Methodische Probleme bei Untersuchungen zur mikrobiellen Stoffaufnahme in Gewässern

Es wird ein seit einigen Jahren in der Gewässermikrobiologie eingeführtes Verfahren zur Bestimmung des "Heterotrophen Potentials" beschrieben. Die Vor- und Nachteile dieser Methode werden diskutiert. Ihre vielfältigen Anwendungsmöglichkeiten werden an Hand einiger Beispiele dargestellt. A method which has been used during the last few years to determine the "relative heterotrophic potential" in aquatic environments is discribed. The advantages and disadvantages involved are discussed. Some examples of the applications of this method are also given

Untersuchungen über den Einfluß des Salzgehaltes auf die Aktivität von Bakterienpopulationen des Süß- und Abwassers

Die mikrobielle Aktivität sowie die Saprophytenzahl in Abhängigkeit vom Salzgehalt wurden in abwasserbelastetem Flußwasser, dessen Salzkonzentration durch Zugabe von NaCl künstlich erhöht worden war, gemessen. Daneben fanden Untersuchungen über die Salzansprüche der 10 häufigsten Bakterienstämme der Probe statt. Außerdem wurde das Wachstum der natürlichen Bakterienpopulationen bei unterschiedlichen Salzkonzentrationen nach Zugabe von Nährstoffen bestimmt. Es zeigte sich, daß die Aktivität und die Zahl der Mikroorganismen durch die Erhöhung des Salzgehaltes stark zurückgingen. Nur eine geringfügige Adaptation konnte festgestellt werden. Nach Zugabe von Nährstoffen trat dagegen eine schnelle Umstellung der Population ein. Die Untersuchungen ergaben, daß die mit dem Flußwasser eingeschwemmten Süß- und Abwasserbakterien nur eine geringe Rolle bei der Selbstreinigung der Küstengewässer spielen. The microbial activity as well as the number of saprophytic bacteria in relation to the salt concentration was measured. The measurements were performed in river water, the salt concentration of which was raised by the addition of NaCl. Also the salinity requirements of the 10 most frequently occurring bacteria were determined. Furthermore the growth rate of the natural bacteria populations in relation to the salt concentration was measured after the addition of nutrients. The activity and the number of bacteria were strongly affected in a negative manner with increasing salt concentrations. Only a slight adaptation could be found. With higher amounts of nutrients, rapid changes in the population were observed. The results showed that the microbial populations carried into the sea by the rivers and sewage effluents can play only a minor role in the self-purification of the coastal waters

Untersuchungen über die Aufnahme von gelöster Glukose unter natürlichen Verhältnissen durch größenfraktioniertes Nano- und Ultrananoplankton

Die Inkorporation von (14C) - Glukose in Konzentrationen von 1µg C/l durch größenfraktioniertes natürliches Plankton wurde in Wasserproben aus der Kieler Förde bestimmt. Die Größenfraktionierung wurde durch Filtration mit Nuclepore-Filtern abgestufter Porengröße durchgeführt. Organismen, deren Durchmesser weniger als 1 µ betragen, waren in erster Linie (zu mehr als 69%) an der Aufnahme der Glukose beteiligt. Hierbei handelt es sich zweifellos um Bakterien. Von den größeren Fraktionen wurde relativ wenig Substrat heterotroph aufgenommen. Durch mikroskopische Untersuchungen und durch Kulturverfahren konnte nachgewiesen werden, daß auch in diesen Größenklassen die Glukose-Aufnahme durch Bakterien (auf Detritus) anteilmäßig beträchtlich ist. Die Beobachtungen führen zu dem Schluß, daß zumindest bei natürlichen Substratkonzentrationen die Aufnahme der gelösten organischen Verbindungen fast ausschließlich auf Bakterien zurückzuführen ist

Planktonic primary production in a tidally influenced mangrove forest on the Pacific coast of Costa Rica.

The seasonal variation of planktonic primary productivity was measured during one year in the main channel in the interior part of the mangrove forest of the Estero de Morales (Estero de Punta Morales), a mangrove system located in the Golfo de Nicoya at the Pacific coast of Costa Rica. Samples were incubated at the surface, 0.5 m and 1.0 m depth and the “light and dark bottle technique” was employed. The annual gross primary productivity (PPg) was 457 and the net primary productivity (PPn) was 278 g C m–2 a-1. Daily PPg ranged from 0.29 to 3.88 and PPn from 0.12 to 2.76 g C m-2 d-1. The highest rates observed in May and September were due to red tide blooms. The seasonal variation of primary productivity inside the mangrove forest depends closely on the PP in the adjacent area of the upper Golfo de Nicoya. Obviously the PP was light-limited since the compensation depth in the ebb current was found at only 1m depth. In the flood current it was somewhat deeper. The planktonic primary productivity inside the mangrove forest was completely restricted to the open channels. A simultaneous measurement demonstrated that PPn of the phytoplankton could not take place under the canopy of the mangroves. Additional studies on the time course of the oxygen concentration in the mouth of the main channel over 24 hrs demonstrated a relation between the O2 and the tidal curves. The ebb current had always lower O2 concentrations than the flood current, regardless of the time of the day. The difference to the foregoing high tide, however, was much smaller when the low tide occurred during the day. This indicates that under the canopy the net primary production and hence O2 liberation of the attached macro- and microalgae, together with the high PPn of the phytoplankton in the channels, helped the oxygen concentration not to decrease as far as during the night. Nevertheless it shows that the consumtion of organic material in the submersed part of the mangrove forest exceeds always its production

Impact of change in climate and policy from 1988 to 2007 on environmental and microbial variables at the time series station Boknis Eck, Baltic Sea

Phytoplankton and bacteria are sensitive indicators of environmental change. The temporal development of these key organisms was monitored from 1988 to the end of 2007 at the time series station Boknis Eck in the western Baltic Sea. This period was characterized by the adaption of the Baltic Sea ecosystem to changes in the environmental conditions caused by the conversion of the political system in the southern and eastern border states, accompanied by the general effects of global climate change. Measured variables were chlorophyll, primary production, bacteria number, -biomass and -production, glucose turnover rate, macro-nutrients, pH, temperature and salinity. Negative trends with time were recorded for chlorophyll, bacteria number, bacterial biomass and bacterial production, nitrate, ammonia, phosphate, silicate, oxygen and salinity while temperature, pH, and the ratio between bacteria numbers and chlorophyll increased. Strongest reductions with time occurred for the annual maximum values, e.g. for chlorophyll during the spring bloom or for nitrate during winter, while the annual minimum values remained more stable. In deep water above sediment the negative trends of oxygen, nitrate, phosphate and bacterial variables as well as the positive trend of temperature were similar to those in the surface while the trends of salinity, ammonia and silicate were opposite to those in the surface. Decreasing oxygen, even in the surface layer, was of particular interest because it suggested enhanced recycling of nutrients from the deep hypoxic zones to the surface by vertical mixing. The long-term seasonal patterns of all variables correlated positively with temperature, except chlorophyll and salinity. Salinity correlated negatively with all bacterial variables (as well as precipitation) and positively with chlorophyll. Surprisingly, bacterial variables did not correlate with chlorophyll, which may be inherent with the time lag between the peaks of phytoplankton and bacteria during spring. Compared to the 20-yr averages of the environmental and microbial variables, the strongest negative deviations of corresponding annual averages were measured about ten years after political change for nitrate and bacterial secondary production (~ −60%), followed by chlorophyll (−50%) and bacterial biomass (−40%). Considering the circulation of surface currents in the Baltic Sea we interpret the observed patterns of the microbial variables at the Boknis Eck time series station as a consequence of the improved management of water resources after 1989 and – to a minor extent – the trends of the climate variables salinity and temperature