A Study of the Effects of Stream Improvement Procedures on Benthic Macroinvertebrates

Abstract

The effects of stream flow alteration on benthic macroinvertebrates and water quality were studied in two regions of Hunting Creek, a cold water stream originating in Catoctin Mountains in northern Frederick County, Maryland. The study involved two sections of stream, both located in the headwaters of Hunting Creek. One stream section was modified for the purpose of this study by building stream improvement devices in the stream channel; the other section of stream was maintained in its natural condition. Permanent collecting stations were established along each stream segment and benthic fauna and water quality were sampled on a regular basis. Monthly, benthic samples were collected for eight months by means of a Surber square foot bottom sampler. Drift net samples also were collected on three occasions during the study. Chemical and physical features of water collected from the two study areas were measured using standard methods for water analysis. Water samples for chemical analysis were collected on three occasions while physical parameters were measured each time benthic samples were collected. Random stream sampling for benthic macroinvertebrates and water quality also was done above and below the study areas to obtain additional data for use in characterizing the two stream sections being studied. The benthic faunas of the study areas were compared on the basis of diversity, density of organisms, species composition, frequency and dominance. The physical features used in evaluating water quality included depth, velocity, volume and temperature. The chemical characteristics measured were dissolved oxygen, pH, nitrate, ammonia, total phosphate, turbidity, total hardness, conductivity, carbon dioxide and hydrogen sulfide. Analysis of chemical and physical data failed to show a statistically significant difference in water quality of the two stream areas. The benthic composition of the two study areas, was found to differ significantly with respect to diversity, density, frequency, dominance, species composition and drift. Data from the improved stream section showed lower values for all biological features evaluated for benthic macroinvertebrates, regardless of stream improvement efforts. The unimproved stream area and random stream sites located above and below Hunting Creek Lake showed similar values that were consistently higher than the improved stream section for all biological characteristics evaluated for the benthic macroinvertebrate fauna.