When biologist Alexandre Meinesz alerted authorities to a deadly alga colonising the seas, he expected quick action. A decade later, he was the only target of attack. Steve Farrar reports.
Alexandre Meinesz slipped into the Mediterranean waters near the spot where the student had reported seeing the mysterious aquatic plant. The French expert had made many such dives over the years, and although he was intrigued by his colleague's report, he expected to see little out of the ordinary. But what he encountered lurking beneath the Monaco seafront that day in August 1989 would prove to be the start of a decade-long struggle against a misplaced and pernicious alien invader.
To the inexperienced eye, the single hectare of lush, green, fern-like fronds, swaying in the gentle swell, looked anything but dangerous. Certainly the divers who accompanied Meinesz felt only awe at the plant's beauty. But as Meinesz, professor of biology at the University of Nice and an expert on tropical algae, swam towards the verdant growth he knew there was something wrong. Something positively sinister.
He had seen the alga before. Called Caulerpa taxifolia, it grew freely in the warm, tropical waters of the Caribbean and the Pacific. The cooler, temperate Mediterranean should have been ill-suited to the invader. Winter temperatures should have been fatal.
Yet the student who alerted Meinesz said it had been growing in the water below the Monaco Museum of Oceanography since 1988. Furthermore, the alga was acting in a very peculiar manner, growing more densely and spreading in a more aggressive manner than he had ever seen it do before.
The small patch was a desert for other species. Caulerpa taxifolia suffocated native species while the toxin in its cells left it untouched by fish that might otherwise have kept it in check.
Meinesz was appalled. Left to its own devices, this invader had the potential to take over an entire sea, driving its competitors before it. "I was very frightened. I could see no reason why it should just stop here," he says. It was obvious this environmental threat had been spotted in the nick of time.
On the face of it, the battle seemed wholly unequal. A small patch of one of nature's most primitive organisms pitted against humans, with all their resources.
But the alga had one great advantage - it was unhindered by bureaucracy, complacency or petty rivalry. It simply continued to spread while its adversaries squabbled and prevaricated. Meinesz was about to be confronted with mankind's inability to deal with the consequences of its actions, with echoes of the BSE disaster across the channel.
At first, his efforts to raise the alarm were thwarted by indifference and cross-border bureaucracy as the local authorities in France and Monaco denied that the alga was within their respective jurisdictions.
No one else seemed overly concerned by his discovery and Meinesz began to question his own conclusions. Maybe the alga would die away that winter.
But Meinesz's hopes were dashed when, in spring 1990, he spotted the delicate, bright green fronds of the alga while diving in French coastal waters a kilometre from the Monaco site. Startled by the implications of this second sighting, he immediately sent a report to the authorities. Nothing was done.
Meinesz refused to give up. In April 1991, he flew to Paris to talk with a government official and deliver a scientific paper on the situation. "She admitted the green alga was strange but told me there were many other problems the ministry faced," he says. "I told her this was a very serious problem and she should do something about it, but again nothing was done."
The alga continued to extend its reach down the French coast, destroying everything in its path, watched over only by Meinesz's team.
Meanwhile, the story of how the alga had got into the Mediterranean in the first place was starting to emerge. It seems the original batch of Caulerpa taxifolia was imported into an aquarium in Germany in the 1970s. Somehow, a highly invasive strain, resistant to low water temperatures, predominated. Either the firm that collected the original sample had chanced upon a mutant or the conditions in the aquarium had produced the variant through natural selection.
From Germany, the strain was sent out to aquariums throughout Europe, including the Monaco Museum of Oceanography. From here, Meinesz maintains, it got flushed accidentally into the sea.
The scientists made their first breakthrough towards the end of 1991. The team determined that the alga was reproducing asexually, an observation backed up later when it was found that all of the fronds were genetically identical. This meant its ability to spread was limited to where sea currents carried pieces of the plant material.
If the authorities banned boats from anchoring along the 2km stretch of contaminated coastline, stopping them from carrying the plant around the Mediterranean, the situation might be containable.
Other scientists were becoming interested: a group of experts met in Nice to discuss the problem and decided to call on officials to act. The authorities responded by appointing four committees to examine different aspects of the problem. Although the groups met regularly, still the authorities failed to act. Meinesz continued to publish reports charting the alga's spread.
From Monaco, the epicentre of the invasion, a variety of reassuring excuses were issued: the alga had spread naturally from the Red Sea; it did not pose a threat to other species; it grew only in polluted waters. Then the personal attacks began.
Meinesz was accused by one senior scientist based in Monaco of being a substandard investigator who wanted only to stir up trouble to gain funding for his laboratory.
The dispute boiled over into the pages of a prestigious journal of the French Academy of Science, which carried a paper claiming the alga was an immigrant from the Red Sea and hence not as great a threat as had previously been suggested. Meinesz's subsequent rebuttal of this research may have pushed the scientific debate in his favour, but it won him few friends in high places.
Nevertheless, the alga's spread coupled with growing public concern prompted a series of piecemeal attempts at control, some involving the French and Spanish navies. All ultimately failed. "In several laboratories, efforts were made to find techniques to get rid of it, but there was no overall strategy," Meinesz says.
Without a coordinated approach, the plant re-established itself in cleared areas and continued its march across the Mediterranean.
There are now 120 independent sites along the Mediterranean coast that have been colonised by Caulerpa taxifolia, from Spain to Croatia. Next year there will be more. The opportunity to halt its spread has long gone. "It took too long between scientists saying there was a problem and the authorities agreeing to do something," Meinesz says. "The price we will have to pay for this will ultimately be the biodiversity of the Mediterranean."
Now all that can be attempted is to mount annual efforts to keep sites of particular ecological importance clear. The rest of the Mediterranean will succumb eventually.
Some - including Meinesz - have suggested that a particular species of slug capable of eating the alga could be introduced to control it. But others fear that introducing another new species to the Mediterranean will just create more problems.
Such invasions are being repeated across the world as species that never met in nature are being introduced to one another. Although mankind is responsible, when problems arise, it seems that people can do nothing but wring their hands and watch.
Alexandre Meinesz's Killer Algae is published by the University of Chicago Press.