Aquatic Macrophytes in Irrigation Canals: Environmental Controls and Impacts on Metabolic Processes

Abstract

Among irrigation canals of the U.S.’s semi-arid west, dense growths of aquatic macrophytes are a persistent issue – slowing water delivery and decreasing canal capacity. We investigated the environmental constraints on macrophyte density and composition and how canal ecosystem metabolism rates are driven by macrophyte abundance in irrigation canals in Fallon, Nevada. We found that total suspended solids were the primary driver of macrophyte density, suggesting that light availability within the water column drives macrophyte growth. Following their annual drainage from November to March, we observed ecosystem development patterns in the canals with net ecosystem production peaking prior to a peak in biomass. Gross primary production rates increased with surface light while ecosystem respiration rates increased with temperature and sediment organic matter.