Environment: A common aquarium grass is killing eagles

One day in the 1950s, someone dumped an overgrown aquarium grass into a Florida waterway.

In 2021, the grass, called hydrilla, has taken over freshwater lakes in the east, south, and Midwest. What hasn’t been known until now is that the invasive plant hosts unique bacteria deadly to birds, including eagles.

That knowledge is the result of a 20-year investigation by U.S., German and Czech researchers into the mysterious incidences of the mass deaths of eagles and water birds.

The first identified mass death was in the fall of 1994 and winter of 1995 when 29 bald eagles died near Lake DeGray in Arkansas. A few years later, mass deaths of eagles, geese, coots, and ducks were found in the Carolinas, Georgia, and Texas. Birds were observed to be stumbling on the ground, unable to fly, and finally appearing paralyzed. The birds then become easy prey for eagles, who eat the birds and get the disease, too. One chilling question stands out: What if humans eat the ducks? There is no answer yet to that food chain murder mystery.

In a paper published in March in the journal Science, an international team of scientists has finally identified the killer: A cyanobacteria. Scientist Susan Wilde, professor of aquatic science at the University of Georgia, named the bacteria Aetokthonos hydrillicola, meaning ‘the eagle killer that grows on hydrilla.’

German scientist Timo Niedermeyer was able to grow the bacteria in a lab, and he identified one other substance on the hydrilla leaves: bromide. An ingredient used in sedatives, fuel additives, and water sanitizers. The plant appears to enhance the bacteria using bromide.

Not all hydrilla-infested waters are infected with the bacteria. The question is: How does the increased presence of bromide occur? It may come from human pollution, or maybe even the herbicides used to kill hydrilla.

While the research continues, it is crucial for people to not dump aquatic plants in waterways. Boaters can remove aquatic plants from propellers and hulls. Report sightings of odd behavior in birds to wildlife agencies.