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At least 253 records · Page 14Linked to original sources
PubMed2003

Relationships of Palearctic and Nearctic 'glacial relict' Myoxocephalus sculpins from mitochondrial DNA data.

The relationships among Myoxocephalus quadricornis complex fish from Arctic coastal waters and from 'glacial relict' populations in Nearctic and Palearctic postglacial lakes were assessed using mtDNA sequence data (1978 bp). A principal phylogeographical split separated the North American continental deepwater sculpin (M. q. thompsonii) from a lineage of the Arctic marine and North European landlocked populations of the fourhorn sculpin (M. q. quadricornis). The North American continental invasion took place several glaciation cycles ago in the Early-to-Middle Pleistocene (0.9% sequence divergence); the divergence of the European and Arctic populations was somewhat later (0.5% divergence). The Nearctic-Palearctic freshwater vicariance in Myoxocephalus, however, appears clearly younger than in similarly distributed 'glacial relict' crustacean taxa; the phylogeographical structure is more similar to that in other northern Holarctic freshwater fish complexes.

Animals↗
PubMed2002

Occurrence and environmental behavior of the bactericide triclosan and its methyl derivative in surface waters and in wastewater.

The bactericide triclosan and methyl triclosan, an environmental transformation product thereof, were detected in lakes and in a river in Switzerland at concentrations of up to 74 and 2 ng L(-1), respectively. Both compounds were emitted via wastewater treatment plants (WWTPs), with methyl triclosan probably being formed by biological methylation. A regional mass balance for a lake (Greifensee) indicated significant removal of triclosan by processes other than flushing. Laboratory experiments showed that triclosan in the dissociated form was rapidly decomposed in lake water when exposed to sunlight (half-life less than 1 h in August at 47 degrees latitude). Methyl triclosan and nondissociated triclosan, however, were relatively stable toward photodegradation. Modeling these experimental data for the situation of lake Greifensee indicated that photodegradation can account for the elimination of triclosan from the lake and suggested a seasonal dependence of the concentrations (lower in summer, higher in winter), consistent with observed concentrations. Although emissions of methyl triclosan from WWTPs were only approximately 2% relative to those of triclosan, its predicted concentration relative to triclosan in the epilimnion of the lake increases to 30% in summer. Passive sampling with semipermeable membrane devices (SPMDs) indicated the presence of methyl triclosan in lakes with inputs from anthropogenic sources but not in a remote mountain lake. Surprisingly, no parent triclosan was observed in the SPMDs from these lakes. Methyl triclosan appears to be preferentially accumulated in SPMDs under the conditions in these lakes, leading to concentrations comparable to those of persistent chlorinated organic pollutants.

Anti-Infective Agents, Local↗
PubMed2005

Environmental evidence of fossil fuel pollution in Laguna Chica de San Pedro lake sediments (Central Chile).

This paper describes lake sediment spheroidal carbonaceous particle (SCP) profiles from Laguna Chica San Pedro, located in the Biobío Region, Chile (36 degrees 51' S, 73 degrees 05' W). The earliest presence of SCPs was found at 16 cm depth, corresponding to the 1915-1937 period, at the very onset of industrial activities in the study area. No SCPs were found at lower depths. SCP concentrations in Laguna Chica San Pedro lake sediments were directly related to local industrial activities. Moreover, no SCPs were found in Galletué lake (38 degrees 41' S, 71 degrees 17.5' W), a pristine high mountain water body used here as a reference site, suggesting that contribution from long distance atmospheric transport could be neglected, unlike published data from remote Northern Hemisphere lakes. These results are the first SCP sediment profiles from Chile, showing a direct relationship with fossil fuel consumption in the region. Cores were dated using the 210Pb technique.

Air Pollutants↗
PubMedDate not supplied

[Fractionation of stable sulfur isotopes during microbiological processes in Slavyansk lakes].

The isotopic content of sulphur in sulphates increases with depth in waters containing hydrogen sulphide of the meromictic lakes Repnoe and Veisovo as a result of microbiological reduction of sulphates. At the same time, hydrogen sulphide enrichments 19 to 25% of the light isotope 32S in the lake Veisovo, and 24 to 32% in the lake Repnoe. The fractionation of sulphur isotopes, manifested in the enrichment of sulphides with lighter isotopes, and that of sulphates with heavier isotopes, was found also in the bottom deposits of the lake Repnoe. The isotope and microbiological data suggest that, in the zone of mass growth of the phototrophic sulphur bacteria in the lake Repnoe, there are two processes of fractionation: (a) due to the bacterial reduction of sulphates; and (b) due to anaerobic oxidation of hydrogen sulphide, resulting in the enrichment of hydrogen sulphide with the light isotope 32S by 5 to 7 promille.

Bacteria↗
PubMed1998

A Hydrological Model for Predicting the Effects of Dams on the Shoreline Vegetation of Lakes and Reservoirs

/ The species richness of shoreline vegetation of unregulated lakes in Nova Scotia, Canada, is known to increase as a function of catchment area, a topographic variable governing water level fluctuations. Predictions based on catchment area however, fail to account for richness patterns at the margins of lakes enlarged by dams. Here, we compare the vegetation and hydrological regimes of regulated and unregulated systems. Hydrological regimes of regulated systems deviated from natural systems of similar catchment area by being either hypovariable or hypervariable for both within-year and among-year fluctuations in water level. Plant communities of dammed systems were less diverse, contained more exotic species, and were, with one exception, devoid of rare shoreline herbs. Data from "recovering," or previously dammed systems indicated that shoreline communities can be restored upon return of the appropriate hydrological regime. Using observed within-year and among-year water level fluctuation data, we propose a general model for the maintenance or restoration of diverse herbaceous wetlands on shorelines of temperate lakes or reservoirs. Managers can manipulate the within-year water level variation within prescribed limits (1-2 m), while ensuring that among-year variation (SD of summer levels) is less than 25% of within-year variation. This preliminary model is based on data from low-fertility, temperate lakes in river systems. To calibrate the model, plant community data from other regions are needed, as are long-term water-level data for unregulated lakes, data which are essential but largely lacking in many areas.KEY WORDS: Catchment area; Regulated lakes; Shoreline restoration; Rare plants; Exotic plants; Diversity

Journal Article↗
PubMed2002

The impact of stocking on the genetic integrity of Arctic charr (Salvelinus) populations from the Alpine region.

There is a long tradition of artificially stocking lakes and rivers with fish in the hope to increase the quality and amount of fish that can be harvested. The animals used for stocking often originate in distant hatcheries or hatcheries that breed fish from remote regions. This stocking practice could have effects on the genetic integrity of resident populations. We have analysed here a case of the influence of stocking on Alpine populations of the Arctic charr (usually included into Salvelinus alpinus, but revised to Salvelinus umbla Kottelat 1997) within a unique geographical and historical setting. The Königssee in the Bavarian Alps (Berchtesgaden) was heavily stocked several times during the last century. However, a sample of the ancestral Königssee population still exists in the Grünsee, which lies close to Königssee, but 1000 m higher. To trace the influence of stocking in Königssee we have analysed more than 300 individuals from 10 lake populations, including the source populations of the fish used for stocking. From these we have sequenced a part of the mitochodrial control region and have typed them at six microsatellite loci. The differential distribution of haplotypes, as well as assignment tests, show that the influence of stocking on the genetic integrity of the Königssee population has been negligible. However, our data reveal that in another lake included in our study (Starnberger See), the ancestral population was apparently replaced completely by the populations used for stocking. The major difference between the lakes is the relative preservation of ecological integrity. Königssee was ecologically stable in the past, whereas Starnberger See was heavily polluted at one point, with charr approaching extinction. Interestingly, in a lake neighbouring Starnberger See, the Ammersee, which was also subject to strong pollution but not stocked, the ancestral population has recovered. Our data suggest that the practice of artificial stocking should be reconsidered, or at least monitored for effectiveness.

Animals↗
PubMed2002

Uptake and elimination of radiocaesium in fish and the "size effect.".

A number of hypotheses have previously been developed concerning the rates of uptake and elimination of radiocaesium (137Cs) in fish. These include the influence of potassium and other water chemical parameters on both uptake and elimination, and the effect of fish size on accumulation. In order to test these hypotheses, we have assembled a data set comprising more than 1,000 measurements of radiocaesium (137Cs) in predatory fish (perch, pike and brown trout) in nine European lakes during the years after Chernobyl. These data have been analysed using simple models for uptake and excretion of 137Cs in fish, showing that: 1. Fish-water concentration factors (CF) were inversely proportional to potassium [K+] concentration of the different lakes, in agreement with previous studies. 2. The uptake rate of 137Cs in fish was negatively correlated with lake [K+], but excretion rate was independent of [K+]. 3. Lower than expected CF values were found in one lake, Iso Valkjärvi, Finland. This is attributed to inhibition of the K+ (and therefore 137Cs) high affinity transport system in aquatic plants and fish by low pH and/or low Ca2+. 4. The inclusion of fish weight as a parameter in our dynamic model significantly improves the ability of the model to fit the observed measurements of 137Cs. 5. The model developed from the above hypotheses was able to fit the data from nine different lakes to within approximately a factor of 3 of the observed values.

Animals↗
PubMed2006

Microbial exposure assessment of an urban recreational lake: a case study of the application of new risk-based guidelines.

New WHO and Australian guidelines promote a risk-management approach for minimising exposure to pathogens in recreational waters. Between 2003 and 2005, they were applied to Lake Parramatta (10 ha, 450 ML), a potential recreation site in Sydney, Australia. A three stage approach was developed involving (1) initial suitability assessment using historic data, (2) revised suitability assessment based on new data and (3) characterisation of hazardous (especially wet weather) events. Contrary to the stage 1 suitability classification, stage 2 baseline data indicated that during dry weather the lake had water quality sufficient for primary contact recreation (95th percentiles for enterococci = 19 MPN/100, n = 50) and the major pathogen source was wildfowl. Guideline principles provided a rationale for collecting microbiological and geographic data needed to understand local cycles of lake contamination/recovery. The concept of hazardous events was particularly useful. Studies of stormwater events led us to identify a transition point (> 10 mm rainfall in 24 h) where human-faecal pathogen risks increased and access needed to be controlled. Together baseline and event data yielded operational tools (i.e. event detection methods, action triggers, auditing criteria, remediation priorities) for minimising bather exposure.

Clostridium perfringens↗
PubMed2004

Speciation in the aqueous H+/H2VO4-/H2O2/citrate system of biomedical interest.

The speciation in the quaternary aqueous H+/H2VO4-/H2O2/citrate (Cit3-) and H+/H2VO4-/Cit3-/L-(+)-lactate (Lac-) systems has been determined at 25 degrees C in the physiological medium of 0.150 M Na(Cl). A combination of 51V NMR integral intensities and chemical shift (Bruker AMX500) as well as potentiometric data (glass electrode) have been collected and evaluated with the computer program LAKE, which is able to treat multimethod data simultaneously. The pKa-values for citric acid have been determined as 2.94, 4.34 and 5.61. Altogether six vanadate-citrate species have been found in the ternary H+/H2VO4-/Cit3- system in the pH region 2-10, only two of which are mononuclear. Reduction of vanadium(V) becomes more pronounced at pH < 2. Solutions, in which reduction occurred to any extent, were excluded from all calculations. In the quaternary H+/H2VO4-/H2O2/Cit3- system, eight complexes have been found in addition to all binary and ternary complexes over the pH region 2-10, including three mononuclear species. Equilibria in general are fast, but the significant and rapid decomposition of peroxide in acidic solutions limited the final model to pH > 4. In the quaternary H+/H2VO4-/Cit3-/Lac- system, two mixed-ligand species have been determined, with the compositions V2CitLac2- and V2CitLac3- (pKa = 5.0). To our knowledge, this is the first time such complexes have been reported for vanadium(V). 51V NMR chemical shifts, compositions and formation constants are given, and equilibrium conditions are illustrated in distribution diagrams as well as the fit of the model to the experimental data. When suitable, structural proposals are given, based on 13C NMR measurements and available literature data of related compounds.

Citrates↗
PubMed2005

An extant cichlid fish radiation emerged in an extinct Pleistocene lake.

The haplochromine cichlid fish of the East African Great Lakes represent some of the fastest and most species-rich adaptive radiations known, but rivers in most of Africa accommodate only a few morphologically similar species of haplochromine cichlid fish. This has been explained by the wealth of ecological opportunity in large lakes compared with rivers. It is therefore surprising that the rivers of southern Africa harbour many, ecologically diverse haplochromines. Here we present genetic, morphological and biogeographical evidence suggesting that these riverine cichlids are products of a recent adaptive radiation in a large lake that dried up in the Holocene. Haplochromine species richness peaks steeply in an area for which geological data reveal the historical existence of Lake palaeo-Makgadikgadi. The centre of this extinct lake is now a saltpan north of the Kalahari Desert, but it once hosted a rapidly evolving fish species radiation, comparable in morphological diversity to that in the extant African Great Lakes. Importantly, this lake seeded all major river systems of southern Africa with ecologically diverse cichlids. This discovery reveals how local evolutionary processes operating during a short window of ecological opportunity can have a major and lasting effect on biodiversity on a continental scale.

Africa, Southern↗
PubMed2005

Effect of declining lake base cation concentration on freshwater critical load calculations.

Steady-state critical load models have been extensively used as the scientific underpinning for air pollution control policies in Europe and are currently being applied to other parts of the world. An important assumption of steady-state models is that critical load estimates do not change through time (or time scale of interest). The most commonly used model for estimating freshwater critical loads is the steady-state water chemistry (SSWC) model. In this study we examined changes in SSWC critical load estimates for 29 lakes in south-central Ontario using data collected 13 years apart (1985-1998), during which time bulk sulfate (SO4(2-)) deposition decreased by 35%. In lakes with the lowest base cation concentrations (<120 microequiv L(-1) Ca2+), the decrease in SO4(2-) concentration was accompanied by an approximately equivalent decrease in base cation concentration, resulting in only a minimal increase in Acid Neutralizing Capacity (ANC) during the 13-year period (median increase 1.6 microequiv L(-1)), and the median critical load for acidity (CL(A)) estimated by the SSWC model decreased by 14.6%. These changes may have been brought about by declining base cation concentrations owing to continued soil acidification in the region. In contrast, in lakes with higher base cation concentrations (>150 microequiv L(-1) Ca2+), the relative decline in base cation concentration was not as great, resulting in a larger increase in ANC (median increase 13.1 microequiv L(-1)) and an increase in the estimated CL(A) (median 5.1%). Lakes with moderate base cation concentrations (120-150 microequiv L(-1) Ca2+) exhibited an intermediate response; the median ANC increased by 8.8 microequiv L(-1) and the estimated CL-(A) decreased by 2.2%. In central Ontario, SSWC critical load estimates based on data taken only 13 years apart change quite dramatically due to changing lake base cation concentrations, and the response appears to depend on the base status of the lakes. The changing values obtained from the SSWC model have important consequences for policy decisions regarding acceptable levels of acid deposition. The application of dynamic models that take into account changes in lake/soil chemistry appears more appropriate for estimating acceptable levels of acid deposition in the region.

Cations↗
PubMed2001

Lead concentrations and isotopic ratios in the sediments of the Sea of Galilee.

The isotopic composition and concentrations of Pb in the sediments of the Sea of Galilee (Lake Kinneret) were measured. The studied sediments have been deposited in the lake since the early 1900s (ca. 1920), hence Pb data record the transition from a period when the lake vicinity was sparsely populated to the present (approximately 100,000 people living in the area around the lake). In general, there is either a constant or a relatively slow increase in Pb concentrations from 40 cm depth (3.5-4.4 microg/g; ca. 1920) to 17 +/- 2 cm below the sediment-water interface (3.7-7.2 microg/g;), which was deposited in the mid-1960s. From 17 +/- 2 cm below the surface, there is a much faster increase up to 7 +/- 2 cm below the surface (from 6.5 to 11.5 microg/g; 1982-1983), and from 7 +/- 2 cm there is a gradual decrease in Pb concentrations toward the sediment-water interface. At station G, near the outlet of the Jordan River, Pb concentrations drop between 29 and 25 cm below the surface, probably reflecting changes in the particulate load of the Jordan River due to the drying out of the Hula Swamp in the early 1950s. 206Pb/207Pb values in all the stations record most of the shifts displayed by Pb concentrations in the sediment. The estimated value of total Pb deposited annually in the lake sediment in the early 1990s is very close to the value obtained from measurements of Pb fluxes to the lake from eolian and fluvial sources. On the basis of the linear relationship between 206Pb/207Pb (or 208Pb/207Pb) and 1/[Pb], we argue that two end-members contribute most of the Pb to the lake sediments. Sources of Pb to the lake include (i) the weathering of basalt from the eastern Galilee and the Golan Heights contributing 2.6 +/- 0.5 microg/g Pb to the sediment and (ii) anthropogenic Pb that is affecting both surface and deep (from 30 to 40 cm) lake sediments. At station S, a third source, Pb released from soils developed on carbonates, should be considered as well.

Isotopes↗
PubMed1988

A study of vital and health statistics of the Kainji Lake Area of Nigeria.

A survey of vital and health statistics, and the evaluation of collection of these data in the registration centres of Kainji Lake Area, are presented. Forty-two per cent of all deaths occurred below 10 years of age, with the largest percentage occurring below 5 years of age. The leading causes of all deaths were malaria, gastro-intestinal disorders and measles. Occurrence of an epidemic was found to be significant to the overall mortality. The role of traditional healers in the control of childhood mortality is discussed. About 34% of the women had married more than once and 56% of the divorces occurred after the first marriage. The causes of divorces were largely due to loss of affection and neglect. The number of deliveries in the hospitals was more than the number of registered births and no death was registered at the centres. A unique system of collection of vital information was suggested for the Kainji Lake Area.

Adolescent↗
PubMed1979

A communication on health and development in the Kainji Lake area of Nigeria.

A study of the health care delivery facilities in the Kainji Lake area of Nigeria (an artificial lake created in 1968) showed that hospitals, a health centre, maternal and child health centres, public health units, dispensaries and leper institutions, controlled by various organizations, are available. Dispensaries and leper settlements/clinics form the most numerous health providers in the rural areas. Analysis of 1973 data from eight dispensaries around Lake Kainji showed that malaria, gastroenteritis, chest and skin infections, venereal diseases and shistosomiasis constitute the major health problems. Observations of the environmental sanitation in the study area by the author support the idea that the diseases emanate particularly from the low standard of environmental health. A suggestion is made for the establishment of a central organization charged with the responsibilities for health planning and development. The evaluation of the impact of hte dispensaries as health providers is needed for future health planning. A health care delivery system supported by operational research should be initiated at the village level.

Delivery of Health Care↗
PubMed1998

ENVIRONMENTAL AUDITING: Regional Lake Trophic Patterns in the Northeastern United States: Three Approaches

/ During the summers of 1991-1994, the Environmental Monitoring and Assessment Program (EMAP) conducted variable probability sampling on 344 lakes throughout the northeastern United States. Trophic state data were analyzed for the Northeast as a whole and for each of its three major ecoregions-the Adirondacks (ADI), the New England Uplands (NEU), and the Coastal Lowland and Plateau (CLP)-and inferred to the entire population of lakes >/=1 ha (N = 11,076). Results were compared to a large, nonrandomly sampled data set for the same area compiled by Rohm and others and contrasted with lake trophic state information published in the National Water Quality Inventory: 1994 Report to Congress [305(b) report. Lakes across the entire Northeast were identified by EMAP data as 37.9% (+/-8.4%) oligotrophic, 40.1% (+/-9.7%) mesotrophic, 12.6% (+/-7.9%) eutrophic, and 9.3% (+/-6.3%) hypereutrophic. Lakes in the ADI and NEU generally are at a low, nearly identical trophic state (96% oligotrophic/mesotrophic), while those in the CLP are much richer (45% eutrophic). EMAP results are similar to results of the Rohm data set across the entire region. In the CLP, however, EMAP identified approximately 45% of the lakes as eutrophic/hypereutrophic, while the Rohm data set identified only 21% in these categories. Across the entire Northeast, the 305(b) report identified a much higher proportion (32.2%) of lakes in eutrophic condition and a much smaller proportion (19.8%) in oligotrophic condition than did the EMAP survey data (12.5% +/- 7.9% and 37.9% +/- 8.5%, respectively). Probability sampling has several advantages over nonrandom sampling when regional resource condition assessment is the goal.KEY WORDS: Lake trophic state; Phosphorus; Probability survey; Regional condition

Journal Article↗
PubMed2002

Great lakes research--important human health findings and their impact on ATSDR's Superfund research program.

The Agency for Toxic Substances and Disease Registry (ATSDR) was created by the Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA) of 1980, commonly known as Superfund. ATSDR is the principal United States federal public health agency involved with issues of public health and applied science concerning the human health impact of living in the vicinity of a hazardous waste site, or emergencies resulting from unplanned releases of hazardous substances into community environments. In pursuing these mandates, ATSDR's mission is to prevent exposure and adverse human health effects and diminished quality of life associated with exposure to hazardous substances from waste sites, unplanned releases, and other sources of pollution present in the environment. There are more than 2,000 toxic substances found at hazardous waste sites in the United States. ATSDR has developed a prioritized list of 275 substances that pose the greatest hazard to human health. In conducting its work ATSDR has identified data gaps in knowledge about the toxicity of various hazardous substances as well as gaps in human exposure characterization. As part of its mandate, ATSDR initiated a Substance-Specific Applied Research Program (SSARP) to address these data gaps. The ATSDR Great Lakes Human Health Effects Research Program (GLHHERP) is a congressionally-mandated research program that characterizes exposure to persistent toxic substances and investigates the potential for adverse health outcome in at-risk populations. The research findings from this program in the areas of exposure, sociodemographic data, and health effects have significant public health implications for ATSDR's Superfund research activities.

Animals↗
PubMed2001

Volatilization of toxaphene from Lakes Michigan and Superior.

The pesticide toxaphene was used extensively on cotton in the southern United States until its use was restricted in 1982. It was previously reported that the upper Great Lakes have received toxaphene by gas absorption following long-range transport from the south and are currently saturated with respect to toxaphene. However, the rate of loss of toxaphene from Lakes Michigan and Superior had been estimated using sparse or estimated data, and thus, these estimates had high uncertainties. For this investigation, samples were collected to provide extensive data on air, water, and sediment concentrations of toxaphene for the upper Great Lakes for the period 1997-98. These data were used to calculate the annual and seasonal fluxes of toxaphene from water to air and sediment. Lake Superior is 200-1000% saturated with toxaphene, and Lake Michigan is 200-500% saturated. It seems clear that both lakes will outgas toxaphene into the atmosphere for some considerable time in the future, and Lake Superior, because of its generally lower water temperatures and higher toxaphene concentration, will outgas toxaphene even longer than will Lake Michigan.

Environmental Monitoring↗