The fauna and distribution of alderfly larvae (Sialidae, Megaloptera) in Northern Fennoscandia and its dependence on natural and anthropogenous factors

The results of a study of alderfly larvae (Sialidae, Megaloptera) from over 400 small lakes and ten large lakes and rivers in Northern Finland, Norway, and Murmansk oblast are presented. The distribution of five species of larvae in relation to the landscape, size of water bodies, hydrological type of water bodies, type of habitats, pH, water color, etc., is considered. Possessing a relatively higher plasticity and tolerance to environmental conditions, Sialis larvae were found more often and made the maximum contribution to the biomass of littoral macroinvertebrate communities in small north taiga and tundra lakes, slow water courses, on soft sediments, in vegetation, in weakly humic waters, and in circumneutral and weakly alkaline waters. High ecological plasticity, including pollution, is found in the larvae of S. morio Klingstedt and S. lutaria L.     

Sulfate control of phosphorus availability in lakes

During summer stratification large amounts of phosphorus (P) accumulate in anoxic bottom waters of many lakes due to release of P from underlying sediments. The availability to phytoplankton of this P is inversely related to the Fe:P ratio in bottom waters. Using data from 51 lakes, we tested the hypothesis that sulfate concentration in lake water may be critical in controlling the Fe:P ratio in anoxic bottom waters. Results showed that Fe:P ratios in bottom waters of lakes were significantly (p<0.001) related to surface water sulfate concentrations. The higher Fe:P ratios in low sulfate systems is due not only to higher iron concentrations in anoxic bottom waters but also to lower P concentrations in anoxic waters. Thus, our results suggest that anthropogenically induced increases in sulfate concentrations of waters (e.g. from fossil fuel burning) may have a double effect on P cycling in lakes. Higher sulfate concentrations can both increase the magnitude of P release from sediments as well as increase the availability of P released from sediments into anoxic bottom waters.     

Dye-coupled electrode system for the rapid determination of cell populations in polluted water.

We determined cell populations in polluted waters by using a fuel cell-type electrode. The electrode was constructed from a platinum anode, a silver peroxide cathode, and a membrane filter for retaining microorganisms. The principle of cell number determination is based on sensing a redox dye reduced by the microorganisms with the electrode. Sample solutions containing microorganisms were membrane filtered, and the resulting filter containing microbial cells was attached to the surface of a platinum anode. The electrode was immersed in phosphate buffer solution (0.05 M, pH 7) containing a redox dye (2,4-dichlorophenol-indophenol), and the current generated was measured. The response time of the electrode system was 10 to 20 min, and the current generated was proportional to cell populations above 10(4) cells/ml.     

The effect of stand age on throughfall chemistry in spruce stands in the Potok Dupniañski catchment in the Silesian Beskid Mountains, southern Poland

The chemical composition of throughfall depends on the age of the Norway spruce (Picea abies Karst) stands and season of the year. The pH of throughfall decreased and the amount of hydrogen ion in throughfall deposited to the soil increased with increasing age of spruce stands, especially in the winter season. Concentrations of K+, H+, SO4(2-), Mn2+, and NH4(+) in throughfall were higher than bulk precipitation for the whole year and K+, H+, and Mn2+ concentrations were higher in throughfall in winter and the growing season. This indicates that these ions were washed out or washed from the surface of needles and/or the bark, and that NO3(-), NH4(+), Ca2+, Mg2+, Fe2+, and Zn2+ were absorbed in the canopy. The effect of high nitrogen deposition, above critical loads, and an increase in the amount of sulfur and in the sum of the strong acids (S-SO4(2-) and N-NO3(-)) that reached the soil with throughfall may have implications for the vitality of spruce stands, especially in older age classes. The application of Principal Component Analysis (PCA) has led to identification of five factors responsible for the data structure ("mineral dust", "acidic emissions", "heavy metals-dust particles", "ammonium [NH4(+)]", and "H+"). They explain more than 60% of the total variance system. The strong positive correlation between stand age class and ionic concentrations in throughfall occurs for all year and the winter period for ions within the following categories: "acidic emissions", SO4(2-) + NO3(-); "heavy metals-dust particles", Fe2+ + Mn2+ + Zn2+; "mineral dust", Na+ + K+ + Ca2+ + Mg2+; "NH4(+)"; and "H+". The strength of the relationship decreases in the growing period, probably due to processes occurring in the canopy (adsorption, leaching, etc.).     

Seasonal dynamics of N in two Sphagnum moss species and the underlying peat treated with 15NH415NO3

Uptake of 15N labelled NH4NO3 by two Sphagnum mosses on a raised bog in north east Scotland was measured at different times of the year. In a field experiment, fortnightly additions of NH4NO3 at natural abundance, equivalent to 3 g N m-2 yr-1, were made over 14 months to cores of Sphagnum capillifolium occupying hummocks and S. recurvum colonizing hollows. Pre-harvested cores were treated with 15NH415NO3 two weeks before harvesting and 15N abundance determined for the total N in the moss, inorganic and dissolved organic N (DON) in the moss water and extractable inorganic, organic and microbial N in the underlying peat. The proportion of added 15N taken up by the mosses two weeks after each addition averaged 72% and ranged between 11 and 100%, tending to be least during October when the rising water table reached the surface, particularly for S. recurvum. A small proportion of the 15N was detected in the moss water as NH4+ (0.01%) and as DON (0.03%) and on occasions a large proportion remained unaccounted for. In waters from S. capillifolium, DON was proportional to the amount of inorganic N added, but this was not the case for S. recurvum. Little or no 15N was detected in the underlying peat partly because of the large size and variability of the NH4+, DON and microbial N pools.     

Spatial variation of redox and trace metal geochemistry in a minerotrophic fen

Pore water and solid phase samples were collected from the upper 50 cm of a peat profile at four sites within a 10 m² area in Kleinstuck Marsh, a minerotropic fen located in Kalamazoo, MI. Although the chosen sites are in close proximity to each other, they differ with respect to vegetation species and density. Pore water analyses for a suite of redox sensitive species (pH, alkalinity, dissolved Mn(II), Fe(II), Fe(III), sulfide, sulfate), together with Fe and Mn distributions inferred from operationally-defined sequential extractions, demonstrate that Fe(III) and Mn(IV) reduction occurs in the shallow peat at three of the four sites. At the fourth site, the only site containing the invasive purple loosestrife (Lythrum salicaria), accumulation of dissolved sulfide in the pore waters and increased levels of oxidizable phases in the shallow peat point to increased net sulfate reduction relative to the other three sites. Speciation calculations indicate that pore water concentrations of phosphate, especially below ∼10 cm depth, are largely controlled by the solubility of phases such as strengite or hydroxylapatite, and that at all but the loosestrife site, dissolved Ca and Mg are likely determined by carbonate solubility. Fe and Mn distribution among operationally defined solid phase fractions are consistent with reductive dissolution of FMO in the uppermost peat, leading to precipitation of Fe sulfides and Mn carbonates deeper in the peat profile. Zn, Co, Cr and Ni distributions are consistent with release from FMO to form sulfides or organic associations deeper in the peat. Pb and Cu may also be released by reductive dissolution of FMO, or more likely, shift from primary association with organic matter to increased association with sulfides under more sulfidic conditions. This study highlights the existence of extreme lateral variations in peat pore water and solid phase geochemical profiles, even over quite small areas.     

A bioelectrochemical polypyrrole-containing Fe(CN)6(3-) interface for the design of a NAD-dependent reagentless biosensor

Ferricyanide ions were immobilized on a platinum electrode surface by means of an electrochemically grown polypyrrole film. The entrapped Fe(CN)6(3-)/Fe(CN)6(4-) redox system displayed a high heterogeneous electron transfer rate. The resulting modified electrode was efficient for the ferricyanide-mediated NADH oxidation catalyzed by a diaphorase. The bioelectrochemical interface was applied to the design of a reagentless amperometric D-lactate biosensor. A weakly polarized two polypyrrole-containing Fe(CN)6(3-) modified electrode system was involved without any reference. An enzymatic solution containing D-lactate dehydrogenase, diaphorase and NAD-dextran was further confined on the sensing electrode using a semi-permeable membrane. The sensitivity and the response time of the reagentless biosensor were similar to those of the analogous sensor working with soluble mediator and cofactor, i.e. 25 microA mM(-1) cm(-2) and 120 s, respectively. The other analytical performances were less satisfactorily: the detection limit was 5 x 10 mmol L(-1) and the linearity range was comprised between 0.1 and 0.5 mmol L(-1).     

金属离子对粪产碱杆菌C16的脱氮和亚硝酸盐积累的影响

【目的】研究不同金属离子对异养氨氧化细菌C16的生长和脱氮性能影响,探讨适于C16生长和脱氮的金属离子及其浓度。【方法】实验选用Mg2+、Mn2+、Fe2+、Cu2+、Zn2+5种金属离子,对C16的生长﹑脱氮性能﹑亚硝酸盐氮积累以及相关酶活性进行研究。【结果】Mg2+明显促进C16的生长和NH4+-N氧化速率;较高浓度Mn2+使得C16无法生长;原培养基中缺少Fe2+会抑制C16的生长和NH4+-N氧化速率;在原培养基中加入0.1 mmol/L的Cu2+对C16的生长和脱氮具有一定的促进作用,Cu2+使得培养基中基本无NO2--N和NH2OH的积累;不同浓度的Zn2+对C16的生长和氨氮去除有抑制作用。酶活实验结果显示,0.1 mmol/L Mg2+促进了羟胺氧化还原酶(HAO)的活性;0.1 mmol/L Cu2+促进了硝酸盐还原酶(Nar)和亚硝酸盐还原酶(Nir)的活性。【结论】Mg2+是C16生长和脱氮过程中的一种重要金属离子;加入Cu2+可避免过量亚硝酸盐积累。     

Functional Groups and Activities of Bacteria in a Highly Acidic Volcanic Mountain Stream and Lake in Patagonia,Argentina

Acidic volcanic waters are naturally occurring extreme habitats that are subject of worldwide geochemical research but have been little investigated with respect to their biology. To fill this gap, the microbial ecology of a volcanic acidic river (pH approximately equal to 0-1.6), Rio Agrio, and the recipient lake Caviahue in Patagonia, Argentina, was studied. Water and sediment samples were investigated for Fe(II), Fe(III), methane, bacterial abundances, biomass, and activities (oxygen consumption, iron oxidation and reduction). The extremely acidic river showed a strong gradient of microbial life with increasing values downstream and few signs of life near the source. Only sulfide-oxidizing and fermentative bacteria could be cultured from the upper part of Rio Agrio. However, in the lower part of the system, microbial biomass and oxygen penetration and consumption in the sediment were comparable to non-extreme aquatic habitats. To characterize similarities and differences of chemically similar natural and man-made acidic waters, our findings were compared to those from acidic mining lakes in Germany. In the lower part of the river and the lake, numbers of iron and sulfur bacteria and total biomass in sediments were comparable to those known from acidic mining lakes. Bacterial abundance in water samples was also very similar for both types of acidic water (around 10(5) mL(-1)). In contrast, Fe(II) oxidation and Fe(III) reduction potentials appeared to be lower despite higher biogenic oxygen consumption and higher photosynthetic activity at the sediment-water interface. Surprisingly, methanogenesis was detected in the presence of high sulfate concentrations in the profundal sediment of Lake Caviahue. In addition to supplementing microbiological knowledge on acidic volcanic waters, our study provides a new view of these extreme sites in the general context of aquatic habitats.     

Isolation and culture conditions of a Klebsiella pneumoniae strain that can utilize ammonium and nitrate ions simultaneously with controlled iron and molybdate ion concentrations

A bacterial strain F-5-2, isolated from soil and identified as Klebsiella pneumoniae, removed NH4+ completely in 24 h of aerobic cultivation in a medium containing 1 mg/ml of NH4NO3. However, 70% of the NO3- originally provided remained. When 100 microM Fe2+ was added to the medium, both NH4+ and NO3- were removed simultaneously and completely from the culture within 6 h of incubation. In addition, the amount of MoO4- in the medium markedly affected the bacterial cell growth and utilization of NH4+ and NO3-. The bacterium could remove 4 mg/ml of NH4NO3 completely in 48 h of aerobic cultivation in a medium containing 100 microM Fe2+ and 0.8 pM MoO4(2-). The total nitrogen in the culture containing its cells was decreased to 14% of that in the NH4NO3 originally provided. GC-MS analysis demonstrated that N2 was generated from the nitrogen atoms of both NH4+ and NO3-.     

Uniform Temperature Dependency in the Phenology of a Keystone Herbivore in Lakes of the Northern Hemisphere

Spring phenologies are advancing in many ecosystems associated with climate warming causing unpredictable changes in ecosystem functioning. Here we establish a phenological model for Daphnia, an aquatic keystone herbivore based on decadal data on water temperatures and the timing of Daphnia population maxima from Lake Constance, a large European lake. We tested this model with long-term time-series data from two lakes (Müggelsee, Germany; Lake Washington, USA), and with observations from a diverse set of 49 lakes/sites distributed widely across the Northern Hemisphere (NH). The model successfully captured the observed temporal variation of Daphnia phenology in the two case study sites (r² = 0.25 and 0.39 for Müggelsee and Lake Washington, respectively) and large-scale spatial variation in the NH (R² = 0.57). These results suggest that Daphnia phenology follows a uniform temperature dependency in NH lakes. Our approach – based on temperature phenologies – has large potential to study and predict phenologies of animal and plant populations across large latitudinal gradients in other ecosystems.     

The influence of pretreatment with different cations on anaerobic nitrite production by excisedPisum sativum roots

The influence of pretreatment with some cations on anaerobic nitrite production (in an assay medium lacking nitrate) by excised primary roots of pea (Pisum sativum L., ov. Raman), detached from six-day-old seedlings germinated in distilled water, was investigated. When the excised roots were precultivated in one-salt-solutions of KNO3, then these roots produced at 9 mM and 15 mM NO3- concentrations under anaerobic conditions significantly more NO2-, than those precultivated in a nutrient solution containing besides K+ ions also Ca2+ and Mg2+ ions, and they produced nitrite for a longer time. The KNO3 dependent increase in anaerobic NO2- production was counteracted most by Ca2+ and to a lesser extent by Mg2+; Na+ was without effect. NH4+ at higher concentrations (12 and 15 mM) significantly depressed nitrite production both by roots precultivated in a solution containing besides NH4+ only K+, and by roots precultivated in a full nutrient solution containing K+, Ca2+ and Mg2+, however at lower NH4+ concentrations (0.6 and 2mMNH4+; 15mMNO3-) the decrease was more conspicuous in the KNO3 solution than in the full nutrient solution. Nitrate reductase level was not influenced by this pretreatment. When 6% and 7.5% n-propanol, which increases membrane permeability and causes mixing of storage and metabolic nitrate pools in the cells, was added to the assay medium lacking nitrate, anaerobic nitrite production increased and the differences caused by the precultivation disappeared. These results show that higher K+ concentrations in unbalanced one-salt-solutions of KNO3 can cause higher membrane permeability by accentuating Ca8+ deficiency, which results in a faster penetration of NO3- from the storage pool to the sites of its reduction and in an easier penetration of NO2- out of the roots, and that higher NH4+ concentrations can change nitrate compartmentation and diminish the metabolic NO3- pool which results in a slower nitrate reduction. Besides that, lower NH4+ concentrations in KNO3 solutions (15mMNO3-) probably partially counteract the K+ dependent increase in membrane permeability. The results obtained show that there is no simple, direct relationship between the so-called metabolic pool of nitrate (i.e. anaerobic nitrite production) and the level of nitrate reductase, but that the velocity of nitrate reduction can be influenced by nitrate compartmentation in the cell.     

The structure and function of fen lakes in relation to water table management in The Netherlands

Most relatively large (> 250 ha) and shallow (< 2 m), Dutch lakes originate from large-scale peat mining. Originally, their water tables were regulated by natural processes such as evapotransporation, precipitation, drainage and seepage (up and downwards). These lakes used to be oligo to mesotrophic, and the phytoplankton consisted mainly of diatoms and green algae. However, 30 years ago filamentous cyanobacteria were also present. Owing to the intensification of agriculture in the surroundings of the lakes, their management developed more and more towards a man-made reservoir function. This management resulted in inflow of eutrophic water from the agricultural areas in winter. In summer the lakes were increasingly used as a water supply. This supply is compensated by water imported mainly from the River Rhine. The impacts of this reservoir function on the limnology of the Dutch fen lakes are discussed with the Tjeukemeer, the Loosdrechtse Plassen and the Reeuwijkse Plassen as examples. All these lakes have become typical eutrophic waters with high turbidity, dominance of filamentous cyanobacteria and bream and complete loss of submerged macrophytes. Finally, methods and results of manipulation procedures to restore these waters are discussed.     

Direct electrochemistry of hemoglobin in dimethyldioctadecyl ammonium bromide film and its electrocatalysis to nitric oxide

Hemoglobin (Hb) was successfully immobilized in dimethyldioctadecyl ammonium bromide (DOAB) film at pyrolytic graphite (PG) electrode. Electrochemical experiments revealed that Hb in DOAB film exhibited a pair of well-defined, quasi-reversible cyclic voltammetric peaks at about -0.160 V versus saturated calomel electrode (SCE) in pH 5.0 buffer, characteristic of the heme Fe(III)/Fe(II) redox couple of Hb. The electron transfer (eT) rate between Hb and the PG electrode was 0.10 s(-1). Positions of the Soret absorbance band indicated that the Hb retained its secondary structure and was similar to its native state. Furthermore, the Hb in DOAB film acted as a biological catalyst towards the reduction of nitric oxide (NO). The voltammetric response of NO at the Hb-DOAB modified electrode could be used to determine the concentration of NO in solution.     

Length–mass relationships for lake macroinvertebrates corrected for back-transformation and preservation effects

Coloured dissolved organic matter (CDOM) modifies the light penetration into water bodies due to stronger absorbance of UV and short wavelengths of light. Therefore, in natural waters with high CDOM concentration, the spectrum of sunlight is shifted towards brown, also referred to as brownification. Here, the relation between the spectrophotometrically measured water colour (CDOM) and landscape properties is examined. These properties explained at best > 40% of the CDOM variability among the study lakes larger than 10 km². The key “permanent” landscape variables were lake percentage (Lake_%) in the uppermost catchment area, and the peat land coverage (Peat_%) of the catchment, which indeed was strongly correlated with lake elevation above the sea level. High Lake % indicated low CDOM concentration, while high Peat_% indicated the opposite. Relative to the Peat_% of the catchment, the CDOM concentrations were, on average, slightly higher in medium-size lakes (area 10–100 km²) than in large lakes (area > 100 km²), while relative to Lake_% the concentrations declined more in medium-size lakes.     

Spectroelectrochemistry of a urea-linked oxo-bridged iron porphyrin dimer

The electrochemical behavior of μ-oxo-N,N-bis- (5-(o-phenyl)-10,15,20-triphenylporphinatoiron(III))- urea mono hydrate, [(FF)Fe]₂0, was investigated at a platinum electrode in both 1,2-dichloroethane and pyridine. In EtCl₂, electroreduction of this oxo-bridged and urea-linked dimer produced a binuclear ferrous hydroxide porphyrin. This latter species could be oxidized to regenerate the μ-oxo dimer in quantitative yield. In pyridine, [(FF)Fe]₂O underwent a chemically irreversible electroreduction producing a hexacoordinate binuclear ferrous porphyrin with pyridine occupying the axial positions of each iron atom. Oxidation of this species also produced the μ-oxo and urea-linked dimer in quantitative yield. These results are in contrast to the redox behavior of [(TPP)Fe]₂O in these solvents. Electron transfer pathways, consistent with voltammetric and spectroelectrochemical results, are proposed for [(FF)Fe]₂O and compared with those found for [(TPP)Fe]₂O. The redox behavior observed for [(FF)Fe]₂O implicates the steric constraint of the urea linkage and hydrogen bonding of the protonated bridging oxygen atom with the amide groups. This marks the first evidence of molecular environmental effects in the redox chemistry of hematin dimers.     

Redox properties of iron-dithiocarbamates and their nitrosyl derivatives: implications for their use as traps of nitric oxide in biological systems

While the Fe(2+)-dithiocarbamate complexes have been commonly used as NO traps to estimate NO production in biological systems, these complexes can undergo complex redox chemistry. Characterization of this redox chemistry is of critical importance for the use of this method as a quantitative assay of NO generation. We observe that the commonly used Fe(2+) complexes of N-methyl-D-glucamine dithiocarbamate (MGD) or diethyldithiocarbamate (DETC) are rapidly oxidized under aerobic conditions to form Fe(3+) complexes. Following exposure to NO, diamagnetic NO-Fe(3+) complexes are formed as demonstrated by the optical, electron paramagnetic resonance and gamma-resonance spectroscopy, chemiluminescence and electrochemical methods. Under anaerobic conditions the aqueous NO-Fe(3+)-MGD and lipid soluble NO-Fe(2+)-DETC complexes gradually self transform by reductive nitrosylation into paramagnetic NO-Fe(2+)-MGD complexes with yield of up to 50% and the balance is converted to Fe(3+)-MGD and nitrite. In dimethylsulfoxide this process is greatly accelerated. More efficient transformation of NO-Fe(3+)-MGD into NO-Fe(2+)-MGD (60-90% levels) was observed after addition of reducing equivalents such as ascorbate, hydroquinone or cysteine or with addition of excess Fe(2+)-MGD. With isotope labeling of the NO-Fe(3+)-MGD with (57)Fe, it was shown that these complexes donate NO to Fe(2+)-MGD. NO-Fe(3+)-MGD complexes were also formed by reversible oxidation of NO-Fe(2+)-MGD in air. The stability of NO-Fe(3+)-MGD and NO-Fe(2+)-MGD complexes increased with increasing the ratio of MGD to Fe. Thus, the iron-dithiocarbamate complexes and their NO derivatives exhibit complex redox chemistry that should be considered in their application for detection of NO in biological systems.     

Regulation of dinitrogenase reductase ADP-ribosyltransferase and dinitrogenase reductase-activating glycohydrolase by a redox-dependent conformational change of nitrogenase Fe protein

The nitrogenase-regulating enzymes dinitrogenase reductase ADP-ribosyltransferase (DRAT) and dinitrogenase reductase-activating glycohydrolase (DRAG), from Rhodospirillum rubrum, were shown to be sensitive to the redox status of the [Fe(4)S(4)](1+/2+) cluster of nitrogenase Fe protein from R. rubrum or Azotobacter vinelandii. DRAG had <2% activity with oxidized R. rubrum Fe protein relative to activity with reduced Fe protein. The activity of DRAG with oxygen-denatured Fe protein or a low molecular weight substrate, N(alpha)-dansyl-N(omega)-(1,N(6)-etheno-ADP-ribosyl)-arginine methyl ester, was independent of redox potential. The redox midpoint potential of DRAG activation of Fe protein was -430 mV versus standard hydrogen electrode, coinciding with the midpoint potential of the [Fe(4)S(4)] cluster from R. rubrum Fe protein. DRAT was found to have a specificity opposite that of DRAG, exhibiting low (<20%) activity with 87% reduced R. rubrum Fe protein relative to activity with fully oxidized Fe protein. A mutant of R. rubrum in which the rate of oxidation of Fe protein was substantially decreased had a markedly slower rate of ADP-ribosylation in vivo in response to 10 mM NH(4)Cl or darkness stimulus. It is concluded that the redox state of Fe protein plays a significant role in regulation of the activities of DRAT and DRAG in vivo.     

Sequence-dependent conformational changes in DNA induced by polynuclear platinum complexes

In this work, the B-->Z transition of poly(dG-dC).poly(dG-dC) and the B-->A transition of poly(dG).poly(dC) and of calf thymus (CT) DNA fragments modified by antitumor bifunctional polynuclear platinum complexes were investigated by circular dichroism (CD). The transition from the B- to Z-form of DNA was inducible with all three compounds studied, as indicated by an inversion of the B-form spectra. The B-->A transition in poly(dG).poly(dC) was induced easily by platinum complex binding alone, while the B-->A transition in CT DNA was induced by ethanol but inhibited by coordination of all polynuclear platinum compounds used here. It was shown that the compound [?cis-PtCl(NH3)2?2 mu-?H2N(CH2)6NH2?] (NO3)2 (1,1/c,c) was most effective at inhibiting the B-->A transition in CT DNA, and [?trans-PtCl(NH3)2?2 mu-?trans-Pt(NH3)2(H2N(CH2)6NH2)2?] (NO3)4 (1,0,1/t,t,t) was least effective, while the effectiveness of [?trans-PtCl(NH3)2?2 mu-?H2N(CH2)6NH2?] (NO3)2 (1,1/t,t) fell between the two. This corresponded to the relative amounts of interstrand crosslinks in double-stranded DNA caused by each compound.