DIATOM COMMUNITIES IN THE CUYAHOGA RIVER (USA) - CHANGES IN SPECIES COMPOSITION BETWEEN 1974 AND 1992 FOLLOWING RENOVATIONS IN WASTE-WATER MANAGEMENT

Periphytic diatom communities along the Cuyahoga River were analyzed f or possible changes in. species composition resulting from improvement s in wastewater management within the river basin during the past 18 y ears. 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 sp ecies, and a reduction in pollution-tolerant species-all indications o f improved water quality, Reductions were evident in the number and. p roportion of pollution-tolerant species such as Gomphonema parvulum, M elosira varians, Navicula cryptocephala, N. pelliculosa, Nitzschia com munis, N. palea, and Synedra ulua. The number and proportion of pollut ion-sensitive species such as Achnanthes linearis, Amphora pediculus, Cocconeis pediculus, Diatoma vulgare, Navicula tripunctata, and Nitzsc hia dissipata increased. Despite changes in species composition, headw aters 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 lo wer river persists despite recent restoration efforts, A major source of pollution occurs upstream from the Akron Water Pollution Control fa cility because sample sites above and below this facility were very si milar in diatom species composition, each dominated by Nitzschia amphi bia (similar to 40%), a well known saprophilic diatom associated with organically polluted water. Overflows from combined stormwater-sanitar y sewers, within the Akron metropolitan area are the most probable cau se of the continued suppression of diatom species diversity.