The Great Lakes are used for the disposal of industrial wastes, sewage effluents and sewer runoff laden with road salts. The associated increase in salinity and total dissolved solids may account for the successful invasion and population development of the marine red algae, Bangia atropurpurea (Roth) A. While the naturally occurring green alga, Cladophora glomerata (L.) Kutz. supports a variety of epiphytes, Bangia ia almost devoid of epiphytic organisms. As Bangia competes with Cladophora and becomes more abundant, there may be alarming repercussions in the foodweb of the Great Lakes. Bangia and Cladophora, two of the dominant algae attached to rocks near shore in northern Lake Michigan, were collected from Grand Traverse Bay on November 11, 1978.