Algae Key To Mass Extinctions?
Friday, 23. October 2009, 13:10:25
There are lots of hypotheses about what causes mass extinctions, one more fanciful than the other. Two ideas taken more seriously are volcanoes and cosmic impacts. Now a new hypothesis suggests algae may be the killer behind the world's great fauna annihilations.
The idea was introduced in "Hypothesis for the role of toxin-producing algae in Phanerozoic mass extinctions based on evidence from the geologic record and modern environments" , a paper published in the March 2009 issue of the peer-reviewed journal Environmental Geosciences, and also presented in a talk on 19 October 2009, at the annual meeting of the Geological Society of American in Portland, Oregon, USA. (The full paper by Castle and Rodgers from March can be downloaded from this Clemson University site).
Castle and Rodgers have spent two years analyzing data from ancient 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 geologic record demonstrates a pronounced increase in abundance and environmental range of algae, including stromatolitic cyanobacterial mats, coincident with the first four of the five major Phanerozoic (the last 545 million years) mass extinctions. During these past events of algal expansion, population decline of animals could have been caused by effects of algal blooms, including algal-produced toxins, at a scale sufficient to generate a fossil record of mass extinction.
Mass extinctions have often been attributed to climate changes, sea level, volcanic activity, and asteroids. Castle and Rodgers claim that these causes are contributors, but algae were the mass killer.
Environmental changes such as climatic warming, sea level fluctuation, and increased nutrient supply may have promoted algal blooms over vast expanses of marine to freshwater environments. and indeed, in my humble opinion toxic algae may just be another contributor together with other factors leading to (too) harsh environmental conditions.
Schematic profiles illustrating the influence of climate-induced sea level change on algal growth. (A) Sea level is low, shelves are narrow, and water temperatures are less favorable for algal growth during periods of cool global climate. (B) During periods of warm global climate, sea level is high resulting in extensive areas of shallow marine and coastal environments favourable for algal growth. Warm water temperatures promote the growth of algal blooms, domal and columnal stromatolites, and stromatolitic mats, which increases the potential for toxin production and release.
The idea was introduced in "Hypothesis for the role of toxin-producing algae in Phanerozoic mass extinctions based on evidence from the geologic record and modern environments" , a paper published in the March 2009 issue of the peer-reviewed journal Environmental Geosciences, and also presented in a talk on 19 October 2009, at the annual meeting of the Geological Society of American in Portland, Oregon, USA. (The full paper by Castle and Rodgers from March can be downloaded from this Clemson University site).
Castle and Rodgers have spent two years analyzing data from ancient 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 geologic record demonstrates a pronounced increase in abundance and environmental range of algae, including stromatolitic cyanobacterial mats, coincident with the first four of the five major Phanerozoic (the last 545 million years) mass extinctions. During these past events of algal expansion, population decline of animals could have been caused by effects of algal blooms, including algal-produced toxins, at a scale sufficient to generate a fossil record of mass extinction.
Mass extinctions have often been attributed to climate changes, sea level, volcanic activity, and asteroids. Castle and Rodgers claim that these causes are contributors, but algae were the mass killer.
Environmental changes such as climatic warming, sea level fluctuation, and increased nutrient supply may have promoted algal blooms over vast expanses of marine to freshwater environments. and indeed, in my humble opinion toxic algae may just be another contributor together with other factors leading to (too) harsh environmental conditions.
Schematic profiles illustrating the influence of climate-induced sea level change on algal growth. (A) Sea level is low, shelves are narrow, and water temperatures are less favorable for algal growth during periods of cool global climate. (B) During periods of warm global climate, sea level is high resulting in extensive areas of shallow marine and coastal environments favourable for algal growth. Warm water temperatures promote the growth of algal blooms, domal and columnal stromatolites, and stromatolitic mats, which increases the potential for toxin production and release.
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http://www.clemson.edu/media-relations/article.php?article_id=2336
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http://www.redorbit.com/news/science/1771782/clemson_researchers_say_algae_key_to_mass_extinctions/index.html?source=r_science
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http://www.terradaily.com/reports/Killer_Algae_A_Key_Player_In_Mass_Extinctions_999.html
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http://www.usnews.com/science/articles/2009/10/21/killer-algae-a-key-player-in-mass-extinctions.html
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