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.

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.

Phosphorus Budgets and Stoichiometry during the Open-Water Season in Two Unmanipulated Lakes in the Experimental Lakes Area, Northwestern Ontario

1994 ◽  
Vol 51 (12) ◽  
pp. 2739-2755 ◽  
Author(s):  
P. Campbell
Keyword(s):  
Water Column ◽  
Bottom Sediments ◽  
Open Water ◽  
Short Term ◽  
Experimental Lakes Area ◽  
Northwestern Ontario ◽  
Phosphorus Budgets ◽  
Mass Balance Approach ◽  
Primary And Secondary Producers ◽  
Column Total

A comparative mass-balance approach is used to describe and quantify phosphorus (P) cycles during the open-water season in two unmanipulated Experimental Lakes Area (ELA) lakes. A bimodal cycle generally prevailed, in which water-column total phosphorus (TP = total dissolved P plus sestonic particulate P) peaked just after ice-out and again late in the summer. Changes in mass of water-column TP were often much larger than corresponding net external inputs. Shifts of P to and from either zooplankton or fish in the water column do not explain the P residuals. Rather, the bottom sediments must have been adding P to the water column. Short-term regeneration of P from the bottom sediments also probably occurs in artificially eutrophied ELA lakes. The mechanism of regeneration is probably biological. Other aspects of P cycling and P stoichiometry are discussed, particularly in relation to nutrient control of population structure and the function of primary and secondary producers.

Decline of Mysis relicta During the Acidification of Lake 223

1983 ◽  
Vol 40 (11) ◽  
pp. 1905-1911 ◽  
Author(s):  
R. W. Nero ◽  
D. W. Schindler
Keyword(s):  
Confidence Limits ◽  
Experimental Lakes Area ◽  
Mysis Relicta ◽  
Ph Values ◽  
Northwestern Ontario ◽  
Population Comparisons ◽  
Acidification Of Lake ◽  
Ph Range ◽  
Shield Lakes ◽  
Direct Toxicity

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.

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.

Fluvial clastic sediment yield in Canada: scaled analysis

1999 ◽  
Vol 36 (8) ◽  
pp. 1267-1280 ◽  
Author(s):  
Michael Church ◽  
Darren Ham ◽  
Marwan Hassan ◽  
Olav Slaymaker
Keyword(s):  
Suspended Sediment ◽  
Sediment Yield ◽  
Sediment Load ◽  
Drainage Basin ◽  
Scaling Relations ◽  
Southern Ontario ◽  
Fluvial Sediment ◽  
Predicted Values ◽  
River Valleys ◽  
Basin Area

This report presents a set of maps of regional fluvial sediment yield in Canada, based mainly on the Water Survey of Canada archive of riverine suspended sediment observations. Regional scaling relations for the variation of suspended sediment load with drainage basin area are established to permit data to be adjusted to common areal bases for portrayal of regional variations. For most regions, the specific sediment yield increases downstream, indicating regional degradation of river valleys. In the southern prairies, however, regional aggradation is occurring, and in southern Ontario similar quantities of fluvial sediment are apparently being yielded, on average, over all scales in the landscape. A smoothed regional portrayal of the results is obtained by kriging, which also yields error estimates for locally predicted values of sediment yield. Maps are presented for the standard areas of 1 km2, 102 km2 (10 km × 10 km), and 104 km2 (102 km × 102 km).

Changes in phytoplankton communities following logging in the drainage basins of three boreal forest lakes in northwestern Ontario (Canada), 1991–2000

2003 ◽  
Vol 60 (1) ◽  
pp. 43-54 ◽  
Author(s):  
K H Nicholls ◽  
R J Steedman ◽  
E C Carney
Keyword(s):  
Boreal Forest ◽  
Drainage Basin ◽  
Forest Harvesting ◽  
Intermediate Disturbance Hypothesis ◽  
Drainage Basins ◽  
Mixing Depth ◽  
Buffer Strip ◽  
Northwestern Ontario ◽  
Phytoplankton Communities ◽  
Forest Lakes

The phytoplankton communities of three small boreal forest lakes (L26, L39, and L42) on Ontario's Precambrian Shield (Canada) were investigated over 10 years for possible effects of forest harvesting (logging) within their drainage basins (5 years before logging vs. 5 years after logging). During the postlogging period, higher biovolumes of several taxa were recorded, consistent with previously reported changes in nutrients, chlorophyll, light penetration, and mixing depth. Among the most dramatic changes were increases of 100 and 266% in Cyanophyceae in L39 and L42, respectively, 167% in Dinophyceae in L26, 51 and 130% in Chlorophyceae in L26 and L42, respectively, 182% in Bacillariophyceae in L26, and 53 and 73% in total phytoplankton in L26 and L42, respectively. Other effects associated with logging in the watersheds of these lakes included an increase in the numbers of taxa (in accordance with the intermediate disturbance hypothesis) and a decrease in interannual variability in phytoplankton community structure (in accordance with the ecosystem diversity–stability hypothesis). The less extensive logging of the L26 drainage basin and the maintenance of an unlogged shoreline buffer strip did not preclude apparent effects on phytoplankton comparable with some of those found in the other two lakes, where drainage basin logging was more extensive.

Determination of the drainage basin characteristics using vector GIS

2006 ◽  
Vol 37 (2) ◽  
pp. 129-142 ◽  
Author(s):  
H. Apaydin ◽  
F. Ozturk ◽  
H. Merdun ◽  
N.M. Aziz
Keyword(s):  
Form Factor ◽  
Drainage Basin ◽  
Drainage Density ◽  
Contour Length ◽  
Stream Length ◽  
Manual Method ◽  
Morphologic Characteristics ◽  
Basin Area ◽  
Relief Ratio

Detailed geomorphologic characteristics need to be compiled for performing hydrologic modeling of a basin. Basin form and hydrologic characteristics are to be related so the basin form must also be represented by quantitative descriptors. The typical morphologic characteristics used in hydrological analyses are basin area, perimeter, mainstream length, total stream length, contour length, basin shape (form factor, circularity ratio, compactness ratio, basin elongation), slope, drainage density, relief (maximum relief, relief ratio, relative relief), effective basin width, and median elevation. The objective of this study is to propose an algorithm to automatically calculate basin characteristics using vector GIS. The results produced by the algorithm were compared to the manual method and the two methods were found statistically similar.

A reconstruction of Moorhead and Emerson Phase environments along the eastern margin of glacial Lake Agassiz, Rainy River basin, northwestern Ontario

2000 ◽  
Vol 37 (10) ◽  
pp. 1335-1353 ◽  
Author(s):  
A F Bajc ◽  
D P Schwert ◽  
B G Warner ◽  
N E Williams
Keyword(s):  
Wide Spectrum ◽  
Open Water ◽  
Glacial Lake ◽  
Lake Agassiz ◽  
Long Distance ◽  
Distinct Component ◽  
Study Region ◽  
Nearshore Processes ◽  
Northwestern Ontario ◽  
Glacial Lake Agassiz

Mapping of Quaternary geology in the Rainy River lowland, northwestern Ontario resulted in discovery of several fossil-bearing localities. Organic remains are associated with both the Moorhead and Emerson phases of glacial Lake Agassiz. Wood samples recovered from Moorhead Phase deposits have radiocarbon ages ranging between 10.8 and 9.9 ka BP. The wood is detrital and cannot be used to date the beginning of the low-water phase. Nearshore, deltaic, alluvial, peatland, open-water wetland, and upland soil environments are represented in the Moorhead Phase sediment records. Emerson Phase transgressive deposits overlie Moorhead Phase sediments and erosional surfaces. Wood samples recovered from flotsam layers in Emerson Phase nearshore deposits have yielded radiocarbon ages ranging between 10.5 and 9.5 ka BP. Stratigraphic and sedimentologic evidence suggests that the transgression began approximately 9.9 ka BP. Pollen, plant macrofossil, insect, and mollusc assemblages have been affected by long-distance transport, sorting, and reworking by fluvial and nearshore processes. They represent a wide spectrum of terrestrial and aquatic habitats indiscriminantly brought together during high-water periods. The Moorhead and Emerson phase assemblages indicate conditions similar to those in the region today, but there is a distinct component whose modern range is much farther north and west of the study region. In this respect, the assemblages are similar to the mixed communities described from other late-glacial sites of the mid-continent.

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.

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