The Role of Spatial Variation in Habitat Quality and Dispersal in Maintaining Diversity and Ecosystem Function Across Spatial Scales in the Urban Hydroscape of the Baltimore Metropolitan Region

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Geography and Environmental Systems


Geography and Environmental Systems

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Anthropogenic drivers of freshwater degradation are resulting in declining freshwater biodiversity world-wide. Urbanization and increases in impervious surface cover have resulted in predictable effects in aquatic systems, such as changes to watershed hydrology and increased loadings of nutrients, metals, pesticides, and other contaminants. An increasingly common feature of the urban hydroscape are stormwater ponds, which are engineered to retain excess storm run-off, and slowly release it into receiving streams. Although stormwater ponds are typically not designed as habitat, various organisms utilize stormwater ponds as novel habitat. In urban environments, stressors, such as management practices and contaminants, can result in not only local extirpation, but also diminished regional species pools of aquatic organisms. My research focuses on the influences of local environmental constraints and regional processes on biodiversity patterns and ecosystem function in urban stormwater ponds. In 2014, I used a field survey and an experimental pond study to investigate the relationship between a local constraint (algal management) and regional processes (dispersal and source pool effects) on zooplankton biodiversity patterns. The results show that local management practices marginally reduced compositional turnover between communities. The results also suggest that dispersal of colonists from managed or unmanaged source pools were important to explaining divergence in community composition. Given that stormwater ponds are likely to experience multiple anthropogenic stressors due to their engineered purposes of stormwater attenuation, in 2015, a field survey and experimental litter decomposition study were used to explore the relationship between community structure and ecosystem function in stormwater ponds and semi-natural ponds. Results indicate no significant difference in conductivity between pond types and that the rate of carbon processing was maintained, yet community composition and abundances were significantly shifted between pond types. In 2016, an experimental pond study was used to investigate the effects of a local environmental constraint (sodium chloride) and dispersal on community structure and the ecosystem function of carbon processing. Results demonstrate a significant effect of sodium chloride on both community composition and ecosystem function, with a diminished rate of litter decay in elevated sodium chloride concentrations. The results of my research highlight the complex effects of both local and regional processes on biodiversity patterns and ecosystem function in urban stormwater ponds.