BIOLOGICAL TOOLS FOR WATER SECURITY IN THE NORTHERN GREAT PLAINS
Phillips, Iain David 1981-
Rivers and streams are a critical component of Northern Great Plains ecosystems and an extremely valuable source of surface water. Despite their importance, these waterbodies have traditionally received much less scientific attention than forested regions. This thesis provides insight into what best available natural communities may still exist, and how alterations in the physical characteristics of rivers and streams can push communities outside of their range of natural variation. Specifically, I show that since the construction of a hydroelectric dam on a large Northern Great Plains river densities of benthic macroinvertebrates have increased significantly through time in the river downstream relative to reference sites and pre-dam conditions. My findings indicate that although there is a notable loss in sensitive taxa such as mayflies and stoneflies, other midge taxa colonize this unique, cold water habitat and create a new community of benthic macroinvertebrates. Further, reaches downstream of the dam are significantly cooler than reference through the summer into August and do not reach the temperature optima of reference reaches. I use these results to develop a reference condition model that assesses current condition and can be used to monitor recovery through mitigation of these perturbations. My results have implications primarily for understanding and quantifying the ecosystem impacts of hydroelectric energy production, but also range expansion of cold-water tolerant taxa, the life-history of select groups of invertebrates, and ultimately the forage resources available to the fish assemblages of this river system. Further, as Northern Great Plains rivers are typified by considerable flow variability, particularly in the presence of water control structures, fine sediment (<63μm) is readily suspended, especially during periods of high discharge. Assessment of the impacts to biota by anthropogenic stressors must therefore occur within the context of dynamic turbidity and background flow conditions. I developed a model in which discharge is a principal determinant of in-stream suspended sediment. This relationship was explored with a case study showing that macroinvertebrate community structure is strongly correlated with suspended sediment gradients and ultimately predicted by discharge. Factors affecting sediment loads and ecosystem responses in managed systems should be considered so that in-stream water quantity and quality needs are met. This new understanding should allow for the development of improved ecosystem based flow management objectives. Finally, I develop a multivariate and predictive model based on the reference condition approach for the Northern Great Plains region of Saskatchewan from benthic macroinvertebrate communities and environmental abiotic data collected at 280 reference sites and 10 test sites. Reference sites were classified into groups characterized by similar macroinvertebrate communities. This model predicted 68.7% of the sites correctly using cross-validation. Of the 10 test sites, two were stressed (one waste water and one urban site) while three were classified as impaired (one waste water and two reservoirs). These models are effective tools that provide a practical means of evaluating biotic condition of streams in the Northern Great Plains.
DegreeDoctor of Philosophy (Ph.D.)
SupervisorChivers, Douglas P
CommitteeJanz, Dave; Johnstone, Jill; Bowman, Michelle F; Wei, Yangdou
Copyright DateOctober 2017
benthic macroinvertebrates, biomonitoring, ordinations, Northern Great Plains, rivers, streams