Killer algae a key player in mass extinctions

Oct 19, 2009
algae

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.

Supervolcanoes and cosmic impacts get all the terrible glory for causing mass extinctions, but a new theory suggests lowly algae may be the killer behind the world's great species annihilations.

Today, just about anywhere there is water, there can be toxic . The microscopic plants usually exist in small concentrations, but a sudden warming in the water or an injection of dust or sediment from land can trigger a bloom that kills thousands of fish, poisons shellfish, or even humans.

James Castle and John Rodgers of Clemson University think the same thing happened during the five largest mass extinctions in Earth's history. Each time a large die off occurred, they found a spike in the number of fossil algae mats called stromatolites strewn around the planet. Castle will be presenting the research on Monday, 19 October at the annual meeting of the Geological Society of American in Portland, Oregon.

"If you go through theories of mass extinctions, there are always some unanswered questions," Castle said. "For example, an impact - how does that cause species to go extinct? Is it , dust in the atmosphere? It's probably not going to kill off all these species on its own."

But as the nutrient-rich fallout from the disaster lands in the water, it becomes food for algae. They explode in population, releasing chemicals that can act as anything from skin irritants to potent neurotoxins. Plants on land can pick up the compounds in their roots, and pass them on to herbivorous animals.

If the theory is right, it answers a lot of questions about how species died off in the ancient world. It also raises concerns for how today's algae may damage the ecosystem in a warmer world.

"Algae growth is favored by warmer temperatures," Castle said. "You get accelerated metabolism and reproduction of these organisms, and the effect appears to be enhanced for species of toxin-producing cyanobacteria."

He added that toxic algae in the United States appear to be migrating slowly northward through the country's ponds and lakes, and along the coast as temperatures creep upward. Their expanding range portends a host of problems for fish and wildlife, but also for humans, as algae increasingly invade reservoirs and other sources of drinking water.

More information: View abstract at gsa.confex.com/gsa/2009AM/fina… /abstract_163685.htm

Source: Geological Society of America

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Graeme
5 / 5 (2) Oct 19, 2009
Stromatolites are normally found in hostile conditions, eg high salinity, rather than high fertility water. Places where animals that eat them do not thrive. So their presence may be an indication that mass extinction has already taken place.

You could expect that where toxic algae dominate over a long period, that some animal that was resistant to the poison could appear and eat them, and do very well.
frogz
4 / 5 (1) Oct 19, 2009
eventually, enough scientists will have enough theories about what killed off the dinosaurs, that all we'll need to do is put them all together and call it the day.
wiserd
5 / 5 (1) Oct 20, 2009
I've always been a big fan of iron fertilization to help revitalize fish stocks and maybe remove some carbolic acid (dissolved CO2) from the water to alkalinize it a bit. I wonder what it would take to make sure the resulting algae bloom is good algae and not some red tide.

Velanarris
not rated yet Oct 20, 2009
I've always been a big fan of iron fertilization to help revitalize fish stocks and maybe remove some carbolic acid (dissolved CO2) from the water to alkalinize it a bit. I wonder what it would take to make sure the resulting algae bloom is good algae and not some red tide.


Iron fertilization would have no effect on Carbonic acid in aqueous solution