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  • 1
    ISSN: 1573-2932
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract Concentrations of Al, Fe, Mn, Zn and Cu were measured monthly at 24 sites in 21 rivers in Ontario and Quebec. Relationships between metal and suspended particulate matter (SPM), turbidity, colour (g440), temperature and system hydrology were quantified, and used to derive empirical models for predicting metal concentrations. In a test of the models using an independent data set, they explained a significant proportion of the variation in Al (90%), Fe (85%), and Mn (57%), but only 37% of the variation in riverine Zn concentrations. Metals concentrations are most strongly associated with SPM concentrations. The proportion of the total metal load associated with particulates (〉0.45 μm) is highly variable below 10 ppm SPM, indicating that this concentration approximates the division between systems dominated by weathered (solution) versus eroded (particulate) inputs. Annual metal exports were calculated, and empirical models for predicting catchment exports were developed using system hydrology and average SPM concentrations. These simple models can be used to estimate metals concentrations and exports from routine water quality monitoring data, without requiring chemical analyses. They also serve to distinguish background levels from those indicating metal contamination, and will, therefore, be useful for water quality evaluation.
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  • 2
    ISSN: 1573-2932
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract A mass-balance approach was used to examine the role of macrophyte beds as a sink or source for 7 metals over time scales varying from two months (the growing season of the plants) to one year. During the growing season the macrophyte beds were found to be net sinks for particulate metals but were net sources of dissolved metals. During senescence, ca. 15–20% of the Al, Fe, and Mn and ca. 25–30% of the Cr, Cu, Ni and Zn within the macrophyte tissues at maximum seasonal biomass was lost to the surrounding waters in a dissolved form. The export of metals from the weeds during senescence was a very small fraction (〈0.01% of Al, Fe to 3.5% of Zn) of the annual allochthonous metal loading to Fitch Bay in L. Memphremagog, Quebec. In L. Weedon however, metal export during senescence was 34% (Mn) to 57%(Cu) of the annual allochthonous load. The time estimated for the plants to recycle the metals within the rooting zone of the sediments was on the order of hundreds of years. These results demonstrate that while weedbeds are net sources of metals during the summer, only a small fraction of metals in littoral sediments are not permanently buried over the longer term.
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  • 3
    ISSN: 1573-515X
    Keywords: catchment export ; catchment retention ; metals ; sediments
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences
    Notes: Abstract Although catchments have been implicated as an important source of metals to lakes, the catchment contribution of different metals is poorly known, and the anthropogenic contribution is not known at all. We determine the anthropogenic lake sediment burdens of Zn, Cu, Ni, Cr, and Pb for several Quebec and Ontario lakes, not subject to point source loading, to obtain estimates of atmospheric loading and inputs from terrestrial sources. To do this, we first collected multiple cores across 11 lake basins to estimate the whole-lake Pb burdens. As the whole-lake Pb burdens did not differ among lakes that spanned over two orders of magnitude in drainage ratios (drainage basin area/lake area), we conclude that catchment retention of anthropogenic Pb is complete. The anthropogenic Pb burdens were then used as a correction for focusing for the other metals. Among the metals, Cr and Ni were the most readily exported from drainage basins, followed by Cu. Zn showed no increase with drainage ratio, indicating Zn to be effectively retained by catchments. The export coefficients of the Pb corrected metals correlate well with ocean residence time, revealing a similar metal sorption/precipitation sequence in both soils and oceans. Sediment metal burdens provide a relatively easy way to obtain not only metal export coefficients from drainage basins, but also the atmospheric deposition of anthropogenic metals (e.g. Pb: S.E. Quebec, 950 mg*m−2: Laurentians, north of Montreal, 420 mg*m−2). The export coefficients are not only simpler to obtain than by mass balance measurements, but, in addition, identify the anthropogenic component.
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  • 4
    ISSN: 1573-5117
    Keywords: aquatic macrophytes ; biomass ; growth forms ; flowering pattern
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The utility of biomass density (biomass per unit volume) as a quantitative descriptor of the growth form of submerged macrophytes is evaluated and confirmed. Biomass density (BD) is a species specific characteristic which does not appear to be influenced by plant development. Secondly, BD reflects the growth form of the dominant species in the stand, because stands of species with a similar growth form also have similar BD's. Lastly, the BD of submerged macrophyte stands is closely related to the flowering pattern of the dominant species, and has important implications for light capture and light competition with neighbouring plants. Thus, BD should be a useful tool in the quantitative analysis of submerged macrophyte community structure.
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  • 5
    ISSN: 1573-5117
    Keywords: bacterioplankton ; respiration ; lakes ; nutrients
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Bacterioplankton and total planktonic community respiration were measured in 14 Canadian lakes during the summer. Total planktonic community respiration (O2 consumption and CO2 production) was best predicted by total phosphorus (TP), with respiratory rates increasing at higher TP levels. The bacterioplankton respiration alone was less well linked to nutrient concentrations. Yet, the rates of both planktonic and bacterial CO2 production changed similarly with changes in the C:N ratio, with the bacterial fraction, on average, contributing about 42% of the total planktonic respiratory rates. Bacterial carbon respired was uncoupled from oxygen consumption, with resultant average planktonic respiratory quotient (RQ) close to 2. Bacterioplankton respiratory rates are affected by a negative relationship between specific aerobic respiration and bacterial biomass. Higher bacterial specific oxygen consumption rates (µg O2 cell-1 d-1) were observed with increasing C:N and C:P ratios, suggesting an increase in maintenance cost at the low cell densities observed in oligotrophic waters. Phosphorus appeared as the limiting nutrient in these lakes and determined total planktonic respiratory rates, however, epilimnetic bacterial respiration was mainly related to the DOC: nutrient ratios.
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  • 6
    ISSN: 1573-515X
    Keywords: aquatic plants ; element composition ; QSAR
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences
    Notes: Abstract A simple view of the role of rooted macrophytes in element cycling sees them as pumps retrieving buried elements from the sediment profile. To investigate the relationship between the elemental composition of plants and sediments, we analysed published data for 39 elements. The best general model explained 84% of the variance of the log of plant element concentration: LPE = - 0.81 + 0.90 Log Sediment Element (ug/g dry wt.) − 0.12 Sediment Organic Content (ug/g drt wt.) + 0.67 Atomic radius (nm) (r 2 = 0.84; n = 39) This close relationship between the concentrations of an element in plant tissues and in the underlying sediment indicates that acquatic plants do not differ markedly in element composition from the sediments in which they grow. T-tests between mean residuals indicated that these aquatic plants do not discriminate between essential and nonessential elements. Model II regression analyses showed no difference between the slopes of the functional relationships for individual elements and that of the general model. When the elements were separated into three groups (alkali, transition and related metals, and halogens), Log Sediment Element accounted for 75–96% of the variation in LPE. Element physicochemical parameters were also significant independent variables explaining an additional 3–12% variation in LPE. The relative importance of the independent variables differed for the three groups of elements.
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  • 7
    ISSN: 1573-0417
    Keywords: constant initial concentration ; constant rate of supply ; 210Pb dating ; sediments
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences
    Notes: Abstract We used sediment chronology data from fourteen published studies of lake cores across much of North America and Scandinavia in order to make a large scale comparison of the different dating techniques. The uncertainty of210Pb derived dates was determined using common sediment event markers: the stable Pb rise, the137Cs rise, and theAmbrosia pollen rise. For all data combined, the 95% confidence intervals for the stable Pb rise and theAmbrosia rise, were approximately 30 years. These 95% confidence intervals are slightly higher than those derived by First-Order Error analysis performed by others on210Pb derived dates. When comparing the concordance of two210Pb models (CRS and CIC) against markers of known history, we found that the CRS model dates (constant rate of supply) had consistently better agreement than the CIC model dates (constant initial concentration). Major discrepancies between137Cs and210Pb were common, but were consistently more severe in sediments of soft water lakes pointing to an inability of sediments with low mineral content to ‘immobilize’ Cs.
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  • 8
    ISSN: 1432-184X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract We collected benthic bacterial production data measured by 3H thymidine incorporation (TTI) (25 studies), frequency of dividing cells (FDC) (3 studies), dark-C02 assimilation (1 study) and 3H-adenine uptake (2 studies) from the literature, which included 18 marine, 6 river, and 2 lake studies. In all of the studies that used the TTI method, 3H-DNA was isolated and incubations were carried out at in situ temperatures. Most of the researchers also determined 3H-DNA extraction efficiencies and isotope dilution, thus interpretable estimates of bacterial production were used in the analysis. In marine sediments, bacterial production rates were linked to bacterial biomass, bacterial abundance, sediment organic matter, temperature, and sediment chlorophyll a, with these variables explaining between 40% and 68% of the variation in production rates. Simple relationships between production and bacterial biomass or bacterial abundance, or between production and sediment organic matter, were improved by also including temperature in the analysis of marine sediments. Sediment organic matter explained an appreciable fraction (58%) of the observed production in freshwater sediments. Temperature was the most powerful predictor of the observed variability in specific growth rates (r 2 = 0.48 and r 2 = 0.58) in marine and freshwater sediments, respectively. Thus, bacterial production and specific growth rates are most closely linked to substrate supply and temperature in marine and freshwater sediments.
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  • 9
    Electronic Resource
    Electronic Resource
    Springer
    Oecologia 69 (1986), S. 612-617 
    ISSN: 1432-1939
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary We examined the effect of grazer size on periphyton biomass, size structure, and species compostion by removing the largest invertebrate grazers on artificial macrophytes planted in the littoral of Lake Memphremagog (Que-Vt). A series of exclosures with increasingly fine mesh prevented colonization by large invertebrates but allowed in smaller grazers. Oligochaetes, chironomids, and cladocerans effectively replaced snails so that total grazer biomass in the various treatments was not significantly different from the controls. With one exception, algal biomass, measured as chlorophyll a, did not differ significantly among the various treatments. However algal size and taxonomy were affected because the dominance of large blue-green colonies was apperantly related to the presence of large grazers. The results of the size manipulations were qualitatively similar to those induced in phytoplankton communities by size selective zooplankton grazing and are consistent with models based on general allometric equations.
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  • 10
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Freshwater biology 29 (1993), S. 0 
    ISSN: 1365-2427
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: 〈list xml:id="l1" style="custom"〉1 Sediments and eleven species of rooted submerged aquatic macrophytes were sampled from twenty-five lakes in southern Quebec to examine species patterns in metal content.2 Linear regression models relating the content of metals in the macrophytes to their sediments demonstrated that the isoetoid (Eleocharis acicitlaris, Eriacaulon septangulare, Isoetes sp. and Sagittaria graminae) and the non-isoetoid species had different plant-sediment relationships. Canopy-forming (Myriophyllum spicatum, Potamogeton amplifalius, P. crispus and P. perfoliatus) and understory species (Elodea canadensis, P. robbinsii and Vallisneria americana) had similar linear regression model slopes, but the understory species had significantly higher intercepts, indicating higher plant metal contents for a given sediment metal concentration.3 We grouped species by their biomass density (biomass (kg)/height (m)), a measure of the packing of the plant canopy, and averaged values for each metal, thereby producing one model per group. Comparison of the models by analysis of covariance revealed no significant differences in metal content. However, the canopy-forming species that occurred in monospecific and mixed species stands (M. spicatum and P. amplifolius) had significantly higher metal content for a given sediment metal content when an understory was present.4 These results show that sediment metal content explains the largest proportion of variation in plant metal content across all sites and species. Deviations from what would be predicted by the most general model are not related to large-scale differences in sediment geochemistry, but to the physical structure of the weedbed within geochemically similar sediments.
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