Showing papers by "Swiss Federal Institute of Aquatic Science and Technology published in 1987"

Oxidation of Dimethyl Sulfide to Dimethyl Sulfoxide by Phototrophic Purple Bacteria

Abstract: Enrichment cultures of phototrophic purple bacteria rapidly oxidized up to 10 mM dimethyl sulfide (DMS) to dimethyl sulfoxide (DMSO). DMSO was qualitatively identified by proton nuclear magnetic resonance. By using a biological assay, DMSO was always quantitatively recovered from the culture media. DMS oxidation was not detected in cultures incubated in the dark, and it was slow in cultures exposed to full daylight. Under optimal conditions, the second-order rate constant for DMS oxidation was 6 day−1 mg of protein−1 ml−1. The rate constant was reduced in the presence of high concentration of sulfide (>1 mM), but was not affected by the addition of acetate. DMS was also oxidized to DMSO by a pure strain (tentatively identified as a Thiocystis sp.) isolated from the enrichment cultures. DMS supported growth of the enrichment cultures and of the pure strain by serving as an electron source for photosynthesis. A determination of the amount of protein produced in the cultures and an estimation of the electron balance suggested that the two electrons liberated during the oxidation of DMS to DMSO were quantitatively used to reduce carbon dioxide to biomass. The oxidation of DMS by phototrophic purple bacteria may be an important source of DMSO detected in anaerobic ponds and marshes.

The Influence of Crustacean Zooplankton on the Size Structure of Algal Biomass and Suspended and Settling Seston (Biomanipulation in Limnocorrals II)

Abstract: In a limnocorral (LC) experiment performed in mesotrophic Lake Lucerne, Switzerland, a control LC containing a planktonic community similar to that in the lake was compared with a LC where the large zooplankton had been removed by filtration at the beginning of the experiment. The herbivorous zooplankton (mainly Daphnia galeata and D. hyalina) reduced algal biomass and primary production, however did not influence the size structure of the phytoplankton and the relative amount of different size classes contributing to the total primary production. Likewise, the seston (POC and PP) concentrations were diminished without changes in particle size composition. Since herbivorous zooplankton transform smaller particles into larger particles (fecal aggregates) through their grazing activity and thus enhanced particle formation owing to coagulation and microbial activity, sedimentation losses of POC and PP were increased in the LC with zooplankton. The importance of planktonic and sestonic particle size structure in aquatic ecosystems is stressed, as the smallest algae (< 12 μm) contributed 80 % of the primary production, which is in contrast to the 33 % contributed to the total POC sedimentation by this particle size class.

Sedimentation rates in the central lake constance determined with210Pb and137Cs

Abstract: Sediment cores from central Lake Constance were dated with210Pb and137Cs. A sedimentation rate of (0.11±0.02) g·cm−2·y−1 was determined with the210Pb method.137Cs measurements revealed sedimentation rates of (0.11±0.01) g·cm−2·y−1 and (0.08±0.01) g·cm−2·y−1 respectively for two different cores sampled at the same location. The lower Cs-dated value indicates incomplete core recovery and demonstrates the sensitivity of this simple dating method to small losses of material at the water/sediment interface. An unambiguous application of the137Cs method is, therefore, only possible if complete core recovery is ensured. Sedimentation rates based on particulate matter, collected in sediment traps at various water depths, agree with the results of the radioisotope methods. Estimates of 30–125 days residence times for suspended particulate matter were calculated from7Be measurements.

Acid deposition in a snow field at 2500 m.a.s.l. in Switzerland

Abstract: In Alpine regions the precipitation is stored as cold snow in the winter half year. Meltwater flowing through the snow cover in springtime carries the impurities along and leads to a strong input of pollution into lakes and underground water systems. During winter 1985/86 three profiles through a snow cover situated 2540 meter above sea level in Switzerland have been analysed for the main chemical trace species. The measurements show that the acidity is dominated by nitric acid, while sulfate is deposited mostly as neutral salt. Hydrochloric acid and formic acid are only minor contributors to the total acidity. As long as no meltwater or rain flows through the snow cover, the main chemical impurities are conservative tracers.

Chemical Transformations in a Snow Cover at Weissfluhjoch, Switzerland, Situated 2500 m.a.s.l.

Abstract: During winter 1985/86 three profiles through a snow cover located at the Swiss Snow and Avalanche Research Institute Weissfluhjoch (Davos) at 2540 m.a.s.l. were analysed for the main chemical impurities including hydrogen peroxide. The concentration profiles of NO3 -, SO4 2-, Cl-, HCOO-, H+, NH4 +, Na+, K+ and Ca2+ do not change as long as the temperature in the snow field is below zero degree celsius. Only the H2O2 content decreases considerably. The disintegration rate depends mainly upon the availability of sunlight, thus photolysis is probably the most important decay process. Organic peroxides are not recorded in the snow.

Régime alimentaire des alevins de Gardons ( Rutilus rutilus (L.)) dans un port du lac Léman. Comparison avec la nourriture disponible

Abstract: In order to determine the food preferences of young roach, gut contents of roach fry (Rutilus rutilus (L.)) were compared with the evolution of the zooplankton community in a littoral area of Lake Geneva during June and July 1985. The food of roach fry up the age of 30 d (10–15 mm standard length) was mainly small Rotifers with some Chronomid larvae. Thereafter, Chironomid larvae constitute the major part of the diet until the fry leave the littoral zone at the age of about 45 d (15–23 mm). The relevance of classical food preference analysis is critically discussed in view of the heterogeneous spatial distribution of invertebrates observed.

Contribution of Ammonia to the Wet Deposition of Sulfur Compounds

Abstract: The wet deposition of sulfur compounds from the atmosphere was investigated. Neutralizing agents such as ammonia and CaCO3 particulates alter the pH and therefore the absorption of SO2 into the liquid phase. The contribution of ammonia to the wet deposition of sulfuric acid is estimated. Additionally ammonium sulfate aerosols may be scavenged by rain, fog and snow. Relative contributions of both pathways to wet sulfur deposition will be discussed. A method for the determination of trace aqueous ammonia in low volume samples, utilizing the technique of gas diffusion flow injection will be described.

The Ubiquinol-Cytochrome C Oxidoreductase of Phototrophic Bacteria

Abstract: The wide use of phototropic bacteria to study electron transfer pathway results from the fact that, in these bacteria, the electron transport can be activated by actinic light. The amount of electrons introduced into the cytochrome system, as well as the starting time of the reactions, can be very precisely determined this way. Additionally, the photosynthetic bacteria are able to grow using different energy sources, e.g. beside anaerobic phototrophic growth, they are also able to aerobically oxidize organic compounds in the dark and use the energy by oxidative phosphorylation in a similar manner to mitochondria.