More than 25 years ago, biologists in Arkansas began to report dozens of bald eagles paralyzed, convulsing, or dead. Their brains were pocked with lesions never seen before in eagles.
Birds were dying at lakes and reservoirs throughout the southeast, and at every lake Susan Wilde, an aquatic ecologist at the University of Georgia, Athens and team visited, they found Hydrilla verticillate. But it was not the hydrilla itself causing the deaths, it was cyanobacteria on the leaves.
A team of researchers have identified a novel neurotoxin produced by cyanobacteria that harms not just birds, but fish, insects, and worms too. An unusual feature of the toxic molecule is the presence of bromine, which is scarce in lakes and rarely found in cyanobacteria.
Bromides are rare in freshwater, but they could be eroding from rocks, or they might originate from coal-fired power plants. Other sources could include brominated flame retardants, fracking fluids, and road salt. Wilde suspects one local source might be an herbicide, diquat dibromide, that is used to kill hydrilla.