Ecological responses of streams to anthropogenic stressors, and watershed cause-effect modeling in the Mid-Atlantic Highlands region of the United States

Ecological Responses of Streams to Anthropogenic Stressors, and Watershed Cause-Effect Modeling in the Mid-Atlantic Highlands Region of the United States Yushun Chen Urban sprawl and related habitat disturbance and acidic deposition are major anthropogenic stressors in the Mid-Atlantic Highlands region of the United States. Little information is available about the impacts of these stressors and cause-effect relationships between these watershed stressors and stream biotic/abiotic conditions in this region. A 10-year study (1997-2006) in the Lost River watershed and a 6-year study (2002-2007) in a South Branch Potomac River watershed were conducted to assess the impacts of Corridor H highway construction on stream biotic and abiotic conditions. Also, a three-decade study (1980-2006) using data from 5 wet deposition stations and 21 major stream sites in West Virginia was conducted to assess long-term stream chemical responses to reduced acidic deposition and the role of watershed attributes in regulation of the responses. In these studies, long-term stream monitoring, laboratory chemical and biological analysis, basic (e.g., paired t tests, analysis of variance or ANOVA, chi-square analysis, and trend analysis) and advanced (e.g., principal components analysis or PCA, structural equation modeling or SEM, and latent growth curve modeling or LGM) statistical methods, and geographical information system (GIS) techniques were used to assess impacts; detect long-term trends; and model watershed cause-effect relationships. Construction of the Appalachian Corridor H highway in the Lost River watershed had statistically significant effects on seven major water quality parameters identified by the PCA analysis. Those parameters include turbidity, total suspended solids (TSS), and total iron during the construction; chloride and sulfate during and after the construction; and acidity and nitrate after the construction. The highway construction had statistically significant impacts on the scores of stream benthic macroinvertebrates index (i.e., WVSCI) after the construction, but the impacts did not change the overall good biological condition. In the South Branch Potomac River 3 watershed, the highway had no significant effects on major water quality parameters during the first year’s construction. Only episodic impacts of the highway construction on turbidity, TSS, iron, and aluminum were observed. The trend analysis found that reduced acidic deposition in the region resulted in homogeneous chemical improving trends in the West Virginia streams for sulfate, alkalinity, hydrogen ion, and total aluminum during the period of 1980-2006. The decreased deposition of acid anions and hydrogen ion explained the increase of pH and alkalinity. The SEM-based LGMs quantified most stream chemical (i.e., chloride, nitrate, sulfate, pH, hardness, and alkalinity) initial conditions (i.e., intercepts) and their changing rates (i.e., slopes) in the 1980s, 1990s, and 2000s in the central Appalachian Mountains. The slopes or trends identified by all acceptable unconditional LGMs were generally consistent with the trends detected by the trend analyses. Watershed area, mean elevation, percentage of developed, percentage of grassland, percentage of shale and sandstone, percentage of barren land, and percentage of soil type Gilpin-Upshur-Vandalia (GUV) regulated streams’ sensitivity to the reduced acidic deposition, and further influenced stream chemical initial conditions and their changing rates in these mountain watersheds. Overall, results of these studies advanced our understanding of stream biotic and abiotic responses to urban sprawl and related habitat disturbance and acidic deposition in the Mid-Atlantic Highlands region of the United States. Construction-impacted water quality parameters should be considered for developing mitigation strategies and refining currently implemented BMPs for future highway constructions in the Mid-Atlantic Highlands region. Special attentions should be paid to those episodically impaired water quality parameters which may temporally stress aquatic organisms in the streams. Further improvements in the chemical and biological conditions of the West Virginia streams may require additional controls of power plants emissions to further reduce acidic deposition in this mountain region. Stream restoration strategies for remediation of acidic deposition impacts should consider the difference of watershed attributes in different areas.