Internal Phosphorus Load in an Oligotrophic Precambrian Shield Lake with an Anoxic Hypolimnion

1986 ◽  
Vol 43 (3) ◽  
pp. 574-580 ◽  
Author(s):  
Gertrud K. Nürnberg ◽  
Margo Shaw ◽  
Peter J. Dillon ◽  
Don J. McQueen
Keyword(s):  
Release Rate ◽  
Lake Ontario ◽  
Phosphorus Release ◽  
Phosphorus Load ◽  
Release Rates ◽  
Eutrophic Lakes ◽  
Precambrian Shield ◽  
Anoxic Water ◽  
Internal Sources ◽  
External Loads

The release of phosphorus from sediments into the anoxic water of oligotrophic Chub Lake, Ontario, determined with three different methods, showed that the average release rate of 2.2 mg∙m−2∙d−1 is much smaller than release rates of more eutrophic lakes (14 mg∙m−2∙d−1). Our hypothesis that anoxic release rates depend on lake trophy was confirmed by the significant positive regression of release rates on lake phosphorus concentrations for 56 lakes from the literature. Despite a comparably small phosphorus release rate, the sediments play an important role in Chub Lake as a source of phosphorus because phosphorus from internal sources is in a highly available form and external loads are small.

Chemical and Biological Changes in Nelson Lake, Ontario Following Experimental Elevation of Lake pH

1977 ◽  
Vol 12 (1) ◽  
pp. 213-232 ◽  
Author(s):  
N.D. Yan ◽  
W.A. Scheider ◽  
P.J. Dillon
Keyword(s):  
Heavy Metal ◽  
Lake Ontario ◽  
Background Concentrations ◽  
Precambrian Shield ◽  
Metal Levels ◽  
Zooplankton Communities ◽  
Shield Lakes

Abstract Intensive studies of Nelson Lake, a Sudbury area lake of intermediate pH ~5.7), were begun in 1975. The chemistry of the lake was typical of that of most PreCambrian Shield lakes except that low alkalinities and high sulphate concentrations were observed along with elevated heavy metal levels. After raising the pH of Nelson Lake to 6.4 by addition of Ca(OH)2 and CaCO3, the metals were reduced to background concentrations. Phytoplankton and Zooplankton communities, which at pH of 5.7 were typical of PreCambrian lakes, were not affected by the experimental elevation of lake pH.

scholarly journals Scotopic rod vision in tetrapods arose from multiple early adaptive shifts in the rate of retinal release

2019 ◽  
Vol 116 (26) ◽  
pp. 12627-12628 ◽  
Author(s):  
Yang Liu ◽  
Yimeng Cui ◽  
Hai Chi ◽  
Yu Xia ◽  
Haonan Liu ◽  
...  
Keyword(s):  
Release Rate ◽  
Spectral Properties ◽  
Light Conditions ◽  
Release Rates ◽  
Low Light ◽  
Scotopic Vision ◽  
Recent Innovation ◽  
Cone Pigments ◽  
Early Vertebrates ◽  
Adaptive Shifts

The ability of vertebrates to occupy diverse niches has been linked to the spectral properties of rhodopsin, conferring rod-based vision in low-light conditions. More recent insights have come from nonspectral kinetics, including the retinal release rate of the active state of rhodopsin, a key aspect of scotopic vision that shows strong associations with light environments in diverse taxa. We examined the retinal release rates in resurrected proteins across early vertebrates and show that the earliest forms were characterized by much faster rates of retinal release than more recent ancestors. We also show that scotopic vision at the origin of tetrapods is a derived state that arose via at least 4 major shifts in retinal release rate. Our results suggest that early rhodopsin had a function intermediate to that of modern rod and cone pigments and that its well-developed adaptation to low light is a relatively recent innovation since the origin of tetrapods.

Alpha-Spectroscopy and Leach Testing of Synroc Doped With Actinide Elements

1999 ◽  
Vol 556 ◽  
Author(s):  
K. P. Hart ◽  
E. R. Vance ◽  
R. Stanojevic ◽  
R. A. Day
Keyword(s):  
Surface Layer ◽  
Surface Area ◽  
Release Rate ◽  
Daily Basis ◽  
Alpha Spectroscopy ◽  
Release Rates ◽  
Monthly Basis ◽  
Surface Examination ◽  
Actinide Elements

AbstractSynroc specimens doped individually with ˜ 1 wt% of Np or Pu have been studied, after leaching for >2,500 days, using α-spectroscopy and SEM. In the last leaching period, the leachant was replaced on either a daily or monthly basis. When the leachant was replaced on a daily basis the release rate of Np was similar to that measured when the samples were first leached, whereas for the monthly replacement the release rates of Np or Pu were about a factor of 20 to 30 lower than that for daily replacement. These findings agree generally with the results obtained from surface examination of the samples which showed that the thickness of actinidedepleted surface layer of anatase was 0.3 μm for monthly replacement but only 0.1 μm when the leachant was replaced frequently. Overall, the results suggest that release of actinides from Synroc are controlled by solubility limiting effects at the surface area to volume ratios employed in MCC-1 tests.

Phosphorus Flux through Epilimnetic Zooplankton from Lake Ontario: Relationship with Body Size and Significance to Phytoplankton

1984 ◽  
Vol 41 (11) ◽  
pp. 1702-1712 ◽  
Author(s):  
W. D. Taylor
Keyword(s):  
Body Size ◽  
Phosphorus Uptake ◽  
Lake Ontario ◽  
Trophic Levels ◽  
Phytoplankton Production ◽  
Unit Size ◽  
Release Rates ◽  
Zooplankton Size ◽  
Uptake Rates ◽  
Phosphorus Flux

The flux of phosphate through epilimnetic zooplankton from Lake Ontario was measured by adding 32PO4 into whole lakewater, monitoring its accumulation by zooplankton over 48 h, and then measuring its release when animals were returned to unlabelled lake water. Phosphorus uptake was calculated as the sum of accumulation and release rates. The 10 species examined ranged in size from 36-μm Codonella cratera to 1-mm Daphnia retrocurva. Phosphorus uptake rates of herbivorous zooplankton ranged about 200-fold and increased with body size both within and among species, although not proportionally. Among species, there was a pronounced allometry, with smaller species having much higher rates per unit size. This allometry is similar to that described for other metabolic parameters and body size. There was no tendency for smaller species to release a greater fraction of the label they took up. These results suggest that the biomass of zooplankton consuming a given phytoplankton production will be much smaller if small zooplankton dominate, and therefore, this phosphorus sink will be much smaller. Further, the flow of phosphorus to higher trophic levels may be reduced. The result of changing the zooplankton size-distribution may be to change the amount of spring total phosphorus available to summer phytoplankton.

Release Rules of Alkali and Alkaline Earth Metals during Coal Gasification in CO2 and O2/CO2

2011 ◽  
Vol 396-398 ◽  
pp. 1206-1209
Author(s):  
Jian Ying Lin ◽  
Yang Liu ◽  
Yu Qiao
Keyword(s):  
Oxygen Concentration ◽  
Ion Chromatography ◽  
Release Rate ◽  
Alkaline Earth ◽  
Coal Gasification ◽  
Alkaline Earth Metals ◽  
Release Rates ◽  
Experimental Conditions

Release rules of alkali and alkaline earth metals during coal gasification in CO2and O2/CO2are studied with fix-bed reactor and ion chromatography. The results show that the release rates of Na, K and Mg increase with the increase of temperature. Temperature has almost no effect on the release rate of Ca under the experimental conditions. Compare with temperature, Oxygen concentration has less effect on AAEM volatilization. The release rates of Na and K are higher than that of Mg and Ca. This indicates that the primary mechanisms of volatilization of Na and K are different from those of Mg and Ca.

Evaluation of Pheromone Dispensers for Use in Gypsy Moth Detection (Lepidoptera: Lymantriidae)2

1992 ◽  
Vol 27 (3) ◽  
pp. 280-284 ◽  
Author(s):  
B. A. Leonhardt ◽  
V. C. Mastro ◽  
E. D. DeVilbiss
Keyword(s):  
Gypsy Moth ◽  
Release Rate ◽  
Field Tests ◽  
Release Rates ◽  
Pheromone Release ◽  
Male Moth ◽  
Effective Attraction ◽  
Pheromone Dispensers ◽  
Pheromone Release Rates ◽  
Pheromone Release Rate

Seven controlled-release dispenser formulations containing 500 μg of gypsy moth pheromone (+)-disparlure, were compared in laboratory and field tests. Pheromone release rates, residual pheromone contents, and male moth captures in traps baited with the dispensers were compared following pre-aging of the dispensers in a greenhouse at 35 °C for 0, 4, 12, and 16 wk. The laminate dispenser, now used in USDA detection traps, became less attractive over time as its pheromone release rate and content dropped below the threshold values previously reported as necessary for effective attraction. A polyvinyl chloride coated twine dispenser produced high male moth captures and gave release rates and residual contents above these thresholds (30 ng/h release rate and 100 μg content) at all aging periods. The tube-A dispenser was the most effective of the new commercially prepared formulations, followed by the membrane and tube-B whose male moth captures and release rates tended to increase with aging time. The capsule and film dispensers were the least effective of the formulations tested.

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