Person in a stream Allegheny County
Home> River Research> Ohio River> Aquatic Invertebrates

Aquatic Invertebrate Biological Assessments Ohio and Comparative Analysis

Michael Koryak, Chief Limnologist
and Linda J. Stafford, Biologist
U.S. Army Corps of Engineers, Pittsburgh District

Aquatic macroinvertebrate communities are sensitive indices of stream water quality and ecological health. In the third phase of a three-year effort to conduct invertebrate-based bioassessments of local urban/suburban streams, chemical and invertebrate samples were collected during the Spring of 2003 at 18 streams stations. All of these stations were located near the mouths of streams tributary to the Ohio River in Allegheny County, Pennsylvania.

Chemically, the study streams tended to be alkaline, hard, and very mineralized. The mean values for pH, alkalinity, hardness, and conductivity were 8.13, 103 mg/l as CaCO3, 280 mg/l as CaCO3, and 914 µmhos/cm, respectively. Calcium concentrations averaged 80.7 mg/l and sodium 71.5 mg/l. Concentrations of ammonia and other nutrients were elevated at a number of stations. These parameters are fingerprints of widespread influences of alkaline mill slag leachates, highway deicing salts, and sewage contamination, and, at some locations, acid mine drainage from bituminous coal mines.

More than 6,558 invertebrate organisms from 68 different taxa were collected, identified, and enumerated at the 18 Ohio River tributary stations. Condition scores were then developed from the invertebrate data for each station, where a score greater than 80% indicates that a stream is non-impaired, 60-79% slightly impaired, 40-59% moderately impaired, and less than 39% severely impaired. All of the stream stations examined were impaired to various degrees; nine severely impaired, eight moderately impaired, and one only slightly impaired. While it is disappointing that there were no Phase 3 study streams without measurable degradation, it is still encouraging that 50% of the streams examined were only slightly to moderately impaired. The diversity of aquatic life found in these streams exceeds what might have been expected from historical memories and impressions of these urban waterways as industrial waste conduits and/or open sewers. The Phase 3 streams with the highest condition scores were Tom Run (77.5), Sewickley Creek (57.8), Thorn Run (56.0), Blackburn Run (54.9), Narrows Run (54.6), Little Sewickley Creek (52.3), Flaugherty Run (48.3), Kilbuck Run (42.9), and Moon Run (40.8).