Browsing by Subject "Phosphorus."
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Item Alder cover drives nitrogen availability and decomposition of grass litter in salmon-rearing headwater streams, Kenai Peninsula, Alaska.(2010-10-08T16:26:59Z) Shaftel, Rebecca S.; King, Ryan Steven, 1972-; Biology.; Baylor University. Dept. of Biology.Terrestrial sources of nitrogen (N), such as N fixed by alder, may be important for sustaining production in headwater streams that typically lack subsidies of nutrients from spawning salmon. High nutrient concentrations in streams increase litter decomposition and can offset the low nutrient quality of grass litter. Alder cover was compared to watershed physiographic variables as predictors of stream N and contrasted over the growing season among 25 headwater streams. Leaf packs of bluejoint grass were deployed for two months across a nutrient gradient of 6 headwater streams. Alder cover explained over 75 – 96% of the variance in stream N. Bluejoint breakdown rates were related to dissolved stream nutrient concentrations and litter quality. A diversity of macroinvertebrate consumers utilized bluejoint for habitat and food. Alder drives stream N concentrations and the breakdown rate of bluejoint, which is an important consumer resource during the summer months when deciduous litter inputs are low.Item The effect of suspended bentonite and kaolinite clay on phosphorus uptake and release by lotic periphyton.(Springer., 2009) Wolfe, June Elmer, 1961-; Lind, Owen T., 1934-; Biology.; Baylor University. Dept. of Biology.Lotic systems act as nutrient buffers to receiving lentic systems. As streams transport allochthonous phosphorus through a watershed, the loads are modified in quantity and quality through biotic and abiotic mechanisms. Lotic systems are frequently dominated by periphyton, the attached benthic community consisting mainly of algae and bacteria. This community exhibits the ability to buffer phosphorus loads to receiving waters through several mechanisms including: biotic uptake, chemical precipitation, and mechanical filtration. Stream sediments, including clays, influence dissolved phosphorus concentrations primarily through equilibrium-driven sorption/desorption reactions. Additionally, suspended clays in aquatic environments are known to: modify food webs, influence species composition, and affect biotic integrity by altering the physical and chemical conditions. Given the influence that suspended clays exert upon aquatic systems, it was hypothesized that suspended clays would modify, either positively or negatively, phosphorus uptake and/or release by lotic periphyton. Experiments were conducted using two clay minerals, dissolved reactive phosphorus, and cultivated periphyton communities. Bentonite and kaolinite were selected to represent two clay types commonly found in aquatic systems. Standardized laboratory procedures were utilized to describe the physical characteristics and phosphorus sorption behavior of the clays. An artificial stream system was designed, tested, and operated to control water conditions necessary to cultivate periphyton communities, support suspend clays, and conduct clay-phosphorus-periphyton interaction studies. Periphyton communities were subjected to different clay and phosphorus concentrations under controlled conditions in artificial streams and laboratory microcosms. Phosphorus uptake rates were unaffected by the presence of clays at several different concentrations in artificial stream settings. Periphyton exposure to heavy clay loads in lotic microcosms, under laboratory conditions, had no effect on the ability of the periphyton to uptake or release phosphorus. The results may be helpful to water resource managers working with water quality issues and researchers interested in basic ecosystem function.Item Effects of stream nutrient enrichment on aquatic insect stoichiometry : importance of life-history traits, sex, and ontogeny.(2014-01-28) Back, Jeffrey Alan.; King, Ryan Steven, 1972-; Biology.; Baylor University. Dept. of Biology.I investigated the effects of stream nutrient enrichment on aquatic insect stoichiometry, particularly in the context of species life-history traits, sex, and ontogeny. The majority of studies investigating nutrient content of organisms preceding this research had assumed that aquatic insect species maintain a homeostatic concentration of carbon, (C) nitrogen (N) and phosphorus (P) content with respect to developmental stage and nutrient enrichment of their food resources. However, P content was shown not to be homeostatic across the ontogeny of 19 species of aquatic insects and C and N were quasihomeostatic. Growth rates for Caenis mayflies were higher on P enriched foods, and smaller individuals grew faster than larger individuals. Further, female mayflies were equal to or larger than males and had equal or higher body P content than males, depending upon species. A phylogenetic pattern in body P content was found for baetid and leptophlebiid mayflies. Male and female baetids declined in % P across their ontogeny, whereas leptophlebiid females increased in the 3 species studied. Finally, a study of streams spanning a steep nutrient enrichment gradient revealed that females of Baetis sp. and Neochoroterpes nanita attained a much larger size than males and were more enriched in P. Body P content of both mayfly species was higher at low P sites, and body size was much larger at high P sites. In insects, P content is a good indicator of growth rate (higher P, faster growth), and body size is a good predictor of fecundity (bigger body, more fecund). Nutrients not only play a role in determining an organism’s reproductive success, growth rate and size. The effects of nutrients are seen in organism nutrient recycling rates, food web organization, and community structure and function.