Melosira normannii

Melosira normannii is not regularly encountered in collections. It prefers oligo- to mesotrophic waters and seems to be more common in more northerly regions. It is a benthic diatom and seems to prefer deep, sandy or fine-grained sediments. Material illustrated here comes from northern Minnesota boreal lakes, a lake in Isle Royale National Park, and from epipsammon on the St. Croix River, Minnesota-Wisconsin. Below are living cells of Melosira undulata var. normannii showing how their short filaments produces large mucilage strands that hold cells among sand grains (St. Croix River, MN). Stoermer (1980) illustrates specimens from Lake Michigan and Lake Superior and notes that it is found in regions that are isolated from direct pollution sources and that its primary habitat is epipelon. Stoermer and Yang (1969) report in Lake Michigan that it is rare in the plankton, can be found as deepwater periphyton, and that the "var. normannii" is more northern than the nominate varety. Reavie and Smol (1998) found it rare in sediment cores from the St. Lawrence River and that it was not observed in modern material.