Browsing by Subject "winter"
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Item Data for Warmer Winters and Ice-Based Cultural Ecosystem Services: Empirical Evidence from USA, Canada, Japan, Germany, Austria, Switzerland, and Sweden(2019-05-09) Knoll, Lesley, B.; Sharma, Sapna; Denfeld, Blaize A; Flaim, Giovanna; Hori, Yukari; Magnuson, John J; Straile, Dietmar; Weyhenmeyer, Gesa A; lbknoll@umn.edu; Knoll, Lesley, BLakes and rivers covered by seasonal ice are extensively used by humans. Although ice cover duration has been declining over the past 150 years for Northern Hemisphere lakes and rivers, we still know relatively little about how inland ice loss directly affects humans. Here we provide empirical examples that give quantitative evidence for a winter warming effect on a wide range of cultural ecosystem services. We show that in recent decades, warmer temperatures delayed the opening date of the James Bay winter ice road in northern Ontario, Canada and led to cancellations of religious celebrations (Lake Suwa, Japan and Lake Constance, Germany/Switzerland/Austria), an ice skating race on Lake Mälaren, Sweden, and winter ice fishing tournaments in Central and Northern Minnesota.Item Effects of environmental temperature on biology of cold-adapted Chironomidae (Diptera) from Minnesota and Iceland(2022-10) Nyquist, CorrieChironomids are an abundant and speciose family of aquatic flies which dominate freshwater environments globally. Additionally, chironomids are important food sources for fish and can be used as bioindicators of water quality. This family includes species that are adapted to emerge as adults in winter and under cold conditions across the globe. Both air and water temperatures influence these insects since they grow in aquatic habitats and then emerge as terrestrial adults. However, little research has focused on the effects of thermal heterogeneity in shaping community structure along stream length, how stream temperatures may influence thermal acclimatization in adult chironomids, and the impacts of warm temperature exposure on biology of Arctic, winter-active chironomids. These questions become significant considering climate change since warming temperatures will threaten aquatic systems and cold-adapted organisms including cold-adapted chironomids. The goal of this dissertation was to investigate the influence of water temperature on winter emerging chironomid species composition and air temperature on adult Arctic chironomid lifespan and reproduction. Field work investigating thermal heterogeneity in streams was conducted in Minnesota. Collections of pupal exuviae along the length of thermally variable groundwater-fed streams revealed thermal portioning in taxa along stream length. Thermal partitioning in chironomids indicates that chironomids develop in and emerge from different thermal regimes, and, thus, may display developmental acclimatization to warm temperatures if they emerge from warm springs. Chironomids were collected from geothermally heated and cold springs in southwestern Iceland and placed into warm and cold incubation treatments. Results indicate that chironomids with long degree-day requirements emerging from warm springs have a maximized lifespan under both cold and warm air temperatures. Investigations of winter-active chironomids have been conducted in Europe and North America with little work focused on the Arctic. Iceland, a near Arctic country, faces increasing climate change threats and, thus, documenting warming effects on cold-adapted biota is essential. Winter-active chironomids were documented in Iceland for the first time and investigations of longevity and oviposition timing revealed susceptibility to warm air temperatures in winter emerging Icelandic chironomids. Chironomids comprise a large portion of aquatic food webs, and in Arctic regions, are the predominant aquatic insects. Investigating how environmental conditions control both community composition and population dynamics will further the conservation of cold-water systems by increasing the understanding of how climate change may impact cold-adapted biota.Item Effects of snow cover manipulation and climate factors on the development of soil frost in forested boreal peatlands in Minnesota, USA(2019-08) Friesen, HannahBlack spruce (Picea mariana) peatlands play an important ecologic and economic role in the temperate-boreal region of North America, providing a valuable timber resource in addition to performing important ecosystem functions. Climate models project decreases in the amount of snowfall throughout the temperate-boreal region by 2100, as average wintertime temperatures increase. While the effect of a loss of snow cover on soil frost dynamics has been well-studied in mineral soil environments through the use of snow removal techniques, similar analysis on decreased snow cover in peatland soils is less common and related effects unclear. To fill this gap in understanding, we used a paired-plot experimental design to assess the effect of snow removal on soil temperature and frost development at six forested peatland sites in northern Minnesota, USA, during the winters of 2017-2018 and 2018-2019. Treatments were either 1) removal of snow throughout the winter, or 2) ambient snow conditions. During both years of the study, there was a significant effect of snow removal by mid-winter that continued into late winter and spring, where removal of snow correlated with increased soil frost depth and colder soil temperatures, as compared to plots with ambient snow cover. Following the first winter of the study, it was found that soil frost persisted much later in snow removal plots, and snow removal plots had colder soils through much of the summer growing season. In addition, during the frozen season, soil temperatures in the removal plots were highly responsive to air temperature fluctuations to depths of 20 cm or more, resulting in increased variability in temperature, whereas the ambient snow cover soils exhibited little fluctuation and maintained temperatures near 0° C for much of the winter season. These results indicate that predicted changes to the amount and form of wintertime precipitation in the temperate-boreal zone may result in increased development of soil frost in forested peatland systems. However, the increased reactivity of soil temperature to air temperature fluctuations may offset the effect of decreased snow cover if average winter air temperatures are higher, as currently predicted.Item Methods for Monitoring and Mitigating the Use of Chloride Deicers(2020-01) Klimbal, DouglasThe winter roadway operations and maintenance community generates a breadth of data detailing the activity and performance of snowplows, deicing practices, and road conditions. While roadway ice clearing is a practical need for communities in temperate climates, one outcome of operations is the distribution of unnaturally high levels of dissolved solids, especially chloride, into environments which are hydraulically connected to maintained roadways and surfaces. The long-term buildup of chloride poses a threat to ecological integrity of freshwater systems. Salt also hastens the oxidation of metals used in the built environment, especially high-iron alloys. A 2007 study of the Twin Cities Metropolitan Area estimated that over a 5-year study period, 70% of road salt applied annually was retained in the landscape or infiltrated to deep groundwater. This research examines the road salt mass balance on a finer scale both spatially and temporally. Continuous monitoring of surface runoff was conducted in a small residential watershed using a novel approach. The results are paired with an analysis of snowplow asset tracking data to estimate what proportion of the total salt added to the catchment in the two-year study enters directly into the stormwater conveyance. Results are followed by a critical discussion of current research and considerations for future research.Item Protected from the Elements: Winter Ecology of Brown Trout in Groundwater Buffered Streams(2014-09) French, WilliamWinter has traditionally been considered a period of dormancy for stream dwelling trout in temperate latitudes. Seasonal changes including low water temperatures, ice formation, and reduced prey availability from aquatic and terrestrial sources often contribute to reductions in trout growth and survival. Consequentially, winter has rarely been the focus of study by fisheries scientists, and relatively little information is available regarding stream trout during winter. However, because of the potential impact on stream trout growth and survival, winter is an important season for trout populations and of particular interest to fisheries managers. The goal of this dissertation was to examine winter trophic ecology of stream dwelling trout populations, and the potential of groundwater input to buffer stream water temperatures and trout from the environmental conditions typically associated with winter. This dissertation consists of three chapters that contribute towards this goal. The first chapter examines winter diet of Brown Trout by quantifying trout consumption, identifies important winter prey taxa , and compares diet composition among a number of trout populations. The second chapter describes Brown Trout winter growth and condition, and examines the influence of groundwater buffering and trout diet composition on growth and condition. The third and final chapter uses stable isotope analyses to examine seasonal variation in Brown Trout diets, and the position of trout within winter food webs of groundwater dominated streams. My dissertation will help managers predict the potential effects of winter on important recreational stream trout fisheries, and allow informed management decisions incorporating the best available information.Item Seasonal community and food web dynamics of planktonic and benthic organisms in temperate lakes, with emphasis on winter(2022-10) Shchapov, KirillLakes of temperate regions are experiencing shortening of the winter period and reductions in the ice-cover duration. Despite these changes, winter ecological and biological processes are still not well understood due to the relatively small number of studies occurring during the ice-on period. However, recent studies showed that the winter season can play an important role for lower trophic level organisms, like zooplankton and benthic communities, in terms of their reproduction, succession, and food availability. With the ongoing changes in winter conditions, lower trophic level organisms could experience changes in abundances and nutritional qualities, which will consequently affect higher trophic level consumers like fish. Further, such disturbances could affect whole food web energy transfer and trophic level interactions of the lake ecosystem. Therefore, lake studies including winter could help to better understand the complete picture of intra-annual lake ecosystem processes. To better understand seasonal changes in lower trophic level organisms' population, community, and trophic dynamics during winter, I conducted research across lakes of different size classes and trophic states with a focus on the wintertime. The objectives of my research were: a) to assess seasonal variations in seston, zooplankton and benthic organisms abundances and environmental drivers affecting them; b) to determine seasonal changes in food sources and trophic positions of planktonic and benthic organisms using carbon and nitrogen stable isotopes; and c) to evaluate nutritional status of the lower-level organisms using fatty acid analysis.Here, I present the results of two studies distributed among four chapters. In the first study, I compared summer and winter environmental parameters and zooplankton communities across 13 lakes in Minnesota and Wisconsin. In the second study, I described the full-year seasonal changes in abundance and nutritional quality of seston, zooplankton, and benthos of Lake Superior, with emphasis on winter. In Chapter 1, I investigated parameters associated with changes in crustacean zooplankton densities, community composition, and their food sources between winter and summer across lakes of varying trophic status. I found that eutrophic lakes had higher zooplankton densities under the ice than dystrophic and oligotrophic lakes. Zooplankton communities were more similar across lakes during winter than during the open water period. Carbon and nitrogen stable isotopes suggested that zooplankton have higher lipid content in winter. In Chapter 2, I conducted a comprehensive full-year study of crustacean zooplankton and the effect of environmental parameters shaping zooplankton communities throughout the year in five nearshore regions of Lake Superior. My results suggested that zooplankton are still active during winter and vary greatly in densities between seasons, with greater variability at shallow than deep stations. I also found that water temperature and food availability were key drivers of total zooplankton abundance and the densities of the main taxonomic groupsthroughout the year. In Chapter 3, I provide the results of a survey study of coarse-level benthic organism seasonal changes across five locations of Lake Superior. This study showed relatively stable benthos abundances across all sampled locations, suggesting a continuous availability of littoral food sources for benthivorous fish throughout the year, including winter. I also found that the benthos diversity index was the highest in fall, while the species richness was similar across all seasons. In Chapter 4, I used stable isotope and fatty acid analysis to assess the origin of energy sources and nutritional values throughout the year in planktonic and benthic organisms. This information was intended to better assess and understand food availability for higher trophic level organisms. My results indicate low zooplankton abundances during winter but higher lipid content of total and essential fatty acids (EFA). Conversely, selected benthic organisms had higher total lipid content in summer than in winter. However, I found that concentrations of EFA (e.g., DHA, EPA, -ALA) in benthic organisms were low despite the high benthos densities throughout the year. This study suggests that different elements of the lower-level food web may vary in their importance as energy and nutrition sources for higher-level organisms like fish throughout the year. Together these four chapters provide important information on the seasonal dynamics of lower trophic level organisms across small and large lake ecosystems. These results help to address the winter ecology knowledge gap in seasonally frozen lakes and contribute to a better understanding of the effect of changing environmental conditions on lower trophic level organisms across a broad range of lake ecosystems. Additionally, the results of these studies provide new insights into the seasonality of freshwater organisms of the lower food web and their importance for higher-level consumers like fish. The detailed information provided in this research on temporal and spatial distribution along with nutritional conditions of seston, zooplankton, and benthic organisms can have important implications for fish productivity and distribution research and management. This study helps to identify future research efforts to charachterize the effect of climate change on food web dynamics in northern temperate lakes.Item Snow Cover and Winter Soil Temperatures at St. Paul, Minnesota(Water Resources Research Center, University of Minnesota, 1971-06) Baker, DonaldThe objectives of this study of winter soil temperatures under a sod cover were to show the configuration of the soil isotherm patterns, in particular that of OC, and to determine which soil thermal characteristics can be estimated by the snow cover. The temperature data were obtained at the University of Minnesota Agricultural Experiment Station plots on the St. Paul campus with copper-constantan thermocouples during the winter of 1961-62 through 1968-69. Based upon the depth and persistence of the snow cover there were in effect 3 kinds of winters: one with deep and persistent snow cover, one with very little snow cover and all other winters. There was a close relationship between the kinds of winters and the maximum depth to which the OC isotherm penetrated, and a fair relationship to the rate of movement of the OC isotherm into the soil. The combination of type of winter (snow depth and duration) with cumulative heating degree days proved to be a simple and effective means of predicting the maximum freezing depth.