CLEMSON — Algae, not asteroids, were the key to the end of the dinosaurs, say two Clemson University researchers. Geologist James W. Castle and ecotoxicologist John H. Rodgers have published findings that toxin producing algae were a deadly factor in mass extinctions millions of years ago. The research not only provides new insights into the past but also offers a caution about the future. The scientists say that current environmental conditions show significant similarity to times when previous mass extinctions occurred.
Castle is presenting the research results at the Geological Society of America meeting in Portland, Oregon. He and Rodgers have spent two years analyzing data from ancient algal deposits — stromatolite structures — finding evidence that blue-green algae, which produce poisons and deplete oxygen, were present in sufficient quantities to kill off untold numbers of plants and animals living on land or in the sea.
The scientists introduced their theory in "Hypothesis for the role of toxin-producing algae in Phanerozoic mass extinctions based on evidence from the geologic record and modern environments." The paper was published in the March 2009 issue of the peer-reviewed journal Environmental Geosciences. A copy of the paper is available on the Clemson News Services Web site: www.clemson.edu/media-relations/.
Castle and Rodgers research confronts current theories that caused five major extinctions and a number of minor die-offs during the 545-plus million years during which life with "hard parts" — skeletons and shells — has flourished and left fossils. Phanerozoic is Greek for "visible life" and is the present eon in the Earth's 4.5 billion year existence. Two eons are generally considered to make up all of geological time since the formation of the Earth. The Cryptozoic — hidden life— is the larger of the two eons, but life forms lacked body parts that could become mineralized.
Other researchers have theorized that climate changes, sea level, volcanic activity, even asteroids were primary causes for deaths of more than 50 percent of life on Earth. Castle and Rodgers claim that these causes are contributors, but algae were the mass killer. They point out that asteroid-caused extinction, a popular theory for the end of dinosaurs, does not fit the evidence. "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."
Perhaps most provocative is the conclusion of Castle and Rodgers that "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." The scientists state that the level of "modern toxin-producing algae is presently increasing, and their geographic distribution is expanding...."
Rodgers has been surprised by the response to the publication of the paper. "Scientists from around the world have been sending us data that support our hypothesis and our concern about the future," said 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."