Found at Fairchild: The Azolla Event

Found at Fairchild: The Azolla Event

A humble fern may have made much of modern life possible

Thursday, July 3, 2014

In summer and fall a fascinating little plant covers much of the shorelines of Fairchild's lakes. It's a lacy green and pink-edged aquatic fern. Yes, a fern that lives completely in water! It's in the Azolla genus. I believe it is the native Azolla caroliniana, aka mosquito fern, though conservationists are on the lookout for an invasive Old World mosquito fern, Azolla pinnata.

Why is Azolla so important and fascinating? Two main reasons: First, it fixes nitrogen, that is, it converts atmospheric nitrogen into a form plants can use, and use it they must! It does this with the symbiotic relationship it's developed with a cyanobacterium. Check out the similar relationship legumes (family Fabaceae) have with Rhizobium bacteria. It's an amazing symbiosis, nearly too perfect to believe. Because of its nitrogen-fixing ability, Azolla is often used in Asia as a companion planting for rice crops. Plus, the cover it provides deprives weeds of light.

Second amazing Azolla fact: The Azolla Event! In short, a greater availability of fresh water in the far northern Arctic allowed massive amounts of Azolla to flourish there—about 50 mya. Scientists have cored samples there to show that Azolla was abundant. It sequestered huge amounts of the greenhouse gas CO2, in turn eventually cooling the then-hothouse conditions prevailing on Earth. The Azolla eventually died out there, but did not decompose; rather it fossilized in the oxygen-free environment, and held onto all that carbon dioxide! The subsequent global cooling led to the world as we inherited it. Don't take my very brief word for it. Read more from National Geographic. There's even hope Azolla can help out our current climate crisis, as well as some other problems.



Here's how fish see Azolla. Note the trailing roots.