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1.
As part of a water quality study on Rattray Marsh, a suburban marsh located on the Lake Ontario shoreline at Mississauga, Ontario, a sedimentary geochemistry study was initiated. In general, Cu, Zn, Pb and Hg were higher in concentration than in local soils, but lower than Lake Ontario recent sediments. Over the past century, an approximate two-fold increase in the sedimentary levels of Cu, Zn, Co, Cr and Ni occurred, while Cd increased nearly 4 ×, and Pb, 8 ×. No correlation was found between metals and organic carbon, and the metals appear to be associated with silts and clays as evidenced by (1) factor analysis of geochemical data, (2) higher concentrations in areas of the marsh subjected to high sediment deposition, and (3) analysis of a suspended sediment sample from Sheridan Creek, the main tributary basin of the marsh. Organochlorine contaminants include p,p1-DDE,p,p1-DDD,p,p1-DDT, a-chlordane, PCB, mirex and HCB.  相似文献   

2.
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.  相似文献   

3.
Ion mass budgets were measured for 2 water yr (June–May, 1981–83) for a high and a ).ow elevation lake and their associated catchments. The lakes are located in the Turkey Lakes Watershed (TLW) in central Ontario, Canada, which is an undeveloped basin located on the Canadian Shield, 50 km north of Sault Ste. Marie. The ionic budgets of the lakes show that atmospheric deposition directly to the lakes' surfaces is the principal input pathway for H+ and NH4, whereas basic cations, SO4, NO3, and probably alkalinity are supplied primarily by inflow from the surrounding terrestrial basin and/or upstream lake. The lakes strongly retain H+ (i.e. output ? input), weakly retain the N species, and are in balance (i.e. output = input) for other ions except Ca and alkalinity which show an excess output compared to measured + estimated inputs. We hypothesize that an input of groundwater and/or seepage accounts for most of the Ca and alkalinity imbalance although the existence of within-lake alkalinity generation is probable also.  相似文献   

4.
As part of a study of the substance budgets of lakes in south-central Ontario, a network of precipitation collectors (8 bulk, 7 wet only) was operated to measure the deposition of nutrients and major ions. Results are reported for total P, total Kjeldahl N, NO 3 ? ?N, NH 4 + ?N, total N, Fe, H+, Ca++, Mg++, Na+, K+, SO 4 = and CL? for a two year period (August 1976–July 1978). On an equivalent basis the dominant anion in both bulk and wet precipitation was SO 4 = , with H+ the dominant cation. Precipitation in the study area is more acidic than that analyzed at any other location on the Canadian Shield to date. Concentrations of ions varied by 1 to 3 orders of magnitude between individual precipitation events and annual deposition varied by as much as 2-fold in the two years of study. Annual wet deposition contributed >60% of bulk deposition for all substances except total P. Seasonal trends in deposition with summer maxima were noted for most ions. For Harp Lake, a small Precambrian Lake with a lake area of 12.6% of its total drainage area, precipitation input directly to the lake surface was an important source of nutrients and major ions. This was especially the case for P, N and H+ because these substances were retained by the terrestrial drainage basin.  相似文献   

5.
Sediment cores were taken from the remote Sagamore and Woods Lakes in New York State's Adirondack acid lake region and analyzed for 3 to 7 ring polycyclic aromatic hydrocarbons (PAHs) and Ag, Al, As, Be, Cd, Cr, Cu, Hg, Ni, Ph, Se, Sn, TI, V, and Zn. With the exception of perylene, all of the parental PAHs, e.g. those without sidechains, and several of the metals, Pb, As, and Cd, were found to be significantly increased in the sediments of both lakes compared to their natural integrated deposits (ng cm?2) and their background concentrations (μg g?1 or ng g?1 dry wt). Although the concentrations were generally much higher in Woods Lake, the total anthropogenic integrated depositions were about the same in both lakes for most of the metals and the 3 to 4 ring PAHs. The prime source of most of the 3 to 7 ring PAHs and trace elements measured is ascribed to anthropogenic combustion. Anthropogenically derived materials decreased in concentration with depth to baseline levels in sediment layers estimated by137Cs analyses to be ～30 yr old, while biogenic or crustal derived species remained constant or fluctuated with core depth.  相似文献   

6.
The concentration of organochlorine insecticides/metabolites, namely, lindane, heptachlor, aldrin, p,p′-DDL, p,p′-DDD, and p,p′-DDT were determined in water samples taken from two lakes, Jalmahal and Mahalon, from June 1985 to July 1986. These lakes are contaminated with moderate to high level of residues of different insecticides. In Mahalon lake the residues were highest (6.6 μg L?1) during October 1985 whereas in Jalmahal lake they were highest (9.6 μg L?1) in September 1985. In both lakes, residues of DDT exceeded the recommended limit for water quality criteria. Lindane was found in most of the samples but in lower quantities. Aldrin was the second most common residue in these lakes.  相似文献   

7.
During the period 1977–1980 we studied the effects of highly acidic precipitation (mean pH 4.1 to 4.2) on the chemistry of three Adirondack lakes: Woods Lake, Panther Lake, and Sagamore Lake. Two of these lakes (Woods and Panther) are enough like those lakes of southern Sweden and Norway studied by Henriksen that they should constitute a valid test of his ‘acidification indicator’ and ‘predictor homograph’. In our comparison we used data from weekly samples taken near the surface of the lakes during unstratified summer and fall conditions over a 3 yr period. The acidification indicator and predictor nomograph were developed using data from lake samples taken under similar conditions in Scandinavia. Our principal finding is that with regard to the empirical line of the acidification indicator (that Henriksen found separated data from lakes receiving precipitation greater or less than pH 4.6) and with the precipitation pH axis of the predictor nomograph, these two methods of evaluation are not directly applicable ‘as is’ to our lakes. The reason for this is that the chemistry of precipitation in the Adirondacks is significantly different from (and for) which the acidification indicator and predictor nomograph were developed. In the Adirondacks, acids other than H2SO4 play a much greater role in the overall acidity of the precipitation. This causes relationships between precipitation pH and lake chemistry in the two regions to be different.  相似文献   

8.

Purpose

Microbial sulfate reduction is an alkalinity-producing process and potentially supports the neutralization of acidic mine pit lakes. In many acidic lakes the process does not occur. Sulfate-reducing bacteria are known to be pH sensitive. There are, however, several reports of sulfate reduction occurring in the sediment of acidic lakes. To find out why sulfate reduction occurs in some acidic lakes but not in others, we conducted a field experiment.

Materials and methods

Surface sediment from lake ML111 (pH?2.6, no sulfate reduction), in the Koyne-Plessa lignite mining district of Lusatia in Germany, was incubated in the less-acidic lake ML117 (pH?3.4, sulfate reduction) and vice versa. After 19?weeks of incubation, the sediments were sampled and analyzed for microbial sulfate reduction rates, bacterial numbers, and geochemical composition.

Results and discussion

Incubation of ML117 sediment in ML111 resulted in a partial inhibition of sulfate reduction while incubation of ML111 sediment in ML117 did not initiate sulfate reduction. We observed a linear relationship between sediment pH and sulfate reduction, while there was no relation with sedimentary iron content. Sulfate reduction was not only affected by the water quality but also by the experimental treatment. Homogenization of the sediment prior to incubation stimulated microbial sulfate and iron reduction. Due to the low pH, incubation in ML111 resulted in the dissolution of reduced inorganic sulfur.

Conclusions

We conclude that the water pH is the major regulator of sulfate reduction in the surface sediment of acidic lakes. The rate of sulfate reduction in the sediment of acidic lakes depends on a fragile equilibrium between proton flux between water and sediment, and buffering reactions in the sediment.  相似文献   

9.
The benthic fauna of 41 nonhumic, soft water lakes situated north of lakes Superior and Huron were sampled during 1980. The pH range of the lakes sampled was 4.6 to 7.7. The benthic infauna displayed regional differences in abundance and composition, with large variation within each district. Total abundance, biomass, and number of taxa were not correlated with lake pH or alkalinity. The Chironomidae displayed a slight change in percent composition of the major species (p < 0.2) with lower pH. The Tanytarsini andChironomus salinarius group decreased, whileC. anthracinus group increased in relative abundance in those lakes with lower pH. Other factors appear to control the distribution of the various invertebrate orders, with depth and sediment nature being important variables.  相似文献   

10.
Several lake surveys have indicated that many lakes in Quebec are sensitive to acidification, but no historical data are available to provide conclusive evidence of lake acidification. Paleolimnological studies can provide such evidence. Chrysophycean algal microfossils were analyzed from the sediments of Lake Bonneville and Lake Truite Rouge in Quebec. The chrysophyte flora in the study lakes was stable until 40 yr ago, but since then the taxa characteristic of acidic or slightly acidic waters increased in abundance. The study provides evidence of recent lake acidification in Quebec.  相似文献   

11.
Data defining the major ion chemistry of lakes located in eastern Canada have been compiled for the purpose of evaluating the current status of surface water quality in relation to acidic deposition. A companion paper for lakes in the eastern United States (i.e. Part II, Linthurst et al., 1986) has been prepared also. Data sources in Canada included the National Inventory Survey, the Ontario Lake Sensitivity data set, and the National Aquatic Data base which provided an overall data base of approximately 5700 lakes. Only recently collected data (largely 1980 or later) were used in the analysis. Frequency distribution statistics were obtained for pH, acid neutralizing capacity (ANC), SO4 and organic anion (A?) concentrations. Acidic and low ANC waters in eastern Canada occur in a pattern explained by a combination of biogeochemical factors and atmospheric deposition. Nova Scotia contained the highest proportion of acidic and ultralow ANC lakes of any region surveyed in eastern North America; since this region receives approximately 20 kg.ha?1.yr?1 wet SO4 deposition, the proposed target loading may be too high to protect the highly sensitive waters of Maritime Canada. Compared to the rest of eastern Canada, lakes in Ontario have relatively high ANCs due to the influence of CaCO3 contained in the glacial till of the area. Variation in the SO4 concentration of lakes approximately follows expected gradients in wet SO4 deposition. Naturally occurring organic acids do not play a dominating role in the acidification of eastern Canadian lakes.  相似文献   

12.
As part of the EPRI funded Lake Acidification Mitigation Project(LAMP), an ongoing study to evaluate the feasibility of acid lake liming, two models (WAM and ALaRM) have been tested for two calibrated Adirondack Mountain study lakes(Woods and Cranberry). A priori predictions of reacidification rates based on Ca carbonate application and historical hydrological data are presented. WAM (Watershed Acidification Model) is a deterministic model that is capable of simulating the movement of water and chemical constituents through a watershed. WAM generates indata in the form of hydrologic and alkalinity to ALaRM (Acid Lake Reacidification Model), a general mass balance model developed for the temporal prediction of the principal chemical species in both the water column and sediment pore water of small lakes and ponds. A matrix of runs to determine model sensitivity to input loadings, kinetic coefficients, and sediment dosage levels indicate that reacidification of the water column is most sensitive to variation in hydrologic loading followed by variation in sediment dosage levels. Baseline estimates (initial water column alkalinity between 400 to 500 μeqL?1) indicate that reacidification to near zero alkalinity occurs after a time period equivalent to approximately two to three average hydraulic retention times.  相似文献   

13.

Purpose

The purpose of this study was to elucidate historical trends, spatial variations, and the sources of polycyclic aromatic hydrocarbons (PAHs) pollution in several Japanese lakes.

Materials and methods

The vertical distributions of PAHs in the core samples of sediments taken at several points in lakes Kasumigaura, Suwa, Kizaki, and Shinji were determined using a gas chromatograph equipped with a mass selective detector and combined with chronological information and the physical/elemental properties of the sediment.

Results and discussion

Seventeen related compounds (congeners) typically had concentration peaks at sediment depths corresponding to the 1960s to 1970s. In Lake Shinji and one bay of Lake Kasumigaura, there was a tendency for PAH concentrations to increase downstream; in contrast, another bay of Lake Kasumigaura showed the reverse trend. During big flood events, the fluxes of PAHs increased due to large inputs of particulate matter, although PAH concentrations were reduced. For the four study lakes and other similar lakes, PAH concentrations of surface sediments were approximately proportional to population densities in the respective watersheds, while the total input of PAHs to the lakes were correlated with their population and watershed area. The source apportionment analysis using isomer ratios for the congener profiles indicated that the principal sources of the PAHs in the lake sediments were gasoline and/or diesel engine exhausts and biomass burning.

Conclusions

The observed concentration peaks showed a deterioration of the chemical quality of atmospheric conditions around 1960?C1970 and a recent tendency for their amelioration. Between-lake differences suggest that the influence of human activity in the watersheds influences sediment PAH concentrations. The PAH sources were identified to be of pyrogenic origin.  相似文献   

14.

Purpose

Determining the dynamics of silicon in lakes, one of the essential nutrients for diatoms, is valuable for understanding aquatic environmental problems. The dissolved silicon (DSi) and biogenic silicon (BSi) budgets in Lake Kasumigaura, a shallow eutrophic lake in Japan, during the last three decades were assessed based on the analysis of dated sediment cores and a water quality database.

Materials and methods

Sediment cores (100?cm long) were taken at the center of Lake Kasumigaura in 2005, 2007, and 2009 and at two other sites in 2007. BSi contents of the dated sediments were determined by wet alkaline digestion. The net sedimentation rates of BSi were defined as the difference between the DSi load from inflowing rivers and the DSi and BSi loads from the outflow of the lake, calculated using DSi concentrations and diatom abundances in the lake from 1980 to 2007 and DSi concentrations of the inflowing rivers during 1994, 2007, and 2009. The gross sedimentation rates of BSi were estimated by multiplying BSi concentrations in lake water by the diatom sinking rate reported by previous studies.

Results and discussion

Budgetary calculations based on the database showed that 60?C70?% of DSi inputs from the inflowing rivers during the 27?years could ultimately be accumulated as diatom frustules in bottom sediments in the lake. The sediment analysis revealed that the amount of BSi accumulated in the lake from 1980 to 2007 was 2.0?C2.6?×?1011?g, similar to the amount based on the database of 1.3?C2.4?×?1011?g. Although the gross sedimentation rates of BSi likely increased, the net sedimentation rates of BSi decreased significantly from 6?C10?×?109?g?year?1 in the 1980s to 2?C6?×?109?g?year?1 in the 2000s, suggesting a fast recycling of BSi in recent years caused by an increase in sediment resuspension and regeneration.

Conclusions

The sediment core information and the water quality database can be used for calculating the long-term silicon budgets in Lake Kasumigaura. An increase in the DSi release rates was identified, which is consistent with recent sediment resuspension. Comparing the sediment core information with the database suggests the long-term dissolution of sediment BSi; however, analysis of the BSi content in sediment cores representing a much longer time period is needed to confirm this.  相似文献   

15.

Purpose

Mining is a common source of metals in aquatic ecosystems. Metal loading in the environment is thought to be a selective pressure that induces compositional and functional changes within the affected microbial community in the sediment. This study aims to explore shifts in the diversity, structure, and functional gene abundance of microbial communities in the sediment of the copper mining-induced contaminated lakes in Finland.

Materials and methods

The sediment microbial community structures and abundance of the functional groups involved in carbon/nitrogen/sulfur cycling in four lakes located downstream from metal mines (Kirkkoselkä (KS), Junttiselkä (JS), Laakajärvi (LJ), and Sysmäjärvi (SJ)) and one reference lake (Parkkimanjärvi (PJ)) in Finland were compared using high throughput sequencing and quantitative PCR.

Results and discussion

Compared to the PJ reference lake sediment, the relative abundances were higher for Bacteroidetes, Gemmatimonadetes, Acidobacteria, and Nitrospirae but lower for Firmicutes and Alphaproteobacteria in the mine-contaminated sediment samples. The number of copies of copper-resistant genes (copA) in the two copper-contaminated sediments (5.34 × 106 and 4.95 × 106 copies ng?1 DNA for KS and JS, respectively) was significantly higher than that in the PJ sediment (1.33 × 106 copies ng?1 DNA). Methanogens (mcrA gene) accounted for 5.09–11.5% of the total archaea (16S rRNA) in these lake sediments. In addition, ammonia-oxidizing archaea (amoA gene) in the LJ sediment accounted for 36.0% of the total archaea but only 0.83–1.63% in the sediment of other lakes. The abundance of eight investigated functional groups accounted for 28.8% of the total bacteria in the PJ sediment but less than 1.3% in the metal-contaminated sediments. The canonical correspondence analysis showed that the microbial community structure of Lake LJ was scattered far from the other lakes and was significantly correlated with nitrate; the community structural change in the JS and KS sediments was positively correlated with copper or negatively correlated with nitrate concentration.

Conclusions

These results indicate that the sedimentary indigenous microbial community may shift its composition and structure as well as its function to increase its adaptability and/or resistance to metal-contaminated freshwater sediments.
  相似文献   

16.

Purpose

A multi-compartment monitoring study was performed to characterize the effect of environmental variables, such as temperature and water flow as well as sediment characteristics, on the distribution and transport of persistent organic pollutants (POPs) in a dynamic river system during 1 year in an industrial region in central Europe.

Materials and methods

Waterborne polycyclic aromatic hydrocarbons (PAHs), polychlorinated biphenyls (PCBs) and organochlorine pesticides (OCPs) were assessed over a period of 1 year at five sampling sites in the Morava River in the Czech Republic. Contaminants were measured monthly in riverbed sediments, freshly deposited sediments, water samples and passive samplers.

Results and discussion

Sediments are the main carrier of POPs in the river. Distinguishable patterns of PAHs, OCPs and PCBs in sediment indicate that their origin is from distinct sources and different transport pathways. The PAHs were identified as the dominant contaminant group of compounds with a mean concentration in sediment of 5,900 μg kg?1. Such concentrations are up to 10 times higher than in the Danube River, into which Morava drains. In contrast, mean concentrations of PCBs, hexachlorocyclohexanes (HCHs), dichlorodiphenyltrichloroethane and its breakdown products (DDTs) and hexachlorobenzene (HCB) of 6.0, 0.4, 4.2 and 6.0 μg kg1, respectively, are similar to those in the Danube. With some exceptions, no significant difference in composition of surficial riverbed sediments and those collected using sediment traps was observed. Despite the presence of potential local pollutant sources, the differences in contaminant concentrations between sites in the region were in most cases not significant. Variations in POP concentrations in sediments are mainly induced by high flow events, whereas seasonal variability was not observed.

Conclusions

The changes in contaminant concentrations in Morava River sediments are induced by episodic high flow events that cause erosion of contaminant-containing particles and their deposition at suitable downstream sites.  相似文献   

17.
Biogeochemical processes contributing to the neutralization of acidic groundwater passing through near-shore sediments of an acidified lake (Dart's Lake) were investigated in a controlled laboratory experiment. Three intact sediment cores collected from the near-shore region of the lake were connected to a system that simulated groundwater flow through lake sediments in a temperature controlled laboratory environment. The effect of sediment biogeochemical processes on groundwater chemistry was determined by evaluating changes in acid/base and metal chemistry for solutions entering and leaving the cores. Aluminum mobilization represented the most significant source of neutralization for each core and contributed up to 99% of H+ removal. Although the sediment cores were collected parallel to the shoreline and over a linear distance of only 0.3 m, significant differences in sediment chemistry were apparent and contributed to variations in the chemistry of water transported from the cores. For one core that exhibited retention of Al from the influent groundwater, retention of Pb by the sediment was similarly observed. Following acidification of this groundwater, Pb was readily remobilized. These results suggest that near-shore lake sediments may be effective at influencing seasonal variations in Al, Pb and base cations in lakes receiving groundwater inputs.  相似文献   

18.

Purpose

Cadmium (Cd) is considered a toxic element and its concentrations are relevant to human health and the environment. Therefore, the purpose of the study was to determine the extent to which the bottom sediments of water bodies (artificial lakes and ponds) in the Silesian Upland in southern Poland are contaminated with Cd; an attempt was also made to determine the factors that condition spatial differences in the concentration of this element between individual water bodies in the region.

Materials and methods

Measurements of the Cd content in bottom sediments were carried out in 35 water bodies in southern Poland in 2011 and 2012. Depending on the surface area and morphometric characteristics, from two to nine samples representative in terms of sediment thickness were collected in each water body. Cadmium concentrations were determined for 92 0.25 g aliquots using the TD-ICP method.

Results and discussion

Cadmium content in all samples (0.7–580.0 mg kg?1) was higher than the natural range of concentrations for this element in the Earth’s crust (0.1–0.3 mg kg?1) and the geochemical background for Poland (0.5 mg kg?1) and, with a few exceptions, was also higher than the preindustrial concentration (1.0 mg kg?1) and the regional geochemical background (2.5 mg kg?1). Adopting natural Cd concentrations in the Earth’s crust (0.1–0.3 mg kg?1) as the baseline for the geoaccumulation index (Igeo), the sediments examined can be classified as extremely and heavily contaminated (and moderately contaminated in a small number of cases). The assessment of sediment quality based on Igeo, with the regional geochemical background (2.5 mg kg?1) adopted as the baseline, results in non-contaminated and moderately contaminated sediments being dominant with a far smaller number of heavily and extremely contaminated ones.

Conclusions

In the case of several water bodies, Cd concentrations were at record levels that have not been found anywhere else in the world. On the basis of the Igeo, sediments of varying quality were found—from virtually uncontaminated to extremely contaminated. The Igeo index as an indicator of the quality of bottom sediments is a measure that requires careful interpretation, especially when different concentration levels regarded as natural are used for determining its value.
  相似文献   

19.
Southwestern Nova Scotia receives acidic precipitation (average pH 4.5 to 4.6), and there are many waterbodies that are susceptible to acidification. This study characterizes the physical and chemical features of three remote, oligotrophic lakes and their watersheds in this region, in order to provide baseline information against which assessments can be made of changes caused by atmospheric depositions. Two of the lakes are small (<0.5 km2) and on headwater watersheds: Beaverskin Lake has an almost completely forested watershed and is moderately acidic and clear (pH 5.3, 5 Hazen units), while the watershed of Pebbleloggitch Lake is about 2/3 forested and 1/3 covered by a Sphagnum-heath bog, and its water is very acidic and highly colored (pH 4.3, 87 Hazen units). Kejimkujik Lake is much larger, its watershed is mostly forested but also contains some boggy terrain, its water is intermediate in acidity and color (pH 4.9, 65 Hazen units), and because it drains a much larger area of watershed it has relatively large concentrations of Ca, Mg, Na, Cl, and SO4.  相似文献   

20.
In order to assess the patterns of distribution of plankton species in relation to acidity, water chemistry, and physical characteristics, twenty lakes in Nova Scotia were selected for examination, with pH ranging from 3.5 to 7.6. Correlation and multiple regression analyses revealed associations between plankton and chemical variables. Patterns of plankton abundance and diversity were noted with respect to both pH and nutrient status, with occasionally conflicting effects of these two factors. Phytoplankton abundance was most closely associated with nutrient status, while zooplankton abundance was related to measures of primary production. pH tended to affect plankton diversity more than abundance or standing crop. Several lakes were outliers from overall patterns, with several possible explanations. Cluster and factor analyses were used to identify associations of plankton species, and to relate these associations to lake characteristics. Certain species were noted with relatively wide distribution, but which never occurred at low pH (<4.6). These were Chroococcus limneticus, Asterionella formosa, Cyclotella meneghiniana, Pinnularia braunii, and Surirella robusta for phytoplankton, and Polyphemus pediculus, Diaptomus oregonensis, and Tropocyclops prasinus for zooplankton.  相似文献   

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