Lake surface temperature (LSTlake) can be obtained and studied in different ways: using in situ measurements, satellite imagery and modeling. Collecting spatially representative in situ data over lakes, especially for large and deep ones, is a real challenge. Satellite data products provide the opportunity to collect continuous data over very large geographic areas even in remote regions. Numerical modeling is also an approach to study the response and the role of lakes in the climate system. Satellite instruments provide spatial information unlike in situ measurements and one-dimensional (1-D) lake models that give vertical information at a single point or a few points in lakes. The advantage of remote sensing also applies to land where temperature measurements are usually taken at meteorological stations whose network is extremely sparse in northern regions. This thesis therefore examined the value of land/lake surface (skin) temperature (LSTland/lake) measurements from satellites as a complement to in situ point measurements and numerical modeling. The thesis is organized into two parts. The first part tested, two 1-D numerical models against in situ and satellite-derived LST measurements. LSTlake and ice phenology were simulated for various points at different depths on Great Slave Lake (GSL) and Great Bear Lake (GBL), two large lakes located in the Mackenzie River Basin in Canada’s Northwest Territories, using the 1-D Freshwater Lake model (FLake) and the Canadian Lake Ice Model (CLIMo) over the 2002-2010 period. Input data from three weather stations (Yellowknife, Hay River and Deline) were used for model simulations. LSTlake model results are compared to those derived from the Moderate Resolution Imaging Spectroradiometer (MODIS) aboard the Earth Observing System Terra and Aqua satellite platforms. The main goal was to examine the performance of the FLake and CLIMo models in simulating LSTlake and ice-cover under different conditions against satellite data products. Both models reveal a good agreement with daily average MODIS LSTlake from GSL and GBL on an annual basis. CLIMo showed a generally better performance than FLake for both lakes, particularly during the ice-cover season. Secondly, MODIS-derived lake and land surface temperature (LSTland/lake) products are used to analyze land and lake surface temperature patterns during the open-water and snow/ice growth seasons for the same period of time in the regions of both GBL and GSL. Land and lake temperatures from MODIS were compared with near-surface air temperature measurements obtained from nearby weather stations and with in situ temperature moorings in GBL. Results show a good agreement between satellite and in situ observations. MODIS data were found to be very useful for investigating both the spatial and temporal (seasonal) evolution of LSTland/lake over lakes and land, and for improving our understanding of thermodynamic processes (heat gains and heat loses) of the lake/land systems. Among other findings, the MODIS satellite imagery showed that the surface temperature of lakes is colder in comparison to the surrounding land from April-August and warmer from September until spring thaw.

Lake surface temperature (LSTlake) can be obtained and studied in different ways: using in situ measurements, satellite imagery and modeling. Collecting spatially representative in situ data over lakes, especially for large and deep ones, is a real challenge. Satellite data products provide the opportunity to collect continuous data over very large geographic areas even in remote regions. Numerical modeling is also an approach to study the response and the role of lakes in the climate system. Satellite instruments provide spatial information unlike in situ measurements and one-dimensional (1-D) lake models that give vertical information at a single point or a few points in lakes. The advantage of remote sensing also applies to land where temperature measurements are usually taken at meteorological stations whose network is extremely sparse in northern regions. This thesis therefore examined the value of land/lake surface (skin) temperature (LSTland/lake) measurements from satellites as a complement to in situ point measurements and numerical modeling. The thesis is organized into two parts. The first part tested, two 1-D numerical models against in situ and satellite-derived LST measurements. LSTlake and ice phenology were simulated for various points at different depths on Great Slave Lake (GSL) and Great Bear Lake (GBL), two large lakes located in the Mackenzie River Basin in Canada’s Northwest Territories, using the 1-D Freshwater Lake model (FLake) and the Canadian Lake Ice Model (CLIMo) over the 2002-2010 period. Input data from three weather stations (Yellowknife, Hay River and Deline) were used for model simulations. LSTlake model results are compared to those derived from the Moderate Resolution Imaging Spectroradiometer (MODIS) aboard the Earth Observing System Terra and Aqua satellite platforms. The main goal was to examine the performance of the FLake and CLIMo models in simulating LSTlake and ice-cover under different conditions against satellite data products. Both models reveal a good agreement with daily average MODIS LSTlake from GSL and GBL on an annual basis. CLIMo showed a generally better performance than FLake for both lakes, particularly during the ice-cover season. Secondly, MODIS-derived lake and land surface temperature (LSTland/lake) products are used to analyze land and lake surface temperature patterns during the open-water and snow/ice growth seasons for the same period of time in the regions of both GBL and GSL. Land and lake temperatures from MODIS were compared with near-surface air temperature measurements obtained from nearby weather stations and with in situ temperature moorings in GBL. Results show a good agreement between satellite and in situ observations. MODIS data were found to be very useful for investigating both the spatial and temporal (seasonal) evolution of LSTland/lake over lakes and land, and for improving our understanding of thermodynamic processes (heat gains and heat loses) of the lake/land systems. Among other findings, the MODIS satellite imagery showed that the surface temperature of lakes is colder in comparison to the surrounding land from April-August and warmer from September until spring thaw.

Twenty-five piston cores 6 to 12 feet long were obtained from the deepwater sediments of Bear Lake, Utah-Idaho. Analyses of these cores revealed that the deep-water sediments of the lake are divided into two major S('f]Uflnces: a younger sequence rich in carbonate minerals, here called the carbonate sequence, and an older sequence rich in silicate minerals, referred to in this paper as the silt sequence. The carbonate sequence is composed of clay-sized quartz, aragonite, calcite, dolomite, montmorillonite, illite, kaolinite, chlorite, and amorphous material. The silt sequence consists of both silt- sized and claysized particles of quartz, calc ite, dolomite, montmorillonite, illite, kaolinite, chlorite, and amorphous material. Aragonite is absent in the silt sequence. The carbo nate sequence is rich in ostracod exoskeletons and pollen grains. Small quantities of woody material and dark, organic-rich wnes occur within the silt sequence. Chemical analyses for Mg, Ca, Fe, Mn, K, Zn, Na , and Sr were reformed on the sediments. Unusually high concentrations of Fe (8.25 percent) were found in the silt sequence, and of Sr (0 .110 percent), in the carbonate sequence. Isotopic analyses for o18 and c13 in the lake sediments indicate that formation of the authigenic carbonate minerals occurred under normal lake-bottom conditions. From the data collected, the following conclusions or inferences are made. The carbonate sequence was deposited in water depths similar to, or grea ter than, those of the present. Within this sequence, aragonite is precipitating at present from solution in such quantities that it is responsible for the inversion of the average Ca/ Mg mole ratio of inflowing water of 2:1 to a Ca/ Mg mole ratio of 1:5 in the lake water. The high concentration of Mg +2 and possible high concentration of Sr+2 in the lake water have resulted in conditions favorable for development of protodolomite. Atypical X-ray diffraction patterns for calcite and dolomite, and the relative abundances of aragonite, calc ite, and dolomite reveal that protodolomite probably is, or has been, forming in Bear Lake. The silt sequence was deposited in water shallow enough for rooted plants to establish themselves . In this shallow environment detrital sediments rich in kaolinitic clay derived from the· Bear Lake Plateau were altered to sediments rich in montmorillonitic clay and amorphous materials. The sharp contact between the silt sequence and the overlying carbonate sequence apparently represents abrupt termination of widespread swampy depositional conditions in the Bear Lake graben, caused by flooding, which possibly resulted from the most recent major episode of downfaulting of Bear Lake Valley.

The Bear Lake Plateau extends north-south across the north central corner of Utah and the southeastern corner of Idaho. North Eden Creek drains westward through part of the plateau and is crossaxial across both strikes of beds and other structures in the area. The formations in the area mapped are of Triassic, Jurassic, and Tertiary age, although only Jurassic and Tertiary rocks contribute sediments to North Eden Creek. The formations consist of sandstones (Nugget), limestones (Twin Creek), and conglomerates (Wasatch). A local extrusion of basalt occurs in the southwestern part of the drainage area. Particle-size analyses of 15 samples from pits dug along North Eden Creek and its tributaries and North Eden Delta show that mean and maximum particle sizes increase downstream due to additions by tributaries and mass-wasting from the coarse-grained, highly jointed Nugget Formation flanking lower parts of the stream. Mineralogic analyses of these samples show that quartzite and chert predominate in the gravel sizes and that quartz and calcite predominate in the sand and silt sizes; kaolinite is the dominant mineral in the clay sizes. Feldspar and dolomite also are present in small quantities. Amorphous material, a common constituent in the sediment of Bear Lake, is abundant in sizes < .00049 mm. The calcite supplied to Bear Lake as clay-sized particles indicates that claysized calcite in Bear Lake is at least partly detrital.

A curvilinear regression model was used to determine an expected stomach capacity for any size Bear Lake sculpin with a standard length between 4-9.5 centimeters. Stomach contents were then expressed as a percent fullness and the change in percent fullness with time intervals was used to compute an instantaneous digestion rate. The instantaneous consumption rate was computed by the formula C=log P1-log P0 +d, where C=instantaneous consumption rate. The amount of food consumed during a time interval was computed from the formula It=CtSt, where It=amount of food ingested during a time interval expressed in percent fullness of stomach. The 24 hour consumption rate was computed by summing the consumption rates for 4 consecutive time intervals of 6 hours each. Studies in September, December, and May give instantaneous digestion rates of -.424, -.214, and -.235 and total food consumption rates of 22.2, 10.2, and 6.1 percent of stomach capacity for each individual fish in the population.

The Bonneville cisco (Prosopium gemmiferum), a small planktivorous whitefish, is an important part of the distinctive fish community of Bear Lake, Utah-Idaho. The Bonneville cisco plays a key role in the trophic structure by converting zooplankton to fish biomass and providing a major forage sour ce for cutthroat and lake trout. Aspects of cisco feeding ecology studied include characterization of the zooplankton community composition and dynamics and cisco feeding habits and prey select ion.

Bear Lake sculpin (Cottus extensus) exhibited an ontogenetic habitat shift during their first year of life. Soon after hatching in the littoral zone, the fry swam to the surface where they dispersed throughout the lake. Most juveniles that initially settled in the profundal zone returned to the littoral zone during their first summer. Patterns in the daily growth increments of otoliths confirmed the history of habitat residence and the individual size at the habitat switch. We used this habitat shift to test a μ/g model incorporating a growth rate-mortality risk trade-off. A trade-off occurred in the littoral zone because both growth rate and mortality risk were greater in this habitat. Given initial profundal residence, the directed movement of juveniles to the more profitable littoral zone was consistent with model predictions. Contrary to model predictions, juvenile sculpin initially occupied both habitats and switched habitats at a wide range of sizes. lack of a discrete switch size may have resulted, in part, from the lack of a strong trade-off or from an inability of fish to respond facultatively to environmental variables at the large spatial scale of this system.

Underyearling Bear Lake sculpin exhibit a diel pattern of vertical migration throughout the pelagic region of Bear Lake (Utah-Idaho) until they are approximately 22 mm standard length. Individuals move from the bottom of the lake (5° C) during the day into the water column (13-16° C) at night. The migration, however, is not related to feeding. Although the dominant copepod in the water column, Epischura nevadensis, do undergo a similar diel vertical migration, stomach analysis of juvenile sculpin captured by trawling shows that they do not feed in the water column. Instead, from July through October, their diet is dominated (70-93%) by benthic copepods and ostracods. Also, gut fullness of sculpin increases through the daylight period and decreases through the night, reaching minimum levels just before the dawn descent. Furthermore, feeding trials conducted in the laboratory show that juvenile sculpin feed most efficiently at light intensities found on the bottom (30-60m) of Bear Lake during the day. Feeding rate coefficients increase markedly from 1013 photons m-2S-1 until peaking at intermediate intensities of 1016 photons m-2S-1 and then decline at higher light levels. Although they do not migrate to feed, the movement into the warmer water appears to increase the sculpin's digestion rate, thereby allowing continued feeding during the day. This supports the hypothesis that diel vertical migration in Bear Lake sculpin is a thermoregulatory strategy that increases growth rate.

Greater sage-grouse (Centrocercus urophasianus; sage-grouse) are a sagebrush obligate species and as such an indicator of sagebrush (Artemisia spp.) habitat quality and quantity. Sage-grouse populations have declined across western North America. This decline has been attributed to habitat loss and degradation of the sagebrush ecosystem. To determine factors that may cause localized declines in sage-grouse populations, managers may need site-specific information on the ecology and habitat use patterns of meta-populations. This information is currently lacking for sage-grouse populations that inhabit the Bear Lake Plateau and Valley (BLPV), encompassing parts of Idaho, Utah and Wyoming. I captured, radio-marked and monitored 153 sage-grouse in the BLPV from 2010–2012 to assess nest success, brood survival, mortality factors, and habitat use. Reproductive success was lower than range-wide averages, with especially low success in 2011. Nesting and brood rearing both showed higher success rates in 2012. Survival was very similar to estimates found elsewhere. Females had higher survival rates than males, and yearlings had higher survival probability than adults. Sage-grouse mortality was highest in summer and spring, and lowest in fall. Individual sage-grouse completed large scale movements, often using habitats in Idaho, Utah, and Wyoming. Important factors in sage-grouse habitat selection included distance to major road, distance to habitat edge, distance to vertical structure (i.e., communication towers, wind turbines, and transmission lines), and vegetation cover types. Sage-grouse tended to avoid major road and vertical structures (i.e., communication towers, wind turbines, and transmission lines). They also selected habitat further away from habitat edge. Vegetation types preferred by sage-grouse included shrubland habitats, wet meadows, and grassland. MaxEnt models did not place highest importance on sagebrush habitats, which are critical for sage-grouse presence. This could have occurred because the vegetation layers used in the model did not assess habitat quality. Models produced using the ten landscape variables and BLPV sage-grouse locations ranked good to excellent fits. State-defined habitat covered a larger extent than MaxEnt predicted habitat. MaxEnt predicted habitat areas may be used to further refine state identified core areas to assist in prioritization of conservation efforts to protect the BLPV sage-grouse population.

I described the spawning ecology of the Bear Lake Bonneville cutthroat trout (BLBCT) in St. Charles Creek. I tracked cutthroat trout with used radio telemetry. I conducted redd counts to describe spawning conditions. Most cutthroat trout in the Big Arm strayed into the Bear River. Cutthroat trout migrations in the Little Arm and main fork were very limited (<4 km). Redd distributions showed very similar patterns between 1989, 2000 and 2001 with most redds being built in the lowest kilometer of stream. Artificial fish transportation changed the redd distribution in 2002. More redds were built in the main fork and redds were distributed throughout the stream. Redds built in the main fork were characterized by lower levels of fine sediment and higher water velocities as compared to the redds built on the Little Arm. The results of this research will be used to aid resource managers in developing a management plan for wild BLBCT.