The Black Tide Legacy
Posted on January 19, 2007 @ 3:25 PM
FOUR YEARS AFTER THE LEAKING OIL TANKER PRESTIGE WENT DOWN OFF GALICIA, TONY BUTT EXAMINES ITS EFFECTS ON THE BAY OF BISCAY.
The significant problems we face cannot be solved at the same level of thinking we were at when we created them. – Albert Einstein
On 19th November 2002, thirty miles off the Costa da Morte, Spain, the single-hulled supertanker Prestige broke in half and sank, distributing 60,000 tonnes of heavy fuel oil all along the Atlantic coastlines of Spain, Portugal and France.
Perhaps I ought to apologise for harping back to some disaster that happened over three years ago; one that perhaps we’d all be better off forgetting. Now that we can surf again, the fishermen can fish and everybody can get on with their lives, why dwell on it?
Well, the answer is, if I could have written this article three years ago, when the Prestige was hot news, I would have. But it was just too early. You see, the overall effects of large oil spills such as the Prestige take years, if not decades, to develop. It is only by studying them for many years afterwards that we can begin to understand their effects.
The Prestige oil spill was an environmental catastrophe of the highest order. Its consequences were far-reaching and profound, affecting every single member of the coastal community; human and non-human. The fishermen couldn’t fish for months; the ‘percebeiros’ (those intrepid and uniquely Galician collectors of shellfish) couldn’t work, and we, the surfers, couldn’t even go in the water. In fact, just to get near it one would sometimes to cross a stinking black mass of crude oil. I remember paddling out at a beach almost a thousand kilometres from where the Prestige went down, more than a year after it happened, and coming out covered in brown-black stains. The list of consequences, immediate or delayed, goes on.
Now, just over three years later, it seems the whole episode has been almost forgotten – as if there had been a huge fuss for nothing. Presumably, the remaining 37,000 tonnes of fuel still leaking out of the ship, 4,000 metres down, has miraculously disappeared. It must have because Repsol YPF, the state-owned oil company ‘contracted’ by the Spanish government to suck the oil out with robots and giant pipelines, didn’t need to do it. Presumably, all the remaining oil under the rocks along the Galician shoreline has also miraculously disappeared. In fact, according to official government reports, the coastline of Galicia has made a “complete recovery”.
But that’s governments for you. Of course Galicia’s coastline hasn’t got over the Prestige disaster. Even though the initial, direct physical impacts are now almost imperceptible, the indirect, long-lasting and extensive impacts haven’t ceased. In fact, it’s absurd to say that the entire coastal system has made a ‘complete recovery’ in such a short space of time.
Scientists are intensively studying the long-term effects of the Prestige and other oil spills. Two important coastal biology studies have recently appeared in the scientific literature, one about the Prestige – the first of its kind so far – the second about the Exxon Valdez, now seventeen years in the past and from which a considerable amount of data is now available. Both these catastrophes happened in coastal areas of outstanding natural beauty, high productivity and high biodiversity. It is ironic that most large oil spills seem to happen on some of the most pristine coastlines in the world. Sadly, it follows that these areas automatically become the best ‘natural laboratories’ for studying the long-term impacts of such events.
PRELIMINARY STUDY OF THE PRESTIGE OIL SPILL
Just by looking at the state of the coastline after the Prestige spill, any fool could tell it would take a miracle for the effects to go away immediately, despite the heavily-censored Spanish news reports. After a year, people were just beginning to get the first ideas of the overall impact on the ecosystem. Then it was really too early to tell, but now, just over three years later, some of the first proper results have emerged concerning the Prestige and its effects on the ecosystem.
Biologists Rosario de la Huz and colleagues from the University of Vigo have just published an extensive study into the biological impacts of the spill on the coastline of Galicia. Their work, covering the entire Galician coast, focused on 18 sandy beaches. They compared data on the diversity and abundance of six categories of small animals from September 1996 (before the spill) until May 2003 (after the spill). The species, termed macrofauna, were grouped into six taxonomic categories, including marine and semi-terrestrial crustaceans and insects. These are considered good examples of species that can be greatly affected by a coastal contamination event, in addition to occupying a relatively low level in the food pyramid. During their post-spill survey in May 2003, the first thing the Huz team did was to write down their initial observations. There was, they noted, a considerable amount of oil in the sediment on all the beaches studied (no surprises there). In fact, on 10 of the 18 beaches the sand was not even visible beneath a thick carpet of black oil. The next thing they did was to count the number of different species present, and compared this with data already available from September 1996. A highly significant decrease in the number of species (effectively, the biodiversity) was observed on all but one of the beaches, in some cases up to two thirds of the species having disappeared.
They then counted, for each taxonomic group, the total population of individual animals per square metre of beach area. This was also found to have decreased considerably.
Perhaps the most surprising result was that, in addition to the oil itself directly affecting the biology, the actual cleaning of the beaches (a secondary consequence of the oil spill) did just as much damage, if not more, as the Prestige. This wasn’t new; in fact it had already been noted from previous spills such as the Exxon Valdez. The main reason for the damage is that vigorous cleaning of the beach removes every last trace of vegetable matter. Algal wrack (a type of seaweed) for example, is used by the macrofauna as food and shelter, particularly on the dry beach and right on the water’s edge. If the macrofauna cannot live, then, obviously, neither can the larger creatures that depend on the macrofauna for food. And if they can’t live, neither can the bigger ones who depend on them for food. And so on up the food pyramid.
After rigorous statistical testing, Huz and colleagues considered that their conclusions (basically, that the ecosystem has seriously been affected by both the oil itself and the cleaning of the beaches) were trustworthy, despite the difficulty in distinguishing changes due to the oil spill from those due to natural variability. They were worried that, since one set of measurements was taken in the spring (May 2003) and the other in the autumn (September 1996), the natural seasonal variation between these two times of year might have influenced the results. Therefore, they performed a special check to estimate this natural variation, which was then subtracted from the total effects of the spill. The results still indicated a major effect on the ecosystem, so their conclusions were deemed reliable.
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