[Coral-List] factorial field experiments on coral and oil

Charles Birkeland charlesb at hawaii.edu
Fri Aug 18 19:03:57 EDT 2006


Although corals can appear to be perfectly healthy after prolonged immersion in oil, factorial field experiments can show that significant stress has occurred. In December 1968, an oil tanker broke apart near the Smithsonian Tropical Research Institute’s Caribbean marine lab at Galeta Point, releasing about 20,000 barrels of Bunker C and marine diesel oil. In 1973 we did factorial experiments at Galeta on the effects of immersion of Porites furcata in rich syrupy Bunker C oil. The corals were never removed from water, but were collected in buckets underwater, then carried in the buckets to water tables and stained by placing them in Alizarin red S for 6 daylight hours. The next morning, the corals were again moved to buckets while never being lifted out of water. This time the buckets had just enough seawater to cover the corals. A hundred milliliters of Bunker C was poured into half of the buckets, the corals in the other buckets were controls. The oil reached the bottom of
 the buckets, then floated upward through the branches of the corals. In the first experiment, half of the buckets were left with oil coating the surface 2.3 mm thick for one hour and the other buckets were left with oil for 2.5 hours. In all the rest of the experiments,  the oil was left for  2.5  hours. The corals treated with oil and the controls were set back out on the reef in pairs, with a control colony for each colony treated with oil. They were left for 61 days at various sites on the reef that appeared to be comparable. The sites were merely considered replicates. The experiment was repeated in January to March and April to June.

After 61 days, all the corals appeared quite healthy. We measured the growth of branches by the distance of white skeleton from the tip of the pink stain of Alizarin to the tip of the living (before being cleaned of tissue) coral. When we did a t-test or 1-way anova between the growth increments of treated and control branches, there was no significance difference. 

However, this looked suspicious because in all pairs from the same time and place, the branches from control colonies always grew more than the branches from treated colonies. Paired comparisons t-tests and (2-way) factorial anovas on growth increments for control and treated branches at the same time and location were significant at p< 0.01  Some branches looked healthy but did not grow at all. Four out of 64 control branches showed no growth and 39 out of 157 oil-treated branches showed no growth. The Fisher exact probability of this outcome is p = 0.0006  The 2-way anova showed the effects of times and places that were about the same to our eyes made a significant difference in the growth of Porties furcata. The variance in growth caused by time and place swamped the variance caused by treatment with Bunker C oil. 

This does not contradict what Gene Shinn says. While the effects of oil on the growth of coral were statistically significant, they were invisible unless the effects of time and place are factored out.  It is possible that while the oil has a statistically significant effect on growth of coral, the clinical effect is not significant. After all, the corals looked quite healthy. On the other hand, it is tempting to speculate that growth might be a sign of vitality, of competitive vigor and resistance to disease. It may be that the widespread deterioration of reefs is abetted by a reduction in vitality in apparently healthy corals from a general increase in nutrients, pollutants and temperature.


Details of these and other oil studies can be found in EPA-GOO/3-76-028 (May 1976) Ecological Research Series “Survey of marine communities in Panama and experiments with oil” (177 pages) by C. Birkeland, A.A. Reimer and J.R. Young. The study was under the guidance of Peter Glynn. I don’t have an electronic copy, but the hard copy I have says “This document is available to the public through the National Technical Information Service, Springfield, Virginia 22161”.


> ------------------------------
> 
> Message: 6
> Date: Fri, 18 Aug 2006 10:59:12 -0400
> From: Gene Shinn <eshinn at marine.usf.edu>
> Subject: [Coral-List] Does oil stick to coral mucus
> To: "To:"@coral.aoml.noaa.gov
> Message-ID: <a06200702c10b85f99c01@[131.247.139.175]>
> Content-Type: text/plain; charset="us-ascii" ; format="flowed"
> 
> 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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> End of Coral-List Digest, Vol 38, Issue 14
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