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Scientists Uncover Genetic Basis for Toxic Algal Blooms

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A diver observes filamentous algae at La Ciotat in the Mediterranean sea, on July 4, 2015. Recent global warming has caused a major algal bloom on the seabed, suffocating flora and causing important biodiversity changes.  (AFP PHOTO / BORIS HORVAT )

Despite decades of research, the trigger that causes algal blooms to begin poisoning their environment has long confounded scientists.

Now, researchers from Scripps and UC San Diego have found the genetic underpinning of domoic acid, a harmful neurotoxin. In a new study published in Scienceresearchers describe three genes responsible for producing domoic acid in the phytoplankton Pseudo-nitzschia. 

Monitoring how the cluster of genes behave could one day yield information on which environmental or biological triggers are responsible for activating them, according to Bradley Moore, a professor of marine chemical biology and geneticist at Scripps and UC San Diego. That information could help fisheries and public health officials predict when harmful algal blooms will occur, allowing them to effectively prepare. 

Moore says that the “very small” cluster of genes responsible for the production of the toxin is a relatively rare phenomena compared to other similar organisms, indicating that they may serve some important biological function.

“It’s not there to make us sick. There are different theories for why it’s there, including serving as a feeding deterrent,” says Moore.


Moore speculates the toxin may deter organisms that would feed upon the algae.  Or it may be that the toxin allows algae to chemically bond to nutrients, such as iron, present in the water.

“The discovery of these genes will allow us to explore these theories,” he says.

Moore and his colleagues focused on Pseudo-nitzschia because it occasionally causes serious economic and environmental damage along coastal communities.

In California, closures due to toxic blooms have become increasingly common. Several popular swimming areas in the Bay Area, including Lake Temescal and Quarry Lakes, were shut down for most of the summer due to harmful algae blooms.

San Jose’s  Lake Cunningham has been closed since January and has yet to reopen.

In humans, the toxin can cause rashes, skin lesions, headaches and stomach pain. There have also been cases of animals dying in Napa County from swallowing the contaminated water.

To monitor local bloom sightings online, check out the Harmful Algae Bloom Portal.

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