Mosquito Fern

This tiny, floating aquatic fern is occasional on quiet backwaters in northern Indiana. It usually bears a reddish color, making it stand out from the little duckweeds with which it grows. Its reproductive cycle is much different than terrestrial ferns (it produces separate male and female spores, each producing their own gametophyte), and it lives in symbiosis with a blue-green algae, Anabaena azollae, which fixes atmospheric nitrogen. There is debate on identification of two species in the Midwest: Azolla caroliniana and Azolla mexicana.

In other parts of the world, Azolla species can be very beneficial in agriculture, covering the water's surface in rice paddies, adding nitrogen to the mix and growing so thick as to keep weeds at bay, but these same tendencies can have disastrous effects in natural wetlands, especially where freezing weather does not occur. When crowded, it tends to grow upwards from the water's surface.

Photographed in a bayou of the Kankakee River in Indiana on November 25, 2011.