The more I learn about the Azolla floating on the surface of the Tualatin River National Wildlife Refuge pond the more excited I get!
Fifty-five million years ago the Earth’s atmosphere had very high levels of CO₂; geoscientists call the climate at that time the “greenhouse Earth.” There were no polar ice caps, north or south. The Arctic Ocean was totally ice-free; the northern hemisphere was tropical with ferns and alligators thriving in what is now Canada and Siberia. It was what today we would think was our worst global warming nightmare. Yet, a relatively rapid climatic change occurred that flipped the Earth’s climate from the steamy greenhouse Earth to today’s icehouse Earth with its episodic glaciations and the Arctic and Antarctic icecaps.
A series of strange things happened to bring about this drastic change, and, surprise, Azolla played a significant part. For millions of years the Arctic Ocean was a vast (4,000,000 km²) nearly landlocked lake. Scientists liken it to the today’s Black Sea where that body of water is connected to the rest of the world’s oceans by a very narrow channel. Fresh water runoff from the surrounding land mass caused the ocean to have frequent surges of fresh water that spread out on top of the denser underlying salt water hundreds of thousands of times. These surges of fresh water over salt water, called “plumes,” occur today at the mouth of the Amazon and some other rivers around the world.
During those ancient plumes Azolla, a freshwater plant that floats on the first couple of inches of the surface, was able of bloom during the long summers. Azolla is one of the most explosively growing plants on Earth. It can double its biomass in two days. One of the reasons for its vigor is that the little fern has a symbiotic relationship with its own pet cyanobacteria (Anabaena azollae). The relationship has been evolving for millions of years and some of the genes from the bacteria have actually migrated into the nucleus of Azolla cells. The bacteria “fixes” nitrogen from the air and creates a nitrogen-rich environment for the fern. As every gardener knows, nitrogen is one of the key elements in plant growth.
In 2005 a polar expedition drilling for core samples from the bottom of today’s Arctic Ocean found something unexpected: samples showed thousands of layers of well-preserved Azolla plants piled up over perhaps a million years in the deep sediment at the bottom of the ocean. The massive mats of Azolla (not unlike the one that covers 90% of the TRNWR pond this very day), sucked so much CO₂ out of the atmosphere–sequestered–that it contributed to the rather swift decline in greenhouse gases and the onset of today’s icehouse Earth.
What blows my mind is that here on the Tualatin River Refuge we have a pond that is practically a microcosm of the ancient Arctic Ocean and the Azolla mats that helped turn the Earth into a habitat that supports the flora and fauna of the planet, including us. Azolla has been termed a “super plant.” There are serious studies afoot to see whether or not Azolla might do an encore and blunt the global warming currently in progress. This seems really worth mentioning to visitors and school classes learning about nature at the refuge.
Much of what I said above is drawn from a timely article in the June 2014 Goescientist Online article, The Arctic Azolla Event, by Jonathan Bujak and Alexandra Bujak. More details are in the article and in earlier articles in Wikipedia, The National Geographic and Nature.