Hydrogeomorphic controls on benthic light availability in rivers Public Deposited

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  • March 21, 2019
Creator
  • Julian, Jason Paul
    • Affiliation: College of Arts and Sciences, Department of Geography
Abstract
  • Light is vital to the dynamics of aquatic ecosystems. It drives photosynthesis and photochemical reactions, affects thermal structure, and influences the behavior of aquatic biota. While the influence of hydrology and geomorphology on other ecosystem-limiting factors have been well studied (e.g., habitat, nutrient cycling), the more fundamental limitation of light availability has received much less attention. In this thesis, I analyzed and quantified the hydrogeomorphic controls on benthic (or riverbed) light availability using a combination of meta-analyses, field studies, laboratory studies, and model simulations. I developed a benthic light availability model (BLAM) that predicts photosynthetically active radiation (PAR) at the riverbed (Ebed) by calculating the amount of above-canopy PAR that is attenuated by all five hydrogeomorphic controls: topography, riparian vegetation, channel geometry, optical water quality, and hydrologic regime. This model was used to assess and characterize broad spatial patterns of Ebed and temporal variations associated with variable flow conditions for a wide range of rivers. BLAM was also used to assess the effects of riparian deforestation and degraded optical water quality associated with agriculturalization on Ebed. BLAM is the first model to quantify Ebed using all five hydrogeomorphic controls, and thus provides a new tool that can be used to investigate the role of light in river ecosystem dynamics and establish light availability targets in water resource management. BLAM also provides a framework for future models to characterize spatiotemporal variations of ultraviolet and infrared radiation in rivers.
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  • Doyle, Martin W.
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