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.

Emergence of Chironomidae (Diptera) in Fertilized and Natural Lakes at Saqvaqjuac, N.W.T.

1988 ◽  
Vol 45 (4) ◽  
pp. 731-737 ◽  
Author(s):  
Harold E. Welch ◽  
John K. Jorgenson ◽  
Martin F. Curtis
Keyword(s):  
Primary Production ◽  
Phytoplankton Production ◽  
Experimental Lakes Area ◽  
Natural Lakes ◽  
Before And After ◽  
Mean Size ◽  
Apparent Reason ◽  
Total Primary Production ◽  
Latitudinal Range ◽  
Lake Fertilization

Chironomid emergence was quantified in four small lakes at Saqvaqjuac, N.W.T. (63°39′N), before and after lake fertilization. Emerging biomass responded immediately to increased phytoplankton production, reaching equilibrium the following year. Emergence from the reference lake was extremely variable, for no apparent reason. The emergence – phytoplankton production relationships found by Davies for the Experimental Lakes Area (~49°N) were generally valid for Saqvaqjuac lakes and Char Lake (74°42′), except that (1) biomass was better correlated than numbers because of increased mean size with increasing latitude and (2) total primary production was a better predictor than phytoplankton production alone because benthic photosynthesis increases with increasing latitude. Chironomid production seems to be a predictable function of total primary production throughout the latitudinal range of the small Canadian lakes examined.

Comparison of Phosphorus Turnover Times in Northern Manitoba Reservoirs with Lakes of the Experimental Lakes Area

1984 ◽  
Vol 41 (4) ◽  
pp. 605-612 ◽  
Author(s):  
Dolores Planas ◽  
R. E. Hecky
Keyword(s):  
Large Range ◽  
Turnover Time ◽  
Unit Weight ◽  
Experimental Lakes Area ◽  
P Deficiency ◽  
Natural Lakes ◽  
Northwestern Ontario ◽  
North Temperate Lakes ◽  
Phosphorus Turnover ◽  
Independent Indicator

The turnover time, τ, of [32P]PO4 was measured during July and September in a natural lake and two lakes in northern Manitoba that were undergoing impoundment in 1976. The τ values were 10–1000 times longer than those observed in the epilimnia and hypolimnia of two lakes being experimentally enriched in northwestern Ontario (Experimental Lakes Area) in the same summer. Algal populations in the Experimental Lakes Area exhibited short τ values over a large range of temperature and light values, which exceeded the ranges of temperatures and light intensities measured in northern Manitoba. In northern Manitoba the shortest τ values occurred in July when an independent indicator of sestonic P deficiency, the particulate alkaline phosphatase activity per unit weight ATP, measured moderate to severe P deficiency. In September in northern Manitoba, τ values were at least 10 times greater than in July and were among the highest reported in the literature. The 2-yr-old Notigi Reservoir had the highest τ values in both July and September, and it deviated strongly from the expected chlorophyll–phosphorus relation for north temperate lakes. These new reservoirs in northern Manitoba are not P limited and even the natural lakes may be only moderately P limited.

Phytoplankton, Nutrients, and Primary Production in Fertilized and Natural Lakes at Saqvaqjuac, N.W.T.

1989 ◽  
Vol 46 (1) ◽  
pp. 90-107 ◽  
Author(s):  
Harold E. Welch ◽  
John A. Legauit ◽  
Hedy J. Kling
Keyword(s):  
Primary Production ◽  
Light Flux ◽  
Phytoplankton Production ◽  
Small Lakes ◽  
Experimental Lakes Area ◽  
Natural Lakes ◽  
Northwestern Ontario ◽  
North Temperate Lakes ◽  
P Addition ◽  
Very High

Whole-lake phosphorus (P) and nitrogen (N) addition experiments at Saqvaqjuac, N.W.T. (63°N in the central Canadian arctic), showed that the lakes were P limited but required both P and N for increased production. Photosynthetic response to 0.1 g P and 1.0 g N∙m−2∙yr−1 was immediate (15→30 g C∙m−2∙yr−1), with simultaneous increases in protozoa, while oligotrophic chrysophyte assemblages gave way to volvocalean greens. Cyanophytes were not important during P-only or P and N additions or in oligotrophic lakes, but formed permanent blooms in several naturally mesotrophic lakes near sea level. Retention of P was naturally low, but high during P addition. Silicon (Si) retention was always very high. Chlorophyll: P ratios were similar to those of subarctic and north-temperate lakes. Saturation light intensity (Ik) tracked surface light flux with a 2- to 3-wk delay, averaging 15 E∙m−2∙s−1 in winter and peaking at 140 E∙m−2∙s−1 in July. Comparison of our data with those for lakes in the Experimental Lakes Area (northwestern Ontario, 50°N) and Char Lake (75°N) shows that with increasing latitude, in small lakes, (a) phytoplankton production decreases, (b) phytoplankton production per unit light decreases less sharply, and (c) the proportion of primary production occurring beneath ice cover increases.

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.

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.

Production of Epilithiphyton in Two Lakes of the Experimental Lakes Area, Northwestern Ontario

1973 ◽  
Vol 30 (10) ◽  
pp. 1511-1524 ◽  
Author(s):  
D. W. Schindler ◽  
V. E. Frost ◽  
R. V. Schmidt
Keyword(s):  
Liquid Scintillation ◽  
Inorganic Carbon ◽  
Dissolved Inorganic Carbon ◽  
Seasonal Effects ◽  
Algal Flora ◽  
Experimental Lakes Area ◽  
New Techniques ◽  
Natural Lakes ◽  
Northwestern Ontario

Two new techniques for measuring photosynthesis by benthic algal flora in waters low in dissolved inorganic carbon are described. The first uses gas chromatography to measure changes in DIC in incubation chambers directly. The second is a variation of the usual 14C procedure, in which disappearance of 14C from the water is measured by liquid scintillation instead of uptake of 14C by the algae. This procedure is simpler than measuring the uptake of 14C, because digestion and/or combustion of samples is not necessary. Results are compared with the commonly employed 14C uptake and O2 release techniques.Tests showed that heterogeneity of substrate was the major source of variation in in situ results, being large enough to make interpretation of seasonal effects and other causal factors extremely difficult.Annual production by epilithiphyton in two natural lakes in the Experimental Lakes Area (ELA) was 5.19 g C and 5.18 g C/m2 of substrate annually for lakes 239 and 240, respectively. These are the lowest values recorded for freshwater lakes at temperate latitudes.Because DIC and O2 concentrations could be measured simultaneously, it was possible to calculate photosynthetic quotients on several dates. These were extremely high, averaging 2.6 for the summer of 1971.

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.

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.

Preliminary Results on Aquatic Insects in the Me Linh Station for Biodiversity, Vinh Phuc Province

2017 ◽  
Vol 33 (4) ◽  
Author(s):  
Nguyen Van Hieu ◽  
Nguyen Van Vinh
Keyword(s):  
Quantitative Analysis ◽  
Aquatic Insects ◽  
Field Survey ◽  
Aquatic Insect ◽  
Insect Species ◽  
Functional Feeding Groups ◽  
Species Number ◽  
Feeding Groups ◽  
Preliminary Results

An intensive field survey on aquatic insects of Me Linh Station for Biodiversity in Vinhphuc province was conducted in December 2015. Specimens were collected at 8 different sites and aquatic insects were collected both quantitatively by Surber net and qualitatively by hand net, pond net. As a result, a total of 110 aquatic insect species belonging to 98 genera, 49 families and 9 orders were recognized. Among these, the order Ephemeroptera had the highest species number with 26 species, followed by Odonata with 25 species, Trichoptera with 18 species, Coleoptera with 15 species, Hemiptera with 11 species, Diptera with 9 species. Lepidoptera, Plecoptera and Megaloptera had the lowest of species number, represented by 3 species of Lepidoptera, 2 species of Plecoptera and 1 species of Megaloptera. Besides, the quantitative analysis results and the functional feeding groups were provided.

Land water linkages: influences of riparian deforestation on lake thermocline depth and possible consequences for cold stenotherms

1997 ◽  
Vol 54 (6) ◽  
pp. 1299-1305 ◽  
Author(s):  
Robert France
Keyword(s):  
Thermal Stratification ◽  
Lake Trout ◽  
Salvelinus Namaycush ◽  
Thermocline Depth ◽  
Experimental Lakes Area ◽  
Northwestern Ontario ◽  
Riparian Trees ◽  
Tree Removal ◽  
Riparian Tree ◽  
Land Water

The purpose of the present study was to determine if riparian deforestation would expose lake surfaces to stronger winds and therefore bring about deepening of thermoclines and resulting habitat losses for cold stenotherms such as lake trout (Salvelinus namaycush). Removal of protective riparian trees through wind blowdown and two wildfires was found to triple the overwater windspeeds and produce thermocline deepening in two lakes at the Experimental Lakes Area. A survey of thermal stratification patterns in 63 northwestern Ontario lakes showed that lakes around which riparian trees had been removed a decade before through either clearcutting or by a wildfire were found to have thermocline depths over 2 m deeper per unit fetch length compared with lakes surrounded by mature forests. Riparian tree removal will therefore exacerbate hypolimnion habitat losses for cold stenotherms that have already been documented to be occurring as a result of lake acidification, eutrophication, and climate warming.

Sign in / Sign up

Export Citation Format

Share Document