Blue-Green algae agglomeration in surface water: a microbiotope of high bacterial activity

European Marine Biology Symposium. 15 1981 Abstract Mass accumulations of filamentous blue-green algae in surface waters of the Baltic Sea cause patches of high bacterial productivity within water masses of low microbial activity. Since these algae are apparently not grazed by zooplankton organisms, their degradation in the surface water layer is mainly due to associated bacteria. The network of algae filaments attracts a wide range of small organisms including rotifers, crustaceans, ciliates and flagellates, resulting in a microbiotope of considerable complexity. The succession of bacterial colonization of Nodularia spumigena and the activity state of the community was investigated by the INT-staining technique and by microautoradiography. The excretion rates of photosynthesized matter by the bluegreen algae agglomerates indicate a high rate of transfer of substrate towards the adherent heterotrophic bacteria. The fate and the final involvement of the agglomerates in the food chain are discussed

Effect of zooplankton-mediated trophic cascades on marine microbial food web components (bacteria, nanoflagellates, ciliates)

To examine the grazing effects of copepod-dominated mesozooplankton on heterotrophic microbial communities, four mesocosm experiments using gradients of zooplankton abundance were carried out at a coastal marine site. The responses of different protist groups (nanoflagellates, ciliates) and bacterioplankton in terms of abundance and additionally, for bacteria, diversity, production, and exoenzymatic activity, were monitored during 1 week of incubation. Independent of the initial experimental abiotic conditions and the dominating copepod species, zooplankton caused order-of-magnitude changes in microbial functional groups in a clear community-wide four-link trophic cascade. The strongest predatory effects were observed for protist concentrations, thus generating inverse relationships between mesozooplankton and ciliates and between ciliates and nanoplankton. Copepod grazing effects propagated even further, not only reducing the abundance, production, and hydrolytic activity of bacterioplankton but also increasing bacterial diversity. The overall strength of this trophic cascade was dampened with respect to bacterial numbers, but more pronounced with respect to bacterial diversity and activity. High predation pressure by heterotrophic nanoflagellates, realized at the highest copepod abundance, was probably the underlying mechanism for these structural changes in the bacterial assemblages. Our results thus suggest a mechanism by which changes in higher trophic levels of marine plankton indirectly affect prokaryotic assemblages and microbially mediated ecosystem functions

Profiles of ectoenzymes in the Indian Ocean: Phenomena of phosphatase activity in the mesopelagic zone

Phosphatase (P-ase) activity was determined together with other extracellular enzyme activities, bacterial abundance and production rates during the 2 SW Monsoon process studies of the German JGOFS Arabian Sea Program. Water samples were collected along the cruise tracks from the equator to the upwelling region at the shelf edge off Oman. Depth profiles of P-ase activity were strikingly different from those of the other enzymes. While values of aminopeptidase and β-glucosidase generally decreased below the euphotic zone, P-ase increased by factors of 1 to 7. The relation between peptidase- and P-ase activity was from 4 to 21 at the surface and from 3 to 5 at 800 m depth. Because P-ase production (dissolved and cell-bound) in deep waters is mainly dependent on bacteria, P-ase activities per bacterial cell were calculated: these were, on average, 37 times higher at 800 m than at the surface. We also observed a positive correlation of P-ase activity with phosphate concentrations in the depth profiles below the euphotic zone, while this relationship was much more variable in the mixed surface layer. These observations suggest that C-limited bacteria in the deep strata did not primarily focus on the phosphate generated by their P-ase activity but on the organic C compounds which were simultaneously produced and which could probably not be taken up prior to the hydrolytic detachment of phosphate. It is hypothesised that a considerable part of the measured P-ase activity was dissolved (though it might have originated from bacteria). These enzymes may be important for the slow, but steady regeneration of phosphate and organic C in mesopelagic waters

Evidence for dependency of bacterial growth on enzymatic hydrolysis of particulate organic matter in the mesopelagic ocean

Organic material entering the oceanic mesopelagic zone may either reenter the euphotic zone or settle into deeper waters. Therefore it is important to know about mechanisms and efficiency of substrate conversion in this water layer. Bacterial biomass, bacteria secondary production (BSP). extra­cellular peptidase activity (EPA) and particulate organic nitrogen (PON) were measured in vertical pro­files of the North Atlantic (46° N 18° W; 57° N 23° W) during the Joint Global Ocean Flux Study (JGOFS) cruise in May 1989. The magnitude of these parameters decreased differently with depth. The strong­est decreases were observed for bacterial production (3H-thymidine incorporation) and peptide turn­over (using the substrate analog leucine-methylcoumarinylamide). Bacterial biomass and peptidase potential activity were not reduced as much in the mesopelagic zone. Peptidase potential per unit cell biomass of mesopelagic bacteria was 2 to 3 times higher than that of bacteria in surface water. Nevertheless bacterial growth at depth was slow, due to slow actual hydrolysis. Values of theoretical PON hydrolysis were calculated from PON measurements and protein hydrolysis rates. These corre­sponded well to bacterial production rates, and the degree of correspondence increased from a factor of 0.63 (PON hydrolysis/ESP) in the mixed surface layer to 0.87 in the mesopelagic zone. Thus we hypothesized an effective coupling between particle hydrolysis and uptake of hydrolysate by bacteria, which depletes the deeper water of easily degradable substrates as hydrolysates usually are. The low enzymatic PON turnover rate of 0.04 d- 1 in the subeuphotic zone suggests that residence time of parti­cles within a depth stratum may be important for its contribution to export. storage and recycling of organic matter

Taxonomische Untersuchungen an Hefen aus der westlichen Ostsee

In der vorliegenden Untersuchung wird zur Ergänzung der quantitativen Bestandsaufnahme (HOPPE 1972) eine taxonomische Übersicht über die im Bereich der westlichen Ostsee vorkommenden Hefen gegeben. Rhodotorula-, Debaryomyces- und Candida-Arten wurden in diesem Areal besonders häufig registriert. In dem Vorfluter für städtische Abwässer bei Bülk (Kieler Bucht) geht der Hefegehalt der Abwasserfahne mit zunehmender Küstenentfernung stark zurück. Dagegen erhöht sich der Anteil roter Hefen und relativ anspruchsloser Organismen an der gesamten Hefeflora beständig. In the present investigation, completing the quantitative record (HOPPE 1972), a taxonomic survey of the yeasts found in the western Baltic Sea is given. Rhodotorula-, Debaryomyces- and Candida-species were especially frequently registered in this area. At the sewage outlet for city waste-effluent at Bülk (Bay ofKiel), the yeast content of the waste water stream decreases, the greater the distance from the shore. On the other hand, the percentage of red yeasts and relatively unpretentious organisms of the total yeast flora continuously increases

Untersuchungen zur Analyse mariner Bakterienpopulationen mit einer autoradiographischen Methode

Untersuchungen über die Zusammensetzung aquatischer Bakterienpopulationen hinsichtlich ihrer Fähigkeit zur Verwertung verschiedener Kohlenstoffquellen sind bisher wenig durchgeführt worden, da es an adäquaten Methoden mangelt. Es wird eine kombinierte Methode mit 14C-markierten Substraten, Nährkartonscheiben, Membranfiltern und Autoradiographie beschrieben, mit der verschiedene physiologische Gruppen erfaßt werden können. Kolonien mit besonderen Eigenschaften (z. B. Phenol oder DDT-Abbauer) können leicht identifiziert und isoliert werden. Die bisherigen Ergebnisse zeigen, daß einige der getesteten Substrate (Glucose, Asparaginsäure, Acetat) stets von fast allen Saprophyten aufgenommen werden können, während die Aufnahme anderer (z. B. Xylose, Lactose, Harnsäure, Phenol, Riboflavin, Fett) sowohl jahreszeitlich bedingte als auch von der Verschmutzung und Küstenentfernung abhängige Fluktuationen aufweist. Von dem größeren Spektrum der Nährstoffverwertung durch Bakterien in Küstengewässern kann eine schnelle Adaptation an Abwasserinhaltsstoffe erwartet werden, während in küstenferneren Gebieten entsprechende Populationen nur sehr schwach vertreten sind. Investigations on the composition of aquatic bacterial populations in respect of their nutritional requirements have been rarely made because of the lack of adequate methods. A combined method using 14C-marked substrates, nutrient pads, membrane filters and autoradiography is described, which enables one to differentiate the physiological groups of bacteria. Colonies with special properties (e.g. degradation of phenol or DDT) can easily be identified and isolated. The preliminary results show that some of the test substrates (glucose, aspartic acid, acetate) can always be taken up by most of the bacteria. Others (e.g. xylose, lactose, uric acid, phenol, riboflavin, fat) show seasonal and environmental fluctuations. The wide spectrum of nutritional requirements of bacterial populations in coastal reagions may lead to a quick adaption to sewage compounds, while in offshore regions the corresponding populations are rather small

Untersuchungen zur Ökologie der Hefen im Bereich der westlichen Ostsee

In der vorliegenden Untersuchung wird eine erste Bestandsaufnahme der quantitativen Hefeverteilung in der westlichen Ostsee gegeben. Zur Begründung der gefundenen zeitlichen und räumlichen Hefeverteilung werden verschiedene biotische und abiotische Faktoren untersucht. Es ergab sich eine starke Abhängigkeit von der jeweils vorherrschenden hydrographischen Situation, der Temperatur und dem Nährstoffgehalt des Ostseewassers. Die Frühjahrs- und Herbstmaxima der Hefeentwicklung traten in der Kieler Förde vor den vergleichsweise ermittelten Maxima der Bakterienzahlen auf. Mit zunehmender Küstenentfernung nimmt die „Biomasse" der Hefen stärker ab als die der Bakterien, im Durchschnitt wird eine Relation von 1 : 124 erreicht. In steril filtriertem Ostseewasser entstand und überlebte eine größere Zellzahl bei niedrigen Temperaturen (4°C, 12°C) als bei höheren Temperaturen (20°C, 25°C) (Rhodotorula-Stamm). Zur ersten Orientierung wurde die Generationszeit des Rhodotorula-Stammes H 25 in Ostseewasser durch eine kontinuierliche Kultur annäherungsweise ermittelt. Sie betrug 178 Stunden (25°C) bei einer Zelldichte von 5020 Zellen/ml und 263 Stunden (12°C) bei einer Zelldichte von 23800 Zellen/ml