Algae could be eating fish alive off the US coast, say researchers. Their finding challenges a long-held belief it is toxins produced by the algae that are to blame for tumbling fish populations. Recent large-scale declines in fish numbers are an economic problem on the US East Coast. A toxin made by 'killer algae' Pfiesteria has been reported to be responsible - but the chemical has never been identified. Now two reports by Wolfgang Vogelbein, of the Virginia Institute of Marine Science in Gloucester Point, and colleagues suggest that the fish-killing algae may be eating their victims rather than poisoning them. In their first study, Vogelbein's team found no trace of a lethal toxin in water containing Pfiesteria. Once the algae had been removed from the water, the fish could survive, they found. In a second report, the team describes the algae swimming towards the fish, latching onto them and gnawing their skin. But some scientists still maintain that an algal toxin is responsible for the fish's demise. The two labs used benign, rather than toxic, strains of Pfiesteria, says JoAnn Burkholder of North Carolina State University in Raleigh, who discovered and named the algae. Her lab is one of the few that house the poisonous strain, she says. After five years of study, using a total of 2,500 litres of algal cultures, Burkholder claims that she and her team are about to publish an identification of the elusive toxin itself. Minute quantities of the small molecule "can kill a fish in five minutes", she says. But Carmelo Tomas, an expert on harmful algae at the University of North Carolina at Wilmington, remains unconvinced. | | Algae Pfiesteria "To many people, [the existence of a toxin from Pfiesteria] is still conjecture," he says. "I'll believe it when I see it." Both new studies used the same "fish-killing strains that are identified by Burkholder's criteria", he adds. Fast-growing algae such as Pfiesteria can form blooms near the surface of water. In 1997, the discovery of thousands of dead fish linked to toxic levels of algae caused widespread panic that cost the Maryland seafood industry $43 million. Whichever mechanism algae use to kill fish in the lab, the results may not help save fish or the fishing industry. Researchers are still unclear how much of a contribution the algae make to the death of fish in the wild. SCUBA FORUMDISCUSS THIS TOPIC - Dive in and have your say at Scuba Forum |
