Dust Composition and Deposition Effects on Ecosystems in the American West

Aerosol transport has the capacity to move a broad range of constituents across ecosystems and upslope to sensitive high-mountain areas. Though direct evidence is still lacking, several lines of inquiry suggest that dust nutrient subsidies lead to aquatic ecosystem shifts and may be driving the loss of pristine, low-nutrient environments. Understanding the effects of dust deposition on ecosystems has been hampered by the fact that traditional monitoring programs focus primarily on particles less than 10 microns, and thus fail to capture to full breath of materials in the atmosphere. Our research has attempted to fill these knowledge gaps through high-frequency temporal and spatial sampling of dust deposition in the American west. Results from 5 years of monitoring indicate that dust deposition rates and composition have marked seasonality with notable shifts in composition along elevation gradients. The experimental addition of dust to aquatic ecosystems revealed shifts in production and community composition. To understand dust-plant dynamics, a controlled greenhouse experiment examined trace nutrient uptake in plants exposed to dust collected from a playa source. Watershed models confirm that dust nutrients delivered to mountain catchments are transported to freshwater systems. Finally, the synthetic fraction of dust (polymers) ranged from 2 to 6%; in study reaches microplastic deposition was sufficient to account for all the microplastics observed in headwater streams.