Concentrations of trace elements in yellow perch (Perca flavescens) from six acidic lakes

Yellow perch (Perca flavescens) were collected from six small acidic lakes in northwestern New Jersey. Analyses of muscle tissue identified a pattern of increased concentrations of Hg in fish from the most acidic lakes; levels of Cd and Pb were greatly elevated in livers of specimens from two of the most acidic lakes. At one site, Sunfish Pond, positive correlations between fish size and Hg levels in muscle and Cd concentrations in livers were detected. In only one case did Hg concentrations in muscle tissue exceed the U.S. FDA action level of 1 μg g^?1 (wet wt).     

Trace element accumulation in the tissues of fish from lakes with different pH values

Two species of fish, omnivorous Catostomus commersoni (white suckers) and carnivorous Perca flavescens (yellow perch) were collected from three natural lakes with different pH ranges (circumneutral, pH 6.5 to 6.8; variable, pH 5.8 to 6.7; and acidic, pH 4.9 to 5.4). The lakes are located in the North Branch of the Big Moose River drainage system in the New York State Adirondack Park Preserve. Concentrations of potentially toxic elements (Al, Cd, Cu, Ph, and Se) were measured by electrothermal atomic absorption spectrophotometry in water, sediment and fish (bone, gill, kidney, liver and muscle) from each lake. The results showed that concentrations of Pb and Cd were significantly higher (P < 0.05) in some of the tissues of the fish collected from the acidic lake. Also, the yellow perch from the acidic take had significantly higher (P<0.05) Se concentrations in their muscle and livers than fish from the other lakes. The concentrations of Al were elevated in the gill tissues of both fish species from the acidic lake relative to fish from the other lakes. Possible mechanisms contributing to these differences in tissue concentration are discussed.     

Metal concentration in the gill,gastrointestinal tract,and carcass of white suckers (Catostomus commersoni) in relation to lake acidity

Adult white suckers were collected from four lakes in Maine that ranged in pH from 7.0 to 5.4. The gastrointestinal tract and remainder of the carcass of fishes of similar age and size from each lake, and gills from additional fishes of similar size, were analyzed for Al, Cd, Pb, and Zn. Carcasses were also analyzed for Hg. Concentrations of Al, Cd, and Pb were highest in the gastrointestinal tract and lowest in the carcass; Zn concentration was highest in the gill. For carcass, all metals except Al differed significantly among lakes, for gill tissue Cd and Pb differed, and for gastrointestinal tract, only Cd differed among lakes. Where differences were significant, patterns among lakes were similar in each tissue analyzed. Concentrations of Cd, Hg, and Pb were negatively correlated with lake water pH, acid neutralizing capacity (ANC), Ca, and lake:watershed area, and positively correlated with lake water SO₄, indicating that concentrations were higher in fish from more acidic lakes. Zinc concentrations in gills were unrelated to lake acidity, and carcass concentrations were higher in the less acidic lakes, which is the opposite of the pattern for the other metals studied. Zinc in gastrointestinal tract did not differ among lakes. Although the lakes we studied were located in undisturbed watersheds and did not receive any point source discharges, fish metal concentrations were comparable to or higher than those reported from waters receiving industrial discharges.     

Trace element concentrations in the dorsal muscle of white suckers and brown bullheads from two acidic Adirondack lakes

Concentrations of 14 elements (Ag, As, Cd, Cr, Cu, Hg, Ni, Pb, Sb, Se, Sn, Tl, V, and Zn) were measured in the dorsal muscle of omnivorous white suckers and brown bullheads, fish likely to ingest sediment while feeding. The fish were collected in two acidic Adirondack lakes known to have elevated concentrations of several of these elements in their surface sediment. Trace element concentrations in the muscle of the white suckers and brown bullheads were compared with government guidelines for edible fish and survey data for concentrations present in commercial species. Only the largest white sucker exceeded the U.S. Food and Drug Administration's guidelines for Hg in food of 1 ppm (wet wt). Concentrations of all the other elements measured were at low or innocuous levels in the edible muscle. A significant positive correlation was found between body weight and Hg concentrations in both species. Zinc was negatively correlated for the same parameters in white suckers. With the possible exception of Hg, our results indicate that elevated levels of potentially toxic elements in the surface sediment of the two acidic Adirondack lakes are not reflected in the edible muscle of the omnivorous bottom feeding fish present in these systems.     

Mercury concentrations in northern pike,Esox lucius L., in small lakes of Evo area,southern Finland

We measured Hg concentrations in northern pike (Esox lucius) from 17 small lakes in Evo forest area, Lammi, southern Finland. The mean Hg concentration in muscle tissue of a 1 kg pike ranged from 0.15 to 1.36 μg g⁻¹ (ww) in the lakes. There was a trend towards higher concentrations in acidic and humic lakes than in circumneutral and clear-water lakes. The Hg content of pike from successive lakes of a lake chain was similar, whereas there were clear differences in the Hg concentrations among seepage lakes and the uppermost lakes of other lake chains. The latter was probably due to special characteristics of the lakes: in one lake pike was the only fish species, two of the lakes were regulated by beaver, and one lake was a groundwater or spring lake. Our observations indicate that Hg concentrations in pike can vary considerably from lake to lake in a small geographical area and that the variation among lakes in the accumulation of Hg in fish largely depends on lake characteristics and on the diet of pike.     

Fates of metal radiotracers added to a whole lake: Accumulation in fathead minnow (Pimephales promelas) and lake trout (Salvelinus namaycush)

Six gamma-emitting isotopes, Se-75, Hg-203, Cs-134, Fe-59, Zn-65 and Co-60, were introduced simultaneously in a single epilimnetic addition to an oligotrophic lake on the Precambrian Shield of northwestern Ontario, Canada. Accumulation of each isotope was monitored in fathead minnow (Pimephales promelas) for 274 days. Isotope accumulation in blood, gill, gut, liver, kidney, spleen, gonad, brain, muscle and gut contents of lake trout (Salvelinus namaycush) was monitored for 352 days. Fish accumulated only traces of Fe-59. Isotopes which occured in water primarily in the charcoal-extracted fraction (Se-75 and Zn-65) were most readily accumulated by fish. Fathead minnow accumulated higher concentrations of all isotopes than lake trout. In lake trout, the highest concentrations of isotopes were found in the following tissues: Se-75, liver; Hg-203 and Co-60, kidney; Cs-134, muscle; Zn-65, gut. Food seemed to be the primary source of all isotopes to fish. Ratios of isotope concentrations in fish to those in water were higher for both fathead minnow and lake trout than ratios reported from laboratory studies using aqueous exposures. Concentration ratios for Cs-134 in both fathead minnow and lake trout from oligotrophic Lake 224 were over an order of magnitude greater than published data for fish from eutrophic lakes.     

Human exposure to mercury may decrease as acidic deposition increases

It has been hypothesized that human mercury (Hg) exposure via fish consumption will increase with increasing acidic deposition. Specifically, acidic deposition leads to reduced lake pH and alkalinity, and increased sulphate ion concentration ([SO₄ ^2?]), which in turn should cause increased Hg levels in fish, ultimately resulting in increased human Hg exposure via fish consumption. Our empirical test of this hypothesis found it to be false. We specifically examined Hg levels in the hair of Ontario Amerindians, who are known consumers of fish from lakes across the province, and observed a weak negative association with increasing sulphate deposition. An examination of Hg levels in lake trout, northern pike and walleye, three freshwater fish species commonly consumed by Ontario Amerindians, found a similar weak negative association with increasing sulphate deposition. Further analysis of these fish data found that fish [Hg] was most significantly (positively) associated with lake water concentrations of dissolved organic carbon (DOC), not pH, alkalinity or [SO₄ ^2?]. Lake DOC levels are lower in regions of greater acidic deposition. We propose an alternate hypothesis whereby human Hg exposure declines with increasing acidic deposition. In particular, we propose that increasing sulphate deposition leads to reduced lake DOC levels, which in turn leads to lower Hg in fish, ultimately reducing human Hg exposure via fish consumption.     

Trace metal concentrations in some Kashmir Himalayan Lakes

The concentrations of trace elements (Pb, Mn, Cu, Zn and Cc) were measured in three Kashmir Himalayan Lakes. Cadmium, Ag, and Hg were not detected. In addition physico-chemical parameters of the lakes were analyzed to asses the water quality. The results indicate that Trigam and Tilwan lakes are more enriched than Khanpur lake. Comparisons of trace metal levels with EPA standards show that Mn and Pb concentrations are well above the permissible levels.     

Distribution of Trace Elements in Sediments and Biota of Songkhla Lake, Southern Thailand

The concentrations of Co, Ni, Cu, Zn, Cd, Pb, As, Fe, Mn, and Al were determined in sediments and biota of Songkhla Lake, a shallow coastal lagoon located in southern Thailand. In June 2006, surface sediments were sampled in 44 stations in the three sections of the lake (inner-, middle-, and outer sections). Sediment cores were also sampled in 13 stations in three cross-sections of the lake. In surface sediments, trace and major elements, organic matter, sediment grain size analysis, and sulfides were determined, and in the sediment cores, redox profiles were made. Soil samples were also collected at garbage dumping sites in the vicinity of the lake. In addition, the metal accumulation in two catfish species (Arius maculatus and Osteogeneiosus militaris) and the crustacean (Apseudes sapensis) was also investigated. Trace element concentrations in sediments of Songkhla Lake show that, especially the Outer section of the lake, in particular the sediments at the mouths of the Phawong, U-Taphao, and Samrong Canals are significantly enriched with trace elements due to municipal, agricultural, and industrial discharges entering the lake through the canals. Aluminum-normalized enrichment factors throughout the lake vary from 0.4 to 1.7 for Ni, 0.3 to 3.3 for Cu, 0.2 to 7 for Zn, 0.1 to 14 for As, 1 to 24 for Cd, 0.7 to 6.8 for Pb, and 0.1 to 7.8 for Mn. Correlations between the elements and sediment characteristics show that Cu, Zn, Cd, and Pb are essentially associated with the sulfide fraction; that Ni and Co are predominantly bound to the clay minerals and iron oxy-hydroxides, and that As is principally bound to iron oxy-hydroxides. The accumulation of trace elements between muscle tissue and liver and eggs of A. maculatus and O. militaris is element-specific, but concentrations of trace elements in fish muscle tissue are well within the limits for human consumption.     

Metal concentration and calcification of bone of white sucker (Catostomus commersoni) in relation to lake pH

The concentrations of 17 elements were determined in the bone of white suckers (Catostomus commersoni) netted from 5 acid (pH range 4.8 to 5.8) and 2 circumneutral (pH=6.2 and 6.3) lakes in south-central Ontario. The bone Ca:P dry weight ratios were similar (2.0:1) for all fish populations except those of George Lake (pH=4.8) which showed a significantly lower Ca:P ratio (1.9:1, P < 0.05). Magnesium was also lower in the bone of these fish and in fish from 2 other acid lakes. Only bone Ba and S concentrations in the 7 fish populations correlated significantly to lake pH (R=?0.9 and R=?0.8, respectively, P < 0.05). Bone Mn concentrations correlated to dissolved lake Mn concentrations (R=0.8, P < 0.05), and was 7 fold greater in the bone of fish from George Lake and 2 fold greater in King Lake (pH=5.0) fish, vs fish from the 2 circumneutral lakes. Bone Zn was significantly greater in white sucker from George Lake, and tended to be higher in this species from King Lake, compared to all other fish populations. Bone concentrations of Fe, Cu, Ni and A1 showed no apparent trends among the 7 fish populations. Cd, Co, Cr, Mo, V and Be were not detected. The occurrence of a reduced Ca:P ratio coincident with the highest concentrations of Mn, Zn and Ba in the bone of fish from the most acidified environment suggests that increased metal concentrations which occur in surface waters coincident with lake acidification may affect bone calcification.     

The role of dissolved organic carbon in the chemistry and bioavailability of mercury in remote Adirondack lakes

A number of recent studies have documented elevated concentrations of mercury (Hg) in fish caught in remote lakes and a pattern of increased concentrations of Hg in fish tissue with decreasing water column pH. Because of the potential linkage between fish Hg and surface water acidification, factors regulating water column concentrations and bioavailability of Hg were investigated in Adirondack lakes through a field study and application of the Mercury Cycling Model (MCM). Concentrations of total Hg and total MeHg were highly variable, with concentrations of total MeHg about 10% of total Hg in lakes which did not show anoxic conditions. In lakes exhibiting anoxic conditions in the hypolimnion during summer stratification, concentrations of total MeHg were elevated. Concentrations of total Hg and total MeHg increased with decreasing pH in remote Adirondack lakes. However, more importantly, concentrations of total Hg and total MeHg increased with increasing concentrations of dissolved organic carbon (DOC) and percent near-shore wetlands in the drainage basin. Mercury concentrations in muscle tissue of yellow perch from Adirondack lakes were elevated above the U.S. FDA action level (1 μg/g Hg) in 7% of the fish sampled or in one or more individual fish from 9 of the 16 lakes sampled. Fish Hg concentrations generally increased with increasing fish length, weight and age. Patterns of increasing Hg concentration with age likely reflect shifts in prey of yellow perch and the bioconcentration of Hg along the food chain. For age 3 to 5 perch, concentrations of Hg increased with increasing concentrations of DOC and percent near-shore wetlands in the drainage basin. However, for a lake with very high DOC concentrations, fish concentrations of Hg declined. Calculations with the MCM also show that concentrations of Hg species increase with increasing DOC due to complexation reactions. Increases in DOC result in increasing concentrations of Hg in biota but decreases in the bioconcentration factor of Hg in fish tissue. This research suggests that DOC is important in the transport of Hg to lake systems. High concentrations of DOC may complex MeHg, diminishing its bioavailability. At high concentrations of monomeric Al, the complexation of MeHg with DOC apparently decreases, enhancing the bioavailability of MeHg.     

MERCURY ACCUMULATION IN DEVILS LAKE,NORTH DAKOTA – EFFECTS OF ENVIRONMENTAL VARIATION IN CLOSED-BASIN LAKES ON MERCURY CHRONOLOGIES

Sediment cores were collected from lakes in the Devils Lake Basin in North Dakota to determine if mercury (Hg) accumulation chronologies from sediment-core data are good indicators of variations in Hg accumulation rates in saline lakes. Sediment cores from Creel Bay and Main Bay, Devils Lake were selected for detailed analysis and interpretation. The maximum Hg concentration in the Creel Bay core was 0.15 micrograms per gram at 8 to 9 centimeters. The maximum Hg concentration in the Main Bay core was 0.07 micrograms per gram at 5 to 7 centimeters. The general decreases in Hg concentrations with depth are attributed to historic variations in atmospheric Hg deposition rate. Hg stratigraphies combined with²¹⁰Pb and¹³⁷Cs dating analyses yield Hg chronologies that indicate a general increase in Hg accumulation rates in Devils Lake since the middle of the 19th century. Mean modern Hg accumulation rates in Creel Bay were 4.9 nanograms per square centimeter per year, and rates in Main Bay were 1.8 nanograms per square centimeter per year. Mean preindustrial Hg accumulation rates in Creel Bay were 1.2 nanograms per square centimeter per year, and rates in Main Bay were 1.6 nanograms per square centimeter per year. Relatively low Hg concentrations in recent sediments in the Devils Lake Basin, along with similarities in Hg accumulation rates between lakes in the Devils Lake Basin and other lakes in the northern interior of North America, indicate that local sources of Hg are not important sources of Hg. Results of the study indicate that accurate Hg chronologies are discernible in sediment cores collected from saline lakes. However, spatial and temporal variations in lake level and water chemistry common to saline lakes make interpretation of radioisotopic and geochemical chronologies difficult. Hg geochemistry in Devils Lake, and presumably in other saline lakes, is dynamic. The results of this study indicate that the absolute amount of sediment transported to Devils Lake, along with the associated Hg and total organic carbon, and the distribution of sedimentation patterns in Devils Lake may be affected by changing lake levels.     

Heavy metals in perch (Perca fluviatilis L.) from two acidified lakes in the salpausselkä esker area in Finland

Hg concentrations in muscle and Cd, Pb, Al, Zn and Fe concentrations in muscle, liver and kidney ofPerca fluviatilis from two acidified lakes in the Salpausselkä esker area in Southern Finland were studied. The metal concentrations in perch from the Tiilijärvi lakes were similar to those in other acidified Finnish lakes. Only Hg concentrations correlated strongly with the age and size of perch. The need for age correction in studies on the Hg concentrations on perch was noticed. The highest concentrations of Cd, Pb and Zn occured in kidney and those of Al and Fe in liver.     

The influence of trophic level as measured by δ15N on mercury concentrations in freshwater organisms

The relationship between mercury (Hg) concentrations in freshwater biota and trophic position, as defined by stable nitrogen isotope ratios (δ¹⁵N), was examined in 6 lakes in northwestern Ontario. The heavier isotope of nitrogen (¹⁵N) increases an average of 3 parts per thousand (‰) from prey to predator and is used as a measure of an organism's trophic position. Dorsal muscle from lake trout, burbot, walleye, northern pike, white sucker, lake cisco, lake whitefish, and yellow perch was analyzed for Hg and δ¹⁵N using flameless atomic absorption and mass spectrometry respectively. Within each lake, log Hg was significantly related to δ¹⁵N (r ² ranged from 0.47 to 0.91,P<0.01). For four species, yellow perch, northern pike, lake cisco, and lake trout, log Hg was positively related to δ¹⁵N (r ² ranged from 0.37 to 0.47,P≤0.09) across all lakes. We also used δ¹⁵N measurements (assuming a 3‰ shift between an organism and its diet) and the developed within-lake regression equations to calculate a prey Hg for each individual fish. These food Hg values were then used to predict predator Hg using Norstromet al's bioenergetics model. Predicted results were strongly correlated to measured Hg concentrations (r=0.91,P<0.001), indicating that δ¹⁵N has potential to be used in modeling.     

Responses of perch,Perca fluviatilis L., from an acidic and a neutral lake to acidic later

Responses to low pH of perch, Perca fluviatilis, from a naturally acid and a neutral lake were compared by 24 hr exposures to pH 4.6, 4.1 and 3.8 and by 72 hr exposures to pH 4.5. Plasma osmolality and plasma concentrations of Na and chloride decreased in fish from both lakes during acid exposures. Significant differences between the populations were observed at pH 4.1 and 4.5. Hematocrits of the fish from the acid lake increased rapidly and at higher pH compared with those of fish from the neutral lake. This was interpreted as an adaptation to their normal acidic environment, connected with the maintenance of red cell oxygen affinity. The perch from the acid lake maintained their muscle water balance at lower pH better than did the fish from the neutral lake.     

Mercury in fish muscle in acidified and limed lakes

The concentration of Hg in muscle was monitored during 10 to 12 years in different size and age groups of pike (Esox lucius) and perch (Perca fluviatilis). The study was performed in one reference and five lime treated lakes. Before liming, the highest levels of Hg in fish were measured in a lake with an annual mean pH just above 5.0. Lower levels were obtained both in lakes which were more acidified and in those which were less acidified. After the start of liming, the fastest and largest changes were obtained in the lakes which were moderately acid before liming (mean pH 5.4–5.8). In small perch, the Hg-concentration was markedly reduced in two years and showed an 80 % decrease in ten years. A slower response was registered in the lakes originally having about 0.5 units lower pH. In the most acidified lake (pH 4.9) the concentrations even increased the first years after liming, but decreased again later on. The possible mechanisms involved are discussed.     

Mercury in vegetation and lake sediments from the U. S. arctic

Global atmospheric concentrations of mercury (Hg) appear to be increasing and with it the potential for ecosystem exposure and ecological effects. From 1990 to 1993 we examined U. S. arctic ecosystems over a broad spatial scale to develop baseline information on current concentrations of trace elements, heavy metals (including Hg), persistent organic compounds, and radionuclides in various components of the terrestrial and freshwater biosphere. Matrices reported here include, vegetation (lichens and mosses) and lake sediments. Total Hg in two lichen and two moss species from Alaska were generally low (0.02–0.112 μg/g dw), compared to reported values from other arctic locations and showed a statistically significant negative relationship between total Hg content and distance from the marine coastline.²¹⁰Pb dated sediment cores indicated that average preindustrial total Hg accumulation rates were over four times greater in arctic Schrader lake than in subarctic Wonder Lake. Both lakes indicated a small increase (5–8%) in total Hg flux to the sediments during the last 145 years, much smaller than similar increases in total mercury for lakes in the north central U. S. The likely source of recent increases in Hg in these Alaskan ecosystems is long range atmospheric transport. While we can detect increases in mercury in lake sediments likely due to anthropogenic activities, values are low and there appears to be no immediate threat to terrestrial environments and inland freshwaters of arctic Alaska from long range atmospheric transport and deposition of Hg.     

Mercury anomalies in lake water and in commercially harvested fish,Kaminak Lake area,district of Keewatin,Canada

Mercury (Hg) was measured in approximately seven hundred samples of surface water collected from Kaminak Lake and nearby small and large lakes in a tundra environment located west of Hudson Bay. Mercury variations were expected to be related to sulphide mineralization, and patterns of Hg enrichment were to be used as pathfinders for locating potentially economic sulphide deposits. Water in the northern part of Kaminak Lake, which is underlain by sedimentary and volcanic bedrock with known potential for sulphide (base metal) mineralization, was consistently enriched in Hg, as were smaller lakes lying along the same bedrock trend. Mercury concentrations in lake trout from a commercial fishery on Kaminak Lake ranged from 0.57 ppm (parts per million = mg/kg or mg/l) to 2.0 ppm Hg (70 samples), exceeding the national consumption guidelines of 0.5 ppm. Subsequently, the Kaminak fishery was abandoned and relocated on nearby Kaminuriak Lake where similar fish species averaged less than 0.5 ppm Hg. High Hg concentrations in fish from this remote, unpopulated region, far from industrial sources of pollution, are related mostly or wholly to local geological phenomena.