Scientists say they have found that "phantom" algae are responsible for mysterious mass kills that have destroyed millions of fish.
The toxic algae, which have not been given a scientific name, were found in the Pamlico and Neuse estuaries in North Carolina. They appear in the water as if out of nowhere, kill hordes of fish in estuaries and fish farms by releasing poisons, and just as quickly disappear.
Because the algae can survive in everything from fresh water to the salinity of the open sea, the scientists say they suspect that these resilient and powerful killers are likely to be widespread.
Researchers suggest that the phantom algae could be the long-sought culprits in many of the mysterious and increasingly frequent die-offs that have cost the world's fishing and aquaculture industries hundreds of millions of dollars in the last two decades.
The discovery was reported today in the journal Nature.
Most of the time the single-celled algae wait, encrusted in a scaly cyst, hidden and dormant on the sea bottom. But as soon as a school of fish begins lingering overhead to feed, the deadly algae somehow detect the fishes' presence.
They shed their coats within minutes and swarm into the water.