Date of Award
Master of Science (MS) in Biology
Chapter 1. Benthic macroinvertebrate (BMI) assemblages are important in the field of aquatic ecology for assessing water quality and ecosystem health. However, knowledge of BMI community structure and seasonal patterns in large impounded rivers is relatively limited in scope. In the Upper Columbia River, WA, the BMI community is of particular concern due to hypothesized starvation of native fish larvae. The population of white sturgeon (Acipenser transmontanus) which inhabits the Upper Columbia and feeds primarily on BMIs has been experiencing high mortality rates at the onset of exogenous feeding, leading to chronic larval recruitment failure. To determine the potential suitability of the BMI community as a prey source in this crucial stage of development, I explored seasonal, annual and zonal differences in BMI density, biomass, diversity and community structure within the area of highest density for first-feeding sturgeon larvae. My results indicate that during periods of high discharge and reservoir drawdown, BMI density is high but diversity is low. This is due to high relative abundance of few taxa, primarily freshwater cnidarians (Hydra sp), and Chironomid larvae (Order Diptera). Community structure changed over the course of the season, with more taxa present later after the second reservoir drawdown, but in lower densities. Chironomids were the only taxon besides Hydra which were present in moderate abundance regardless of season. Along with evidence of consumption of Chironomids by sturgeon larvae in other populations, this suggests that they may be the most suitable prey source for Upper Columbia white sturgeon larvae at this time. Further study is needed to directly connect BMI community structure with prey selection behaviors in this population.
Chapter 2. In the summers of 2007-2010, the Spokane Tribe of Indians collected benthic macroinvertebrates (BMIs) from the Upper Columbia River using three techniques: benthic sled, benthic drift, and artificial substrates. An analysis of the samples collected by these methods revealed significant discrepancies in the types of organisms caught. Benthic sled and drift methods collected mainly planktonic taxa, primarily small crustaceans. This varies significantly from the community structure of the artificial substrate samples (p<0.001), which contained primarily Cnidarian polyps (Hydra sp.), and Chironomids. Collectively, these two taxa made up an average of 93.6% of the individuals in artificial substrates in 2007, and 63.7% in 2010. Though artificial substrate samples were less diverse than samples collected by other methods (p<0.001), the samples contained more benthic oriented taxa. These data suggest that, of the benthic sampling methods presented, artificial substrates are most applicable to the study area, as they provided a more accurate representation of the BMI community with little or no overlap with the zooplankton community.
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Hindle, Sarah J., "Patterns of variation in the benthic macroinvertebrate community of the Upper Columbia River, WA" (2018). EWU Masters Thesis Collection. 499.