Dozens of Arctic Terns were found dead at a nesting colony near Juneau, Alaska in the summer of 2019. Three years later, scientists confirmed the killer: a potent neurotoxin produced by microscopic algae.  

Researchers analyzed samples from the site and found elevated concentrations of saxitoxin in the terns and their prey, providing a compelling link between harmful algal blooms and unexpected seabird deaths. They recently published on their findings.

“Although harmful algal blooms are not new to Alaska, their impacts on wildlife appear to be intensifying,” Caroline Van Hemert, a research wildlife biologist with the USGS who led the study, said. “We’re just beginning to understand what this might mean for seabirds and ecosystem health more generally.”  

Harmful algal blooms that produce saxitoxin have been intensifying in many locations around the world as ocean temperatures rise. In Alaska, where the effects of climate change are especially pronounced, unusual seabird mortality events have been occurring annually since 2015.  

Although starvation has been linked to many of these events, saxitoxin has been lurking as a potential killer. With this new study, researchers are better able to understand the effects of harmful algal blooms on the ecosystem and future threats to seabirds and marine wildlife.  

The following comic takes you back to the scene of the crime in Southeast Alaska, when Arctic Terns were found dead at their nest sites.