Distribution of cadmium and lead in a stream ecosystem

Cadmium and lead were detected in all components of the stream that were examined. Cadmium was present in similar concentrations in both fishes and sediments. Aquatic insects, however, exhibited higher concentrations of cadmium than did sediments. Lead concentrations in sediments and aquatic insects were similar, but higher than concentrations in fishes. Snails contained the highest level of lead and had noticeably greater amounts of the metal than did aquatic insects. In general, concentrations of both metals increased successively from water to fish to sediments to aquatic invertebrates.     

Zooplankton,and related phytoplankton cycles,in a eutrophic lake

The seasonal cycles of zooplankton were determined for 18 consecutive months in a sewage-enriched lake in northern Canada and were related to algal availability and utilization, food consumption, temperature and the density of predators. Most of the common species (Daphnia pulex, Daphnia middenorffiana, Keratella cochlearis, Keratella quadrata, Polyarthra vulgaris) increased in abundance in May and June, reached a mid-summer maximum, and declined sharply in the fall. Phytoplankton densities increased sharply in May, peaked early in June and gradually decreased through the summer and fall. Since the quantity of algae in the guts remained constant during this period, algal availability and utilization had no direct impact on the seasonal cycles of any species. Furthermore, the amount of ingested material in D. pulex and D. middendorffiana was similar regardless of time of year, implying that the total quantity of food in the environment did not restrict development. Although temperature was the most important factor influencing variations in the densities of all species, predation by Cyclops spp. probably had little effect on the population dynamics of the fauna.     

Benthic nutrient fluxes in a eutrophic,polymictic lake

Sediment release rates of soluble reactive phosphorus (SRP) and ammonium (NH₄) were determined seasonally at three sites (water depth 7, 14 and 20 m) in Lake Rotorua using in situ benthic chamber incubations. Rates of release of SRP ranged from 2.2 to 85.6 mg P m⁻² d⁻¹ and were largely independent of dissolved oxygen (DO) concentration. Two phases of NH₄ release were observed in the chamber incubations; high initial rates of up to 2,200 mg N m⁻² d⁻¹ in the first 12 h of deployment followed by lower rates of up to 270 mg N m⁻² d⁻¹ in the remaining 36 h of deployment. Releases of SRP and NH₄ were highest in summer and at the deepest of the three sites. High organic matter supply rates to the sediments may be important for sustaining high rates of sediment nutrient release. A nutrient budget of Lake Rotorua indicates that internal nutrient sources derived from benthic fluxes are more important than external nutrient sources to the lake.     

5'-nucleotidase activity in a eutrophic lake and an oligotrophic lake

Differences in enzymatic hydrolysis of dissolved organic phosphorus and subsequent phosphorus uptake were compared by using dual-labeled (gamma-P and 2-H) ATP in oligotrophic Lake Michigan and a moderately eutrophic lake in southeastern Michigan. More than 50% of the phosphate that was hydrolyzed was immediately taken up into bacterium-sized particles in the eutrophic lake and at a near-shore site in Lake Michigan. Less than 50% of the hydrolyzed phosphate was taken up into bacterium-sized particles at an offshore site in Lake Michigan. It is hypothesized that differences in size-fractionated uptake were the result of greater phosphorus utilization capacity in bacteria in habitats where loading of organic carbon is greater. Substantial isotope dilution of labeled phosphate uptake by unlabeled phosphate occurred, which implied that the phosphate was hydrolyzed extracellularly in both systems. Comparable nucleotidase activities were measured in the eutrophic lake and Lake Michigan, but the significance of the phosphate regenerated relative to particulate phosphorus pools was an order of magnitude greater in Lake Michigan. Seventy percent of the nucleotidase activity was inhibited by 100 muM phosphate in the eutrophic lake, which suggests that most hydrolysis was by phosphatase. Therefore, nucleotidase activity may be more important to phosphorus regeneration in oligotrophic habitats than phosphatase activity.     

Biosorption of lead, cadmium and mercury by immobilized Microcystis aeruginosa in a column

Immobilized Microcystis aeruginosa in a flow-through sorption column was evaluated for the potential to remove Pb²⁺, Cd²⁺ and Hg²⁺ from aqueous solutions. M. aeruginosa showed high affinity for the three heavy metals with removal efficiency of 90% for Cd²⁺ and Hg²⁺, and 80% for Pb²⁺ at saturation conditions. Competitive sorption experiments conducted in paired and ternary systems indicated that Pb²⁺ was sequestered preferentially over Cd²⁺ and Hg²⁺. The presence of Cd²⁺ interfered only slightly with the uptake of Hg²⁺, as Pb²⁺ and Hg²⁺ did with Cd²⁺. In contrast, Hg²⁺ sorption was affected by Pb²⁺ to a great extent. Desorption with 1 M HCl was completed within 25 min with high efficiency and effectiveness for the three metals. The results of this study indicate that M. aeruginosa is to be a potential biosorbent material except when Hg²⁺ and Pb²⁺ are in the same contaminated solution.     

Alcian Blue-stained particles in a eutrophic lake

We used a neutral solution of Alcian Blue to stain transparentparticles in eutrophic Lake Frederiksborg Slotss0, Denmark.Alcian Blue-stained particles (ABSP) appeared to be similarto the so-called transparent exopolymer particles (TEP) identifiedwith an acidic solution of Alcian Blue. Our results on the abundance,size distribution and bacterial colonization of ABSP thereforereflect general patterns of TEP. The abundance of ABSP in thesize range 3–162 µm and retained by 3mu;m pore sizefilters averaged 3.62.4910⁵ ml^–1 (SD), which is amongthe highest concentrations reported for comparable size spectraof TEP. On average, 35 % of ABSP (by number) were colonizedby bacteria and 8.610⁵ bacteria ml^–1 lake water wereattached to ABSP, which corresponds to 7% of the total bacterialabundance.     

Blood and placental concentrations of cadmium, lead, and mercury in mothers and their newborns

Placental transfer of cadmium, lead and mercury was studied under the conditions of environmental exposures of pregnant women to these heavy metals. Fifty pregnant women from industrial area and a similar control group from a semirural area were examined. Cadmium, lead and total mercury levels were determined in maternal erythrocytes and plasma, in placenta, and in erythrocytes and plasma of umbilical cord blood using atomic absorption spectrophotometry. Except for the cadmium plasma concentration in the control area, levels of the three metals were higher in maternal than in cord blood. The mean plasma values (arithmetic mean) of cadmium, lead, and mercury in industrial area were 0.53, 6.37, and 0.37 micrograms.100 ml-1 in maternal blood and 0.30, 4.82, and 0.31 micrograms.100 ml-1 in cord blood. Highest values of the correlation coefficients were found between the cadmium and mercury concentrations in maternal and cord blood erythrocytes. No striking effect of the place of residence of pregnant women on the heavy metal concentrations in biological materials could be found.     

Endogenic development of sediments in a eutrophic lake

Sedimentation in the Gouet reservoir (France), measured for 2 years at 8 stations, was maximal during summer, when river inputs were minimal. Physical and chemical conditions in the deposits indicate that the endogenous part of sedimentation was about 70% and resulted from significant diatom production. The high sedimentation rate on the bottom was favoured by the funnel morphology of the reservoir, the chronic lack of oxygen in the water column, and the repeated copper sulfate treatment. The former river meanders of the reservoir were the preferential deposit sites.     

Report on the levels of cadmium, lead, and mercury in imported rice grain samples

In an attempt to know whether highly consumed food might contribute to metal exposure, we analyzed cadmium, lead, and mercury in 27 rice grain samples commonly consumed in Saudi Arabia by atomic absorption spectrometry after acid digestion. The mean concentrations and ranges of cadmium, lead, and mercury in tested rice samples were 20.261 (range <DL-178.026 μg/kg), 134.819 (range 23.1–1529.0 μg/kg), and 3.186 (range <DL-43.573 μg/kg), respectively. The results showed high concentrations of metals and in some cases exceeded the Provisional Tolerance Weekly Intake (PTWI) recommended by FAO/WHO. It was also noted that different rice grain samples had varying concentrations of these metals. Because the bulk of literature warns against the cumulative effects of prolonged heavy metal exposure, regular consumption of rice by local populations might pose potential health problems.     

Detoxification of mercury, cadmium, and lead in Klebsiella aerogenes NCTC 418 growing in continuous culture

Klebsiella aerogenes NCTC 418 growing in the presence of cadmium under glucose-, sulfate-, or phosphate-limited conditions in continuous culture exhibited sulfide formation and Pi accumulation as the only demonstrable detoxification mechanisms. In the presence of mercury under similar conditions only HgS formation could be confirmed, by an increased sensitivity to mercury under sulfate-limited conditions, among others. The fact that the cells were most sensitive to cadmium under conditions of phosphate limitation and most sensitive to mercury under conditions of sulfate limitation led to the hypothesis that these inorganic detoxification mechanisms generally depended on a kind of "facilitated precipitation". The process was coined thus because heavy metals were probably accumulated and precipitated near the cell perimeter due to the relatively high local concentrations of sulfide and phosphate there. Depending on the growth-limiting nutrient, mercury proved to be 25-fold (phosphate limitation), 75-fold (glycerol limitation), or 150-fold (sulfate limitation) more toxic than cadmium to this organism. In the presence of lead, PbS formation was suggested. Since no other detoxification mechanisms were detected, for example, rendering heavy metal ions innocuous as metallo-organic compounds, it was concluded that formation of heavy metal precipitates is crucially important to this organism. In addition, it was observed that several components of a defined mineral medium were able to reduce mercuric ions to elemental mercury. This abiotic mercury volatilization was studied in detail, and its general and environmental implications are discussed.     

Contamination of breast milk with lead,mercury, arsenic,and cadmium in Iran: a systematic review and meta-analysis

BioMetals - Breast milk is a complete food for the development of the newborn, but it can also be an important route for environmental pollutants transmission to the infants. This study was aimed...     

The plankton community of a young, eutrophic, Antarctic saline lake

A shallow, saline lake (Rookery Lake) close to the sea and surrounded by a penguin rookery was investigated during the austral spring and summer of 1996/1997. The proximity to the sea means that the lake is likely to have been formed recently during isostatic uplift. Inputs of carbon and nutrients from the penguin rookery have rendered Rookery Lake eutrophic compared with other brackish and saline lakes in the Vestfold Hills. Chlorophyll a concentration, bacterioplankton, heterotrophic nanoflagellate and phototrophic nanoflagellate abundances were all significantly higher than in other non-enriched lakes. The high productivity created seasonal anoxia during winter and spring below ice cover. The ciliate community resembled the marine community, and was dissimilar to that seen in older saline lakes within the Vestfold Hills. Thus Rookery Lake provides valuable evidence of the impact of natural eutrophication on an Antarctic lake, as well as of the evolution of the typical microbial community which dominates the older lakes of the Vestfold Hills. Accepted: 2 May 1999     

Macromolecular interactions with cadmium and the effects of zinc,copper, lead,and mercury ions

Interactions of cadmium (Cd) ions with bovine serum albumin (BSA), bovine hepatic metallothionein (MT), calf thymus histone and deoxyribonucleic acid (DNA), and bovine hepatic chromatins were studied in the presence and absence of divalent zinc (Zn), copper (Cu), mercury (Hg), or lead (Pb) ions, using equilibrium dialysis at pH 7 and at 37°C. The BSA had 3.5 Cd-binding sites with an apparent affinity constant of 1×10⁵. The other metal ions inhibited the binding by reducing the affinity constant and the number of Cd-binding sites in BSA. There were 6 high affinity and 13 low affinity Cd-binding sites in the MT. Zinc ions had poor efficacy in reducing the binding of Cd to the MT. However, the Cu²⁺ and Hg²⁺ ions inhibited the Cd binding to a considerable extent, the former ions being more potent in this respect. Histone did not bind Cd. There were two kinds of Cd-binding sites in DNA: One mole of Cd per four moles DNA-phosphorus at low affinity sites, and one mole of Cd per 6.7 moles DNA-phosphorus at high affinity sites. Their apparent association constants were 8.3×10⁵ and 4.4×10⁶ M, respectively. The other metal ions had inhibitory effects on the binding of Cd to DNA. Histone reduced the Cd-DNA interactions to only a minor extent. The other metal ions reduced the binding of Cd to DNA-histone complex to a small extent. Cadmium binds to the euchromatin (Euch), heterochromatin (Het), and Euch-Het mixture almost equally. The other metal ions reduced the binding maximally in Euch-Het followed next in order by Het and Euch. Cupric ions were the most potent inhibitors of the interactions of Cd with the nuclear materials.     

Vertical and seasonal distributions of micro-organisms,zooplankton and phytoplankton in a eutrophic lake

The vertical distributions of bacteria, picoalgae,protozoan and metazoan zooplankton, and phytoplanktonin the highly eutrophic Lake Köyliönjärvi(SW Finland) were studied monthly during the period ofice-cover in January-April 1996. For comparison, wealso provide some data on the distributions of theplankton during the summer. The whole watercolumn remained oxic during the ice-covered period,although the near-bottom oxygen concentrations werealways very low. The heterotrophic nanoflagellateswere more abundant in winter than in summer, butciliates, picoalgae and bacteria were more numerous insummer. In general both zooplankton and phytoplanktonhad low biomass during the ice-covered period.However, the biomass of the diatom Aulacoseiraislandica ssp. islandica was high under the icein April. The calanoid copepod Eudiaptomusgraciloides was the dominant zooplankton species fromJanuary to March, but had almost disappeared by thebeginning of April and did not increase again until inJune. The dominant rotifer species in winterwere Keratella cochlearis, Filinia terminalis,and Filinia longiseta in the surface water andRotaria neptunia near the bottom.     

Dynamic status of primary production in lake yunoko,a small eutrophic subalpine lake in central Japan

Investigation was made of the primary productivity of Lake Yunoko. The concentrations of PO₄-P and NH₃-N were highest in summer. The total amount of chlorophylla in the entire water column varied from 45 mg/m² to 405 mg/m² during the year with the maximum values occurring in late spring and in December. These values are very high compared with those reported for other lakes in the same district. The standing crop of phytoplankton as organic carbon was approximately 50∼70% of the total particulate organic carbon in the lake with values as high as 80∼90% being obtained in the spring and autumn. The rate of phytosynthesis under saturated light conditions was 3.7 mg C/mg chla/hr in the case of phytoplankton of the sun type and 1.2∼1.6 mg C/mg chla/hr in those of the shade type. The daily gross primary production in the lake varied from a low of 134 mg C/m² to a high of 1,003 mg C/m² during the year, the mean value being 372 mg C/m². The total amount of daily microbial respiration varied from 177 mg C/m² in winter to 1,476 mg C/m² in summer. Thus, the daily balance of production and consumption of organic matter in the lake itself was concluded to be negative. The main factor contributing to the rectification of this imbalance of material budget seems to be the leaf litter coming from the forest surrounding the lake. In conclusion, Lake Yunoko is a very productive and at the same time, fairly heterotrophic lake. Special Project Research supported by the Ministry of Education on Dynamic State of Biosphere. This study was carried out as part of JIBP-PF.     

The hypolimnetic protozoan plankton of a eutrophic lake

The seasonal distribution of benthic species in the water column above and below the thermocline in a small eutrophic lake is described. During summer stratification populations of Spirostomum spp, Loxodes spp., Plagiopyla and Deltopylum become established in the plankton on or below the oxycline/thermocline. At shallow sites no migration occurred and populations of the migratory species in the benthos were sparse, with the exception of Plagiopyla which occurred in high densities in the sediment. Two distinct planktonic populations are established during stratification: an epilimnetic community of obligate planktonic ciliates and a hypolimnetic community of benthic migrants.     

Zooplankton grazing on bacteria and cyanobacteria in a eutrophic lake

During in situ experiments in a cyanobacteria- and copepod-dominatedeutrophic subtropical lake, all taxa of protozoa and metazoanzooplankton grazed fluorescently labelled bacteria and all metazoanzooplankton taxa grazed large filamentous and colonial cyanobacteria.     

Detoxification of mercury, cadmium, and lead in Klebsiella aerogenes NCTC 418 growing in continuous culture.

Klebsiella aerogenes NCTC 418 growing in the presence of cadmium under glucose-, sulfate-, or phosphate-limited conditions in continuous culture exhibited sulfide formation and Pi accumulation as the only demonstrable detoxification mechanisms. In the presence of mercury under similar conditions only HgS formation could be confirmed, by an increased sensitivity to mercury under sulfate-limited conditions, among others. The fact that the cells were most sensitive to cadmium under conditions of phosphate limitation and most sensitive to mercury under conditions of sulfate limitation led to the hypothesis that these inorganic detoxification mechanisms generally depended on a kind of "facilitated precipitation". The process was coined thus because heavy metals were probably accumulated and precipitated near the cell perimeter due to the relatively high local concentrations of sulfide and phosphate there. Depending on the growth-limiting nutrient, mercury proved to be 25-fold (phosphate limitation), 75-fold (glycerol limitation), or 150-fold (sulfate limitation) more toxic than cadmium to this organism. In the presence of lead, PbS formation was suggested. Since no other detoxification mechanisms were detected, for example, rendering heavy metal ions innocuous as metallo-organic compounds, it was concluded that formation of heavy metal precipitates is crucially important to this organism. In addition, it was observed that several components of a defined mineral medium were able to reduce mercuric ions to elemental mercury. This abiotic mercury volatilization was studied in detail, and its general and environmental implications are discussed.