Changes in methyl mercury concentrations in zooplankton from four experimental reservoirs with differing amounts of carbon in the flooded catchmentsThis paper is part of the series “Forty Years of Aquatic Research at the Experimental Lakes Area”.

2009 ◽  
Vol 66 (11) ◽  
pp. 1910-1919 ◽  
Author(s):  
Britt D. Hall ◽  
Katharine A. Cherewyk ◽  
Michael J. Paterson ◽  
R. (Drew) A. Bodaly
Keyword(s):  
Food Web ◽  
Methyl Mercury ◽  
Dry Weight ◽  
Experimental Lakes Area ◽  
Organic C ◽  
Dissolved Organic C ◽  
Northwestern Ontario ◽  
Highly Correlated ◽  
Source Waters

Methyl mercury (MeHg) concentrations in zooplankton were compared from four experimental reservoirs at the Experimental Lakes Area in northwestern Ontario, Canada, to test the hypothesis that increases in concentrations of MeHg in zooplankton would be proportional to C availability. The experimental reservoirs included three upland reservoirs flooded between 1999 and 2003 that differed in amounts of flooded organic terrestrial C (high, medium, and low C) and an experimental reservoir created over a wetland–peatland complex in 1993. After flooding, MeHg in zooplankton increased from <100 ng·g dry weight–1 in inflow source waters to >500 ng·g dry weight–1 in all reservoirs. In the first two years of flooding, MeHg in zooplankton was not correlated with amounts of flooded C, but the rates of decline in mean annual concentrations were negatively correlated with the amount of C stored in flooded catchments. Concentrations of MeHg in zooplankton were highly correlated with MeHg concentrations in unfiltered water, with reductions in bioaccumulation associated with increases in dissolved organic C and decreases in pH. Overall, our results suggest that reservoir designs that minimize the amount of flooded terrestrial C should result in shorter periods of elevated MeHg in the food web.

Responses of Benthic Communities to Episodic Acid Disturbances in a Lake Outflow Stream at the Experimental Lakes Area, Ontario

1994 ◽  
Vol 51 (8) ◽  
pp. 1877-1892 ◽  
Author(s):  
Ronald J. Hall
Keyword(s):  
Water Chemistry ◽  
New Hampshire ◽  
Benthic Communities ◽  
Experimental Lakes Area ◽  
Organic C ◽  
Dissolved Organic C ◽  
Northwestern Ontario ◽  
South Central ◽  
Drift Density ◽  
Reference Areas

Effects of episodic experimental pH depressions on water chemistry and structure of benthic communities were investigated in northwestern Ontario, a location with low H+ deposition. Acidity levels were increased from background values of pH 6.9 to 5.0, 4.5, and 4.0 to simulate snowmelt and rainstorm events observed in south-central Ontario. Conductivity and concentrations of Ca and Mn increased significantly for all three pH disturbances. Fe and dissolved organic C remained unchanged at pH 4.5 and 4.0 but Fe increased at pH 5.0. Total and inorganic monomeric Al increased at pH 4.5 and 4.0 relative to reference areas. At pH 5.0, density decreases were observed for Baetis, Ectemnia, Simulium, and Prosimulium, at pH 4.5 for Baetis, Lepidostoma, Micropsectra, Simulium, and Prosimulium, and at pH 4.0 for Baetis, Tanytarsus, and Cricotopus. Densities of collector/filterers and clingers decreased at all pH levels, but diversity decreased in the experimental reach at pH 4.0 only. Drift density of the above genera was correlated with H+ concentration. Large reductions in macroinvertebrate densities occurred at higher pH (5.0) and during shorter exposure times compared with previous experiments in areas of higher H+ deposition in south-central Ontario and New Hampshire.

Methyl mercury in aquatic insects from an experimental reservoir

1998 ◽  
Vol 55 (9) ◽  
pp. 2036-2047 ◽  
Author(s):  
B D Hall ◽  
D M Rosenberg ◽  
A P Wiens
Keyword(s):  
Aquatic Insects ◽  
Methyl Mercury ◽  
Fold Increase ◽  
Fish Tissue ◽  
Functional Feeding Groups ◽  
Experimental Lakes Area ◽  
Major Pathway ◽  
Natural Lakes ◽  
Northwestern Ontario ◽  
Before And After

Our objective was to study the effects of experimental flooding of a small wetland lake on the methyl mercury (MeHg) concentrations in aquatic insects and to compare MeHg concentrations in insects with those in water and fish from the same system. Insects were collected from the shorelines of the experimental reservoir before and after flooding, an undisturbed wetland lake, and an oligotrophic lake, all in the Experimental Lakes Area in northwestern Ontario. Samples were identified to the lowest possible taxon and categorized into functional feeding groups (FFGs; predators or collector/shredders). The insects were analyzed for MeHg and total Hg using clean techniques. Contamination was not a problem because levels of MeHg in insects were much higher than background concentrations. Odonata, Corixidae, Gerridae, Gyrinidae, and Phryganeidae/Polycentropodidae exhibited increases in MeHg concentrations in response to flooding. When data were grouped into FFGs, increases were observed in predators. There were insufficient numbers of collector/shredders collected to make a definitive conclusion on MeHg increases. Predators exhibited an approximately threefold increase in MeHg concentrations after flooding compared with a 20-fold increase in water concentrations and a four- to five-fold increase in fish concentrations. Trends in MeHg concentrations in aquatic insects from reservoirs and natural lakes in Finland and northern Québec were similar to ours. Evidence of an increase in MeHg concentrations in the lower food web helps explain increases in MeHg concentrations in fish from reservoirs because food is the major pathway of MeHg uptake in fish tissue.

Measurements of Specific Rates of Net Methyl Mercury Production in the Water Column and Surface Sediments of Acidified and Circumneutral Lakes

1987 ◽  
Vol 44 (4) ◽  
pp. 750-757 ◽  
Author(s):  
Luying Xun ◽  
N. E. R. Campbell ◽  
John W. M. Rudd
Keyword(s):  
Water Column ◽  
Water Samples ◽  
Methyl Mercury ◽  
Lake Acidification ◽  
Sediment Surface ◽  
Mercury Methylation ◽  
Experimental Lakes Area ◽  
Northwestern Ontario ◽  
Decreasing Ph ◽  
Mercury Production

Specific rates of mercury methylation and demethylation were determined for water and surficial sediment samples taken from several lakes located in the Experimental Lakes Area, northwestern Ontario. Specific rates of mercury methylation were found to increase with decreasing pH in epilimnetic water samples in which pH was adjusted prior to incubation and in epilimnetic water samples taken from lakes of different pH. Reduction of pH also increased methyl mercury production at the sediment surface. Both increases and decreases in pH reduced specific rates of mercury demethylation. However, these changes were smaller than for methylation. Proportionally, specific rates of methylation increased faster than increasing concentrations of Hg2+, while specific rates of mercury demethylation increased linearly with increasing concentrations of methyl mercury. Overall, this study predicts that the net rate of methyl mercury production in the water column and at the sediment–water surface will increase as a result of lake acidification, and this may at least partially explain why the mercury concentration of fish appears to increase during lake acidification.

Relationships between total mercury in sediments and methyl mercury in the freshwater gastropod prosobranch Bithynia tentaculata in the St. Lawrence River, Quebec

2000 ◽  
Vol 57 (S1) ◽  
pp. 164-173 ◽  
Author(s):  
JC Désy ◽  
J -F Archambault ◽  
B Pinel-Alloul ◽  
J Hubert ◽  
P GC Campbell
Keyword(s):  
Methyl Mercury ◽  
Linear Models ◽  
Dry Weight ◽  
Gut Contents ◽  
Freshwater Gastropod ◽  
Bithynia Tentaculata ◽  
Total Hg ◽  
Highly Correlated ◽  
The Relationship ◽  
St Lawrence River

Total Hg concentrations in sediment and methyl mercury (MeHg) levels in the gastropod species Bithynia tentaculata were evaluated at 21 stations in the fluvial corridor of the St. Lawrence River (Quebec, Canada). In the sediments (n = 21), total Hg concentrations ranged from 34 to 2790 ng·g dry weight-1. In the gastropods, MeHg concentrations varied from 15 to 290 ng·g dry weight-1 in undepurated gastropods (n = 20) and from 41 to 420 ng·g dry weight-1 in depurated gastropods (n = 13; without gut contents). The southern sector of Lake St. Louis, located near the Îles-de-la-Paix, had significantly higher Hg concentrations than any other sectors under study, both for total Hg in the sediments and MeHg in the gastropods. We established linear models to describe the relationships between Hg contamination in sediments and molluscs for the fluvial corridor of the St. Lawrence River and for the Lake St. Louis sector. Total Hg in sediments and MeHg in gastropods were highly correlated for all pooled stations (r = 0.83), and the relationship was even stronger for the Lake St. Louis stations (r = 0.92). Our study suggests that the gastropod B. tentaculata is a promising biomonitor species for assessing Hg contamination in the fluvial corridor and lakes of the St. Lawrence River.

The Effect of pH on Methyl Mercury Production and Decomposition in Lake Sediments

1985 ◽  
Vol 42 (4) ◽  
pp. 685-692 ◽  
Author(s):  
P. S. Ramial ◽  
John W. M Rudd ◽  
Akira Furutam ◽  
Luying Xun
Keyword(s):  
Lake Sediments ◽  
Methyl Mercury ◽  
Inorganic Mercury ◽  
Mercury Methylation ◽  
Surficial Sediments ◽  
Experimental Lakes Area ◽  
Effect Of Ph ◽  
Northwestern Ontario ◽  
Acidified Lakes ◽  
Mercury Production

Mercury methylation was measured in surficial sediments taken from unacidified and experimentally acidified lakes in the Experimental Lakes Area, northwestern Ontario. A reduction in the pH of sediments lowered the rate of 203Hg methylation. Methylation was undetectable at pH <5.0. This decrease in mercury methylation was probably related to a shortage of available inorganic mercury when the pH of the sediment porewater was reduced. Below pH 6.0, inorganic mercury concentrations in porewater, measured with 203Hg, were reduced to less than 20% of that found at unaltered pH. A comparison of methylation and demethylation rates was made at various pH's. The rate of demethylation decreased to a lesser extent than methylation as the pH was lowered. This research indicates that enhanced mercury methylation in the sediment is not responsible for the observed increase in mercury levels in fish from acidified lakes.

Vertical Distribution and Seasonal Abundance of Zooplankton in Two Shallow Lakes of the Experimental Lakes Area, Northwestern Ontario

1971 ◽  
Vol 28 (2) ◽  
pp. 245-256 ◽  
Author(s):  
D. W. Schindler ◽  
Bengt Novén
Keyword(s):  
Vertical Distribution ◽  
Dry Weight ◽  
Distribution Patterns ◽  
Zooplankton Biomass ◽  
Seasonal Abundance ◽  
Experimental Lakes Area ◽  
Leptodora Kindtii ◽  
Northwestern Ontario ◽  
Vertical Distributions ◽  
Diurnal Movement

Seasonal variations in the abundance of zooplankton were studied in lakes 122 and 132 for a period of 10 months beginning in mid-May 1968. Seasonal dynamics of various species are discussed in relation to their patterns in the Canadian Shield and in other localities.Day and night vertical distributions for each lake were sampled on two dates in summer. Three species of rotifers migrated diurnally in lake 122, but no evidence of diurnal movement was found in lake 132. All crustaceans studied in both lakes migrated vertically to some degree, except for nauplius larvae and Leptodora kindtii. There was little difference in vertical distribution patterns on the two dates studied.Average zooplankton biomass in the two lakes was calculated and compared with that found in other studies. Average zooplankton biomass during the ice-free season was 72 and 156 mg/m3 dry weight for lakes 122 and 132, respectively. Dominant species in both lakes were Diaptomus minutus, Cyclops bicuspidatus thomasi, Holopedium gibberum, and Bosmina longirostris. Ecological tolerances for rotifer species agreed well with those found for Swedish waters.

Methyl mercury in pristine and impounded boreal peatlands, Experimental Lakes Area, Ontario

2000 ◽  
Vol 57 (11) ◽  
pp. 2211-2222 ◽  
Author(s):  
A Heyes ◽  
T R Moore ◽  
J WM Rudd ◽  
J J Dugoua
Keyword(s):  
Surface Water ◽  
Methyl Mercury ◽  
Important Variable ◽  
Mehg Concentration ◽  
Experimental Lakes Area ◽  
Riparian Wetland ◽  
Near Surface ◽  
Boreal Peatlands ◽  
Northwestern Ontario ◽  
Peat Surface

Methyl mercury (MeHg) concentrations were measured in peat and peat porewater of pristine wetlands and an impounded riparian wetland at the Experimental Lakes Area in northwestern Ontario, Canada. In pristine wetlands, MeHg concentrations in peat ranged from 0.1 to 60 ng·g-1 and in peat porewater from 0.02 (the detection limit) to 7.3 ng·L-1, with higher concentrations in wetlands that received upland runoff. Impoundment increased the average MeHg concentration in the near-surface peat porewater from 0.2 to 1.0 ng·L-1. As the increase was most dramatic near the peat - surface water interface, we suggest that the elevated MeHg concentrations resulted from an increase in net MeHg production associated with the decomposition of inundated vegetation. Impoundment increases the area of potential Hg methylation by imposing anoxia over the entire wetland surface and by facilitating the exchange of nutrients and MeHg between the peat surface and the surface water. No clear chemical control on MeHg concentration was observed among the pristine wetlands or in the impounded wetland. However, in laboratory incubations of peat, porewater MeHg concentration increased upon the addition of sulfate. We propose that sulfate availability is an important variable in Hg methylation in pristine northern wetlands.

Mercury concentrations in northern pike ( Esox lucius) from boreal lakes with logged, burned, or undisturbed catchments

2000 ◽  
Vol 57 (S2) ◽  
pp. 129-135 ◽  
Author(s):  
Edenise Garcia ◽  
Richard Carignan
Keyword(s):  
Methyl Mercury ◽  
Trophic Position ◽  
Light Attenuation ◽  
Dry Weight ◽  
Northern Pike ◽  
Esox Lucius ◽  
Boreal Lakes ◽  
Total N ◽  
Organic C ◽  
Pike Esox Lucius

We measured total Hg and stable isotopes (δ13C and δ15N) in northern pike (Esox lucius) from 19 Boreal Shield lakes with undisturbed, logged, or burned watersheds. Average Hg level in standard 560-mm northern pike, on a dry weight basis, was significantly higher in logged lakes (3.4 µg·g-1) than in reference lakes (1.9 µg·g-1). Average Hg concentrations in burned lakes (3.0 µg·g -1) did not differ significantly from those in logged and references lakes. Concentrations of Hg normalized to trophic position determined from isotopic composition yielded similar results. Mercury levels were above the WHO safe consumption limit in all logged lakes. Mercury in northern pike was correlated with methyl mercury in zooplankton (+), total N (+), pH (-), alkalinity (-), sulfate (+), dissolved organic C loading (+), and light attenuation in lake water (+). Stepwise multiple regressions explained 79% of the variability in Hg in fish and included methyl mercury in zooplankton, pH, and sulfate as independent variables. Explained variability increased to 92% when a second-order lake with an exceptionally large drainage area was excluded. Our results suggest that extensive logging activities may disrupt the natural cycling of Hg in watersheds and increase Hg levels in the aquatic biota.

Chemistry of Surface Sediments of Sixteen Lakes in the Experimental Lakes Area, Northwestern Ontario

1971 ◽  
Vol 28 (2) ◽  
pp. 277-294 ◽  
Author(s):  
G. J. Brunskill ◽  
D. Povoledo ◽  
B. W. Graham ◽  
M. P. Stainton
Keyword(s):  
Lake Sediments ◽  
Lake Sediment ◽  
Chemical Weathering ◽  
Major Ions ◽  
Fine Fraction ◽  
Dry Weight ◽  
Terrestrial Vegetation ◽  
Experimental Lakes Area ◽  
Sediment Samples ◽  
Northwestern Ontario

This paper contains some descriptive chemical data on bedrock, soils, and profundal lake sediments of the Experimental Lakes Area (ELA). The acid granodiorite bedrock and the plagioclase–K-feldspar–quartz glacial drift of the region exhibit low rates of chemical weathering. Terrestrial vegetation, soil organic matter, and the fine fraction of the glacial drift are concentrated in the lake sediments. The major minerals of the lake sediments are quartz, plagioclase, K-feldspar, illite, chlorite, kaolinite. Loss on ignition for the lake sediment samples varies from 18 to 62% dry weight, organic carbon from 8 to 34% dry weight, total nitrogen from 0.9 to 3.5% dry weight, and total phosphorus from 0.1 to 0.3% dry weight. These surficial lake sediment samples are 88–96% water, and concentrations of major ions in sediment interstitial water are 1.5–5 times the concentration of major ions in lake water.

Relationships Between Dipteran Emergence and Phytoplankton Production in the Experimental Lakes Area, Northwestern Ontario

1980 ◽  
Vol 37 (3) ◽  
pp. 523-533 ◽  
Author(s):  
I. J. Davies
Keyword(s):  
Euphotic Zone ◽  
Dry Weight ◽  
Single Equation ◽  
Phosphorus Loading ◽  
Phytoplankton Production ◽  
Lake Depth ◽  
Lake Productivity ◽  
Experimental Lakes Area ◽  
Surface Distribution ◽  
Northwestern Ontario

Dipteran emergence was monitored at the Experimental Lakes Area (ELA) between 1973 and 1977 in seven lakes of different trophic status. The data were used to develop a number of equations which related the quantity and spatial distribution of average annual emergence to lake productivity. These models explained > 94% of the variation in mean emergent biomass among lakes or > 76% of the variation in numbers of emergent Diptera in terms of phytoplankton production or phosphorus loading. On average, ELA lakes produced 40.8 dipteran adults (9 mg dry weight) per gram carbon fixed by phytoplankton. A single equation for all lakes predicts the surface distribution of emergent biomass, relative to lake depth at any location, from vertical profiles of phytoplankton production. The mean size of dipteran adults was related to lake depth at the point of emergence and average phytoplankton production. An empirical model which used data on the vertical profile, and lake average, of phytoplankton production was developed to predict the number of Diptera emerging from each depth. The maximum depth of emergence was related to depth of the euphotic zone and average phytoplankton production in each lake. Initial tests suggested that the models may provide useful predictions of dipteran emergence for a wider spectrum of lakes.Key words: aquatic insects, Diptera, Chironomidae, eutrophication, primary production

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