Water Resources Research Act Program

Details for Project ID 2017CO334B

Effects of Water Velocity on Algal-Nutrient Interactions in Streams of the Poudre Watershed, Colorado

Institute: Colorado
Year Established: 2017 Start Date: 2017-03-01 End Date: 2018-02-28
Total Federal Funds: $5,000 Total Non-Federal Funds: $2,550

Principal Investigators: N. Leroy Poff

Abstract: Algae form the base of many stream food webs, facilitate nutrient recycling, and provide habitat for aquatic insects. However, nuisance algal blooms can form when streams have high nitrogen and phosphorus concentrations. This is an issue of state and national concern because algal blooms lower stream dissolved oxygen, a required resource for insects and fish, and degrade recreational opportunities. Managers have thus focused on reducing nutrient loads in waterways, and Colorado has recently proposed in-stream nutrient water quality criteria. However, a little-explored research area is how stream water velocity can regulate the development of these blooms by a) influencing algal uptake of nutrients, b) scouring algae from rocks and other surfaces, and c) regulating insect grazing activity. I propose to complete field experiments in mountain streams of the Poudre watershed to investigate how water velocity interacts with nutrient additions to control algal biomass. Objective 1 will determine how current velocity affects algal biomass responses to nitrogen and phosphorus additions. For this experiment, I will deploy nutrient diffusing vials in two different current velocities at eight streams, and measure algal and microbial growth over three weeks. Objective 2 will determine how current velocity affects nutrient uptake rates of algal and microbial communities. For this experiment, I will release nutrients and a tracer in two different current velocities of eight streams, and will measure how quickly nutrients are taken up from the water column over space and time. Finally, Objective 3 will involve synthesizing and communicating results to scientific and non-scientific audiences. Completing these objectives will provide managers with data on how stream velocity can be manipulated to control algal populations, and also how currently-proposed streamflow regimes (e.g., for fish populations) will subsequently affect algae. This basic research is required to highlight stream heterogeneity and inform nutrient management plans under different streamflow conditions. Additionally, these experiments are a fundamental component of my larger dissertation that seeks to improve models of algal accumulation by considering temporally-variable factors like streamflow, temperature, and aquatic insect activity.