33 research outputs found
Temperature response of denitrification and anammox reveals the adaptation of microbial communities to in situ temperatures in permeable marine sediments that span 50° in latitude
Despite decades of research on the physiology and biochemistry of nitrate/nitrite-respiring microorganisms, little is known regarding their metabolic response to temperature, especially under in situ conditions. The temperature regulation of microbial communities that mediate anammox and denitrification was investigated in near shore permeable sediments at polar, temperate, and subtropical sites with annual mean temperatures ranging from -5 to 23 degrees C. Total N-2 production rates were determined using the isotope pairing technique in intact core incubations under diffusive and simulated advection conditions and ranged from 2 to 359 mu mol N m(-2) d(-1). For the majority of sites studied, N-2 removal was 2-7 times more rapid under simulated advective flow conditions. Anammox comprised 6-14% of total N-2 production at temperate and polar sites and was not detected at the subtropical site. Potential rates of denitrification and anammox were determined in anaerobic slurries in a temperature gradient block incubator across a temperature range of -1 degrees C to 42 degrees C. The highest optimum temperature (T-opt) for denitrification was 36 degrees C and was observed in subtropical sediments, while the lowest T-opt of 21 degrees C was observed at the polar site. Seasonal variation in the T-opt was observed at the temperate site with values of 26 and 34 degrees C in winter and summer, respectively. The T-opt values for anammox were 9 and 26 degrees C at the polar and temperate sites, respectively. The results demonstrate adaptation of denitrifying communities to in situ temperatures in permeable marine sediments across a wide range of temperatures, whereas marine anammox bacteria may be predominately psychrophilic to psychrotolerant. The adaptation of microbial communities to in situ temperatures suggests that the relationship between temperature and rates of N removal is highly dependent on community structure
Corrigendum to "Temperature response of denitrification and anammox reveals the adaptation of microbial communities to in situ temperatures in permeable marine sediments that span 50° in latitude" published in Biogeosciences, 11, 309â320, 2014
No abstract available
The Effect of Structural Complexity, Prey Density, and âPredator-Free Spaceâ on Prey Survivorship at Created Oyster Reef Mesocosms
Interactions between predators and their prey are influenced by the habitat they occupy. Using created oyster (Crassostrea virginica) reef mesocosms, we conducted a series of laboratory experiments that created structure and manipulated complexity as well as prey density and âpredator-free spaceâ to examine the relationship between structural complexity and prey survivorship. Specifically, volume and spatial arrangement of oysters as well as prey density were manipulated, and the survivorship of prey (grass shrimp, Palaemonetes pugio) in the presence of a predator (wild red drum, Sciaenops ocellatus) was quantified. We found that the presence of structure increased prey survivorship, and that increasing complexity of this structure further increased survivorship, but only to a point. This agrees with the theory that structural complexity may influence predator-prey dynamics, but that a threshold exists with diminishing returns. These results held true even when prey density was scaled to structural complexity, or the amount of âpredator-free spaceâ was manipulated within our created reef mesocosms. The presence of structure and its complexity (oyster shell volume) were more important in facilitating prey survivorship than perceived refugia or density-dependent prey effects. A more accurate indicator of refugia might require âpredator-free spaceâ measures that also account for the available area within the structure itself (i.e., volume) and not just on the surface of a structure. Creating experiments that better mimic natural conditions and test a wider range of âpredator-free spaceâ are suggested to better understand the role of structural complexity in oyster reefs and other complex habitats
Trace analysis of Indonesian volcanic ash using thermal and epithermal neutron activation analysis
There is continued great interest in determining the trace element and heavy metal content of volcanic ash for a variety of reasons. The motivation stems from the desire to understand the geochemistry of volcanic ash in imbedded geological formations, the impact on seawater, and the possible release of toxic elements into the environment that may impact livestock grazing and water systems. Ash from volcanic plumes can go as high 8-18 km thus affecting climate and air traffic. We have employed Compton suppression neutron activation analysis (NAA) with thermal and epithermal neutrons to determine trace elements in volcanic ash from Indonesian eruption of Mount Merapi in October 2010. We found a wide range of elements, including several rare earth elements
Modélisation de la dissolution de l'UO en milieu nitrique, vers un modÚle macroscopique des réacteurs de dissolution
National audienceDissolution is a key step for the recycling of uranium dioxyde, mainly present in spent nuclear fuel.Reactions are particularly complex in those cases as they are triphasics and catalyzed by one of their products.This work focuses on developping a model including all the characteristics of the dissolution and their effects on the kinetic
Temperature response of denitrification and anaerobic ammonium oxidation rates and microbial community structure in Arctic fjord sediments
The temperature dependency of denitrification and anaerobic ammonium oxidation (anammox) rates from Arctic fjord sediments was investigated in a temperature gradient block incubator for temperatures ranging from -1 to 40 degrees C. Community structure in intact sediments and slurry incubations was determined using Illumina SSU rRNA gene sequencing. The optimal temperature (T-opt) for denitrification was 25-27 degrees C, whereas anammox rates were optimal at 12-17 degrees C. Both denitrification and anammox exhibited temperature responses consistent with a psychrophilic community, but anammox bacteria may be more specialized for psychrophilic activity. Long-term (1-2 months) warming experiments indicated that temperature increases of 5-10 degrees C above in situ had little effect on the microbial community structure or the temperature response of denitrification and anammox. Increases of 25 degrees C shifted denitrification temperature responses to mesophilic with concurrent community shifts, and anammox activity was eliminated above 25 degrees C. Additions of low molecular weight organic substrates (acetate and lactate) caused increases in denitrification rates, corroborating the hypothesis that the supply of organic substrates is a more dominant control of respiration rates than low temperature. These results suggest that climate-related changes in sinking particulate flux will likely alter rates of N removal more rapidly than warming
Etude de la dissolution du dioxyde d'uranium dans l'acide nitrique, vers un modÚle macroscopique des réacteurs de dissolution
National audienc
Temperature response of denitrification and anammox reveals the adaptation of microbial communities to in situ temperatures in permeable marine sediments that span 50 degrees in latitude
Despite decades of research on the physiology and biochemistry of nitrate/nitrite-respiring microorganisms, little is known regarding their metabolic
response to temperature, especially under in situ conditions. The
temperature regulation of microbial communities that mediate anammox and
denitrification was investigated in near shore permeable sediments at polar,
temperate, and subtropical sites with annual mean temperatures ranging from
â5 to 23 °C. Total N2 production rates were determined using
the isotope pairing technique in intact core incubations under diffusive and
simulated advection conditions and ranged from 2 to 359 ÎŒmol N mâ2 dâ1.
For the majority of sites studied, N2 removal was 2â7 times more rapid under simulated advective flow conditions. Anammox
comprised 6â14% of total N2 production at temperate and polar
sites and was not detected at the subtropical site. Potential rates of
denitrification and anammox were determined in anaerobic slurries in a
temperature gradient block incubator across a temperature range of â1 °C
to 42 °C. The highest optimum temperature
(Topt) for denitrification was 36 °C and was observed in
subtropical sediments, while the lowest Topt of 21 °C was
observed at the polar site. Seasonal variation in the Topt was observed
at the temperate site with values of 26 and 34 °C
in winter and summer, respectively. The Topt values for anammox were
9 and 26 °C at the polar and temperate sites,
respectively. The results demonstrate adaptation of denitrifying communities
to in situ temperatures in permeable marine sediments across a wide range of
temperatures, whereas marine anammox bacteria may be predominately
psychrophilic to psychrotolerant. The adaptation of microbial communities to
in situ temperatures suggests that the relationship between temperature and
rates of N removal is highly dependent on community structure