Biogeochemical Processes
Mostrando 25-35 de 35 artigos, teses e dissertações.
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25. The current biodiversity extinction event: Scenarios for mitigation and recovery
The current massive degradation of habitat and extinction of species is taking place on a catastrophically short timescale, and their effects will fundamentally reset the future evolution of the planet's biota. The fossil record suggests that recovery of global ecosystems has required millions or even tens of millions of years. Thus, intervention by hum
The National Academy of Sciences.
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26. Soil animals alter plant litter diversity effects on decomposition
Most of the terrestrial net primary production enters the decomposer system as dead organic matter, and the subsequent recycling of C and nutrients are key processes for the functioning of ecosystems and the delivery of ecosystem goods and services. Although climatic and substrate quality controls are reasonably well understood, the functional role of biodiv
National Academy of Sciences.
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27. Evidence for the presence of Mn(III) intermediates in the bacterial oxidation of Mn(II)
Bacterial oxidation of Mn(II) to Mn(IV) is believed to drive the oxidative segment of the global biogeochemical Mn cycle and regulates the concentration of dissolved Mn(II) in the oceanic water column, where it is a critical nutrient for planktonic primary productivity. Mn(II) oxidizing activity is expressed by numerous phylogenetically diverse bacteria and
National Academy of Sciences.
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28. Long-range transport of mineral dust in the global atmosphere: Impact of African dust on the environment of the southeastern United States
Soil dust is a major constituent of airborne particles in the global atmosphere. Dust plumes frequently cover huge areas of the earth; they are one of the most prominent and commonly visible features in satellite imagery. Dust is believed to play a role in many biogeochemical processes, but the importance of dust in these processes is not well understoo
The National Academy of Sciences.
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29. Environmental control of diatom community size structure varies across aquatic ecosystems
Changes in the size structure of photoautotrophs influence food web structure and the biogeochemical cycling of carbon. Decreases in the median size of diatoms within communities, in concert with climate warming and water column stratification, have been observed over the Cenozoic in the ocean and over the last 50 years in Lake Tahoe. Decreases in the propor
The Royal Society.
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30. Microbiological and Geochemical Characterization of Fluvially Deposited Sulfidic Mine Tailings
The fluvial deposition of mine tailings generated from historic mining operations near Butte, Montana, has resulted in substantial surface and shallow groundwater contamination along Silver Bow Creek. Biogeochemical processes in the sediment and underlying hyporheic zone were studied in an attempt to characterize interactions consequential to heavy-metal con
American Society for Microbiology.
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31. Simultaneous Recovery of Extracellular and Intracellular DNA Suitable for Molecular Studies from Marine Sediments
The occurrence of high extracellular DNA concentrations in aquatic sediments (concentrations that are 3 to 4 orders of magnitude greater than those in the water column) might play an important role in biogeochemical cycling, as well as in horizontal gene transfer through natural transformation. Since isolation of extracellular DNA from sediments is a difficu
American Society for Microbiology.
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32. Composition and Function of Sulfate-Reducing Prokaryotes in Eutrophic and Pristine Areas of the Florida Everglades†
As a result of agricultural activities in regions adjacent to the northern boundary of the Florida Everglades, a nutrient gradient developed that resulted in physicochemical and ecological changes from the original system. Sulfate input from agricultural runoff and groundwater is present in soils of the Northern Everglades, and sulfate-reducing prokaryotes (
American Society for Microbiology.
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33. Initial Effects of the Mount St. Helens Eruption on Nitrogen Cycle and Related Chemical Processes in Ryan Lake
Ryan Lake, a 1.6-hectare basin lake near the periphery of the tree blowdown area in the blast zone 19 km north of Mount St. Helens, was studied from August to October 1980 to determine the microbial and chemical response of the lake to the eruption. Nutrient enrichment through the addition of fresh volcanic material and the organic debris from the surroundin
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34. Dissimilatory Fe(III) and Mn(IV) reduction.
The oxidation of organic matter coupled to the reduction of Fe(III) or Mn(IV) is one of the most important biogeochemical reactions in aquatic sediments, soils, and groundwater. This process, which may have been the first globally significant mechanism for the oxidation of organic matter to carbon dioxide, plays an important role in the oxidation of natural
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35. Viral Impacts on Total Abundance and Clonal Composition of the Harmful Bloom-Forming Phytoplankton Heterosigma akashiwo
Recent observations that viruses are very abundant and biologically active components in marine ecosystems suggest that they probably influence various biogeochemical and ecological processes. In this study, the population dynamics of the harmful bloom-forming phytoplankton Heterosigma akashiwo (Raphidophyceae) and the infectious H. akashiwo viruses (HaV) we
American Society for Microbiology.