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‘Killer algae’ could have taken down the dinosaurs

By James G. Robertson, National Geographic Digital Media

Large algae blooms could have been a major contributing factor to the last five mass extinctions and smaller die-offs throughout history, researchers at Clemson University announced yesterday, challenging the theories that a major cataclysmic event, like an asteroid strike, alone caused the extinctions.

Today, a change in sediment or water temperature can cause large algae blooms, which can remove oxygen from the water and create toxins that suffocate fish and poison other organisms. The toxins created by some types of algae can creep into groundwater and poison plants, too, which causes problems up the food chain.

The researchers found evidence of spikes in fossilized algae, called stromatolites, about the same time the mass extinctions occurred, leading them to believe that algae had a role in disrupting the food chain by killing off fish or poisoning herbivorous creatures. The blooms could have been caused by fallout from volcanoes or asteroid collisions, or simply from climate change.

While it is a theory about the past, the theory could have an impact on the future as well.

“This hypothesis gives us cause for concern and underscores the importance of careful and strategic monitoring as we move into an era of global climate change,” wrote James W. Castle and John H. Rodgers, the authors of the study that was presented at the 2009 meeting of the Geological Society of America.

There is evidence that toxic algae has been creeping northward due to climate change, says Castle, potentially causing problems for wildlife and humans as the planet gets warmer.

You can read more about developments in the asteroid extinction theory at National Geographic News.