Reproductive status, blood chemistry, gill histology and growth of perch (Perca fluviatilis) in three acidic lakes

Perch (Perca fluviatilis L.) were sampled soon after spawning in three small acidic lakes (pH 4.3-6.1, Al(lab) 5-106 microg litre(-1), Ca2+ 0.01-0.08 mmol litre(-1)) and in one circumneutral lake (pH 5.9-6.4, Al(lab) 4-12 microg litre(-1), Ca2+ 0.06-0.07 mmol litre(-1)) in southern Finland. Due to the delayed spawning of perch in the acidic lakes, sampling in those lakes was performed later than in the reference lake. In spite of that, the gonadosomatic index (GSI) of males in all the acidic lakes was significantly greater than in the reference lake. Of the two lakes with similar low water pH, the effects on reproduction were more prominent in the lake with higher water Al content. The plasma Ca2+ concentrations of females in the acidic lakes were significantly smaller than in the females of the reference lake. The low female:male plasma Ca2+ ratio (1.0-1.32) depicted delay of spawning. Stress in perch in acidic water was also seen in elevated blood haematocrit values, especially in females. On the other hand, a low plasma Cl- level, a common response to acidic water in salmonids, was not detected in perch in the most acidic lakes. The amount of Al accumulated in the gill epithelium was highest in the most acidified lake with high Al concentration, but was also pronounced in a lake with low pH and low Al concentration.     

Towards a model of acidification effects on waterfowl in Eastern Canada

Data from 212 lakes in central Ontario were used to examine the relationship between presence of breeding waterfowl and loons and the following lake characteristics: pH, presence of fish, lake area, dissolved organic carbon (DOC) and total phosphorus (TP) concentration. In univariate analyses, the two fish-eating species preferred large, high pH lakes with fish, while insectivorous species showed little consistent pattern of lake association. Logistic regression analyses confirmed that large lake size and presence of fish were important determinants of presence of piscivores, though the residual effect of pH differed between the two species. Broods of three of the four insectivorous species avoided lakes with fish, and independently showed a positive response to pH. By calculating the probability that fish will be present on a lake of given area and pH, it is possible to estimate the net effect of pH change on these waterfowl. Relationships such as those presented here can, with some assumptions, be linked to models of lake acidification to estimate response of waterfowl to predicted changes in acidic deposition.     

Effects of acidic water on freshwater snails: results from a study of 1000 lakes throughout Norway

This paper summarizes some results from a monograph which focused on ecological and biogeographical aspects of the biota in Norwegian lakes and rivers with particular reference to the snail fauna. Field studies were made in the course of 20 summers within the period of 1953-1987. Acidic water is the main reason why snails are absent from some 4000 lakes in a low-calcium area in southern Norway ('Acid south'). This area is heavily influenced by acidic precipitation. Snails were not detected in lakes with pH below 5.2. In one lake, three snail species disappeared in parallel with acidification from pH 5.2 to 4.2. The calcium level modified the effect of low pH.     

Lake acidity and mercury content of fish in Darwin National Reserve, Russia

Darwin National Reserve is a protected natural area on the north-west shore of the Rybinsk Reservoir, 350 km north of Moscow. In June 1989, six lakes in the Reserve and the reservoir were surveyed to assess lake acidity and the mercury content of perch, Perca fluviatilis. Five were seepage lakes with no permanent inlets or outlets and one was a drainage lake with both an inlet and an outlet. The seepage lakes were acidic (mean pH 4.6-4.8) and varied in colour from 20 to 200 Hazen units. The drainage lake and reservoir were alkaline (mean pH 8.0-8.1) and colour spanned a similar range. The mean mercury content of perch dorsal epaxial muscle ranged from 0.5 to 1.1 microg g(-1) wet weight in the five acidic lakes and from 0.1 to 0.2 microg g(-1) in the alkaline lakes. Fish mercury content was negatively correlated with lake pH (r=-0.93, P=0.002) if all waters were considered together, and positively correlated with apparent colour (r=0.91, P=0.03) in the seepage lakes.     

Recolonization of acid-damaged lakes by the benthic invertebrates Stenacron interpunctatum,Stenonema femoratum and Hyalella azteca

The recolonization of acid-damaged lakes in Killarney Park, Canada is described for 3 species of benthic invertebrates; 2 mayflies (Stenonema femoratum, Stenacron interpunctatum) and an amphipod (Hyalella azteca). Synoptic surveys of 119 lakes for amphipods and 77 lakes for mayflies were conducted between 1995 and 1997 and defined pH thresholds of 5.6 for S. femoratum and H. azteca and pH 5.3 for S. interpunctatum. In an intensive study of 2 acid-damaged lakes and 2 reference lakes from 1997 to 2002, reestablishment of S. interpunctatum, S. femoratum and H. azteca occurred, when timing of the events could be estimated, less than 4-8 years after pH thresholds for specific taxa were reached. Dispersal of S. interpunctatum to all habitat patches within a lake was completed 3 years after recolonization was detected in the smallest lake (11 ha). It is anticipated that dispersal throughout the largest lake (189 ha) will take much longer. The time lag from estimated pH recovery to reestablishment and subsequent dispersal of mayflies to all suitable habitats within a lake was as much as 11 to 22+ years. The density of S. interpunctatum increased in the recovering lakes to levels higher than in reference lakes, but stable endpoints have not yet been reached during 6 years of monitoring.     

Lake variability: key factors controlling mercury concentrations in New York State fish

A 4year study surveyed 131 lakes across New York State beginning in 2003 to improve our understanding of mercury and gather information from previously untested waters. Our study focused on largemouth and smallmouth bass, walleye and yellow perch, common piscivorous fish shown to accumulate high mercury concentrations and species important to local fisheries. Fish from Adirondack and Catskill Forest Preserve lakes generally had higher mercury concentrations than those from lakes in other areas of the state. Variability between nearby individual lakes was observed, and could be due to differences in water chemistry, lake productivity or the abundance of wetlands in the watershed. We found the following factors impact mercury bioaccumulation: fish length, lake pH, specific conductivity, chlorophyll a, mercury concentration in the water, presence of an outlet dam and amount of contiguous wetlands.     

Effects of environmental and maternally derived methylmercury on the embryonic and larval stages of walleye (Stizostedion vitreum)

The effects of environmental and maternally derived methylmercury (MeHg) on the embryonic and larval stages of walleye (Stizostedion vitreum) were investigated using eggs collected during two successive spawning seasons. Eggs were collected from fish in a mercury (Hg)-polluted environment (Clay Lake, Ontario, Canada), and from fish in two relatively pristine lakes (Lakes Manitoba and Winnipeg, in the province of Manitoba). Both bioaccumulation of Hg into muscle and its mobilization into eggs was significantly higher in Clay Lake females. Maternal muscle MeHg concentration was positively correlated with female length and egg MeHg was positively correlated with muscle MeHg concentration in all three populations. Hatching success of eggs from all three stocks declined significantly with increasing waterborne MeHg (0.1-7.8 ng l-1). Hatching success was not significantly affected by egg MeHg concentration. Embryonic heart rate declined with increasing waterborne MeHg concentration, but larval growth was not affected. Occurrence of larval deformities was negatively correlated with size of female, but was not significantly correlated with MeHg in either eggs or water. Larval MeHg was positively correlated with the concentrations of MeHg in eggs demonstrating transmission of MeHg from females. Uptake of ambient MeHg was higher in larvae exposed to higher waterborne MeHg concentrations.     

Sublethal toxicity of two wastewater treatment polymers to lake trout fry (Salvelinus namaycush)

Lake trout fry (Salvelinus namaycush) were exposed in laboratory experiments to two wastewater treatment polymers, one anionic (MagnaFloc 156) and one cationic (MagnaFloc 368; Ciba Speciality Chemical), to determine if these chemicals which are used and discharged by mining operations in Canada's North pose a significant hazard to juvenile fishes. The cationic polymer was substantially more toxic to lake trout fry than the anionic polymer, with 96-h LC50 estimates of 2.08 and >600 mg/l, respectively. Separate 30-d exposure experiments yielded no observed and lowest observed effect concentrations, respectively, of 0.25 and 0.5mg/l for MagnaFloc 368, and 75 and 150 mg/l for MagnaFloc 156. In both cases, behavioural responses, especially startle response, were the most sensitive test endpoints. Histopathological assessment revealed that gill pathology appeared within a few days of exposure to both polymers, apparently as a result of localized hypoxia. Acute (4 d) effects included cloudy swelling of epithelial cells, increased gill vascularization, and thickening and shortening of the gill lamella. Chronic (30 d) polymer exposure produced only slightly greater pathological effects than acute exposure, with comparable responses observed only at >1.0mg/l MagnaFloc 368 and 150 mg/l MagnaFloc 156, suggesting that the fish displayed some level of both behavioural and physiological adaptation to the respiratory stress imposed by the two polymers.     

Fluctuating asymmetry of invertebrate populations as a biological indicator of environmental quality

Fluctuating asymmetry (FA) of populations of the shrimp, Palaemon elegans, and the blood worm, Chironomus salinarius, was used to assess the environmental impact of a fertilizer manufacturing facility on the surrounding marine and freshwater ecosystems, respectively. Populations of both species were found to have elevated levels of asymmetry compared with control populations, indicating that the facility was having a significant impact on organism development. The use of FA of invertebrate populations as a simple, sensitive and cost-effective biomonitoring system for the detection of environmental stress is discussed.     

Nutrient dynamics in shallow lakes of northern greece

GOAL, SCOPE, BACKGROUND: Shallow lakes display a number of features that set them apart from the more frequently studied deeper systems. The majority of lakes in Northern Greece are small to moderate in size with a relatively low depth and are considered as sites of high value of the wetland habitat. However, the water quality of these lakes has only been evaluated segmentally and occasionally. OBJECTIVE: The objectives of this study were to thoroughly investigate nitrogen and phosphorus speciation in lakes of a high ecological significance located in N. Greece, in order to evaluate their eutrophication status and possible nutrient limitation factors, and to investigate the main factors/sources that affect the water quality of these systems. METHODS: An extensive survey was carried out during the period from 1998-1999. Water samples were collected on a monthly basis from lakes Koronia, Volvi, Doirani, Mikri Prespa and Megali Prespa located in N. Greece. Water quality parameters (temperature, dissolved oxygen, pH and conductivity), organic indices (COD, BOD5), and N- and P-species (NO3(-), NO2(-), NH4(+), and PO4(3-), Kieldahl nitrogen and acid-hydrolysable phosphorus) were determined according to standard methods for surface water. Statistical treatment of the data was employed. RESULTS AND CONCLUSIONS: The physicochemical parameters determined in the lakes studied revealed a high temporal variation. The trophic state of the lakes ranged from meso- to hypertrophic. The nutrient limiting factor varied among lakes suggesting either P-limitation conditions or mixed conditions changing from P- to N-limitation throughout the year. Urban/industrial activities and agricultural runoff are the major factors affecting all lakes, although with a varying contribution. RECOMMENDATION AND OUTLOOK: This lake-specific research offers valuable information about water quality and nutrient dynamics in lakes of significant ecological value located in N. Greece that can be useful for an effective pollution control/management of these systems. Due to the large intra-annual variability of certain physicochemical parameters, a properly designed monitoring program of lake water is recommended.     

Effects of experimental acidification on mobilisation of metals from sediments of limed and non-limed lakes

In order to study the influence of pH on the mobilisation of metals from lake sediments, intact sediment cores with overlying water were sampled from one lime treated lake and one acidified lake. The overlying water of two cores from each lake was successively acidified to pH 4.2 over a period of 3 months. In the acid treated samples from the limed lake, the initial concentrations of Al, Cd, Mn, Pb and Zn in the overlying water were generally lower and the final concentrations were higher than in the acid treated samples from the acidified lake. The labile inorganic fraction of Al (Al(i)) was increasingly dominating as pH decreased. Redox potential and pH in the sediment indicated that the upper two centimetres were involved in the exchange reactions. The experiment showed that mobilisation of metals from sediments can occur and the results indicated that mobilisation could contribute to increased concentrations of metals in lake water during reacidification of formerly lime treated lakes.     

Leeches as indicators of dietary mercury exposure in non-piscivorous waterfowl in central Ontario, Canada

We collected and analysed 113 leeches (Hirudinea) from 17 small lakes in the acid-stressed Muskoka region of central Ontario, Canada to examine the relationship between lake chemistry and mercury (Hg) concentrations in leeches, and thus determine whether leeches and other benthic invertebrates posed a dietary risk of Hg exposure for non-piscivorous waterfowl. Hg concentrations in leeches were generally low and only a few-fold above the detection limit (0.78 ng g(-1) wet weight (ww)). Mean Hg concentration in the bloodsucker Macrobdella decora was 6.94 +/- 0.78 SE ng g(-1) ww (n=49) and was 5.98 +/- 0.46 ng g(-1) ww (n=64) in the scavenger Percymoorensis marmoratis. Leech Hg concentrations were correlated with calcium and dissolved organic carbon concentrations in the water, respectively. These data suggest that leeches are not suitable monitors of Hg (usually as methylmercury) biomagnification in central Ontario lakes, and do not pose a dietary risk to non-piscivorous waterfowl.     

Selenium speciation and localization in chironomids from lakes receiving treated metal mine effluent

A lake system in northern Saskatchewan receiving treated metal mine and mill effluent contains elevated levels of selenium (Se). An important step in the trophic transfer of Se is the bioaccumulation of Se by benthic invertebrates, especially primary consumers serving as a food source for higher trophic level organisms. Chironomids, ubiquitous components of many northern aquatic ecosystems, were sampled at lakes downstream of the milling operation and were found to contain Se concentrations ranging from 7 to 80 mg kg⁻¹ dry weight. For comparison, laboratory-reared Chironomus dilutus were exposed to waterborne selenate, selenite, or seleno-DL-methionine under laboratory conditions at the average total Se concentrations found in lakes near the operation. Similarities in Se localization and speciation in laboratory and field chironomids were observed using synchrotron-based X-ray fluorescence (XRF) imaging and X-ray absorption spectroscopy (XAS). Selenium localized primarily in the head capsule, brain, salivary glands and gut lining, with organic Se species modeled as selenocystine and selenomethionine being the most abundant. Similarities between field chironomids and C. dilutus exposed in the laboratory to waterborne selenomethionine suggest that selenomethionine-like species are most readily accumulated, whether from diet or water.     

Mercury Concentrations in Lentic Fish Populations Related to Ecosystem and Watershed Characteristics

Predicting mercury (Hg) concentrations of fishes at large spatial scales is a fundamental environmental challenge with the potential to improve human health. In this study, mercury concentrations were examined for five species across 161 lakes and ecosystem, and watershed parameters were investigated as explanatory variables in statistical models. For all species, Hg concentrations were significantly, positively related to wetland coverage. For three species (largemouth bass, pike, and walleye), Hg concentrations were significantly, negatively related to lake trophic state index (TSI), suggestive of growth biodilution. There were no significant relationships between ecosystem size and mercury concentrations. However, Hg concentrations were strongly, positively related to ecosystem size across species. Scores of small or remote lakes that have never been tested could be prioritized for testing using models akin to those presented in this article. Such an approach could also be useful for exploring how Hg concentrations of fishes might respond to natural or anthropogenic changes to ecosystems over time.     

Mercury content in roach (Rutilus rutilus L.) in circumneutral lakes--effects of catchment area and water chemistry

The environmental influence on the mercury content in roach (Rutilus rutilus L.) is investigated using partial least square regression on 46 environmental variables describing the land use in the catchment area, various catchment area and lake characteristics, lake water chemistry, and fish stock. The Hg content in the fish from the 78 investigated circumneutral lakes is heavily influenced by the land use in their surroundings. The boreal forest lakes possessed the highest Hg levels in roach, whereas fish from lakes surrounded by arable land had lower levels. The Hg levels also showed a negative relationship to the amount of dissolved ions and the total amount of nutrients in lake water. Lake pH did not have any significant influence on the Hg content in roach in these non-acidified lakes. The Hg levels in lakes influenced by large amounts of wetland were less well explained by the presently investigated environmental variables, which implies that the Hg burden in fish from this kind of lake is governed by other factors.     

Fluoride toxicity to aquatic organisms: a review

Published data on the toxicity of fluoride (F-) to algae, aquatic plants, invertebrates and fishes are reviewed. Aquatic organisms living in soft waters may be more adversely affected by fluoride pollution than those living in hard or seawaters because the bioavailability of fluoride ions is reduced with increasing water hardness. Fluoride can either inhibit or enhance the population growth of algae, depending upon fluoride concentration, exposure time and algal species. Aquatic plants seem to be effective in removing fluoride from contaminated water under laboratory and field conditions. In aquatic animals, fluoride tends to be accumulated in the exoskeleton of invertebrates and in the bone tissue of fishes. The toxic action of fluoride resides in the fact that fluoride ions act as enzymatic poisons, inhibiting enzyme activity and, ultimately, interrupting metabolic processes such as glycolysis and synthesis of proteins. Fluoride toxicity to aquatic invertebrates and fishes increases with increasing fluoride concentration, exposure time and water temperature, and decreases with increasing intraspecific body size and water content of calcium and chloride. Freshwater invertebrates and fishes, especially net-spinning caddisfly larvae and upstream-migrating adult salmons, appear to be more sensitive to fluoride toxicity than estuarine and marine animals. Because, in soft waters with low ionic content, a fluoride concentration as low as 0.5 mg F-/l can adversely affect invertebrates and fishes, safe levels below this fluoride/l concentration are recommended in order to protect freshwater animals from fluoride pollution.     

Inhibition of trout gill and soybean lipoxygenases by organotin compounds

Activity of trout gill and soybean lipoxygenase was inhibited by various low concentrations of tri-n-butyltin, di-n-butyltin and n-butyltin chlorides at pH 7.8. Tri-n-butyltin (0.044-0.19 mM; 8-100% inhibition) was significantly more inhibitory against trout gill lipoxygenase than di-n-butyltin (0.1-0.27 mM; 17-39% inhibition) or n-butyltin (1.2-3.6 mM; 26-43% inhibition). Soybean lipoxygenase displayed a similar sensitivity to the inhibitory effects of organotin compounds at pH 7.8. Although tri-n-butyltin (0.067-0.2 mM; 13-68% inhibition) was less inhibitory to soybean lipoxygenase, di-n-butyltin (0.134-0.537 mM; 51-75% inhibition) and n-butyltin (0.41-1.23 mM; 33-75% inhibition) were more inhibitory towards soybean lipoxygenase compared with trout gill lipoxygenase. Concentrations of butyltins required to provide substantial inhibition of trout gill lipoxygenase were of the order of magnitude of those reported for lethal water exposure concentrations of these compounds for trout and other fishes when bioaccumulation factors are considered. Thus, it is proposed that inhibition of lipoxygenase likely contributes to the biocidal activity of organotin compounds.     

Response of sediment calcium and magnesium species to the regional acid deposition in eutrophic Taihu Lake,China

Acid deposition causes carbonate dissolution in watersheds and leads to profound impacts on water chemistry of lakes. Here, we presented a detailed study on the seasonal, spatial, and vertical variations of calcium and magnesium species in the overlying water, interstitial water, and sediment profiles in eutrophic Taihu Lake under the circumstance of regional acid deposition. The result showed that both the acid deposition and biomineralization in Taihu Lake had effects on Ca and Mg species. In the lake water, calcium carbonate was saturated or over-saturated based on long-term statistical calculation of the saturation index (SI). On the sediment profiles, significant difference in Ca and Mg species existed between the surface sediment (0–10 cm) and deeper sediments (>10 cm). The interstitial water Ca²⁺ and Mg²⁺, ion-exchangeable Ca and Mg in the surface sediment were higher than those in the deeper sediment. In the spring, when the acid deposition is more intensive, the acid-extracted Ca and Mg in the surface sediment were lower than that in the deeper sediment in the northwest lake, due to carbonate dissolution caused by the regional acid deposition. Spatially, the higher concentration of acid-extracted Ca and Mg in the northwest surface sediment than that in the east lake was observed, indicating the pronounced carbonate biomineralization by algae bloom in the northwest lake. Statistical analysis showed that acid deposition exerted a stronger impact on the variation of acid-extracted Ca and Mg in the surface sediment than the biomineralization in Taihu Lake. For the total Ca and Mg concentration in the spring, however, no significant change between the surface and deeper sediment in the northwest lake was observed, indicating that the carbonate precipitation via biomineralization and the carbonate dissolution due to acidic deposition were in a dynamic balance. These features are of major importance for the understanding of combined effects of acid deposition and eutrophication on freshwater lakes.

     

Contemporary (1979-1988) and inferred historical status of headwater lakes in North Central Ontario, Canada

Fifty-six headwater Canadian Shield lakes were repetitively sampled from 1979 to 88 to determine their response to changes in acidic deposition of the period. Annual wet sulphate loadings varied between 38 and 83 meq m(-2), with highest deposition in the late 1970s followed by somewhat lower but variable deposition in the 1980s. Median pH of the lakes increased 0.42 pH units from 1979 to 1985 and decreased by 0.15 units between 1985 and 1988. Short water renewal times (x=1.1 y) promoted rapid equilibration. Since lake were so responsive to changes in SO4(2-) inputs, they were at or near steady state at all times. Comparison of predicted original pH and ANC with 1979 data indicate a median decline of 0.45 pH units and a loss of 34 microeq litre(-1). ANC. Four of 9 lakes were found to be historically fishless, based on the continued presence of Chaoborus americanus in sediment cores. The remaining five lakes historically had fish populations, but fish were not collected in 1979 when pH ranged betwen 4.6 and 5.3. By 1987, fish species were found in five of these lakes where pH had increased on average by 0.9 pH units. Our data indicate that water quality improvements could allow for the reinvasion or resumption of recruitment for a significant number of Ontario lakes.     

Monitoring contaminants from oil production at sea by measuring gill EROD activity in Atlantic cod (Gadus morhua)

An ex vivo gill EROD assay was applied in Atlantic cod (Gadus morhua) as a biomarker for waterborne CYP1A-inducing compounds derived from oil production at sea. Exposure to nominal concentrations of 1 ppm or 10 ppm North Sea crude oil in a static water system for 24 h caused a concentration-dependent gill EROD induction. Further, exposure of cod for 14 days to environmentally relevant concentrations of produced water (PW, diluted 1:200 or 1:1000) from a platform in the North Sea using a flow-through system resulted in a concentration-dependent induction of gill EROD. Crude oil (0.2 ppm) from the same oil field also proved to induce EROD. Finally, gill EROD activity in cod caged for 6 weeks at 500-10 000 m from two platforms outside Norway was measured. The activities in these fish were very low and did not differ from those in fish caged at reference sites.