According to geologist James W. Castle and ecotoxicologist John H. Rodgers, both of the Clemson University in South Carolina, toxin-producing algae caused or contributed to the mass extinction of dinosaurs.

After spending two years analyzing data from ancient algal deposits, so called stromatolite structures, the researchers have found evidence that blue-green algae where present in sufficient quantities to kill off countless numbers of plants and animals living in the ocean or on land at the time. Blue-green algae may not seem very harmful, but they produce toxins and deplete oxygen.

Other researchers have suggested that phenomena such as volcanic activity, climate change, sea level changes or asteroids are responsible for the five major extinctions and a number of other significant die-offs during the part of Earths history during which life with skeletons or shells have existed. According to Castle and Rodgers, all these phenomena contributed to the mass deaths but algae was the most important factor.

“The fossil record indicates that mass extinctions… occurred in response to environmental changes at the end of the Cretaceous; however, these extinctions occurred more gradually than expected if caused solely by a catastrophic event,” Castle and Roger argue in their work.

The part of the study that has caused the most debate so far is the warning that current global warming may cause similar die-offs, since our current environmental conditions show significant similarity to times when mass die-offs have occurred.

“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,” Castle and Roger writes, adding that the level of “modern toxin-producing algae is presently increasing, and their geographic distribution is expanding… “

The paper has already gained a lot of attention within the scientific community.

“Scientists from around the world have been sending us data that support our hypothesis and our concern about the future,” says Rodgers. “I look forward to the debate this work will generate. I hope it helps focus attention on climate change and the consequences we may face.”

You can download the entire “Hypothesis for the role of toxin-producing algae in Phanerozoic mass extinctions based on evidence from the geologic record and modern environments” from Clemson University.

http://www.clemson.edu/media-relations/files/articles/2009/2336_295_mass_extinctions.pdf

The work has also been published in the March 2009 issue of the journal Environmental Geosciences.