LONGITUDINAL VARIATION 

 IN THE MACROINVERTEBRATE FAUNA 

 AND WATER CHEMISTRY OF AN EASTERN 

 PENNSYLVANIA TROUT STREAM 



PATRICIA T. BRADT, Department of Biology, Lehigh University, 

 Bethlehem, Pennsylvania 



ABSTRACT 



Chemical and biological parameters in Bushkill Creek, Northampton County, 

 Pennsylvania, were sampled for 17 months to evaluate the benthic macro- 

 invertebrate population and to estimate the future of the stream as habitat for 

 reproducing brown trout. Continuing development in the drainage basin has 

 placed increasing stress on the stream. 



Longitudinal zonation was noted both in the macroinvertebrate fauna and in 

 the water chemistry. Total alkalinity, pH, conductivity, nitrate, chloride, and 

 total iron increased downstream. Biomass, total numbers, and number of taxa of 

 benthic macroinvertebrates peaked at a station 10 km above the mouth, then 

 decreased at the downstream station that was located in an urban area. Diversity 

 was highest at the rural upstream station and decreased downstream. Dominant 

 taxa of macroinvertebrates changed from Stenonema (Ephemeroptera) at the 

 upstream station, to Hydropsyche (Trichoptera) at the two midstream stations, 

 and to Chironomidae (Diptera) at the downstream station. Hydropsyche and the 

 Chironomidae are tolerant of a wide range of environmental conditions. 



If the stream is to continue to support a reproducing brown trout population 

 in the lower reaches, the stresses on the stream from urbanization must be 

 minimized. 



During the past 10 years, Bushkill Creek in Northampton County, 

 Pennsylvania has been subjected to various stresses, including (1) the 

 straightening of 3.2 km of streambed (1968—1969) in conjunction 

 with road building, (2) increased residential and commercial develop- 

 ment in the drainage basin, and (3) increasing levels of nutrients. 



This study, which covered the period 1972—1974, was under- 

 taken to evaluate the status of the benthic macroinvertebrate 

 community and to estimate the future of the stream as a brown trout 

 habitat. 



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