Showing papers by "Swiss Federal Institute of Aquatic Science and Technology published in 1977"

Primary production, mineralization, and sedimentation in the euphotic zone of two Swiss lakes

Abstract: Phosphorus and nitrogen concentrations, phytoplankton, bacteria, detritus, primary production, and sedimentation have been investigated over a year in two Swiss lakes of different trophic state. Inflow and outflow of the lakes were calculated, as well as the eddy diffusion of P and N from the metalimnion into the epilimnion, and from these data a balance of the cpilimnetic phosphorus and nitrogen cycle was drawn up. Different methods of calculation all suggested a high intensity of the internal nutrient cycle in the epilimnion. By means of autolysis, destruction, and excretion, about 35-75s of the nitrogen and 55-85s of the phosphorus needed for the measured primary production can thus be regenerated. The carbon, nitrogen, and phosphorus cycles in lakes are influenced by both external and internal events. The turnover of these nutrients depends mainly on rates of primary production, mineralization, and sedimentation. Some aspects of these processes were studied in 1969-1970 in the mesotrophic Horw Bay ( Llake of Lucerne) and the highly eutrophic Rotsee with special emphasis on the nitrogen and phosphorus cycle (Stadelmann 1971; Schegg 1971; Bloesch 1974). In this paper, we quantify the regeneration of nitrogen and phosphorus in the euphotic zone and estimate the importance of such regeneration for the productivity of a lake. The two lakes are situated in the prealpine region of central Switzerland. The sampling sites are shown in Fig. 1, and some representative data are given in Table 1.

Gum phases for glass capillary columns; a recommendation for users, a challenge for polymer scientists

Abstract: Based on the above-mentioned fundamental advantages, gums should be considered the ideal phases for capillary GLC. Therefore, we strongly recommend users to select a gum whenever it is not precluded because of critical polarity/selectivity requirements. On the other hand we emphasize the great need for a much wider choice of gum phases. We are convinced that developing new and especially, more polar, gum phases is one of the best services that can be rendered to our analytical field. It is our hope that this may be a challange for some polymer scientists.

Dynamics of O2 and CO2 exchange, photosynthesis, and respiration in rivers from time-delayed correlations with ideal sunlight

Abstract: The oxygen exchange constant, photosynthetic rate, and respiration rate for several Swiss rivers have been determined using only the continuous data record of a single oxygen electrode, the measured tcmpcrature, and an assumed ideal light intensity curve in conjunction with a simple model rate equation and a novel cross-correlation computational technique. The method can, in favorable circumstances, be extended to determine also total carbonate dynamics from continuous pH measurements. For the Aare at Bern in March 1974, the oxygen exchange constant was 0.38 h-l, the respiration rate was 0.6 mg liter-’ h-l, and mean photosynthetic rate was 0.28 mg liter-l h-l. The exchange rate for dissolved (but not hydrated or ionized) COti was 0.91 times that for dissolved oxygen. and the ratio of 02 molecules released to COP molecules consumed during photosynthesis was about 1.2. It has long been recognized that the three most important kinetic processes governing dissolved oxygen in rivers are exchange with the atmosphere, total respiration, and photosynthetic production. Although direct measurements of gas exchange rates have been made for a few rivers using radioactive tracers, a technique pioneered by Tsivoglou (1967) and Tsivoglou et al. ( 1965, 1970)) both photosynthesis and respiration appear to be accessible only by indirect methods-model building and parameter estimation. Since the classic work of Streeter and Phelps (1925) many indirect methods have been proposed, but none of these attempts to dctermine more than two of the three critical kinetic rates. Moreover, application of the elegant theory of parameter estimation in linearly distributed systems, as suggested recently by Koivo and Koivo ( 1973), will require in each case a rather large quantity of “distributed” data. Kelly et al. (1974) have proposed a sophistication of the simple upstreamdownstream method of Odum (1956) that yields greatly improved accuracy in dcterminations of net oxygen production. This method requires several experimental observations for the determination of rates of both photosynthesis and respiration: continuous records of two spatially separated oxygen monitors; the stream velocity; the light intensity; an independent measuremcnt or estimate of the exchange constant; and the stream temperature from which to calculate the oxygen saturation value. In addition a requirement for uniform light intensity along the stretch considered means that only days with either clear weather or uniform cloud cover are generally suitable. The method does permit the observation of day-to-day variations in respiration and photosynthetic efficiency, at least during uniform weather. The value of light intensity measurements together with the use of an array of oxygen monitors for determining the kinetics of processes occurring on a brief time scale can hardly be overstated. Indeed, Kelly and coworkers (personal communication) presently have work in progress in which the incident light intensity and dissolved oxygen data from a single station, along with the measured temperature, are used to dctermint values of, and day-to-day variations in, the exchange constant and photosynthetic rate. LIMNOLOGY AND OCEANOGRAF’HY 208 MARCH 1977, V. 22 (2) 0, dynamics in rivers 209 We propose here a simple indirect method for determining average values ( over a l-month period) of the exchange constant, photosynthetic rate, and respiration rate from just the continuous data record of a single oxygen electrode and the (constant) temperature. The effects of random temporal and spatial light modulation by clouds and atmospheric dust are eliminated by computing the cross-correlation function between the dissolved oxygen and an assumed ideal relative light intensity curve. This method is comparatively inexpensive, and can also be applied to data collected in the past. Moreover, it offers several internal criteria for consistency, which, when not satisfied, indicate failure of one or more of the assumptions of the model. Basically, the method relies on three observed quantities, the time-lag ( behind the sunlight) and amplitude of the 24-h periodic response of the dissolved oxygen and the time-average value, to determine the three kinetic rates of the model. The rivers examined in this study all exhibited diurnal temperature fluctuations negligible in the sense that predicted changes in oxygen saturation values were of much smaller magnitude (i.e. a few percent or less) and of opposite sign than the changes in dissolved oxygen observed. Even in the most extreme case the diurnal temperature fluctuations were 3 mg ml-l 210 Schurr and Ruchti Table 1. Equations 1-7. (1) !$$ = -v g kb0 t kfOA B + aI(x,t) (2) 1(x,-t) = + AI(x,t) (3) 0(x,-t) q + AO(x,t) (4) a > kb =' kfOA B + a

Bodenfaunistische Untersuchungen in Aare und Rhein

Abstract: In 1969–1972 the benthos of the rivers Aare (near Beznau) and Rhine (near Kaiseraugst) was investigated At every two stations of both rivers, we collected 8 samples regularly distributed over the river width Both collecting and counting were performed quantitatively Physical and chemical data, and grain size analyses of the substratum are given for both rivers The results of the extensive counts were summarized in a list of quantitative abundance The benthic biocoenoses are dominated in both rivers by oligochaetes and chironomids; in the Aare the trichopteran larvae ofHydropsyche sp are also highly abundant In the Aare 79 species or genera and an average of 48,100 individuals per square meter were collected This benthic fauna is richer and denser than in the Rhine, where 41 species or genera and an average of 11,400 individuals per square meter were recorded The distribution of the organisms is inhomogeneous (contagious), and within a square meter the total number of individuals per 855 cm2 ranged between 4056 and 23,140 In the Aare the average biomass is 86–415 g/m2, again higher than in the Rhine (05–31 g/m2) The Rhine river bed is covered with gravel and sand, whereas in the Aare the bed is muddy As the physical and chemical conditions are quite the same in both rivers, we relate the different population densities to the differences in the substratum En 1969–1972, les invertebres de l'Aar (pres de Beznau) et du Rhin (pres de Kaiseraugst) ont ete examines Deux stations de prelevement ont ete choisies pour chaque cours d'eau et a chacune d'elles, 8 echantillons ont ete pris, repartis regulierement sur toute la largeur Les organismes ont ete collectionnes et denombres d'une maniere quantitative Pour comparer la biologie des deux cours d'eau, on a etudie les resultats physico-chimiques et les analyses de granulometrie du fond Les resultats des nombreux comptages ont ete resumes dans une liste quantitative d'abondance Dans les deux cours d'eau, les oligochetes et les chironomides dominent les biocenoses benthiques; en outre, dans l'Aar, la larve du trichoptereHydropsyche sp joue un role assez important L'Aar, contenant 79 especes ou genres et en moyenne 48 100 individus par m2, est plus riche et plus dense en organismes benthiques repartition des organismes est tres heterogene (contagieuse) et sur 1 m2, le nombre total des individus par 855 cm2 varie entre 4056 et 23 140 Enfin, dans l'Aar, on trouve aussi une biomasse plus grande (en moyenne 8,6–41,5 g/m2) que dans le Rhin (en moyenne 0,5–3,1 g/m2) La nature du fond du Rhin est graveleuse-sablonneuse, tandis que dans l'Aar le limon predomine Puisque les conditions physico-chimiques sont assez semblables dans les deux cours d'eau, la difference de densite des populations est expliquee par la nature meme des deux types de substratum

Determinations of particle size distributions in natural waters use of Zeiss Micro-Videomat image analyzer

Abstract: Use of a Zeiss Micro-Videomat electronic image analyzer for routine measurements of size distributions of particles found in natural waters greater than 0.3 μm has been investigated.

7. Symposium über Fragen der Cyanophytentaxonomie in Lednice (ČSSR), 29. Juli bis 8. August 1976 Verhandlungsbericht

Abstract: Das 7. Symposium der Internationalen Arbeitsgemeinschaft ftir Cyanophytenforschung wich yon den sechs frtiheren Tagungen [ 16] * t) in zweifacher Hinsicht ab: Wegen Bauarbeiten zur Erweiterung des Seenforschungslaboratoriums der EAWAG/ETH war die Durchftihrung im gewohnten Rahmen in Kastanienbaum am Vierwaldst~ittersee nicht m6glich. Auf Anregung und Ersuchen bisheriger Teilnehmer erklarten sich erfreulicherweise tschechoslowakische Kollegen bereit, die Veranstaltung in ihrem Lande durchzuftihren. Besonderer Dalik gebiihrt der Tschechoslowakischen Akademie der Wissenschaften, welche das Patronat iibernahm. Die Organisation lag in den H~inden der Hydrobotanischen Abteilung des Botanischen Institutes in T~ebofi. Die Landwirtschaftliche Hochschule Brno stellte in grossziagiger Weise ihre Hydrobiologische Station im Schloss Lednice in Si~dmahren als Tagungsst~itte zur VerFtigung. Zum grossen Bedauern aller Teilnehmer musste Herr Professor Dr. Otto Jaag, der Begrtinder und begeisternde Spiritus rector der ersten sechs Symposien, aus gesundheitlichen Grilnden auf die Teilnahme verzichten. Der Leiter des vorbereitenden Komitees, Dr. Ji~i Kom~trek, konnte an der Er6ffnungssitzung die folgenden Teilnehmer willkommen heissen:

Zur Resistenz von Blaualgen gegen kurzwellige Strahlung

Abstract: 13 Klone von Blaualgen verschiedener taxonomischer Stellung (Chroococcales, Chamaesiphonales, Nostocales) und verschiedener okologischer Gruppen (Plankter, Litoralformen, Aerophyten schattiger und sonniger Standorte), wurden mit Gamma-und UV-Strahlen behandelt. Plankter erwiesen sich unabhangig von ihrer taxonomischen Stellung als wenig widerstandsfahig: Die maximale Gammastrahlentoleranz betrug je nach Klon 65 bis 260 krad bei Bestrahlungszeiten von rund 10 bis 40 Minuten, die maximale UV_Strahlentoleranz belief sich (mit einer Ausnahme) unter unseren Versuchsbedingungen auf eine Bestrahlungszeit von 32 Minuten. Begleitbakterien tolerierten durchwegs hohere Strahlendosen. Dagegen erwiesen sich Aerophyten bzw. Lithophyten von Standorten mit extremem naturlichem Strahlungsklima auch im Experiment als sehr resistent. So uberlebtenChamaesiphon polonicus undScytonema burmanicum siebenstundige Exposition in Gammastrahlen (totale Dosis 2500 krad) sowie vierstundige UV-Bestrahlung. Begleitbakterien uberlebten zwar die UV-Behandlung, nicht aber die hohen Gammastrahlendosen. Behandlung mit Gammastrahlen eignet sich daher zur Gewinnung axenischer Kulturen von Cyanophyten extremer Naturstandorte.

Tritium-Verteilung, Durchmischungsverhältnisse und Altersstruktur der Wassermasse im Vierwaldstättersee

Abstract: Untersuchungen an vier Tiefenprofilen im Vierwaldstattersee ergaben, dass Messungen von Tritium thermonuklearen Ursprungs Informationen uber die Durchmischungsverhaltnisse in der betrachteten Wassermasse vermitteln. Aufgrund eines einfachen Modells konnte ferner die Altersstruktur des Seewassers approximativ bestimmt werden.

Der Sauerstoffhaushalt von Fliessgewässern: Kritische Prüfung eines mathematischen Sauerstoffmodells anhand der Identifikation seiner Parameter in Flüssen und Künstlichen Rinnen

Abstract: Results obtained by a previously published cross-correlation identification technique applied to the modified Streeter-Phelps river model suggest that the oxygen exchange rate, the oxygen invasion rate, an apparent photosynthesis rate and the respiration rate can be identified using oxygen measurements from a single point of observation. This hypothesis is examined here using the alternative method of differential approximation and the gradient method. It is found that the simple solely time dependent model is inadequate for the description of the dissolved oxygen concentration in a river and that consequently its parameters can not be identified using the measurements from a single point only.