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Reflectance spectroscopy has made it possible to rapidly and nondestructively assess the chlorophyll content of plants and natural waters. However, to date this approach has not been applied to chlorophyll and chlorophyll derivatives preserved in lake sediments. Here, we explore the relationships between visible-near-infrared spectral properties of lake sediments and measured pigment concentrations for lakes that have been exposed recently to anthropogenic nitrogen deposition. Down-core decreases in pigment concentrations and changes in reflectance properties effectively chronicle increases in whole-lake primary production since 1950. Specifically, reflectance spectra of sediments from four alpine lakes in Rocky...
We employed a spatially explicit simulation model to assess growth rate potential for lake trout (Salvelinus namaycush) in Flaming Gorge Reservoir, Utah-Wyoming. Late-summer water temperatures and forage fish densities in 168 habitat cells were collected from 1989 to 1996 and were used to estimate the potential growth of lake trout inhabiting each cell. Results of model simulations indicated that habitat quality for lake trout growth had decreased from 1990 to 1993. This decrease in lake trout growth rate potential was related to decreased forage fish densities during this period. Lake trout condition, as measured using length-weight analyses of individuals captured in spring gillnetting surveys, also decreased...
We used a bioenergetic model to determine if cutthroat trout (Oncorhynchus clarkii bouvieri) abundance was related to net energy intake rates (NEI) and the proportion of suitable habitat and to evaluate potential changes in habitat quality due to climate change and stream fertilization efforts. We conducted monthly sampling of cutthroat trout, invertebrate drift, and physical habitat features in pool and riffle habitats. Fish in this study selected foraging positions that enabled them to maximize NEI, and most fish were capable of sustaining high growth rates from July to September. Mean NEI and the proportion of suitable habitat at sites were greater in pools relative to riffle habitats and declined from July to...
Identifying the differences in ecology between closely related species occupying the same environment contributes to our understanding of community diversity, ecosystem structure, and species conservation. Endemic Bear Lake whitefish (Prosopium abyssicola) and Bonneville whitefish (Prosopium spilonotus) are benthic, morphologically similar, and closely related, yet the extent of differential resource use remains poorly understood. To determine the ecological differences between these two species, we studied their seasonal distribution and diet in Bear Lake, Utah?Idaho. We used bottom-set gill nets to examine how catch of each species of whitefish varied in relation to depth and season (spring and summer). In both...
    map background search result map search result map Inferring sedimentary chlorophyll concentrations with reflectance spectroscopy: a novel approach to reconstructing historical changes in the trophic status of mountain lakes Inferring sedimentary chlorophyll concentrations with reflectance spectroscopy: a novel approach to reconstructing historical changes in the trophic status of mountain lakes