Overpopulation
October 2, 2010 7:06 AM   Subscribe

Did red algae once take over the entire planet?

I remember reading something to this effect in a book about the history of Earth. The algae was very efficient and lived off only sunlight and some common nutrient, so it covered the entire planet. Then it used up all the food, so it went extinct.

Am I just imagining this? If I am, what's the closest real example from evolutionary biology?
posted by shii to Science & Nature (7 answers total) 5 users marked this as a favorite
 
I remember something like that being a fictional story in a book about science. I think it was called Oos but I can't remember what book it was or what author wrote it - it likely would've been an AskMe from me at some point.

Hope this wasn't a hijack.
posted by codswallop at 8:05 AM on October 2, 2010


Best answer: Are you thinking of the Azolla event?

To summarise - the Earth was one in a greenhouse state where greenhouse gases were present in the atmosphere to the extent that the whole Earth was tropical, as far as the poles. Turtles once swam in the Arctic.

Vast blooms of the fern Azolla existed in the Arctic. As they sank to the sea floor, they were incorporated into the sediment and drew down carbon dioxide (a greenhouse gas) to the extent that the Earth's climate changed to an 'icehouse state' - less greenhouse gases meaning that deserts and frozen poles (and Ice Ages) are possible.

Some scientists are sceptical and believe that the Azolla may have been swept into the Arctic Ocean from river systems, but that is the gist. See 'great green north' for more detail.

The possible deposits of fossil fuels in the Arctic which are causing such interest (especially if parts of the Arctic become more accessible due to human-caused global warming...) may be Azolla.
posted by plep at 8:24 AM on October 2, 2010 [5 favorites]


Sorry - link on oil exploration in the Arctic.
posted by plep at 8:26 AM on October 2, 2010


Best answer: Do yo mean The Great Oxygen Catastrophe? It was a long, long time ago.
posted by chairface at 8:27 AM on October 2, 2010 [2 favorites]


Our sun puts out a lot of green light, so from an engineering perspective it puzzling why most plants don't use green light. It's one of those great cases that illustrate how unintelligent the designs of evolution can be. You can read about it here The bottom line is that purple photosynthetic bacteria evolved first, they used green light and reflected red & blue. So a later organism evolved to use those colors which meant it was green. Over time the green plants won the competition because their process of turning light into sugar was more efficient than the purple, even though there was more light available for the purple.
posted by Long Way To Go at 10:49 AM on October 2, 2010


Best answer: This is a great article, which may describe the event(s) you're thinking of. It was on the Blue previously. The algae themselves weren't red, but the geological record they left is.
posted by lekvar at 1:57 PM on October 2, 2010


Response by poster: chairface and lekvar, that's is exactly what I was thinking of:
With iron reactions steadily removing oxygen from the atmosphere, anaerobic bacteria thrived for a time. But eventually, there was no more free iron. Once that point was reached, oxygen started to build up in the atmosphere. Heedless, the bacteria kept churning it out - until a toxic tipping point was reached, and the Earth's atmosphere was changed to such an extent that it became poisonous to Earth's life. The consequence was mass death among the planet's abundant bacterial colonies - an oxygen holocaust that knocked life back down to nearly nothing. Only a few anaerobes survived, in isolated nooks and crannies where the deadly gas did not reach.

After this catastrophe, the planet would have seen several million years of relative quiet.
I remember this story because it shows the catastrophic extent of organic climate change. I'm glad to see that that crucial part really did happen, even though I remembered it totally wrong.

plep, your answer is equally fascinating. Thank you all!
posted by shii at 9:57 PM on October 2, 2010


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