Scholarship & Research
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Item The effects of temperature on stream ecosystem structure, secondary production, and food web dynamics(Montana State University - Bozeman, College of Letters & Science, 2019) Junker, James Robert; Chairperson, Graduate Committee: Wyatt F. Cross; Wyatt F. Cross, Jonathan P. Benstead, Alexander D. Huryn, James M. Hood, Daniel Nelson, Gísli M. Gíslason and Jón Ólafsson were co-authors of the article, 'Patterns and drivers of ecosystem-level biomass and stoichiometry in streams' submitted to the journal 'Ecosystems' which is contained within this thesis.; Wyatt F. Cross, Jonathan P. Benstead, Alexander D. Huryn, James M. Hood, Daniel Nelson, Gísli M. Gíslason and Jón Ólafsson were co-authors of the article, 'Resources govern the temperature-dependence of animal production at multiple timescales' submitted to the journal 'Ecology letters' which is contained within this thesis.; Wyatt F. Cross, Jonathan P. Benstead, Alexander D. Huryn, James M. Hood, Daniel Nelson, Gísli M. Gíslason and Jón Ólafsson were co-authors of the article, 'Responses of food web organic matter fluxes to temperature and their implications for food web stability' which is contained within this thesis.Since 1880, Earth's mean temperature has risen ~0.85 °C, and increases >1.5 °C are likely by the end of the 21st century. Warming temperatures will continue to shuffle and restructure ecological communities and the consequences of these changes for ecosystem processes and services are largely unknown because of the difficulties in measurement and understanding in complex ecological systems. Yet, isolating temperature's influence is crucial to predicting how ecosystems will look and operate in a 'no-analog' future and to begin to integrate warming with the myriad other stressors affecting natural systems. In this dissertation, I leverage a natural stream temperature gradient (~5 - 25 °C) within a geothermal watershed to investigate the effects of temperature on stream ecosystems--with three specific questions: 1) what is the relative influence of temperature and stream flow on whole-ecosystem biomass and element storage? 2) how does temperature shape patterns of animal production across and within streams? and 3) how does temperature modify the seasonal patterns of consumer-resource interactions in stream food webs? I found stream flow to have primacy in driving the 2 orders of magnitude variation in ecosystem biomass and element storage--mediated through flow's effect on plant body size. At higher trophic levels, temperature strongly shaped the patterns of secondary production coinciding with a 45-fold increase in annual secondary production across streams. This positive relationship was mediated through covariation between temperature and basal resource availability, both across and within streams. Consumer interactions with basal resources showed differing seasonality with increasing temperature. At higher temperatures, consumer demand and resource availability were strongly coupled seasonally compared to cooler streams. Tighter coupling between consumers and resources with temperature lead to more consistent, if higher, interaction strengths through the year. My work shows temperature as an important structuring driver of ecosystem structure and process, however, a common thread through each chapter shows the influence of temperature is mediated through its interactions with other ecosystem drivers. Ultimately, as the covariation between temperature and other environmental drivers (e.g., disturbance, nutrient and light availability, etc.) shift globally, recognizing these interactions is increasingly important.Item Environmental drivers of salmonfly ecology in southwest Montana(Montana State University - Bozeman, College of Letters & Science, 2018) Anderson, Heidi Elise; Chairperson, Graduate Committee: Lindsey Albertson; Lindsey K. Albertson and David M. Walters were co-authors of the article, 'Temperature-driven range contraction and body size reduction of an iconic aquatic insect' submitted to the journal 'Freshwater science' which is contained within this thesis.; Lindsey K. Albertson and David M. Walters were co-authors of the article, 'Landscape features drive synchronicity of an aquatic insect resource pulse' submitted to the journal 'Ecological applications' which is contained within this thesis.Aquatic insects have ecological, cultural, and economic value throughout the American West. They can control the processing of in-stream nutrients, are a vital component of both aquatic and terrestrial food webs, and support economically important species such as trout and the eco-tourism industries structured around these fisheries. Salmonflies (Pteronarcys californica) are one of the most well-known aquatic insects in the American West due to their large size and popularity among fly-fishers. However, mounting anecdotal evidence suggests that salmonfly populations could be in decline. We conducted surveys and compiled historical datasets that quantified salmonfly abundance, body size, and emergence timing along the Gallatin and Madison Rivers in southwest Montana to determine the status of salmonfly populations in these rivers, understand environmental drivers that are constraining their distribution and driving their development, and initiate long-term monitoring. Most notably, we found evidence for temperature-driven changes in salmonfly distribution and body size along the Madison River in the last four decades and observed marked differences in salmonfly emergence phenology and duration at multiple spatial scales between the Madison and Gallatin Rivers. Above-optimal summer water temperatures appear to be the major constraint on salmonfly populations in the Madison River, but only play a minimal role in dictating salmonfly distribution along the Gallatin River. This research provides rare empirical evidence of long-term biological change of an aquatic insect and highlights the importance of combining temporal and spatial datasets to explicitly address species' responses to environmental stressors across multiple spatial and temporal scales. Freshwater habitats are increasingly imperiled by climate change and human-induced habitat alteration, which will invariably continue to impact the ecology of aquatic insects like salmonflies. This work contributes to the understanding of how these ongoing changes will influence the structure of aquatic communities, the flow and transfer of energy and nutrients, consumer-resource dynamics, and stream--riparian food web linkages.Item Canyon Ferry Reservoir zooplankton population dynamics(Montana State University - Bozeman, College of Agriculture, 1975) Martin, Chadwick LeeItem Stream morphology and fish populations in relation to floodplain use(Montana State University - Bozeman, College of Letters & Science, 1966) Gunderson, Donald RaymondItem Physiological ecology of aquatic macrophytes in the Madison River of Yellowstone National Park, Wyoming(Montana State University - Bozeman, College of Agriculture, 1977) Klarich, Duane A.Item The benthos and drift fauna of a riffle in the Madison River, Yellowstone National Park(Montana State University - Bozeman, College of Agriculture, 1966) Heaton, John R.Item The use of aquatic macroinvertebrates as water quality indicators in mountain streams in Montana(Montana State University - Bozeman, College of Agriculture, 1996) Richards, David C.Item Changes in zooplankton species composition in newly filled Bighorn Lake, Montana and Wyoming(Montana State University - Bozeman, College of Agriculture, 1977) Horpestad, Abraham AndrewItem Composition and structure of macrophyte vegetation of the Firehole River, Yellowstone National Park as related to physical and chemical factors(Montana State University - Bozeman, College of Agriculture, 1968) Rasmussen, Sheila MayItem Factors affecting the distribution and abundance of aquatic macrophytes in parts of the Madison, Firehole and Gibbon rivers(Montana State University - Bozeman, College of Agriculture, 1969) Horpestad, Abraham Andrew