Radiochemical Analysis of Orthophosphate Concentrations and Seasonal Changes in the Flux of Orthophosphate to Seston in Two Canadian Shield Lakes

1980 ◽  
Vol 37 (3) ◽  
pp. 479-487 ◽  
Author(s):  
S. N. Levine ◽  
D. W. Schindler

Seasonal changes in the concentration and dynamics of phosphate–phosphorus were studied in two small lakes, one oligotrophic and one artificially eutrophied. Because the molybdate blue phosphate technique frequently overestimates phosphate concentrations, three radiochemical assays were used. One, involving sephadex fractionation, was unsatisfactory because of the long period required for high molecular weight phosphorus fractions to reach isotopic equilibrium. The second method was unusable both for epilimnion waters within the Experimental Lakes Area, because of its low sensitivity, and for hypolimnion waters, due to interference from nonphosphate compounds. The third method, Rigler's bioassay, indicated that PO4-P in both lakes seldom exceeded 0.1 μg∙L−1, even under anoxic conditions. Organisms, and not mineral reactions, appeared to regulate the phosphate concentration at all depths in the lakes.Key words: phosphorus dynamics, orthophosphate

1998 ◽  
Vol 55 (1) ◽  
pp. 170-179 ◽  
Author(s):  
Todd J Sellers ◽  
Brian R Parker ◽  
David W Schindler ◽  
William M Tonn

The distribution of lake trout (Salvelinus namaycush) with respect to water temperature, dissolved oxygen, and light intensity was surveyed in three small Canadian Shield lakes at the Experimental Lakes Area, northwestern Ontario. Based on hydroacoustic and gillnet surveys, there was considerable variation among lakes in temperatures occupied by lake trout during the summer. During the day, lake trout were concentrated at 4-8°C in Lake 375, broadly distributed from 6 to 15°C in Lake 442, and concentrated in the epilimnion at 19°C in Lake 468. At night, lake trout in all lakes occupied epilimnetic waters at 19-20°C. Lake trout inhabited highly oxygenated water, with 75-90% of fish at >6 mg dissolved oxygen ·L-1 throughout the spring and summer in all three lakes. Light intensity did not affect lake trout distribution in Lake 468 but may have contributed to lake trout daytime descent into cool waters in Lakes 375 and 442. We suggest that previously assumed niche boundaries of lake trout do not adequately describe critical habitat for the species in small lakes, the same lakes that are likely most sensitive to erosion of such habitat.


1984 ◽  
Vol 19 (2) ◽  
pp. 97-109 ◽  
Author(s):  
R.J. Cornett ◽  
L. Chant ◽  
D. Link

Abstract The average annual flux of Pb-210 from the atmosphere to lake surfaces and to the bottom sediments was measured in seven small lakes located on the Laurentian Shield. Direct atmospheric fallout of Pb-210 was 136 ± 16 Bq m-2 a-1 Streams from the lakes' catchments input an additional 5 to 473 Bq m-2 a-1. Only 16 to 80 percent of the total input was found in the lake sediments. The fractional rate constant for Pb-210 sedimentation from the water column ranged from 0.25 to 5.3 per annum.


1883 ◽  
Vol 29 (125) ◽  
pp. 111-117
Author(s):  
B. F. C. Costelloe

During the long period embraced in the present Retrospect, the most important incident that has happened in the philosophical circles of this country is the death of Professor T. H. Green, of Oxford—a man who for many years had been silently acquiring, not only by his power of thinking but by his strong and blameless personal character, a marked position and a unique influence among the leaders of thought in England. His philosophical position would perhaps best be defined by saying that he became the chief of that small, but notable, band of speculative students, centred mainly in Oxford, Glasgow, and Edinburgh, who are reviving the spirit of the systems of Kant and Hegel, in its application to the new scientific, political, and religious problems of the day. His distinguishing characteristics were his modesty and his earnest sense of duty—qualities perhaps not so conspicuous as they might be amongst the better known of modern psychologists. His modesty was such that he never assumed that he had mastered the secret of any writer, until he had bestowed the most extravagant labour and thought in exploring difficulties and obscurities on which the man himself had probably never bestowed a second thought. His earnestness was so thorough that he believed it to be merely his duty to struggle with the fundamental questions of the Sphinx of modern criticism, and find for himself and others not a negative but a constructive answer, no matter what toil and trouble it might cost. For he held that those who contribute, as we all in some way do, to the formation of public opinion upon the vital subjects of life and conduct, are under a terrible responsibility if they mislead their neighbours, or even if they refuse by sloth or vanity or cynicism that healthy guidance which their own attainments would enable them to give. These remarks are suggested by the fact that the first article of the April number of “Mind” is from Prof. Green's pen. Indeed it is one of the last pieces of work he ever personally sent to press; although we are glad to know that the groat Ethical work on which he had long been engaged is left with his philosophical friends in so complete a form that it will be published immediately. The April article is the second of three essays on the question, “Can there be a natural science of man?” of which the third holds the leading place in the July number. The scope of the essays, as well as of the “Prolegomena to Ethics,” to which they were in a sense introductory, will be best indicated if we quote a note added in the July number by Prof. Green's literary executor, Mr. A. C. Bradley.


1983 ◽  
Vol 40 (11) ◽  
pp. 1905-1911 ◽  
Author(s):  
R. W. Nero ◽  
D. W. Schindler

The population size of Mysis relicta in Lake 223 of the Experimental Lakes Area, northwestern Ontario, decreased from 6 700 000 ± 1 330 000 (± 95% confidence limits) during August of 1978, to 270 000 ± 75 000 during August of 1979, a 96% decrease. Because Mysis, a cold stenotherm, is restricted to the metalimnion and hypolimnion of lakes during summer, the pH range encountered by the population was 5.51 to 6.32 in 1978 and 5.23 to 6.10 in 1979, even though mean pH values in epilimnion waters for the 2 yr were 5.84 and 5.60. A decrease in pH of its habitat from 6.2 to 5.6 during fall overturn in 1979 caused the elimination of the remaining 4% of the population. Comparisons with four control lakes suggested that the decline and disappearance were not normal occurrences in unstressed lakes. Concentrations of Zn, Al, Mn, Fe, Cd, Cu, Ni, and Hg in Lake 223 water were low, and concentrations in Mysis were less than or equal to those in animals from five control lakes, suggesting that the decline in this species was not due to the toxic effects of metals. All size classes were affected, so that direct toxicity of hydrogen ion may be responsible for this abrupt population collapse. These results suggest that Mysis may be a useful early indicator of acidification damage to Precambrian Shield lakes.


PEDIATRICS ◽  
1956 ◽  
Vol 17 (1) ◽  
pp. 44-44

During the course of investigations of maternal red cell volume, employing transfusions with radioactive iron, an opportunity was afforded to measure the persistence and utilization of iron transferred across the placenta to the infant. A wealth of fundamental data was obtained concerning the importance of iron obtained from the mother in hematopoiesis during infancy. As the donors' cells containing radioactive iron which were transfused during pregnancy were broken down, radioactive iron was released into the general supply of the mother and fetus. At birth the blood of each infant contained a measurable ratio of radioactive iron to packed red cells. The ratio of radioactive iron to hemoglobin and to hemoglobin iron could then be calculated. Further calculations gave information concerning the amounts of hemoglobin iron of transplacental and dietary origin. The results indicated that there was little or no utilization of dietary iron for hemoglobin formation by the infants until 3 to 4 months after birth. Incorporation of the radioactive iron obtained transplacentally into hemoglobin during the growth of the infant indicated that normal infants utilize iron obtained during fetal life throughout infancy. Data from infants followed for a long period suggest that after 3 to 4 months dietary iron continues to be added to transplacental iron for the production of hemoglobin and gradually begins to replace transplacental iron in hemoglobin formation during the third year.


2001 ◽  
Vol 7 (S2) ◽  
pp. 164-165
Author(s):  
Sara E. Miller ◽  
David N. Howell

Infectious diseases are the leading cause of death worldwide and the third leading cause in the US. Among these maladies are many that can be classified as emerging diseases. Some of these disorders may be caused by truly novel pathogens. in others, the causative organisms have been present for many years (for some, probably millennia), but have escaped detection until recently. Still others represent the re-emergence of known pathogenic organisms after a long period of quiescence. The mention of emerging pathogens brings to mind sensational exotic and feared microorganisms such as Ebola virus, human immunodeficiency virus (HIV), hantavirus, West Nile virus, Yersinia pestis (plague), and prion diseases such as bovine spongiform encephalitis (BSE, “mad cow” disease) which have been associated with variant Creutzfeldt- Jakob disease (CJD) in humans. However, other organisms that have been known for some time can be classified as emerging pathogens as they continually mutate, recombine, and adapt, causing misery and death.


1994 ◽  
Vol 51 (12) ◽  
pp. 2769-2783 ◽  
Author(s):  
S. J. Guildford ◽  
L. L. Hendzel ◽  
H. J. Kling ◽  
E. J. Fee ◽  
G. G. C. Robinson ◽  
...  

Phytoplankton nutrient status measurements (C/P, C/N, C/chlorophyll, N/P, alkaline phosphatase activity, and N debt) were measured for 6 yr in seven remote Canadian Shield lakes. Lakes Nipigon and Superior were also studied for 2 yr. These lakes varied in surface area from 29 to 8.223 × 10 ha, they all stratified fully during the summer and had water renewal times > 5 yr. All lakes were severely P deficient; however, the large lakes (> 2000 ha) were consistently less P deficient than small lakes. A growth-rate indicator (photosynthesis normalized to particulate C) agreed with nutrient status indicators, in that small lakes had lower rates than large lakes. Total P was a good predictor of chlorophyll, but factors related to lake size (temperature and mixed depth) were equally good or better predictors of nutrient status. Decreasing mean water column light intensity could not explain the lower P deficiency of large lakes. The deeper, more energetic mixed layers in large lakes apparently cause P to be recycled more efficiently. Extrapolation of observations or experimental results from small to large lakes requires recognition that phytoplankton in large lakes are less nutrient deficient and may have higher growth rates.


The author had pointed out, in a paper published in the Philosophical Transactions for 1828, on the corrections of the elements of Delambre’s Solar Tables, that the comparison of the corrections of the epochs of the sun and the sun’s perigee, given by the late observations, with the corrections given by the observations of the last century, appears to indicate the existence of some inequality not included in the arguments of those tables. As it was necessary, therefore, to seek for some inequality of long period, he commenced an examination of the mean motions of the planets, with the view of discovering one whose ratio to the mean motion of the earth could be expressed very nearly by a proportion of which the terms are small. The appearances of Venus are found to recur in very nearly the same order every eight years; some multiple, therefore, of the periodic time of Venus is nearly equal to eight years. It is easily seen that this multiple must be thirteen; and consequently eight times the mean motion of Venus is nearly equal to thirteen times the mean motion of the earth. The difference is about one 240th of the mean annual motion of the earth; and it implies the existence of an inequality of which the period is about 240 years. No term has yet been calculated whose period is so long with respect to the periodic time of the planets disturbed. The value of the principal term, calculated from the theory, was given by the author in a postscript to the paper above referred to. In the present memoir he gives an account of the method of calculation, and includes also other terms which are necessarily connected with the principal inequality. The first part treats of the perturbation of the earth’s longitude and radius victor; the second of the perturbation of the earth in latitude; and the third of the perturbations of Venus depending upon the same arguments.


2015 ◽  
Vol 129 (2) ◽  
pp. 165 ◽  
Author(s):  
Michele E. Nicholson ◽  
Michael D. Rennie ◽  
Kenneth H. Mills

We examined the long-term effects on prey fish communities of introducing Northern Pike (Esox lucius), a top predator fish, into small, Boreal Shield lakes lacking natural piscivore populations. During 1987–1994, Northern Pike were introduced into Lakes 110, 221, and 227 in the Experimental Lakes Area in northwestern Ontario, Canada. In Lake 227, prey fish were undetectable three years after the addition of Northern Pike. Although Northern Pike were removed from the lake by 1996, multiple independent visual and trapping surveys have yielded no evidence of any fish in Lake 227 since then. In 1994–1995, 85% of the Northern Pike were removed from Lake 221. In 2012, despite intensive sampling efforts using baited minnow traps, fyke nets, trap netting, gill netting, angling, and visual observation, no forage fish of any species was observed or caught in Lake 110 or 221. In all three lakes where Northern Pike were added, prey fish populations were extirpated or too small to detect. In Lake 221, we estimated the current population of Northern Pike to be 49 ± 37, a 59% decrease since 2000 when prey fish were still present. The mean total length and body condition of Northern Pike in Lake 221 had not changed since the prey community collapsed. Our findings suggest that the introduction of Northern Pike into lakes without natural piscivore populations has long-lasting effects on fish community structure, to the detriment of both Northern Pike and prey fish populations.Note: an erratum for this article was published in the subsequent issue, and is attached to the end of this article's pdf. Table 2 had not been justified properly; the revised table corrects this issue.


2015 ◽  
Vol 25 (1) ◽  
pp. 31-36 ◽  
Author(s):  
Piotr Wesołowski ◽  
Adam Brysiewicz

Abstract Due to poor ecological status of Lake Starzyc, lake restoration measures were undertaken in 2003 to improve aerobic conditions of near-bottom waters and to decrease phosphorus concentrations. To do this, a wind-driven pulverising aerator was installed in the lake. The aim of this study was to analyse variability of oxygen and nitrogen concentrations in lake water near the aerator in the third year of its operation and later on in the three-year-long period of the years 2008–2010. It was found that concentrations of ammonium-nitrogen, nitrate-nitrogen and dissolved oxygen near the aerator did not differ from those in sites 4 and 5, which evidenced similar abiotic conditions in analysed waters. Higher concentrations of dissolved oxygen and lower concentrations of nitrate-nitrogen were found in the years 2008–2010 than in 2005.


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