Biophysical Coupling

Biological elements of a system do not just respond to physical changes but can also induce changes in the physical or chemical aspects of a system. We investigate how change propagates through coupled biophysical systems.

f1_InteractionDiagram5We have developed a coupled biophysical model of freshwater mussel population response to long term dynamic changes in hydrology, suspended sediment and food availability. Without including the complex and dynamic coupling between these drivers, we would not have captured the biological response to multiple chronic stressors.  Right: Process interaction network showing the streamflow-driven, coupled hydro-geo-biological system that is incorporated into a dynamic model and applied to the Minnesota River Basin and St. Croix River.  Black dashed lines show weak interactions and black solid lines show strong interactions, which are either positive (+) or negative (-).

mussel_LoRes

The variations and transport of organic matter in streams and rivers likely have important consequences for ecosystem processes and biota. Especially, filter-feeding and collecting microinvertebrates are two groups of biota that feed on suspended and deposited particulate organic matter. We are investigating how their growth might reflect the patterns and variability of flow conditions and organic matter and lead to eliciting the linkages between physical processes, such as hydrology and sediment transport, and biologic processes, such as the structure and function of food webs and the carbon that supports them.

We have carried out laboratory and field experiments to understand and quantify the relationships among vegetation establishment, hydrology, and sediment transport towards guiding management actions and the identification of priority management zones to reduce sediment related impairments. Our work has shown that riparian vegetation is the primary control on river morphology by adding surface cohesion and by trapping and storing suspended sediment and that the dynamic interaction of hydrology with point bar vegetation during low and high flows plays a significant role in determining the long-term ecological and sedimentological state of the river.  Right: Overbank deposition of fine sediment within a patch of vegetation (alfalfa, Medicago sativa).