IT’S a poisoned gift that just keeps on giving. A powerful neurotoxin produced by some algal blooms has been found in the deep ocean, where it can stay for weeks after a bloom has died.
Fish such as sardines and anchovies eat algae, some species of which contain the toxin domoic acid. If consumed in sufficient quantities, the toxin can affect sea lions, birds and humans. Fertilisers leaching into coastal waters are triggering more and more blooms, and beach closures have cost the US economy millions. In people, the poison can cause symptoms such as headaches and memory loss, and can even be fatal.
The toxin’s effects can be seen in animals long after a bloom has gone, but why was something of a mystery. of the University of South Carolina in Columbia and colleagues are the first to look for domoic acid in alga particles and sediment up to 800 metres down, where they found the toxin at concentrations more than five times the US federal limit for shellfish sold as food (Nature Geoscience, ).
Advertisement
The researchers believe dead algae form dense clumps at the surface that sink rapidly and protect the toxin from dissolving in seawater. “This is the missing link to explain why domoic acid also shows up in benthic organisms like crabs, shellfish and flatfish,” says at the University of Santa Cruz in California.