Browsing by Subject "Pond"

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    Data for: Internal Loading in Stormwater Ponds as a Phosphorus Source to Downstream Waters
    (2019-04-15) Taguchi, Vinicius J; Olsen, Tyler A; Natarajan, Poornima; Janke, Benjamin D; Gulliver, John S; Finlay, Jacques C; Stefan, Heinz G; ; taguc006@umn.edu; Taguchi, Vinicius J; University of Minnesota - St. Anthony Falls Laboratory - Stormwater Research Group
    Stormwater ponds remove phosphorus through sedimentation before releasing captured water downstream. Internal loading can impair net phosphorus removal but is understudied in these highly modified systems. Using a combination of methods, we assessed the prevalence and potential causes of sediment phosphorus release in urban ponds. In a three-year, 98-pond dataset, nearly 40% of ponds had median water column total phosphorus concentrations exceeding the 95% confidence interval for runoff values (0.38 mg/L), suggesting widespread internal loading. In a subsequent intensive monitoring study of four ponds, strong stratification prevented spring and summer diurnal mixing, resulting in persistent hypolimnion anoxia (<1 mg/L dissolved oxygen). Incubated sediment cores from seven ponds demonstrated high anoxic phosphorus release. Sediment analysis revealed high labile organic and redox-sensitive phosphorus fractions with release potential at anoxia onset. Our analyses suggest phosphorus accumulated in stormwater ponds is highly sensitive to internal loading, reducing net removal and contributing to downstream eutrophication.
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    Small Size, Huge Impact: Disproportionate Effects of Ponds on Aquatic Carbon Cycling and Atmospheric Greenhouse Gases
    (2023-05) Rabaey, Joseph
    The carbon cycle is essential for all life and is a major driver of Earth’s climate. Freshwater ecosystems (such as lakes, ponds, rivers, wetlands, etc.) play an outsized role in the global carbon cycle, acting in the transport, storage, and emission of carbon to the atmosphere. Freshwaters are significant sources of the greenhouse gases carbon dioxide (CO2) and methane (CH4) to the atmosphere despite only covering 1% of Earth’s surface area, and they have become critical a piece in global greenhouse gas models. Surprisingly, the freshwater ecosystems that may contribute the most to global emissions are small ponds, though causes of emissions and variation across ponds are not well understood. My dissertation aims to more fully understand carbon cycling in ponds and identify key factors that influence greenhouse gas emissions. Through measurements of ecosystem metabolism (i.e., the balance of photosynthesis and aerobic respiration), I found that production and respiration rates in ponds are some of the highest across all freshwater ecosystems, with shallow depths influencing many factors that lead to high rates. By measuring greenhouse gas emissions from a wide range of ponds, I found that the absence of oxygen and high phosphorus concentrations can combine to lead to elevated CH4 emissions. In addition, duckweed on the surface of ponds can exacerbate these conditions and is potentially a target for management strategies. Finally, I monitored greenhouse gas emissions in four ponds throughout an entire year and found that water column mixing and stratification greatly impacts the seasonal timing and magnitude of greenhouse gas emissions. Overall, this work emphasizes that ponds are dynamic ecosystems with high rates of carbon cycling and greenhouse gas emissions, with implications for management and global greenhouse gas dynamics.