| The effect of anthropogenic disturbance on river systems is gaining attention, and concerns about the state of freshwater natural resources are increasing globally, as are efforts to restore habitat that has been degraded by disturbance. In rivers, non-point source pollution affects the physical characteristics of the habitat and the endemic biotic assemblages. Aquatic macroinvertebrates are numerous and exhibit graded responses to various types of disturbance in the river, and may be used as indicators of habitat conditions. In this dissertation, macroinvertebrates were examined as bioindicators in the Umatilla River in eastern Oregon. The first study is a bioassessment of the impacts of agriculture on the benthic macroinvertebrate community in adjacent streams. The results of this study show that there are physical differences in habitat associated with adjacent land use, and the macroinvertebrate communities responded to these differences with changes in taxa richness and evenness. Indicator species analysis identified thirteen taxa which were indicative of habitat conditions associated with ideal habitat used as a reference condition, degraded habitat associated with agricultural land use, and transitional habitat associated with conservation/restoration management. The second study is a laboratory study in which the effects of temperature of a common mayfly nymph, Epeorus albertae (McDunnough) (Ephemeroptera: Heptageniidae) were evaluated. The study showed that not only the developmental rate of the nymphs was affected by temperature treatment (within a range of 18°C and 28°C), but the location of accumulated body tissues over time varied by temperature, with significant difference in the type of growth observed for insects held at the highest temperature. The third study examined the response of six indicator taxa to environmental variables as predictors of abundance in a non-parametric multiplicative regression. This study found that for all taxa examined, the two best predictors of abundance in the Umatilla River were turbidity and conductivity. Increased turbidity and conductivity are common effects of intensive agriculture in streams located in agro-ecosystems, but may potentially be mitigated by vegetative buffer strips and sustainable land use practices. Long term agricultural disturbance in the landscape has been shown to have lasting effects in the ecosystem which may be further exacerbated as global climate change increases dependence on freshwater resources. Understanding anthropogenic impacts on organismal communities and natural resources is vital to establishment of effective conservation, restoration, and maintenance of a healthy ecosystem. |
