Benthic macroinvertebrates and ecological assessments: Examining the biological potential of urban stream restoration in the San Francisco Bay area

Urbanization is a growing land-use change that has complex and pervasive impacts on aquatic communities. Alterations associated with urbanization can cause dramatic shifts in biological assemblages of benthic macroinvertebrates in urban streams, including reductions in the abundance and richness of sensitive taxa. The decline of biological communities in urban areas can result from a wide variety of stressors, which makes management and restoration of these systems difficult. This dissertation examines biological potential thresholds that can be used to simplify the complexity of urban stressors and facilitate the protection and restoration of aquatic resources in urbanized catchments.;As the impact of urbanization on aquatic communities increases, the preservation of unimpacted areas is crucial for understanding natural systems in the absence of disturbance. Therefore, I studied the life history of an undescribed species of egg-mass predator (Diptera: Scathophagidae: Acanthocnema) of a pollution-sensitive caddisfly species (Trichoptera: Uenoidae: Neophylax rickeri) in a catchment located in a peri-urban area. This predator exhibited a bivoltine life cycle in which the winter cohort fed exclusively on N. rickeri egg masses and the spring cohort fed on several different egg mass types.;I also conducted multifaceted post-project assessments of several urban stream restoration projects in the San Francisco East Bay (including Baxter Creek in El Cerrito, California and Strawberry Creek on the University of California, Berkeley campus). Results from the Baxter Creek study found initial increases in biological and habitat condition within the first 1-3 years following the project's completion, but no further improvements over the long-term (3-10 years). The second study of a riparian revegetation project along Strawberry Creek found that native plant cover and diversity successfully increased post-restoration.;Lastly, I examined the response of benthic macroinvertebrates (as biological indicators) across a gradient of urbanization in three climatic regions of the United States (Pacific coast, Midwest, and Mid-Atlantic) and used quantile regression to define biological potential thresholds. The resulting multi-metric index (composed of compositional, functional feeding group, and habit metrics) showed a similar response among regions. The biological potential thresholds are intended to use in setting realistic restoration objectives within urban streams.