The upper Great Lakes contain a diverse array of benthic algal communities. Characteristic communities occupy substrates from the supralittoral to depths in excess of 30 m. Diatoms are the dominant taxonomic group present in terms of numbers, and usually in terms of biomass, except in eutrophic areas. Communities in areas receiving minimal direct anthropogenic impact are extremely diverse in terms of both species richness and population evenness. The populations which comprise these communities are generally reported from extremely oligotrophic habitats. A significant number of populations found in undisturbed habitats in the upper Great Lakes have not been previously reported from North America. Benthic communities in more eutrophic areas are characterized by a greater abundance of eurytopic and widely distributed taxa. Many of these species are familiar elements of the floras of smaller, mesotrophic to eutrophic lakes. The communities of directly impacted areas contain a more limited suite of very tolerant populations, usually occurring in high abundance.

"July 1980." "Project Officer: Nelson A. Thomas." Includes bibliographical references (pages 24-25). "Grant No. 803037."