick at
the coral and paid not attention to the overlying layer of crude oil.
After 24 hrs the fish was sacrificed and taken back to Texas A and M
to be analyzed for oil components. I never heard the results and
nothing was published. I simply documented it all on 16 mm movie
film.
The lesson from this and other research was that if and when the
oil from this spill reaches the Florida Keys the damage will be to
limited mainly to mangrove shoreline habitats, sea birds, and
beaches. Dive boat operations will likely be affected but it will not
harm corals or reef fish.
The crude, which will likely be in the form of tar balls, will
simply float over the areas of living corals. Under no circumstances
should dispersants be used on an oil slick in the vicinity of a coral
reef. Dispersants soluabilize the oil and allow it dissolve in the
water and come in direct contact with coral and fish. In addition,
oil containment booms should not be deployed in the vicinity of coral
reefs because of possible entanglement and physical destruction. The
history of oil spills is that clean up efforts, such as use of live
steam, solvents, and digging, often do more damage than the oil.
The best teacher is history. The Keys and the east coast of the
US were often awash in oil from torpedoed tankers during WWII and
there have been numerous tanker spills and oil from bilge cleaning
over the past 50 years with no documented impact to Florida's coral
reefs. An exception is the disastrous onshore oil tank spill at
Goleta Point, Panama in the early 1980s. The spill was at the
landward end of a lagoon that opened out to a coral reef being
studied by personnel at the adjacent Smithsonian Institution Marine
Laboratory. Unfortunately surfactants were added to break up and
soluabilize the oil in an enclosed area with poor circulation with
disastrous results. Many reef flat organisms and corals were killed.
Richard Dodge conducted extensive research on the effects of that
spill which is well documented.
In the present case by the time the spilled oil reaches the
Florida Keys (weeks) the more toxic aromatics components will have
evaporated and bacterial breakdown will have reduced the oil to a
less toxic gooey mess that can foul beaches, mangroves, and affect
sea birds. It will not harm corals or reef fish, Hopefully this
knowledge will relieve some tension and fear for the reefs as the
floating oil nears Florida's coral reefs. Nevertheless be prepared
for one heck of a mess at the shoreline before this is all over. Lets
hope it is over soon. Gene
--
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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