Long-term effects of successive Ca(OH)2 and CaCO3 treatments on the water quality of two eutrophic hardwater lakes

1. Whole-lake experiments were conducted in two hardwater lakes (Halfmoon and Figure Eight) in Alberta, Canada, to investigate the effectiveness of repeated lime (slaked lime: Ca(OH)₂ and/or calcite: CaCO₃) treatments (5–78 mg L^–1) for up to 7 years.
2. Randomized intervention analysis of intersystem differences between the experimental and three reference lakes demonstrated a decline in euphotic total phosphorus and chlorophyll a concentrations in the experimental lakes after repeated lime treatments.
3. After the second lime application to Halfmoon Lake, mean winter total phosphorus release rates (TPRR) decreased to < 1 mg m^–2 day^–1 compared with 3.6 mg m^–2 day^–1 during the winter after initial treatment. In the final year of lime application, mean summer TPRR decreased to 4.5 mg m^–2 day^–1 compared with 7.6 mg m^–2 day^–1 in the pre-treatment year.
4. Mean macrophyte biomass declined and species composition was altered at 1 and 2 m depths in Figure Eight Lake during lime application. Over the first 6 years of treatment, macrophyte biomass at 2 m declined by 95% compared with concentrations recorded during the initial treatment year. In the last year of the study, macrophyte biomass at 2 m reached initial treatment concentrations, which coincided with the greatest water transparency. Over the treatment period, macrophyte species shifted from floating to rooted plants.
5. Multiple lime applications can improve water quality in eutrophic hardwater lakes for periods of up to 7 years.     

Effects of single Ca(OH)2 doses on phosphorus concentration and macrophyte biomass of two boreal eutrophic lakes over 2 years

1. Two hardwater eutrophic lakes of central Alberta were subjected to single doses of Ca(OH)₂ (74 or 107 mg L^–1). The effects of lime treatment on phosphorus (P) precipitation, sediment P release, and macrophyte biomass were assessed for up to 2 years.
2. In both lakes, sediment P release was reduced to 16 and 27%, respectively, of pre-treatment values by the first winter following treatment. However, sediment P release returned to pre-treatment values during the following year.
3. In contrast to these short-term effects, macrophyte biomass decreased by as much as 80% after lime application and remained there for at least 2 years.
4. Our results indicate that a single dose of Ca(OH)₂ may give short-term (< 1 year) control of P and long-term control (> 1 year) of macrophytes in hardwater eutrophic lakes of Alberta.     

Lime treatment and its effects on the chemistry and biota of hardwater eutrophic lakes

1. The main focus of this study was to investigate the effects of single and multiple moderate doses of lime (slaked lime, Ca(OH)₂, and/or calcite, CaCO₃) on eutrophic hardwater lakes. This information would contribute to strategies to manage phytoplankton and macrophyte biomass in eutrophic lakes.
2. Water chemistry and biota were monitored for up to 7 years after initial lime treatment and results were compared with reference systems.
3. Complementary studies investigated the effect of lime on macrophytes in ponds, irrigation canals and microcosm experiments.
4. When water pH was kept within its natural range (≤ 10), single and multiple lime applications to lakes and ponds controlled macrophyte biomass, without negatively affecting invertebrate communities.
5. Single lime treatments at moderate dosages of lakes and ponds resulted in variable and mostly temporary changes in chlorophyll a (chl a ) and phosphorus (P) concentration. Although sediment P release was reduced in single-dose lakes during the first winter following treatment, reductions appeared temporary.
6. Multiple treatments of lakes and ponds were effective at reducing both chl a and P concentrations over longer periods. Mean winter P release rate was also reduced after initial treatment.
7. In laboratory studies, sediment cores were incubated with eight different treatments to assess P release. Redox-sensitive treatments were no more effective at lowering total P concentration in overlying water than some redox-insensitive treatments. Lime reduced total P concentrations, but was not as effective as treatments with alum.
8. The use of lime in managing macrophyte and phytoplankton biomass in shallow, hardwater lakes and ponds may be preferable over other treatments, because lime is economical and non-toxic as long as pH is kept within a natural range.     

Polyaluminum chloride-enhanced concentration efficiency of poliovirus and f2 phage from sewage water

Aims:  To enhance the recovery of f₂ bacteriophage and poliovirus by an established method based on the adsorption to and elution from positively-charged Al(OH)₃-treated silica gel.
Methods and Results:  Polyaluminum Chloride (PAC) was added to water samples to neutralize the negatively charged materials, which can reduce virus recovery by providing a competing adsorption mode on the media surface. Using this improved process (PAC 30 mg l⁻¹, pH 6·5, temperature 20∼30°C), the recoveries of Poliovirus I and f₂ from small-volume sewage (100 ml) were 110·76 ± 36·0% and 92·06 ± 8·65%, respectively ( P  < 0·05 vs. traditional methods). Recovery from a 20-L volume of sewage averaged 85·65 ± 4·43% for f₂ and 88·73 ± 9·76% for poliovirus, significantly higher than the recoveries in the traditional methods ( P  < 0·05).
Conclusions:  PAC could enhance concentration efficiency of poliovirus and f₂ phage from sewage water.
Significance and Impact of the Study:  This method should significantly improve the recovery of viruses from sewage.     

Ecophysiological diversity of alpine populations of Gammarus lacustris in relation to environmental calcium

1. The contribution of environmental calcium to ecophysiological diversity among populations of Gammarus lacustris was investigated by comparing five alpine lakes in France.
2. Calcium concentrations in the water varied with substratum lithology, ranging from 6 mg L^–1 in lakes on crystalline (igneous) rocks to 32.7 mg L^–1 in lakes on limestone, and up to 248 mg L^–1 in a lake with a gypsum environment.
3. The duration of the moult cycle and mortality rate were compared between populations by means of field and in situ laboratory and translocation experiments on adult males. Animals from water with low calcium concentrations showed a significantly longer moult cycle and higher mortality rate than those from water with high calcium concentrations. A significant increase in the duration of the moult cycle was observed in animals translocated to water of lower calcium concentration and vice versa.
4. These results suggest the existence of different physiological races of G. lacustris with an ecophysiological plasticity of calcium metabolism narrower than that of river-dwelling gammarids such as G. fossarum. This may be a consequence of geographic isolation among lacustrine populations together with the relatively stable environmental parameters in lakes.     

Groundwater controls on nutrient cycling in a Mojave desert stream

1. Groundwater fluxes of nitrogen and dissolved organic carbon (DOC) were investigated in Grape Vine Canyon Stream in the Mojave Desert focusing on the rate of inputs and the fate of groundwater-derived nutrients in the stream. Discharge rates from different ground waters were measured using an end-member mixing model coupled with injections of a conservative solute tracer into the stream channel.
2. In surface water, nitrate concentration averaged 1.13 mg N L^–1 and DOC concentration averaged 1.82 mg C L^–1.
3. Groundwater discharge into Grape Vine Canyon Stream was derived from three sources. Nitrate concentration varied among the three groundwater sources with mean concentrations of 0.56, 0.94 and 0.08 mg N L^–1. DOC, in contrast, did not vary among ground water sources, with an overall average concentration of 2.96 mg C L^–1.
4. In the surface stream, nitrate concentration was two-fold greater than the concentration predicted from groundwater input, indicating that in-stream processes generated nitrate. Stream DOC concentration was lower than predicted based upon groundwater input rate. The production of nitrate and loss of DOC suggest that DOC is lost through mineralisation of dissolved organic matter, possibly resulting in the mineralisation of dissolved organic nitrogen to ammonium and subsequent transformation to nitrate via nitrification. In further support of this hypothesised linkage, DOC loss explained 80–89% of the variance in nitrate production in Grape Vine Canyon Stream.     

Swimming performance, oxygen consumption and excess post-exercise oxygen consumption in adult transgenic and ocean-ranched coho salmon

Routine oxygen consumption ( M o ₂) was 35% higher in 1 day starved and 21% higher in 4 day starved adult transgenic coho salmon Oncorhynchus kisutch relative to end of migration ocean-ranched coho salmon. Critical swimming speed ( U _crit) and M o ₂ at U _crit ( M o _2max) were significantly lower in 4 day starved transgenic coho salmon (1·25 BL s⁻¹; 8·79 mg O₂ kg⁻¹ min⁻¹) compared to ocean-ranched coho salmon (1·60 BL s⁻¹; 9·87 mg O₂ kg⁻¹ min⁻¹). Transgenic fish swam energetically less efficiently than ocean-ranched fish, as indicated by a poorer swimming economy at U _crit ( M o _2max     ). Although M o _2max was lower in transgenic coho salmon, the excess post-exercise oxygen consumption (EPOC) measured during the first 20 min of recovery was significantly larger in transgenic coho salmon (44·1 mg O₂ kg⁻¹) compared with ocean-ranched coho salmon (34·2 mg O₂ kg⁻¹), which had a faster rate of recovery.     

Spatio-temporal variation in macroinvertebrate assemblages of glacial streams in the Swiss Alps

1. Changes in water chemistry, benthic organic matter (BOM), and macroinvertebrates were examined in four different glacial streams over an annual cycle. The streams experienced strong seasonal changes in water chemistry that reflected temporal changes in the influence from the source glacier, especially in water turbidity, particulate phosphorus and conductivity.
2. Nitrogen concentrations were high (nitrate-N values were 130–274 μg L^–1), especially during spring snowmelt runoff. Benthic organic matter attained >600 g m^–2 dry mass at certain times, peaks being associated with seasonal blooms of the alga Hydrurus foetidus .
3. Macroinvertebrate taxon richness was two to three times higher (also numbers and biomass) in winter than summer suggesting winter may be a more favourable period for these animals. Benthic densities averaged 1140–3820 ind. m^–2, although peaking as high as 9000 ind. m^–2. Average annual biomass ranged from 102 to 721 mg m^–2, and reached >2000 mg m^–2 at one site in autumn.
4. Taxa common to all sites included the dipterans Diamesa spp. and Rhypholophus sp., the plecopterans Leuctra spp. and Rhabdiopteryx alpina , and the ephemeropterans Baetis alpinus and Rhithrogena spp. Principal components analysis clearly separated winter assemblages from those found in summer.     

Neuropeptide Y inhibits [Ca2+]i changes in rat retinal neurons through NPY Y1, Y4, and Y5 receptors

Neuropeptide Y (NPY) and NPY receptors are widely distributed in the CNS, including the retina, but the role of NPY in the retina is largely unknown. The aim of this study was to investigate whether NPY modulates intracellular calcium concentration ([Ca²⁺]_i) changes in retinal neurons and identify the NPY receptors involved. As NPY decreased the [Ca²⁺]_i amplitudes evoked by 30 mM KCl in only 50% of neurons analyzed, we divided them in two populations: NPY-non-responsive neurons (Δ2/Δ1 ≥ 0.80) and NPY-responsive neurons (Δ2/Δ1 < 0.80), being the Δ2/Δ1 the ratio between the amplitude of [Ca²⁺]_i increase evoked by the second (Δ2) and the first (Δ1) stimuli of KCl. The NPY Y₁/Y₅, Y₄, and Y₅ receptor agonists (100 nM), but not the Y₂ receptor agonist (300 nM), inhibited the [Ca²⁺]_i increase induced by KCl. In addition, the inhibitory effect of NPY on evoked-[Ca²⁺]_i changes was reduced in the presence of the Y₁ or the Y₅ receptor antagonists. In conclusion, NPY inhibits KCl-evoked [Ca²⁺]_i increase in retinal neurons through the activation of NPY Y₁, Y₄, and Y₅ receptors. This effect may be viewed as a potential neuroprotective mechanism of NPY against retinal neurodegeneration.     

Symbiotic N2 fixation in a high Alpine grassland: effects of four growing seasons of elevated CO2

1. Increasing carbon dioxide concentration (E: 680 μl CO₂ litre^–1 vs ambient, A: 355 μl CO₂ litre^–1) around late-successional Alpine sedge communities of the Swiss Central Alps (2450 m) for four growing seasons (1992–1995) had no detectable effect on symbiotic N₂ fixation in Trifolium alpinum —the sole N₂-fixing plant species in these communities (74 ± 30 mg N m^–2 year^–1, A and E plots pooled).
2. This result is based on data collected in the fourth growing season showing that elevated CO₂ had no effect on Trifolium above-ground biomass (4·4 ± 1·7 g m^–2, A and E plots pooled, n = 24) or N content per unit land area (124 ± 51 mg N m^–2, A and E pooled), or on the percentage of N Trifolium derived from the atmosphere through symbiotic N₂ fixation (%Ndfa: 61·0 ± 4·1 across A and E plots) estimated using the ¹⁵N dilution method.
3. Thus, it appears that N inputs to this ecosystem via symbiotic N₂ fixation will not be dramatically affected in the foreseeable future even as atmospheric CO₂ continues to rise.     

In situ responses to elevated CO2 in tropical forest understorey plants

1. Plants growing in deep shade and high temperature, such as in the understorey of humid tropical forests, have been predicted to be particularly sensitive to rising atmospheric CO₂. We tested this hypothesis in five species whose microhabitat quantum flux density (QFD) was documented as a covariable. After 7 (tree seedlings of Tachigalia versicolor and Beilschmiedia pendula ) and 18 months (shrubs Piper cordulatum and Psychotria limonensis, and grass Pharus latifolius ) of elevated CO₂ treatment ( c. 700 μl litre^–1) under mean QFD of less than 11 μmol m^–2 s^–1, all species produced more biomass (25–76%) under elevated CO₂.
2. Total plant biomass tended to increase with microhabitat QFD (daytime means varying from 5 to 11μmol m^–2 s^–1) but the relative stimulation by elevated CO₂ was higher at low QFD except in Pharus .
3. Non-structural carbohydrate concentrations in leaves increased significantly in Pharus (+ 27%) and Tachigalia (+ 40%).
4. The data support the hypothesis that tropical plants growing near the photosynthetic light compensation point are responsive to elevated CO₂. An improved plant carbon balance in deep shade is likely to influence understorey plant recruitment and competition as atmospheric CO₂ continues to rise.     

Nutrient limitation of bacterioplankton and phytoplankton in humic lakes in northern Sweden

1. Two small humic lakes in northern Sweden with concentrations of dissolved organic carbon (DOC) between 15 and 20 mg L^–1 were fertilized with inorganic phosphorus (P) and inorganic nitrogen (N), respectively. A third lake was unfertilized and served as a control. In addition to this lake fertilization experiment, data from different regional surveys were used to assess the role of different limiting factors.
2. The P fertilization had no effects on bacterioplankton or phytoplankton, while phytoplankton were significantly stimulated by N fertilization. Inorganic nutrient limitation of bacterioplankton was a function of DOC concentration in water of the investigated region and nutrient-limited bacteria were found only in lakes with DOC concentrations less than around 15 mg L^–1
3. The fertilization experiments demonstrated that the DOC-rich experimental lakes contained a bioavailable pool of P that was not utilized to its full potential under natural conditions. The overall mobilization of energy (bacterioplankton plus phytoplankton) in the experimental lakes was restricted by lack of inorganic N.     

Responses of tree sap-feeding herbivores to elevated CO2

Five species of sap-feeding homoptera were studied on Fagus sylvatica and Acer pseudoplatanus and exposed to elevated concentrations of carbon dioxide (600 μL L^–1). The concentration of total soluble amino acids in foliage of F. sylvatica was unaffected by growing saplings in elevated atmospheric CO₂ concentrations. Although experiments on individual aphids indicated poorer performance of Phyllaphis fagi (fewer, smaller nymphs produced), resultant populations did not differ from those in ambient (350 μL L^–1) conditions. The area of beech foliage stippled by the leafhopper Fagocyba cruenta was similar at ambient and elevated CO₂ concentrations. The concentration of total amino acids and that of serine of A. pseudoplatanus foliage were significantly lower at elevated CO₂ concentrations. However, the relative growth rates of two aphid species Drepanosiphum platanoidis and Periphyllus testudinaceus and one leafhopper Ossiannilssonola callosa were not significantly different in elevated CO₂. No evidence was found that, under the conditions of these experiments, populations of aphids and leafhoppers will change as concentrations of CO₂ increase.     

The density dependence of plant responses to elevated CO2

1 Stands of the annual Brassica kaber were grown at a range of six densities in both ambient and elevated CO₂ environments, and measurements of shoot growth were made from seedling emergence through to reproduction.
2 Early in stand development (21 days following emergence), CO₂ enhancement (β) for above-ground biomass was highly density-dependent, ranging from 1.41 at the lowest density (20 plants m−2) to 0.59 at the highest density (652 plants m−2).
3 As stands matured and total biomass exceeded a relatively low threshold level (<10.0 g m^{−2; c.}  20% of final yield), the density-dependence of β disappeared. Above this shoot biomass threshold, β-values remained remarkably stable (β = 0.34) across a broad range of stand biomass, independent of a stand's initial density or age.
4 Average stand-level reproductive β-values at a final harvest were very similar to biomass values (β = 0.38) and, as with biomass values at later stages, showed no apparent density-dependence.
5 These results highlight the importance of considering density and the time-course of stand development simultaneously when assessing the potential for CO₂-induced growth enhancements in plants.     

Changes in abundance, composition and controls within the plankton of a fertilised arctic lake

1. An oligotrophic arctic lake was fertilised with inorganic nitrogen and phosphorus as (NH₄)₂ NO₃ and H₃PO₄ for five summers. The loading rate was 1.7–2.5 mmol N m^–2 day^–1 and 0.136–0.20 mmol P m^–2 day^–1 which is two to three times the annual loading of lakes in the area. The heterotrophic microzooplankton community was enumerated during the experiment as well as 1 year pre- and post-treatment.
2. The structure of the microplankton community changed from a nutrient limited system, dominated by oligotrich protozoans and small-particle feeding rotifers, to a system dominated by a succession of peritrich protozoans and predatory rotifers. These peritrich protozoans and predatory rotifers were not present prior to fertilisation and never constituted more than a small fraction of the biomass in other lakes at the research site. The average biomass of the rotifers and protozoans was more than seven and a half times larger by the end of fertilisation than it was initially.
3. Because of the increases in numbers of individuals in these new taxa, the structure of the microbial food web changed. When fertilisation stopped, most parameters returned to prefertilisation levels within 1 year.     

Molecular Determinants of General Anesthetic Action: Role of GABAA Receptor Structure

Abstract: Using receptors expressed from mouse brain mRNA in Xenopus oocytes, we found that enhancement of type A γ-aminobutyric acid (GABA_A) receptor-gated Cl⁻ channel response is a common action of structurally diverse anesthetics, suggesting that the GABA_A receptor plays an important role in anesthesia. To determine if GABA_A receptor subunit composition influences actions of anesthetics, we expressed subunit cRNAs in Xenopus oocytes and measured effects of enflurane on GABA-activated Cl⁻ currents. Potentiation of GABA-activated currents by enflurane was dependent on the composition of GABA_A receptor protein subunits; the order of sensitivity was α₁β₁ > α₁β₁γ_2s=α₁β₁γ_2L > total mRNA. The results suggest that anesthetics with simple structures may act on the GABA_A receptor protein complex to modulate the Cl⁻ channel activity and provide a molecular explanation for the synergistic clinical interactions between benzodiazepines and general anesthetics.     

Inhibitory Effect of Omeprazole, a Specific Inhibitor of H+, K+-ATPase, on Spicule Formation in Sea Urchin Embryos and in Cultured Micromere-Derived Cells.

Embryos kept with omeprazole, a specific H⁺, K⁺-ATPase inhibitor, in a period of development between the mesenchyme blastula and the pluteus corresponding stage became abnormal plutei having quite small spicules, somewhat poor pluteus arms and apparently normal archenterons. In micro-mere-derived cells, kept with omeprazole at pH 8.2 in a period between 15 and 40 hr of culture at 20°C, omeprazole strongly inhibited spicule formation but did not block the outgrowth of pseudopodial cables, in which spicule rods were to be formed. These indicate that omeprazole probably exerts no obvious inhibitory effects other than spicule rods formation. Omeprazole-sensitive H⁺, K⁺-ATPase, an H⁺pump, seems to be indispensable for CaCO₃ deposition (formation of spicule rod) in these spicule forming cells. H⁺, produced in overall reaction for CaCO₃ formation: Ca²⁺+ CO₂+H₂O°CaCO₃+2H⁺, is probably released from the cells by this H⁺pump and hence, this reaction tends to go to CaCO₃ production to form spicule rods. Omeprazole, known to become effective following its conversion to a specific inhibitor of H⁺, K⁺-ATPase at acidic pH, is able to inhibit formation of spicule rod at alkaline pH in sea water. This is probably due to an acidification of sea water near the cell surface by H⁺ejection in H⁺, K⁺-ATPase reaction.     

Cav1 L-type Ca2+ channel signaling complexes in neurons

Ca_v1 L-type Ca²⁺ channels play crucial and diverse roles in the nervous system. The pre- and post-synaptic functions of Ca_v1 channels not only depend on their intrinsic biophysical properties but also their dynamic regulation by a host of cellular influences. These include protein kinases and phosphatases, G-protein coupled receptors, scaffolding proteins, and Ca²⁺-binding proteins. The cytoplasmic domains of the main pore forming α₁ subunit of Ca_v1 offer a number of binding sites for these modulators, permitting fast and localized regulation of Ca²⁺ entry. Through effects on Ca_v1 gating, localization, and coupling to effectors, protein modulators are efficiently positioned to adjust Ca_v1 Ca²⁺ signals that control neuronal excitability, synaptic plasticity, and gene expression.     

K+ATP channel opening prevents succinate-dependent H2O2 generation by plant mitochondria

The role of a recently identified K⁺_ATP channel in preventing H₂O₂ formation was examined in isolated pea stem mitochondria. The succinate-dependent H₂O₂ formation was progressively inhibited, when mitochondria were resuspended in media containing increasing concentration of KCl (from 0.05 to 0.15  M ). This inhibition was linked to a partial dissipation of the transmembrane electrical potential (ΔΨ) induced by KCl. Conversely, the malate plus glutamate-dependent H₂O₂ formation was not influenced. The succinate-sustained H₂O₂ generation was also unaffected by nigericin (a H⁺/K⁺ exchanger), but completely prevented by valinomycin (a K⁺ ionophore). In addition, cyclosporin A (a K⁺_ATP channel opener) inhibited this H₂O₂ formation, while ATP (an inhibitor of the channel opening) slightly increased it. The inhibitory effect of ATP was strongly stimulated in the presence of atractylate (an inhibitor of the adenine nucleotide translocase), thus suggesting that the receptor for ATP on the K⁺ channel faces the intermembrane space. Finally, the succinate-dependent H₂O₂ formation was partially prevented by phenylarsine oxide (a thiol oxidant).     

Inheritance of Anthracnose Resistance in the Common Bean Differential Cultivar G 2333 and Identification of a New Molecular Marker Linked to the Co-42 gene

The inheritance of anthracnose resistance of the common bean ( Phaseolus vulgaris L.) differential cultivar G 2333 to Colletotrichum lindemuthianum races 73 and 89 was studied in crosses with the susceptible cultivar Rudá. The segregation ratios of 15 : 1 in the F₂ and 3 : 1 in the backcrosses to Rudá indicate that for each of the races tested there are two independent resistance loci in G 2333. A random amplified polymorphic DNA (RAPD) molecular marker (OPH18_1200C) linked in resistance to race 73 was identified in a BC₃F_2:3 population derived from crosses between Rudá and G 2333. A RAPD molecular marker OPAS13_950C, previously identified as linked to gene Co-4² , was also amplified in this population. Co-segregation analyses showed that these two markers are located at 5.6 (OPH18_1200C) and 11.2 (OPAS13_950C) cM of the Co-4² gene. These markers were not present in BC₁F_2:3 plants resistant to race 89 indicating that this population carries a different resistance gene. DNA amplification of BC₁F_2:3 plants with RAPD molecular marker OPAB_450C, previously identified as linked to gene Co-5 , indicated that this gene is present in this population.