Unsteady hydrodynamic conditions and biological/biogeochemical processes

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The long-term objective of my research program is to understand how hydrodynamic factors affect biologically and biogeochemically relevant mass transport (i.e., the movement of mass) in the environment. Environmental flows are turbulent and are characterized by unsteady flow conditions caused by variations in flow and fluid-structure interactions in the benthos (bottom region), which are difficult to reproduce in the laboratory and to model mathematically. Consequently, simplified well-behaved and idealized hydrodynamic conditions are typically used in laboratory and/or computational models. This proposal is directed toward a better understanding of how unsteady conditions affect the mass transport of dissolved (e.g., gases and nutrients) and particulate (e.g., algae, and gametes) matter in aquatic systems; it will be achieved through laboratory, field, and computational experiments. Results will benefit the physical and natural sciences because I will examine both the hydrodynamics and the ecophysiology of the organism/system using an interdisciplinary approach. Ultimately insights from these results will be applied more commonly in laboratory as well as be incorporated into models and used in computational studies. Unsteady flows, caused by changes in flow, disturbances, instabilities and by fluid-structure interactions (vortex-induced vibration; VIV), affect the transport of mass and the organisms using the matter. The proposed research will advance our understanding of how unsteady conditions affect the uptake of dissolved matter in macrophytes (i.e., aquatic plants), the capture of particulates on structures, and particulate matter clearance by mussels (i.e., suspension feeding), as well as biogeochemical flux that occur in the benthic and hyporheic zones of aquatic systems. My proposed research will focus on the fundamental mechanisms and theoretical constructs underlying mass transfer to better understand how it occurs in these systems. My specific objective over the next five years is to determine how unsteady flow affects: (1) the uptake of dissolved inorganic carbon by aquatic macrophytes with and without oscillations caused by VIV; (2) suspension feeding rates in freshwater mussels in flow chambers and benthic-pelagic coupling in the field; (3) the fate of suspended matter (e.g., particles, algae, larvae) transported in rough-turbulent boundaries in which roughness leads to unsteady conditions the field; and (4) the transport of environmentally relevant scalars (e.g., oxygen, temperature) to and from sediments and hyporheic zones in the field. These themes are linked because they are components of my long-term objective to understand how hydrodynamic factors affect environmental mass transport.  Importantly, addressing these themes will lead to a better understanding of the productivity and functioning of aquatic ecosystems, which has important implications to water quality, conservation, fisheries, and climate change.