Jake Loveless, Utah Valley University
Life Sciences
Macroinvertebrate assemblage composition was assessed in two perennial streams, Pleasant Creek, and Sulphur Creek in Capitol Reef National Park, Utah, during the summer of 2014. Individuals collected were identified to genus. This information was used to compare assemblage composition, nutrient availability, and water quality between the two streams. Five collection trips were made (May 27, June 10,17, July 1,15). Sampling was conducted randomly using mesh kick nets with four samples being collected per site, per trip. Heavy rains caused flash flooding on July 15 prohibiting sampling, so a total of sixteen samples per site were taken. Samples were stored in 90% isopropyl alcohol until they could besorted and identified using a dissecting microscope. Water quality estimates were determined by taking the weighted average of the tolerance values, and the final classification was made using the family-level biotic index. Pleasant Creek showed the highest number of taxa present, fourteen, compared to six in Sulphur Creek. Both streams followed the predictions of the River Continuum Concept consisting of collector-dominated functional feeding groups, with Pleasant Creek showing a higher percentage of predators 35.7% to 16.6%. Tolerance values of collected taxa were used to estimate organic pollution indicating good water quality in Pleasant Creek, and fairly poor water quality in Sulphur Creek. The differences in the macroinvertebrate assemblage composition in this study were likely multi-causal. Stream size is a major factor influencing the structure of macroinvertebrate assemblages; in general, as stream size increases, more taxa are added. Pleasant Creek is a much larger stream with a well-established channel, while Sulphur Creek is shallow with depths never exceeding fifteen centimeters. The shallow channel of Sulphur Creek also made it prone to frequent flooding. Isolated floods have little impact on macroinvertebrate communities due to availability of aerial adults nearby to recolonize rapidly, however, frequent flooding may have long-term effects through extirpation of taxa with high mortality. The difference in water quality was the most surprising finding in this study. The fairly poor water quality of Sulphur Creek may also be a factor in the lack of genera found there. Organic pollution effects primary productivity in streams, and while primary productivity was not measured in this study, visual observations found very little algae or aquatic vegetation at Sulphur Creek.