Diatom Communities in the Cuyahoga River (USA): Changes in Species Composition Between 1974 and 1992 Following Renovations in Wastewater Management

Periphytic diatom communities along the Cuyahoga River were analyzed for possible changes in species composition resulting from improvements in wastewater management within the river basin during the past 18 years. The results, compared to a similar study conducted in 1974, and controlled for seasonality and microhabitat effects, show an increase in total diatom species (75 to 105), especially pollution-sensitive species, and a reduction in pollution-tolerant species-all indications of improved water quality. Reductions were evident in the number and proportion of pollution-tolerant species such as Gomphonema parvulum, Melosira varians, Navicula cryptocephala, N. pelliculosa, Nitzschia communis, N. palea, and Synedra ulna. The number and proportion of pollution-sensitive species such as Achnanthes linearis, Amphora pediculus, Cocconeis pediculus, Diatoma vulgare, Navicula tripunctata, and Nitzschia dissipata increased. Despite changes in species composition, headwaters of the river, managed as a domestic water supply and Ohio Scenic River, continue to support 2-3 X more taxa than the lower river below the City of Akron. Substantial degradation of water quality in the lower river persists despite recent restoration efforts. A major source of pollution occurs upstream from the Akron Water Pollution Control facility because sample sites above and below this facility were very similar in diatom species composition, each dominated by Nitzschia amphibia ( similar to 40%), a well known saprophilic diatom associated with organically polluted water. Overflows from combined stormwater-sanitary sewers, within the Akron metropolitan area are the most probable cause of the continued suppression of diatom species diversity.