Research Experiences for Undergraduates
Program in Water Research at 
Colorado State University

Mentor Information

Name N. LeRoy Poff

Title Assistant Professor

Department Biology

Work Phone 491-2079

FAX 491-0649


Project Title Ecological effects of streamflow diversions in Colorado algal community responses

Project Abstract The primary objective of this research program is to assess how streamflow diversion projects have influenced aquatic ecosystem functions in the Fraser River basin, Grand County, Colorado. As part of the larger context for the work proposed here, we are currently quantifying how water depletion programs influence invertebrate communities, secondary production, and food web dynamics in small subalpine streams. Our proposed REU project will address the question of how reach-scale algal assemblage composition and biomass differ in reaches above versus below long-established diversion structures on 6 streams in the Fraser River basin. Differences in algal assemblages are likely the result of increased hydrologic, habitat, and thermal stability in diverted vs. undiverted reaches. These reaches are infrequently disturbed by high-flow events and a greater proportion of their surface flow is attributable to thermally-moderated groundwater discharge. Because of these factors, we hypothesize:

1. Algal assemblages associated with diverted reaches (i.e., reaches below diversion structures) will have higher total taxa richness than those from naturally-flowing reaches (i.e., reaches above diversion structures).

2. Algal assemblages collected from diverted reaches on separate streams will be more similar to each other than to assemblages from undiverted reaches on the same stream.

3. Total abundance of all algae (diatoms, green algae, bluegreen algae) will be higher in diverted reaches, whereas diatom relative abundance will be higher in naturally-flowing reaches.

We will address these hypotheses by sampling algae from all substrata and habitats in proportion to their areal coverage in each reach after spring snowmelt runoff. Three such composite samples of algae will be collected from reaches in 2 diversion categories (naturally-flowing and diverted) on each of 6 streams. Samples will be preserved in the field and returned to the laboratory where algae will be identified to the lowest practicable taxonomic level. We’ll use an ANOVA design to test for habitat and stream effects using several commonly-used metrics of water quality including algae relative abundance, algae taxa richness, diatom relative abundance, diatom richness, total taxa richness, and percent similarity among sites.