Theses and Dissertations from UMD
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Item LONGITUDINAL STREAM SYNOPTIC (LSS) MONITORING TO EVALUATE WATER QUALITY IN RESTORED STREAMS(2023) Malin, Joseph Thomas; Kaushal, Sujay S; Geology; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Many kilometers of streams are being restored in the Chesapeake Bay watershed and elsewhere in efforts to stabilize streambanks, protect infrastructure, and improve water quality. Urban development and impervious surface cover increase peak flows, which degrade streams. Restoration strategies often employ engineering approaches to enhance stream-floodplain reconnection, dissipate erosive forces from urban runoff, and enhance contaminant retention. In this study, longitudinal stream synoptic (LSS) monitoring (sampling multiple points along flowpaths across both space and time) was conducted to assess the effectiveness of different forms of stream restoration in attenuating pollutants downstream. Spatial and temporal monitoring of carbon, nutrients, salt ions, and metals were conducted across five watersheds experiencing varying levels of stream-floodplain reconnection and stormwater management within the Chesapeake Bay region. Study sites included Sligo Creek (minimal floodplain reconnection), Paint Branch (streambank stabilization without significant reconnection), Scotts Level Branch (engineered stream-floodplain reconnection), Little Paint Branch (natural floodplain reconnection from sedimentation), and Campus Creek (regenerative stormwater conveyance with engineered floodplain reconnection). We investigated: (1) whether changes in water chemistry can be detected along longitudinal flowpaths in response to stream-floodplain reconnection, and (2) which monitoring scales across space and time can provide useful information regarding the effectiveness of restoration. Results from this work suggest that longitudinal synoptic monitoring can track the fate and transport of multiple contaminants and evaluate restoration strategies across high spatial-resolution scales. Along all five watersheds, stream water chemistry varied substantially across finer spatial scales (sometimes within hundreds of meters) in response to changes in landscapes, restoration features, or local hydrology. There were significant declining concentrations (p<0.05) or stable concentrations of nutrients, salts, and metals as streams flowed through restoration features. There were significant increasing trends in chemical concentrations (e.g. Na+, Ca2+, K+) in unrestored stream reaches with increasing impervious surface cover. Principal component analysis (PCA) also indicated that there were changes in the chemical compositions of mixtures of salts, metals, and nutrients in response to restoration projects, storm events, and seasons. Interestingly, dissolved Fe and Mn concentrations showed significant increasing trends along some stream reaches with hydrologically connected floodplains. Fe and Mn also showed significant decreasing trends along some unrestored stream reaches surrounded by increasing impervious surfaces. Increased concentrations of dissolved Fe and Mn may have been an indicator of increased hydrologic connectivity between groundwater and surface water and decreased redox potentials. Overall, longitudinal water quality changes over meters and kilometers can be useful in detecting effects of stream restoration on water quality at the watershed scale. Results suggest that water quality in urban streams can change locally in response to restoration projects for multiple chemicals, but the incremental changes associated with different forms of stream restoration and riparian conservation can also be overwhelmed across broader watershed spatial scales and during storm events.Item The Diversity of Burrowing Benthic Invertebrates and their Impact on Phosphorus Dynamics in Agricultural Drainage Ditches(2014) Leslie, Alan William; Lamp, William O; Entomology; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Agriculture remains the most widespread cause of impairment of freshwater habitats, but farm lands with artificial drainage structures such as ditches have specific locations where natural physical and biogeochemical processes can be used to reduce nutrients delivered to local watersheds. Agricultural drainage ditches can also be sources of biodiversity, serving as patches of uncropped aquatic habitat that may provide a significant amount of diversity to agricultural landscapes. Macroinvertebrate communities play important roles in nutrient cycling in natural aquatic ecosystems, but to this date no information exists on the role of invertebrate communities in biogeochemical processes occurring in ditches. The overall goal of my dissertation was to determine the structure of the aquatic macroinvertebrate community of agricultural drainage ditches, and to determine the functions these species play in nutrient cycling. First, I performed a broad survey of aquatic macroinvertebrates in drainage ditches and related the community composition to environmental conditions. Ditches support different communities of macroinvertebrates, and community composition is correlated with physical habitat characteristics such as flow velocity (r2=0.58) and ditch size (r2=0.56), rather than water quality. I then measured the burrowing community of small (field) and large (collection) ditches over a year to determine how size class and seasonality affect taxonomic and functional group composition. I found small and large ditches support different taxa due to the intermittent water condition of small ditches, but both types of ditches support similar functional groups. There is limited diversity among functional feeding groups in ditches, but the majority of macroinvertebrates (101 of 140 taxa) are benthic taxa that may cause bioturbation of ditch sediments. I used microcosms to measure the effect that different burrowing species (Ilyodrilus templetoni, Limnodrilus hoffmeisteri, Crangonyx sp., Chironomus decorus S.G.) have on phosphorus dynamics between ditch sediments and water. Results show different species can increase (0.28 to 2.05 mg/L) or decrease (0.08 to 0.41 mg/L) soluble, reactive phosphorus concentrations in surface water, depending on the type of burrowing and environmental conditions. Different types of burrowers likely alter phosphorus dynamics through different mechanisms, and increasing diversity of burrowers could have non-additive effects on phosphorus uptake by ditch sediments.Item Nitrogen saturation in streams and forests of the Maryland Piedmont(2009) Craig, Laura Shawn; Palmer, Margaret A; Behavior, Ecology, Evolution and Systematics; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Human activities have dramatically increased nitrogen (N) inputs to the landscape. Consequently, delivery of N to coastal waters, largely as nitrate (NO3-N), has increased, resulting in widespread eutrophication and harmful hypoxic conditions. The ability to mitigate the downstream effects of elevated N inputs requires a clear understanding of the transport and transformation of N in stream ecosystems. Here, I examine N processing in urban and forested watersheds of the Maryland Piedmont. I provide extensive evidence that three high-N streams draining urban and forested watersheds of the Maryland Piedmont are unable to remove NO3-N as a result of both N saturation and phosphorus limitation. My findings illustrate that when elevated NO3-N concentrations occur in the absence of other stressors that stimulate autotrophic activity (e.g. reduced canopy cover, increased nutrients) uptake cannot compensate for increased N loads. A review of the literature indicates that systems that are similarly unable to remove NO3-N vary widely in terms of land use and background N concentrations, highlighting the limitations of our understanding of N saturation in stream ecosystems. I also provide the first documentation of N saturation in both the aquatic and terrestrial components of an un-manipulated forested watershed. Detailed examination of N dynamics within the forested watershed reveals that the forest is severely N-saturated despite receiving atmospheric N inputs that are small relative to other parts of the Northeast and Mid-Atlantic. Because groundwater delivers a disproportionate fraction of the N load to the channel, in-stream N concentrations are elevated when deep groundwater flowpaths dominate, and the watershed is a source of N during dry periods, I hypothesize that hydrogeologic factors that control groundwater susceptibility to NO3-N contamination and promote delivery of NO3-N via subsurface flowpaths may exacerbate N-saturation response. My results suggest that we cannot rely on in-stream processing to reduce N loads even in minimally impacted watersheds. As a result, it is critical that management efforts reduce N loading to streams and take advantage of opportunities for increasing N removal in impaired systems only after other options have been exhausted.