Cadmium,copper and lead in aquatic macrophytes in Shoal Lake (Manitoba-Ontario)

Cadmium, copper and lead concentrations were surveyed in several species of submerged aquatic macrophytes in a Precambrian Shield Lake. Values were variable within each species and interspecific differences in metal concentration were not significant over the season as a whole. Cadmium concentration increased during the season in Potamogeton foliosus and Myriophyllum exalbescens, while copper and lead declined in P. foliosus. No identifiable seasonal trends were seen in P. zosteriformis and P. robbinsii. In P. foliosus, copper and lead concentrations increased with water depth. Few significant correlations were found between metal concentrations in the shoots and each of several water chemistry parameters, temperature, and shoot chlorophyll, soluble sugar and starch content. Roots yielded greater metal concentrations than shoots.     

Likely effects of salinity on acute copper toxicity to the fisheries of the lake George-Edward basin

Alkaline, saline waters are common in the Western Rift Valley of East Africa, in which the lake George-Edward basin is situated. A growing copper mining industry in the area makes it important to understand the limnology of the lakes in this basin before copper pollution occurs. The fish could possibly suffer from acute (or chronic) toxicity if copper levels increase.Abiotic factors within the alkaline, saline waters of this basin reduce the acute toxic effects of copper to fish. The most important factor is salinity, which is a measure of the total dissolved mineral salts. The relatively highly concentrations of mineral salts of these waters will to reduce the effective copper ionic activity through adsorption, precipitation, and ionic interference. The high concentrations of organic compounds in the waters, also complex and chelate the ionic Cu²⁺, thus reducing further its effective concentration. This will therefore act as a check on the copper toxicity to the fish of the lake basin.     

Effect of sublethal concentrations of copper on the growth performance of Oreochromis niloticus

The study evaluated the effect of different sublethal concentrations of copper in water (0, 0.15, 0.3 and 0.5 p.p.m.) on the behavioural response, growth performance, and whole body and liver composition of Oreochromis niloticus. Hyperactivity and reduced exploratory behaviour were observed when fishes were subjected to different levels of copper in water as compared with the control. Fish refused to accept the feed immediately after exposure and only began taking it up after about 4–5 h as compared with the control. Weight gain, specific growth rate and condition factor (k) decreased significantly (P < 0.05) as compared with the control; this decrease was linearly correlated with the increase of copper concentration in water. Exposure of the fish to different copper concentrations in water significantly (P < 0.05) reduced their feed consumption as compared with the control. Values for the feed conversion ratio increased (P < 0.05) whereas the protein efficiency ratio and net protein retention values decreased (P < 0.05) with the copper level increase in water. The hepatosomatic index increased with the copper concentration increase in water. Body moisture and ash contents were the highest (P < 0.05) whereas the fat and gross energy contents were the lowest (P < 0.05) in fish reared in water containing 0.5 p.p.m. of copper as compared with others. No significant (P < 0.05) differences were observed in the whole body crude protein content of fish exposed to different concentrations of copper as compared with the control. Liver moisture and ash contents increased (P < 0.05) whereas the crude protein, fat, nitrogen free extract and gross energy contents decreased (P < 0.05) when the fish were exposed to different concentrations of copper as compared with the control. The liver glycogen level decreased whereas the copper level in the whole body and liver increased significantly (P < 0.05) with the copper concentration increase in water.     

Evidence for the role of copper in the injury process of coliform bacteria in drinking water

Low levels of copper in chlorine-free distribution water caused injury of coliform populations. Monitoring of 44 drinking water samples indicated that 64% of the coliform population was injured. Physical and chemical parameters were measured, including three heavy metals (Cu, Cd, and Pb). Copper concentrations were important, ranging from 0.007 to 0.54 mg/liter. Statistical analyses of these factors were used to develop a model to predict coliform injury. The model predicted almost 90% injury with a copper concentration near the mean observed value (0.158 mg/liter) in distribution waters. Laboratory studies with copper concentrations of 0.025 and 0.050 mg/liter in an inorganic carbon buffer under controlled conditions of temperature and pH caused over 90% injury within 6 and 2 days, respectively. Studies of the metabolism of injured Escherichia coli cells indicated that the respiratory chain is at least one site of damage in injured cells.     

Evidence for the role of copper in the injury process of coliform bacteria in drinking water.

Low levels of copper in chlorine-free distribution water caused injury of coliform populations. Monitoring of 44 drinking water samples indicated that 64% of the coliform population was injured. Physical and chemical parameters were measured, including three heavy metals (Cu, Cd, and Pb). Copper concentrations were important, ranging from 0.007 to 0.54 mg/liter. Statistical analyses of these factors were used to develop a model to predict coliform injury. The model predicted almost 90% injury with a copper concentration near the mean observed value (0.158 mg/liter) in distribution waters. Laboratory studies with copper concentrations of 0.025 and 0.050 mg/liter in an inorganic carbon buffer under controlled conditions of temperature and pH caused over 90% injury within 6 and 2 days, respectively. Studies of the metabolism of injured Escherichia coli cells indicated that the respiratory chain is at least one site of damage in injured cells.     

Iron and copper in Plagioscion squamosissimus (Piscis: Sciaenidae) from the Orinoco river, Venezuela

Bauxite explotation of the Orinoco River in recent years is an important source of heavy metals discharge in the ecosystem, changing the natural biochemical flow of these elements and their concentrations in water, sediment and organisms. Iron and copper concentrations were measured in the fish Plagioscion squamosissimus in the Orinoco river, by sampling the fish population for three months (September-November 1998) in the main channel of the middle Orinoco (07 degrees 38' 21.2" N; 66 degrees 19' 10.9" W) and in Castillero lagoon (7 degrees 39' 09" N; 66 degrees 09' 00" W) with 2 and 4 cm mesh sizes. The internal organs of 30 fishes per month and site were stove-dried at 80 degrees C, pulverized and dried in disecator for 30 min to use as indicators with the acid digestion method for predicting the effect of heavy metals. We found relatively high values of iron and copper concentrations in fishes of the lagoon, and high seasonal variations in the iron concentration.     

沉水植物菹草在低温条件下对重金属Cu、Pb、Zn的吸附和富集

在10℃的较低温度条件下,研究了冬春季节生长旺盛的沉水植物菹草(Potamogeton crispus L.)对重金属离子Cu²⁺,Pb²⁺,Zn²⁺的生物吸附特征及解吸情况,对不同初始浓度重金属水体中的重金属离子去除率情况,以及在此过程中菹草各器官(叶、茎、根茎、根)对重金属离子的富集情况。结果表明,菹草对Cu²⁺,Zn²⁺的吸附在20 min内达到平衡,对Pb²⁺的吸附在50 min内达到平衡,吸附动力学结果符合伪二级动力学方程,决定系数分别达1,1,0.997 8。Freundlich等温线可较好地拟合菹草吸附Cu²⁺,Pb²⁺,Zn²⁺的过程,Cu²⁺,Pb²⁺,Zn²⁺的吸附容量分别达到66.900 6,26.543 0,30.371 8 mg·L^-1。以去离子水作洗脱剂,解吸液中3种重金属离子浓度均低于仪器检出限(0.01 mg·L^-1),解吸程度微弱。投放菹草后,随着初始处理浓度的升高,水体Cu²⁺的去除率先降低后升高,Pb²⁺的去除率的变化趋势与Cu²⁺类似。Zn²⁺去除率则随水体Zn²⁺初始浓度的升高而逐渐升高。菹草各器官对水体3种重金属离子的富集能力不同,排序为Cu²⁺＞Zn²⁺＞Pb²⁺。不同器官对同一种重金属离子的富集量差异显著,叶是富集重金属离子的主要器官。水体重金属离子的初始浓度会影响菹草各器官富集重金属离子的能力,一般随水体重金属初始浓度升高,菹草各器官的重金属离子富集量虽有不同程度的增加但富集系数持续减小。     

牛组织重金属含量与饲养环境的相关性

通过选择不同污染程度的区域进行取样,分析了贵州地区不同污染水平下牛组织中重金属(Cu、Zn、Pb、Cd)的含量和与饲养环境的相关性.结果表明:贵州不同污染水平下牛组织中的Cu、Zn基本符合国家食品卫生要求,Pb只有污染地区的肝脏和肾脏超过限量标准,Cd污染较严重,除非污染区肝脏外,牛肾脏和肝脏中Cd的平均含量均超过国家肉类制品卫生限量标准,但肌肉组织符合卫生标准;牛组织重金属元素含量与饲养环境中的土壤、饲料和饮用水源的重金属含量和污染程度密切相关,尤其是肾脏组织,其相关系数r＞0.78.饲料向牛组织的重金属迁移系数,随饲料元素含量的增加而逐渐降低,其中Cd的迁移系数最大,Pb的迁移系数最低;必需元素和有害元素在不同组织中的比值,随污染程度的增加而降低.肾脏的Cu/Cd和Zn/Cd值比其它组织低得多,Cd主要在肾脏中蓄积,Cu主要在肝脏组织蓄积,Zn主要在肌肉和肝脏,Pb主要在肾脏和肝脏.     

Spatially variable effects of copper on sessile invertebrates across a marina

Heavy metals often occur at elevated concentrations in bays and estuaries surrounded by urbanised areas and can cause substantial ecological changes to marine communities. The toxic effect of heavy metals can be modified by a several physico-chemical processes in the marine environment. These processes can vary greatly over small scales, so it is likely that the ecological effects of heavy metals on marine biota also vary substantially over similar spatial scales. We used a manipulative field experiment to assess the spatial variation in the effect of copper on sessile invertebrates within a marina and tested whether this variation was influenced by variation in localised water flow. Effects of copper were not consistent over relatively small spatial scales (i.e. metres) for all sessile invertebrate species. Three of the twenty sessile invertebrates from our experimental assemblages showed significant small scale variation in the effect of copper at the scale of metres. For these taxa, the effect of copper varied in magnitude and direction. We had predicted that the effect of copper would diminish with increased water flow, but this did not occur for any taxa. We suggest that variations in the presence of organic or inorganic compounds or in pH within the marina may provide alternative explanations for the spatially variable effects detected in this study. Our study's findings highlight the need for future field assessments of the complex physical, chemical and biological influences on the ecological effects of heavy metals, particularly at small spatial scales. Such studies are the key to improving our prediction about the effects of heavy metals on marine organisms and aid in better characterisation of the risk of heavy metals in the marine environment.     

Copper contamination in the Patuxent River,Maryland

Copper contamination was studied in the Patuxent River, Maryland, which flows from the western shore of the Chesapeake Bay. The only heavy industry on this river is a coal-fired power plant situated 35 km from the river mouth. The plant uses river water for cooling purposes and had been implicated in early studies as a source of localized copper pollution from copper: nickel condenser tubing. Average cooling water usage exceeded average natural river flow over the study period by a factor of 3. This investigation showed high levels of both dissolved and particulate copper at this point source, with a high ratio of particulate: dissolved copper at the point of discharge. A copper budget achieved through comparison of industrial intake/outflow data showed that when natural river flow was considered, output from this single point source could conservatively account for a total copper concentration in the river of 6.7 g 1^–1 above background. This considerably exceeded the measured figure of 2.6 g 1^–1 (relative to the upstream station). Part of this discrepancy was probably due to copper deposition close to the power plant. Although copper concentrations declined downstream from this source, they still remained high in absolute terms and were comparable with a much more heavily industrialized river system. Even at the river mouth, copper concentration remained elevated and it was speculated that anti-fouling paints associated with heavy recreational boat traffic may be particularly responsible for this.     

Effects of silt loading on the feeding and mortality of the mysid Mesopodopsis africana in the St. Lucia Estuary, South Africa

Mesopodopsis africana is an abundant zooplankton species in the currently drought stricken St. Lucia Estuary. The estuary is freshwater-starved, partly because its connection with the large Mfolozi catchment has been discontinued. This is due to the extremely high silt load carried by its waters. A series of in vitro experiments were conducted in May, July, August and December 2006, in order to determine the effect of silt loading on the feeding rate and mortality of M. africana. Mysids were subjected to different sediment concentrations in controlled experiments for a 12-hour period. The turbidity regimes were generated by adding pre-weighed silt concentrations, ranging from 0.03 g/L to 13 g/L, to natural estuarine water. Results in all cases showed a major effect of high silt levels upon food availability, as water chlorophyll losses increased with increased silt concentration. Hindrance in the food collecting abilities appears to have a compounding influence as on two occasions, May and August, ingestion rates decreased with an increase in silt concentration. However, in July, mysid ingestion and clearance rates were higher under increased suspended silt concentrations. In such cases, mysids may be clearing more water under conditions of low food concentration, or alternatively, they may switch to feeding on metazoan prey. In the December experiment, there was no relationship between ingestion rate and silt concentration, possibly because food supplies were sufficient to sustain constant ingestion rates or because mysids increased their clearance rates in the more turbid treatments to compensate for any negative effects of silt. Mysid health also declined, with the mean percentage of survivors decreasing consistently with an increase in silt concentration. Results indicate that the overall effect of increased silt load is negative, and subsequently, increased silt loading in the St. Lucia estuary is expected to have detrimental effects on communities of mysids within the estuary.     

Solution chemistry profiles of mixed-conifer forests before and after fire

Solution chemistry profiles of mixed-conifer forests in granitic catchments of the Sierra Nevada were measured for three years before (1987–1990) and three years after (1990–1993) prescribed fire. Wet deposition, throughfall and soil solution samplers were installed in both white-fir and giant-sequoia dominated forest stands underlain by poorly developed inceptisols. Stream water chemistry was monitored as part of an ongoing study of catchment outputs. Calcium, NO ₃ ^– and Cl^– were the major ions in precipitation. Canopy leaching increased mean concentrations of all major ions, especially K⁺ and Ca²⁺. Water flux through the soil occurred largely during spring snowmelt. Forest floor leachate represented the most concentrated solutions of major ions. Interaction with the mineral soil decreased mean concentrations of most species and the average composition of soil solutions closely resembled stream water at baseflow. Bicarbonate alkalinity, Ca²⁺, Mg²⁺, and Na⁺ were enriched in stream water relative to precipitation whereas inputs of H⁺, NH ₄ ⁺ , NO ₃ ^– and SO ₄ ^2– were retained within the catchments.Burning of the forest understory and litter layer increased solute concentrations in soil solution and stream water. Mean soil solution Ca²⁺, Mg²⁺ and K⁺ concentrations increased more than 10 fold, but the relative predominance of these cations was not affected by burning. Sulfate concentration, which was very low in soil solutions of undisturbed stands (<25 mmol_c m^–3), increased more than 100 times following fire. Ammonium concentration exhibited a rapid, short-term increase and then a decrease below pre-burn levels. Changes in soil solution chemistry were reflected in catchment outputs.Corresponding author.     

Landscape Controls on Organic and Inorganic Nitrogen Leaching across an Alpine/Subalpine Ecotone,Green Lakes Valley,Colorado Front Range

Here we report measurements of organic and inorganic nitrogen (N) fluxes from the high-elevation Green Lakes Valley catchment in the Colorado Front Range for two snowmelt seasons (1998 and 1999). Surface water and soil samples were collected along an elevational gradient extending from the lightly vegetated alpine to the forested subalpine to assess how changes in land cover and basin area affect yields and concentrations of ammonium-N (NH₄-N), nitrate-N (NO₃-N), dissolved organic N (DON), and particulate organic N (PON). Streamwater yields of NO₃-N decreased downstream from 4.3 kg ha⁻¹ in the alpine to 0.75 kg ha⁻¹ at treeline, while yields of DON were much less variable (0.40–0.34 kg ha⁻¹). Yields of NH₄-N and PON were low and showed little variation with basin area. NO₃-N accounted for 40%–90% of total N along the sample transect and was the dominant form of N at all but the lowest elevation site. Concentrations of DON ranged from approximately 10% of total N in the alpine to 45% in the subalpine. For all sites, volume-weighted mean concentrations of total dissolved nitrogen (TDN) were significantly related to the DIN:DON ratio (R ² = 0.81, P < 0.001) Concentrations of NO₃-N were significantly higher at forested sites that received streamflow from the lightly vegetated alpine reaches of the catchment than in a control catchment that was entirely subalpine forest, suggesting that the alpine may subsidize downstream forested systems with inorganic N. KCl-extractable inorganic N and microbial biomass N showed no relationship to changes in soil properties and vegetative cover moving downstream in catchment. In contrast, soil carbon–nitrogen (C:N) ratios increased with increasing vegetative cover in catchment and were significantly higher in the subalpine compared to the alpine (P < 0.0001) Soil C:N ratios along the sample transect explained 78% of the variation in dissolved organic carbon (DOC) concentrations and 70% of the variation in DON concentrations. These findings suggest that DON is an important vector for N loss in high-elevation ecosystems and that streamwater losses of DON are at least partially dependent on catchment soil organic matter stoichiometry. Received 26 July 2001; accepted 6 May 2002.     

Temporal variations in metal enrichment in suspended particulate matter during rainfall events in a rural stream

We studied enrichment of heavy metals (V, Zn, Cr, Ni, Cu, Pb, As, Sb, and Cd) in a rural stream of the Kuji River basin in central Japan in suspended particulate matter, and associated transport flux during two rainfall events (in November 2003 and in April 2008). The concentration of heavy metals in suspended particulate matter (SPM) exhibited a distinctive temporal variation, wherein the concentrations decreased with increasing water discharge and then increased as the discharge decreased. Concentration of dissolved metal forms showed a slight increase with scatters around the flow rate peak. Enrichment factors for those metals in the SPM decreased sharply as the flow rate increased, making an obvious concave shaped curve (the November 2003 rainfall event). The metal enrichment factors under low flow conditions had a similarity to those found in atmospheric deposits at a foot of the Kuji River basin, suggesting atmospheric source would contribute to enriching the SPM with those metals in part. Mineralogical analyses and carbon content analysis (the April 2008 rainfall event) of the SPM suggests the SPM matrix became more lithological as the flow rate increased. The changes observed in the matrix are thought to be directly related to progressive changes in metal enrichment within the SPM. Concerning the transport phase of several heavy metals, a dynamic change in transport phase partitioning within a rainfall event was suggested. The present enrichment factor study and the SPM matrix characterization implied the partitioning change is due to an increase in lithologic solids during high flow conditions.     

The effect of copper on osmoregulation in the freshwater amphipod Gammarus pulex

The influence of copper on osmoregulation in the freshwater amphipod Gammarus pulex was determined from the analysis of water permeability, haemolymph sodium concentration, sodium influx and gill Na(+)/K(+) ATPase and Mg(2+) ATPase activity. Exposure to nominal copper concentrations of 100 microg l(-1) or greater caused a significant reduction in both haemolymph sodium concentration and sodium influx within 4 h. Measurements of water permeability, expressed as the half-time of exchange of body water (t(1/2)), excluded structural gill damage as the cause of this fall in haemolymph sodium. Copper at 10 microg l(-1) or above in the assay solution significantly reduced gill Na(+)/K(+) ATPase activity. In contrast gill Mg(2+) ATPase activity was markedly less affected by copper. These differences in enzyme sensitivity were considered with respect to the potential mechanisms of copper toxicity.     

Estimation of nitrate removal by riparian wetlands and streams in agricultural catchments: effect of discharge and stream order

1. Assessment of the role of landscape structures such as buffers is a necessary prerequisite for the sustainable management of water resources in an agricultural setting. 2. We monitored nitrate concentrations during interstorm periods at the outlet of 16 subcatchments of different orders within a catchment of 378 km². We characterised stream network, wetlands, agricultural practices and land cover and identified their relationships with nitrate fluxes and concentrations. 3. Two main factors controlled annual nitrate fluxes: the agricultural nitrogen surplus and the nature of the system comprising the wetland zone and adjoining watercourses. In the latter case, nitrate fluxes were reduced in proportion to the surface area of the riparian wetland and the flowpath distance of fluxes in the stream network. At the scale of the order‐6 stream, 53% of annual nitrate flux during interstorm periods was removed during transfer via the wetland and the river, corresponding to 21.1 kg N ha^?1 per year. 4. The influence of the riparian wetland zone/watercourse system increased during periods of low water level, explaining up to 64% of nitrate concentration variation among locations within the river network, but only 9% during periods of high water level. 5. The buffering role was stronger at higher stream orders, and the dependence on stream order was more apparent at low water level, when we observed mean nitrate concentrations in the order‐6 stream that were 47% lower than observed in order‐2 or order‐3 streams.     

The effect of water deficit and excess copper on proline metabolism in Nicotiana benthamiana

Fluctuation in proline content is a widespread phenomenon among plants in response to heavy metal stress. To distinguish between the participation of water deficit and copper on changes in proline metabolism, potted plants and floating leaf discs of tobacco were subjected to CuSO₄ treatments. The application of copper increased the proline content in the leaves concomitantly with decreased leaf relative water content and increased abscisic acid (ABA) content in the potted plant. Excess copper increased the expression of two proline synthesis genes, pyrroline-5-carboxylate synthetase (P5CS) and ornithine aminotransferase (OAT) and suppressed proline catabolism gene, proline dehydrogenase (PDH). However, in the experiment with tobacco leaf discs floating on CuSO₄ solutions, the excess copper decreased proline content and suppressed the expression of the P5CS, OAT and PDH genes. Therefore, proline accumulation in the potted tobacco plants treated with excess Cu treatment might not be the consequence of the increased copper content in tobacco leaves but rather by the accompanied decrease in water content and/or increased ABA content.     

Blockade of heavy metals accumulation in Chlorella vulgaris cells by 24-epibrassinolide

This study was conducted on the influence of 24-epibrassinolide (24-epiBL) mixed with varying concentrations of heavy metals (copper, lead, cadmium, zinc) upon the growth and accumulation of these heavy metals in the cell of the alga Chlorella vulgaris Beijerinck (Chlorophyceae). Heavy metals at the concentration of 10^–3 M, alone or mixed with 24-epiBL, showed a lethal effect on C. vulgaris. At metal concentrations of 10^–6–10^–4 M, a combination with 24-epiBL appeared to have a stronger stimulatory effect on a number of cells than a single metal (a stronger inhibitory effect). 24-EpiBL at the concentration of 10^–8 M in combination with heavy metals (in the range 10^–6–10^–4 M) blocked metal accumulation in algal cells. 24-EpiBL has an anti-stress effect on C. vulgaris contaminated by heavy metals. The inhibitory effect on metal accumulation of 24-epiBL mixed with different heavy metals was arranged in the following order: zinc > cadmium > lead > copper. This process is correlated with the stimulation of growth of C. vulgaris. The stimulatory effect of 24-epiBL mixed with heavy metals leading to an increased pH in the medium (5.28–6.20) was significantly higher than the impact due to the increased acidity in the medium due to metals alone (pH 3.10–5.85). Lower pH increased the toxicity of heavy metals in C. vulgaris cells.     

TOC fluctuations in a humic lake as related to catchment acidification, season and climate

Studies of fluctuations in total organic carbon (TOC) were performedin both the reference basin and the acidified basin of experimental LakeSkjervatjern, in order to separate effects of various catchment and in-lakeprocesses. Nearly five years of catchment acidification did not inducesignificant changes in TOC. TOC concentrations was not related clearly toprecipitation or runoff. In both basins, there was a regular, seasonal patternwith a gradual increase in TOC concentrations from spring to late autumn.Minima in concentrations occurred during periods with frozen ground inwinter, irrespective of discharge patterns. The decrease from 10 mg C l^-1 in autumn to 1--2 mg C l^-1 in latewinter, was only seen in surface layers. Runoff was the major loss routefor surface TOC in the lake. Photo-oxidation, bacterial oxidation, andsedimentation combined yielded maximum loss rates of 3%of surface TOC d^-1. Below a depth of 1 m 0.5%d^-1 was lost to these same processes. The surface microlayerhad 5--10 times more TOC than the bulk water on average, and could haveeffects on gas exchange and sub-surface light. Despite the oxidation ofTOC, the short residence time of the lake and rapid replacement of TOCfrom the catchment was the major determinant of lake water TOC.     

Cyanophytes and chlorophytes versus raphidophytes in humic lakes with different catchment basins

The aim of the study was to evaluate the effects of coniferous forest cover in the catchment basin and relative catchment area (catchment area to lake volume ratio) on phytoplankton composition in humic lakes. The study was carried out in 11 small and shallow lakes situated in the West Polesie region (Eastern Poland). The lakes were divided with respect to forest cover in their catchment basins into two groups: high forest cover — HFC (more than 60%) and low forest cover — LFC (less than 60%). The study showed that both, land use in the catchments (proportion of forests) and the relative catchment area determined physicochemical and biological parameters in the lakes. The high relative catchment area affects their high productivity expressed by high chlorophyll a concentration and low water visibility. The lakes of the LFC group had low water colour as well as high concentration of total phosphorus (P_tot), reaction (pH), and conductivity of water and a large number of cyanophytes and chlorophytes. The dominant species, e.g., Planktolyngbya limnetica, Limnothrix planctonica, Planktothrix agardhii, Coenococcus planctonicus, were characteristic of high trophic status. In the lakes of the HFC group, P_tot, pH, conductivity of water and the contribution of cyanophytes and chlorophytes was considerably lower, whereas the water colour and the number of raphidophytes represented by Gonyostomum semen was high. The large number of raphidophytes and the small amount of chlorophytes and cyanophytes in the lakes of the HFC group indicated the lake naturalness.