Diel and Annual Cycles of Net Plankton Photosynthesis in Lake Ontario

1973 ◽  
Vol 30 (12) ◽  
pp. 1779-1787 ◽  
Author(s):  
G. P. Harris
Keyword(s):  
Inverse Correlation ◽  
Lake Ontario ◽  
Rate Of Change ◽  
Annual Cycles ◽  
Light Regimes ◽  
Static Water ◽  
Different Depths ◽  
Diel Fluctuations ◽  
Photosynthesis And Respiration ◽  
Net Phytoplankton

Photosynthesis measurements on net plankton have been carried out for the period April, 1972 to January, 1973 in Lake Ontario. The rising and falling light regimes used on the net phytoplankton (> 64 μ) give marked photosynthetic hysteresis effects in winter and in spring for diatom-dominated populations. Diel fluctuations in photosynthesis and "sun" or "shade" adaptations showed a close interaction between the phytoplankton and the surface light intensity. Systematic seasonal changes have been recorded in the magnitude of the photosynthetic hysteresis effect, saturation light intensities, compensation points, maximum photosynthesis, and respiration rates. An inverse correlation has been found between net plankton mean maximum photosynthesis rates and the rate of change of water temperature. Also phytoplankton respiration rate is largely a function of temperature.The data have been unified to give a picture of daily photosynthesis patterns at different depths in a static water column. The data compare well with 14C moored bottle experiments. Predictive equations have been calculated for maximum photosynthesis rates at different times of the year.

scholarly journals Properties, processes and regimes of soil solutions and surface waters

2020 ◽  
Vol 175 ◽  
pp. 12022
Author(s):  
Guriyat Podvolotskaya ◽  
Sergey Belopukhov ◽  
Vitaly Savich ◽  
Andrey Sorokin ◽  
Nikolay Tyutrin
Keyword(s):  
Biological Activity ◽  
Surface Water ◽  
Surface Waters ◽  
Pair Correlation ◽  
Rate Of Change ◽  
Water Soluble ◽  
Soil Solutions ◽  
Different Depths ◽  
Different Soils

Soil solutions and the surface waters are characterized by properties, processes and regimes. Soil solutions of different soils and their surface water have different biological activity and change the activity of dissolved stimulants and inhibitors. The object of the study are soil solutions of the main types of soils obtained in the model experiments with the ratio of soils: water equal to 1:1 and 1: 2, soil solutions and surface water in the flooding of soils with water for 1 week – 3 months. The research method consisted in the assessment of pH, Eh, activity of K, NO3, NH4, Ca, Mg by conventional methods, assessment of concentrations of water-soluble compounds extracted from soils by ionite membranes, in the assessment of biological activity of solutions using biotests. The following is suggested for additional evaluation: the using of cation and anion membranes, determination of interrelation between the properties of waters, equation of pair correlation and multiply regression. The informative value of the gradient of surface water concentrations at different distances from the floor of the reservoir, at different depths of the overwatered soils is shown. The mobility of Ca, Mg, Fe, Mn in soils and the content of their water-soluble forms depends on both pH and Eh, whose influence on the content of water-soluble forms of the considered cations shows the effects of synergy and antagonism. The rate of change in the composition of soil solutions during soil flooding depends on a combination of soil properties, temperature, and duration of flooding. Soil solutions of different soils and their surface waters have differentrates.

HYSTERESIS EFFECTS IN SOIL MOISTURE MOVEMENT

1962 ◽  
Vol 42 (2) ◽  
pp. 247-253 ◽  
Author(s):  
W. J. Staple
Keyword(s):  
Moisture Content ◽  
Past History ◽  
Rate Of Change ◽  
Moisture Loss ◽  
Time Intervals ◽  
Moisture Movement ◽  
Wetting And Drying ◽  
The Past ◽  
History Of ◽  
Different Depths

Hysteresis was assessed by measuring the tension and moisture content of sections of soil at different time intervals during the redistribution of moisture in uniformly packed columns of Grenville silt loam. Moisture tension was measured by a null method and moisture content was measured gravimetrically.The rate of change of tension with moisture content dψ/dθ and hence the diffusivity, in the tension range 25 to 400 centimeters of water was more than twice as great for drying as for wetting. During redistribution of moisture, when both drying and wetting were involved, different ψ, vs. θ relationships existed at different depths, and the slopes dψ/dθ and diffusivities in the profile were often lower than those for either drying or wetting alone.Further work is needed to assess the importance of hysteresis on moisture movement in practical problems. It seems possible that data on hysteresis, and a knowledge of the past history of wetting and drying, may provide estimates of moisture loss and conservation in fallowed fields.

scholarly journals Arctic mid-winter phytoplankton growth revealed by autonomous profilers

2020 ◽  
Vol 6 (39) ◽  
pp. eabc2678 ◽  
Author(s):  
Achim Randelhoff ◽  
Léo Lacour ◽  
Claudie Marec ◽  
Edouard Leymarie ◽  
José Lagunas ◽  
...  
Keyword(s):  
Phytoplankton Growth ◽  
Marine Phytoplankton ◽  
Ocean Optics ◽  
Light Conditions ◽  
Polar Night ◽  
Low Light ◽  
Annual Cycles ◽  
Baffin Bay ◽  
Arctic Sea ◽  
Net Phytoplankton

It is widely believed that during winter and spring, Arctic marine phytoplankton cannot grow until sea ice and snow cover start melting and transmit sufficient irradiance, but there is little observational evidence for that paradigm. To explore the life of phytoplankton during and after the polar night, we used robotic ice-avoiding profiling floats to measure ocean optics and phytoplankton characteristics continuously through two annual cycles in Baffin Bay, an Arctic sea that is covered by ice for 7 months a year. We demonstrate that net phytoplankton growth occurred even under 100% ice cover as early as February and that it resulted at least partly from photosynthesis. This highlights the adaptation of Arctic phytoplankton to extreme low-light conditions, which may be key to their survival before seeding the spring bloom.

Diel changes of inorganic chemistry in a macrophyte-dominated, softwater stream

2005 ◽  
Vol 56 (8) ◽  
pp. 1165 ◽  
Author(s):  
Robert J. Wilcock ◽  
Steven C. Chapra
Keyword(s):  
Inorganic Carbon ◽  
Solubility Product ◽  
Low Flow ◽  
Total Inorganic Carbon ◽  
Diel Cycles ◽  
Early Evening ◽  
Diel Variations ◽  
Calcium Magnesium ◽  
Diel Fluctuations ◽  
Photosynthesis And Respiration

Diel fluctuations of conductivity and alkalinity were measured in a macrophyte-dominated stretch of the Piako River, a rural, lowland, softwater stream in New Zealand. Both quantities exhibited elevated levels at dawn and depressed levels in the early evening suggesting that the variations might be connected with the diel cycles of macrophyte photosynthesis and respiration. A chemical analysis was used to determine which ions induced the diel variations. For low-flow periods with minimal allochthonous inputs, the changes in conductivity were correlated with calcium, magnesium and the ionised components of total inorganic carbon (bicarbonate, HCO3–, and carbonate, CO32–). The changes in alkalinity were correlated with fluctuations of calcium and magnesium. The latter result was not anticipated based on solubility product calculations. Diel cycles of groundwater inputs explained 60% of average conductivity variations and 30% of average alkalinity variations between dusk and dawn. Other mechanisms also contribute to the observed changes and we speculate that localised calcite production and dissolution may be occurring.

Primary Production in Relation to Temperature Structure, Biomass Concentration, and Light Conditions at an Inshore and Offshore Station in Lake Ontario

1974 ◽  
Vol 31 (7) ◽  
pp. 1215-1232 ◽  
Author(s):  
P. Stadelmann ◽  
J. E. Moore ◽  
E. Pickett
Keyword(s):  
Primary Production ◽  
Biomass Concentration ◽  
Lake Ontario ◽  
Early Summer ◽  
Temperature Structure ◽  
Turnover Rates ◽  
Available Energy ◽  
Offshore Station ◽  
Photosynthesis Efficiency ◽  
Different Depths

Annual primary production rates of 270 and 170 g C m−2 yr−1, respectively, were estimated for an inshore and offshore station in Lake Ontario using the in situ 14C technique. A lag in increase of both biomass and photosynthesis rate at the offshore station in early summer was attributed to deep vertical mixing.Production/biomass quotients were computed using different biomass parameters such as particulate organic carbon, nitrogen, and chlorophyll a. Carbon turnover rates of the seston on an areal basis (m2) were found to vary between 0.04–0.18 day−1 and 0.01–0.21 day−1 at the inshore and offshore station, respectively. Daily photosynthesis efficiency (energy fixed by photosynthesis/available energy) ranged from 0.1 to 1.8% at the two stations. Atypical photosynthesis–light intensity curves showed that algal populations behaved differently at different depths during the stratified period.

Utility of MRI-based disproportionately enlarged subarachnoid space hydrocephalus scoring for predicting prognosis after surgery for idiopathic normal pressure hydrocephalus: clinical research

2017 ◽  
Vol 127 (6) ◽  
pp. 1436-1442 ◽  
Author(s):  
Narihide Shinoda ◽  
Osamu Hirai ◽  
Shinya Hori ◽  
Kazuyuki Mikami ◽  
Toshiaki Bando ◽  
...  
Keyword(s):  
Normal Pressure Hydrocephalus ◽  
Subarachnoid Space ◽  
Inverse Correlation ◽  
Normal Pressure ◽  
Idiopathic Normal Pressure Hydrocephalus ◽  
Rate Of Change ◽  
White Matter Hyperintensity ◽  
Secondary Outcome ◽  
Mri Findings ◽  
The Mean

OBJECTIVEThe presence of disproportionately enlarged subarachnoid space hydrocephalus (DESH) on brain imaging is a recognized finding of idiopathic normal pressure hydrocephalus (iNPH), but the features of DESH can vary across patients. The aim of this study was to evaluate the utility of MRI-based DESH scoring for predicting prognosis after surgery.METHODSIn this single-center, retrospective cohort study, the DESH score was determined by consensus between a group of neurosurgeons, neurologists, and a neuroradiologist based on the preoperative MRI findings of the patients with suspected iNPH. The DESH score was composed of the following 5 items, each scored from 0 to 2 (maximum score 10 points): ventriculomegaly, dilated sylvian fissures, tight high convexity, acute callosal angle, and focal sulcal dilation. The association between the DESH score and improvement of the scores on the modified Rankin Scale (mRS), iNPH Grading Scale (iNPHGS), Mini–Mental State Examination (MMSE), Trail Making Test-A (TMT-A), and Timed 3-Meter Up and Go Test (TUG-t) was examined. The primary end point was improvement in the mRS score at 1 year after surgery, and the secondary outcome measures were the iNPHGS, MMSE, TMT-A, and TUG-t scores at 1 year after surgery. Improvement was determined as improvement of 1 or more levels on mRS, ≥ 1 point on iNPHGS, ≥ 3 points on MMSE, a decrease of > 30% on TMT-A, and a decrease of > 10% on TUG-t.RESULTSThe mean DESH score for the 50 patients (mean age 77.6 ± 5.9 years) reviewed in this study was 5.58 ± 2.01. The mean rate of change in the mRS score was −0.50 ± 0.93, indicating an inverse correlation between the DESH score and rate of change in the mRS score (r = −0.749). Patients who showed no improvement in mRS score tended to have a low DESH score as well as low preoperative MMSE and TMT-A scores. There were no differences in the areas of deep white matter hyperintensity and periventricular hyperintensity on the images between patients with and without an improved mRS score (15.6% vs 16.7%, respectively; p = 1.000). The DESH score did differ significantly between patients with and without improved scores on the iNPHGS (6.39 ± 1.76 vs 4.26 ± 1.69, respectively; p < 0.001), MMSE (6.63 ± 1.82 vs 5.09 ± 1.93; p = 0.010), TMT-A (6.32 ± 1.97 seconds vs 5.13 ± 1.93 seconds; p = 0.042), and TUG-t (6.48 ± 1.81 seconds vs 4.33 ± 1.59 seconds; p < 0.001).CONCLUSIONSMRI-based DESH scoring is useful for the prediction of neurological improvement and prognosis after surgery for iNPH.

scholarly journals Siliceous algae response to the “Great Acceleration” of the mid-20th century in Crawford Lake (Ontario, Canada): A potential candidate for the Anthropocene GSSP

2021 ◽  
pp. 205301962110460
Author(s):  
Cale AC Gushulak ◽  
Matthew Marshall ◽  
Brian F Cumming ◽  
Brendan Llew-Williams ◽  
R Timothy Patterson ◽  
...  
Keyword(s):  
20Th Century ◽  
Environmental Changes ◽  
Additive Model ◽  
Lake Ontario ◽  
Rate Of Change ◽  
Potential Candidate ◽  
Change Analysis ◽  
Siliceous Algae ◽  
Great Acceleration ◽  
Crawford Lake

Diatom and chrysophyte assemblages from varved sediments of meromictic Crawford Lake, Ontario record major environmental changes resulting from spatially broadening anthropogenic environmental stressors related to the “Great Acceleration” in the mid-20th century. Biannual assessment of diatom and chrysophyte assemblages over the last ~200 years allowed for rate of change analysis between adjacent samples that increased substantially during the mid-20th century, concurrent with significant generalized additive model trends. Changes in diatom and chrysophyte assemblages were likely driven by multiple anthropogenic stressors including local forestry harvesting, agriculture, and milling activities, acidic deposition from regional industrial processes, and anthropogenic climate warming. Novel siliceous algal assemblages now exist in Crawford Lake, likely related to the complexities of the above mentioned local and regional stressors. The major assemblage changes at the proposed base of the Anthropocene Epoch detected in this study support the laminated sequence from Crawford Lake as a strong potential candidate for the Anthropocene GSSP.

scholarly journals Effects of self-induction in an Iron cylinder when traversed by alternating currents

1908 ◽  
Vol 80 (539) ◽  
pp. 369-378
Keyword(s):  
Magnetic Induction ◽  
Alternating Current ◽  
Initial Position ◽  
Rate Of Change ◽  
Direction Parallel ◽  
Zero Current ◽  
In Series ◽  
Continuous Current ◽  
Different Depths ◽  
Flow Through

In a previous paper the effects of self-induction in an iron cylinder were studied when a continuous current flowing through the cylinder in a direction parallel with its axis of figure was suddenly reversed and again maintained steady. In the experiments reported in the present paper the currents in the cylinder were made to alternate in the following manner. A continuous current dynamo, capable of giving currents up to 2000 amperes or more, was weakly excited and its brushes were short-circuited by the cylinder to be experimented upon in series with the shunt of a moving-coil ampere meter. The brushes were moved round the commutator by aid of a worm and worm-wheel from the position of maximum to that of zero current. The field was then reversed and the brushes moved back to their initial position. By continuing these operations an alternating current was caused to flow through the cylinder, and its periodic time was controlled by the speed at which the brushes were moved. The worm axle was uniformly rotated by hand at a speed determined by the operator listening to a seconds clock. Simultaneously readings were taken at known epochs on ( a ) each of three dead-beat galvanometers connected to exploring coils threaded through holes in the mass of the cylinder for the purpose of obtaining the E. M. F. 's at different depths due to the rate of change of the magnetic induction, and on ( b ) the moving-coil ampere-meter.

scholarly journals Trends in U.S. Hourly Precipitation Variance 1949–2009

2018 ◽  
Vol 19 (3) ◽  
pp. 599-608 ◽  
Author(s):  
L. M. Canel ◽  
J. I. Katz
Keyword(s):  
Los Angeles ◽  
Statistical Power ◽  
Upper Bounds ◽  
Rate Of Change ◽  
Precipitation Data ◽  
Logarithmic Function ◽  
Los Angeles Basin ◽  
Annual Cycles ◽  
Hourly Precipitation ◽  
The Mean

Abstract Drawing from a NOAA database of hourly precipitation data from 5995 stations in the contiguous United States over the period 1949–2009, the authors investigate possible trends in the variance of the hourly precipitation, averaged over the diurnal and annual cycles and normalized by the square of the mean precipitation at that site. This normalized variance is a measure of storminess, distinct from increases in precipitation attributable to warming. For the 1722 stations surviving quality control with data on at least 80% of days in at least 30 years, the authors compute the rate of change of the logarithm of the normalized variance at each station and set bounds on its mean (over stations) trend. The logarithmic function weights the trends at calm stations equally to those at stormy stations and enhances the statistical power of the mean. The authors find a logarithmic rate of change of the mean normalized variance of yr−1 (). The upper bounds on any continentally averaged trend, increasing or decreasing, are about 0.001 yr−1 (doubling or halving times &gt; 1000 years). It is found that the normalized variance in the Los Angeles basin has increased at a statistically significant rate. This may be attributable to a decrease in the number of aerosol condensation nuclei. Upper bounds are set on any effect of the 11-yr solar cycle.

scholarly journals Plankton studies in a mangrove environment: I first assessment of standing stock and principal ecological factors

1962 ◽  
Vol 12 (3) ◽  
pp. 101-124 ◽  
Author(s):  
Clovis Teixeira ◽  
Miryam B. Kutner
Keyword(s):  
Organic Matter ◽  
Standing Stock ◽  
High Tide ◽  
Ecological Factors ◽  
Inverse Correlation ◽  
Dry Weight ◽  
Quantitative Relation ◽  
Cell Counts ◽  
Mangrove Environment ◽  
Net Phytoplankton

1 - The quantitative relation between net phytoplankton, nanoplankton and zooplankton during the high and low tide for five days at a fixed station is reported here. The samples were collected at surface, 2 and 4 m near the Baguassu river, a typical region of mangrove environment. 2 - Measurements were made of transparence, salinity, temperature, pH, dissolved oxygen, suspended matter and dry weight (inorganic + organic). Culture of bacteria was also carried out to determine the degree of contamination of the water. 3 - Total phytoplankton cell counts were lower during high tide showing a good inverse correlation to salinity. 4 - The total organic matter varied from 6.80 to 16.80 mg/l and the dry organic matter of net plankton varied from 0.084 to 3.64 mg/m³. These results are presumably due to a great portion of the particulate matter that may be originated from nanoplankton and fine detritus. 5 - The average of nanoplankton was 97% greater than net phytoplankton and the net phytoplankton was in average 99,7% greater than zooplankton.

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