Effects of Lake Size on Nutrient Availability in the Mixed Layer during Summer Stratification

1994 ◽  
Vol 51 (12) ◽  
pp. 2756-2768 ◽  
Author(s):  
E. J. Fee ◽  
R. E. Hecky ◽  
G. W. Regehr ◽  
L. L. Hendzel ◽  
P. Wilkinson
Keyword(s):  
Mixed Layer ◽  
Nutrient Recycling ◽  
Nutrient Regeneration ◽  
Small Lakes ◽  
Large Lakes ◽  
Total N ◽  
Northwestern Ontario ◽  
Mixed Layers ◽  
Shield Lakes ◽  
Lake Size

Fluxes to the summer mixed layer of N, Si, and P were estimated in a size series of northwestern Ontario Canadian Shield lakes. Increasing turbulence caused upward fluxes through the thermocline to increase with lake size for nutrients that increased in concentration below the thermocline (soluble reactive Si, total inorganic N, and NO3−; but not total N or any form of P). Precipitation and terrestrial runoff were equally important sources of N and P in all but very small lakes (< 100 ha), where precipitation supplied much more than runoff. Runoff was the only important source of Si, except in very large lakes (> 100 000 ha) where mixing through the thermocline was important. N2-fixation was unimportant except in intermediate-sized fakes (700–2000 ha). Si fluxes nearly equaled phytoplankton requirements, but N and P were below requirements, and recycling within the mixed layer must be the most important source of these nutrients. N and P deficits increased progressively with lake size, implying that the efficiency of nutrient recycling increased with lake size; mixed layers in large lakes are more turbulent and thicker than in small lakes and these processes increase the probability of nutrient regeneration within the mixed layer.

Effects of Lake Size on Phytoplankton Nutrient Status

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 ◽  
...  
Keyword(s):  
Nutrient Status ◽  
Canadian Shield ◽  
Small Lakes ◽  
Large Lakes ◽  
P Deficiency ◽  
Water Renewal ◽  
Mixed Layers ◽  
Shield Lakes ◽  
Lake Size ◽  
Total P

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.

scholarly journals The size-distribution of Earth’s lakes

2016 ◽  
Vol 6 (1) ◽  
Author(s):  
B. B. Cael ◽  
D. A. Seekell
Keyword(s):  
Power Law ◽  
Theoretical Explanation ◽  
Lake Area ◽  
Power Law Distribution ◽  
Small Lakes ◽  
Large Lakes ◽  
Lake Ecology ◽  
Empirical Distributions ◽  
Theoretical Predictions ◽  
Lake Size

Abstract Globally, there are millions of small lakes, but a small number of large lakes. Most key ecosystem patterns and processes scale with lake size, thus this asymmetry between area and abundance is a fundamental constraint on broad-scale patterns in lake ecology. Nonetheless, descriptions of lake size-distributions are scarce and empirical distributions are rarely evaluated relative to theoretical predictions. Here we develop expectations for Earth’s lake area-distribution based on percolation theory and evaluate these expectations with data from a global lake census. Lake surface areas ≥0.46 km2 are power-law distributed with a tail exponent (τ = 2.14) and fractal dimension (d = 1.4), similar to theoretical expectations (τ = 2.05; d = 4/3). Lakes <0.46 km2 are not power-law distributed. An independently developed regional lake census exhibits a similar transition and consistency with theoretical predictions. Small lakes deviate from the power-law distribution because smaller lakes are more susceptible to dynamical change and topographic behavior at sub-kilometer scales is not self-similar. Our results provide a robust characterization and theoretical explanation for the lake size-abundance relationship, and form a fundamental basis for understanding and predicting patterns in lake ecology at broad scales.

Effects of Lake Size on Phytoplankton Photosynthesis

1992 ◽  
Vol 49 (12) ◽  
pp. 2445-2459 ◽  
Author(s):  
E. J. Fee ◽  
J. A. Shearer ◽  
E. R. DeBruyn ◽  
E. U. Schindler
Keyword(s):  
Interannual Variation ◽  
Additional Data ◽  
Climatic Warming ◽  
Lake Surface ◽  
Total Rainfall ◽  
Large Lakes ◽  
Growing Seasons ◽  
Shield Lakes ◽  
Lake Size ◽  
Phytoplankton Photosynthesis

Phytoplankton photosynthesis (PP) was measured for 6 yr in seven remote Canadian Shield lakes that stratify fully during the summer and have water renewal times > 5 yr but vary from 29 to 34 700 ha; Lakes Nipigon and Superior were also studied in two years. Chlorophyll and PP at optimum light were low in the smallest and largest lakes and increased systematically to values nearly five times higher in midsized lakes (~103 ha). Daily PP per square metre of lake surface and annual PP per cubic metre of the mixed layer also varied in this manner, but annual PP per square metre was high in large lakes (despite their low density rates) because of their long growing seasons. Additional data are needed to determine whether the photosynthesis maximum in midsized lakes is inherently size related or an accidental statistical result. Intraannually, chlorophyll-based photosynthesis parameters ([Formula: see text], αB) were similar in all lake sizes, but interannually they varied by two to three times; this interannual variation was significantly correlated with total rainfall during May and June. Implications for extrapolating experimental results from small to large lakes, selecting lakes for interregional comparison studies and predicting how climatic warming would affect phytoplankton photosynthesis are discussed.

Pelagic distribution of lake trout (Salvelinus namaycush) in small Canadian Shield lakes with respect to temperature, dissolved oxygen, and light

1998 ◽  
Vol 55 (1) ◽  
pp. 170-179 ◽  
Author(s):  
Todd J Sellers ◽  
Brian R Parker ◽  
David W Schindler ◽  
William M Tonn
Keyword(s):  
Light Intensity ◽  
Dissolved Oxygen ◽  
Lake Trout ◽  
Salvelinus Namaycush ◽  
Canadian Shield ◽  
Small Lakes ◽  
Experimental Lakes Area ◽  
Northwestern Ontario ◽  
Oxygenated Water ◽  
Shield Lakes

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.

Mercury Concentrations in Fish Related to Size of Remote Canadian Shield Lakes

1993 ◽  
Vol 50 (5) ◽  
pp. 980-987 ◽  
Author(s):  
R. A. Bodaly ◽  
J. W. M. Rudd ◽  
R. J. P. Fudge ◽  
C. A. Kelly
Keyword(s):  
Drainage Basin ◽  
Open Water ◽  
Mercury Contamination ◽  
Anthropogenic Influences ◽  
Temperature Dependent ◽  
Northwestern Ontario ◽  
Shield Lakes ◽  
Basin Area ◽  
Lake Size ◽  
Benthivorous Fishes

Mercury concentrations in planktivorous, omnivorous, and piscivorous fishes were inversely related to lake size in six lakes in northwestern Ontario. The lakes were remote from direct anthropogenic influences and ranged in surface area from 89 to 35 000 ha. Fish mercury concentrations were not related to ratios of drainage basin area to lake size, to ratios of epilimnetic area to lake size, to lake alkalinity, or to the concentration of mercury in lake sediments. Rates of mercury methylation (M) were positively dependent on water temperature whereas rates of methyl mercury demethylation (D) were inversely related to temperature. Thus, M/D was strongly temperature dependent. Mercury concentrations in four fish species were significantly positively correlated with mean epilimnetic water temperatures (r2's ranged from 0.66 to 0.88). This suggested that higher water temperatures in smaller lakes during the open-water season influenced M/D ratios and were the cause of higher fish mercury levels. No lake size related variation was observed in the mercury concentrations in benthivorous fishes. Our hypothesis that epilimnetic temperature affects mercury concentrations in fish deserves further attention, given the possible effects of climate warming on mercury contamination of fishery resources.

Sedimentation of Pb-210 in Laurentian Shield Lakes

1984 ◽  
Vol 19 (2) ◽  
pp. 97-109 ◽  
Author(s):  
R.J. Cornett ◽  
L. Chant ◽  
D. Link
Keyword(s):  
Lake Sediments ◽  
Water Column ◽  
Rate Constant ◽  
Bottom Sediments ◽  
Atmospheric Fallout ◽  
Small Lakes ◽  
Fractional Rate ◽  
Total Input ◽  
Shield Lakes ◽  
Annual Flux

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.

Variations in mixed-layer illite/smectite diagenesis in the rift and post-rift sediments of the Jeanne d'Arc Basin, Grand Banks offshore Newfoundland, Canada

2004 ◽  
Vol 41 (4) ◽  
pp. 401-429 ◽  
Author(s):  
Iftikhar A Abid ◽  
Reinhard Hesse ◽  
John D Harper
Keyword(s):  
Mixed Layer ◽  
Fine Fraction ◽  
Upper Jurassic ◽  
Grand Banks ◽  
Depth Profiles ◽  
Jeanne D'arc Basin ◽  
Central Ridge ◽  
Jeanne D'arc ◽  
Layer I ◽  
Mixed Layers

Mixed-layer illite/smectite (I/S) clays were analyzed from 22 deep exploration wells from the Jeanne d'Arc Basin on the Grand Banks offshore Newfoundland, the host of large commercial hydrocarbon accumulations discovered in the last two and a half decades. The fine fraction of the clays (<0.1 µm) consists mainly of mixed-layer I/S with minor amounts of kaolinite, illite, and chlorite. Smectite and (or) smectite-rich I/S clays were supplied to the Jeanne d'Arc Basin from Upper Jurassic to Tertiary times. Smectite-rich I/S clays occur only in shallow samples irrespective of geologic age. The proportion of illite in I/S mixed-layers, as well as the degree of ordering, increase with depth and temperature indicating that smectite-rich I/S clays have been progressively illitized in both rift and post-rift sediments of the Jeanne d'Arc Basin during burial. The transition from random to R1-ordered I/S occurs between subsurface depths of 1940 and 3720 m and crosses major stratigraphic boundaries. The transition from R1- to R3-ordered I/S generally occurs below 4000 m depth. Variable shapes of I/S depth profiles reflect the influence of temperature, fluid migration, subsidence history, basin structure, lithology, and salt diapirism on I/S diagenesis. Based on these variations, the basin can be subdivided into 4 regions with different illitization gradients. In the Southern Jeanne d'Ac Basin, advanced I/S diagenesis probably reflects uplift and denudation and (or) higher paleogeothermal gradients. Rapid increase of percent illite in I/S with depth in the Trans-Basinal Fault area is most likely controlled by upward flow of hot, K+-bearing fluids along faults. The migration of hydrocarbons probably followed the same pathways as the illitizing fluids. Delayed illitization in the Northern Jeanne d'Arc Basin and Central Ridge area reflects insufficient K+ supply because of a lack of detrital K-feldspar in the host sediment, the absence of faulting, and the presence of thick shale intervals. These findings show that I/S depth profiles may vary within the same sedimentary basin due to a variety of geological factors. Single wells generally cannot be considered representative for the basin as a whole.

Parameterization of Mixed Layer Eddies. Part I: Theory and Diagnosis

2008 ◽  
Vol 38 (6) ◽  
pp. 1145-1165 ◽  
Author(s):  
Baylor Fox-Kemper ◽  
Raffaele Ferrari ◽  
Robert Hallberg
Keyword(s):  
Mixed Layer ◽  
Mixed Layer Depth ◽  
Baroclinic Instability ◽  
Finite Amplitude ◽  
Climate Impacts ◽  
Surface Mixed Layer ◽  
Rotation Rates ◽  
Wide Range ◽  
Horizontal Density Gradient ◽  
Mixed Layers

Abstract Ageostrophic baroclinic instabilities develop within the surface mixed layer of the ocean at horizontal fronts and efficiently restratify the upper ocean. In this paper a parameterization for the restratification driven by finite-amplitude baroclinic instabilities of the mixed layer is proposed in terms of an overturning streamfunction that tilts isopycnals from the vertical to the horizontal. The streamfunction is proportional to the product of the horizontal density gradient, the mixed layer depth squared, and the inertial period. Hence restratification proceeds faster at strong fronts in deep mixed layers with a weak latitude dependence. In this paper the parameterization is theoretically motivated, confirmed to perform well for a wide range of mixed layer depths, rotation rates, and vertical and horizontal stratifications. It is shown to be superior to alternative extant parameterizations of baroclinic instability for the problem of mixed layer restratification. Two companion papers discuss the numerical implementation and the climate impacts of this parameterization.

Diet selection and productivity of sheep grazing contrasting pastures

2002 ◽  
Vol 53 (5) ◽  
pp. 529 ◽  
Author(s):  
W. Chen ◽  
J. Scott ◽  
G. Blair ◽  
R. Lefroy ◽  
K. Hutchinson ◽  
...  
Keyword(s):  
White Clover ◽  
Nutrient Recycling ◽  
Diet Selection ◽  
Total N ◽  
Preferential Selection ◽  
Pasture Degradation ◽  
Dietary Nutrient ◽  
Alternative Species ◽  
Sheep Production ◽  
Over Time

A grazing experiment was conducted at the Big Ridge 2 site CSIRO, Chiswick (30˚31′S, 151˚39′E), 20 km south of Armidale, New South Wales, Australia. The site was established in 1955. In March 1966, phalaris and white clover were sown and pastures were fertilised annually with superphosphate until 1993. There were 3 pasture treatments, each with 2 replicates: degraded pasture (low phalaris content), phalaris-dominant, and phalaris–white clover. The effect of pasture type on animal production (liveweight gain and wool) was only significant in 1996, when there were large differences in pasture composition and production between the 3 pasture types. n-Alkane based estimates showed that pasture degradation affected diet selection and nutrient intake and thus sheep production. The estimates in this study also showed no clear preference for a single pasture species over time and lack of strong preferential selection for clovers when sheep were grazing 3 contrasting pastures. Preferential selection of a particular species varied over time depending on the presence and availability of alternative species. Although there were large differences in total N and S intake and faecal output between the 3 pastures, the proportion of the dietary nutrient used for production was similar. This observation reveals the importance of further improving pasture and grazing management, particularly in productive phalaris–white clover pasture with high nutrient flux, to improve nutrient recycling through plant uptake and retention by animals in the grazing ecosystem, and reduce losses.

scholarly journals Ultramicrosensors based on transition metal hexacyanoferrates for scanning electrochemical microscopy

2013 ◽  
Vol 4 ◽  
pp. 649-654 ◽  
Author(s):  
Maria A Komkova ◽  
Angelika Holzinger ◽  
Andreas Hartmann ◽  
Alexei R Khokhlov ◽  
Christine Kranz ◽  
...  
Keyword(s):  
Hydrogen Peroxide ◽  
Detection Limit ◽  
Transition Metal ◽  
Prussian Blue ◽  
Electrochemical Deposition ◽  
Mixed Layer ◽  
Scanning Electrochemical Microscopy ◽  
The Stability ◽  
Mixed Layers ◽  
Electrochemical Microscopy

We report here a way for improving the stability of ultramicroelectrodes (UME) based on hexacyanoferrate-modified metals for the detection of hydrogen peroxide. The most stable sensors were obtained by electrochemical deposition of six layers of hexacyanoferrates (HCF), more specifically, an alternating pattern of three layers of Prussian Blue and three layers of Ni–HCF. The microelectrodes modified with mixed layers were continuously monitored in 1 mM hydrogen peroxide and proved to be stable for more than 5 h under these conditions. The mixed layer microelectrodes exhibited a stability which is five times as high as the stability of conventional Prussian Blue-modified UMEs. The sensitivity of the mixed layer sensor was 0.32 A·M−1·cm−2, and the detection limit was 10 µM. The mixed layer-based UMEs were used as sensors in scanning electrochemical microscopy (SECM) experiments for imaging of hydrogen peroxide evolution.

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