SchussenAktivplus: reduction of micropollutants and of potentially pathogenic bacteria for further water quality improvement of the river Schussen, a tributary of Lake Constance, Germany

The project focuses on the efficiency of combined technologies to reduce the release of micropollutants and bacteria into surface waters via sewage treatment plants of different size and via stormwater overflow basins of different types. As a model river in a highly populated catchment area, the river Schussen and, as a control, the river Argen, two tributaries of Lake Constance, Southern Germany, are under investigation in this project. The efficiency of the different cleaning technologies is monitored by a wide range of exposure and effect analyses including chemical and microbiological techniques as well as effect studies ranging from molecules to communities

NON-SPREADING CYTOPHAGAS IN ACTIVATED SLUDGE

Spreading and non-spreading colonies of yellow pigmented, flexirubin- positive bacteria were observed regularly on agar plates inoculated with samples from different activated sludge and trickling filter sources. One part of the non-spreading colonies formed spreading colonies after transfer to more suitable growth media. The other part was never observed to form spreading colonies on various growth media tested. However, when examined microscopically in wet mount preparations most of the non-spreading isolates showed the same type of gliding motility as the spreading isolates. In order to test the taxonomic homogeneity as well as possible relationships to "classical" cytophagas, 25 non-spreading isolates were examined for 41 morphological and physiological characteristics. Of the strains tested, 19 had more than 80 % of the characteristics in common. Besides their deviating colony growth, the isolates differed from "classical" cytophagas by their more complex growth requirements and by a less wide spectrum of degradation capacities. It is concluded that the nonspreading isolates represent a distinct cluster within a Cytophaga group comprising all strains with gliding motility, flexirubin pigmentation and a G + C base ratio in the range of 32 - 36 %

Ectoenzymatic activities and heterotrophic bacteria decomposing detritus

15 pages, 6 figures, 1 tableOne of the largest fluxes of carbon in most of the ecosystems is that from the detritus to microorganisms. Microbial ectoenzymes play a basic role in the degradation of detritus. However, the role of ectoenzymes in dependence of the detritus composition has not been studied. In a microcosm experiment we have followed the development of nine ectoenzymatic activities and hydrolytic bacteria during the degradation of four sources of detritus (macrophytes, algae, leaves and chitin). Throughout the degradation of algae and macrophytes, a succession of ectoenzymatic activities could be observed. This succession started with the hydrolysis of oligosaccharides and starch (high α-glucosidase, β-glucosidase, exocellulase and amylase activities), and was followed by the hydrolysis of plant structural polysaccharides (endocellulase and endoxylanase activities). Such a succession was neither found in the enrichments with leaves, with lower peaks of activity, nor of chitin. This latter was characterized by a high chitinolytic activity and the highest alkaline phosphatase/peptidase ratio. Along the experiment, the number of hydrolytic colonies (amylolytic, cellulolytic, xylanolytic, chitinolytic) varied between 2-52 % of the total CFUs, amylolytic colonies generally being the most abundant (up to 35 % of total CPUs). For 20 isolates, their ability to hydrolyze starch, cellulose, xylane and chitin when offered as single carbon source was checked. Of the isolates, 55 % could use more than one polymer. Very likely, the ability to hydrolyze several carbon sources offers these bacteria the possibility to shift or even express simultaneously various enzymes. During the process of microbial decomposition of detritus shown here, characterized by changes in the available molecules, bacteria with the ability to hydrolyze several carbohydrates would have an advantage to persist in the system in contrast to bacteria that could only hydrolyze one of the tested polymers. In aquatic environments exposed to changing inputs of organic matter such as the littoral zones, bacteria with multiple hydrolytic potential would very likely show a better adaptationThe study was supported by the joint research project “Cycling of organic matter in Lake Constance”Peer Reviewe

Seasonal dynamics of pelagic and benthic (littoral and profundal) bacterial abundances and activities in a deep prealpine lake (L. Constance)

19 pages, 5 figures, 1 tableIn order to obtain a first insight into the characteristics of pelagic, littoral and profundal bacterial communities and their potential role for the degradation of organic matter in the deep prealpine Lake Constance, we compared the seasonal dynamics of bacterial abundances and activities during the annual cycle in the epilimnetic water of a central station as well as in surface layers of sediments at a central profundal and a littoral site. For this purpose, bacterial abundances (DAPI counts), rates of leucine incorporation, respiration of 14C-labeled substrates (glucose, phenol) and ectoenzymatic activities were measured biweekly-monthly at the different sampling sites. Bacterial densities in lake sediments generally exceeded those of epilimnetic waters by at least two orders of magnitude with higher values in profundal sediments. A seasonal pattern was well expressed for bacterioplankton, less pronounced for benthic littoral bacteria and hardly visible for profundal bacteria. Compared to pelagic bacteria, benthic bacteria exhibited lower specific rates of leucine incorporation, especially during the warmer periods. For profundal benthic communities specific rates of glucose respiration and of enzyme activities were permanently low with little seasonal fluctuation. In contrast, littoral benthic communities showed the highest values for these specific metabolic activities among the three sites tested. Additionally, the capacity of metabolism of phenol (used here as a representative of more recalcitrant aromatic substances) was by far highest respired for littoral communities, and almost lacking for pelagic communities. Evidence from the literature suggests that the qualitatively and quantitatively enhanced level of degradation capacities observed for littoral bacteriobenthos may be predominantly a result of the combined effect of increased supply of additional organic matter (e.g. allochthonous matter and macrophytes), an enriched bacterial gene reservoir in sediments, and frequent resuspension. Littoral benthic communities showed the highest specific metabolic activities exceeding those of bacterioplankton and profundal bacteriobenthos by an order of magnitude. As a whole, our results indicate that the overall contribution of the littoral area to degradation of organic matter must be comparable to that of the total pelagic water body although it comprises less than 10% of the lake surfaceThis study was supported by the joint research project "Cycling of organic matter in Lake Constance" and both by a FPI fellowship grant from the Spanish Ministry os Science and Education and a CSIC I3P post-doctoral contract financed by the Fondo Social Europeo to M.M.S.Peer reviewe

Influence of metazoan zooplankton on the microbial community before and after the onset of the spring clear-water phase in Lake Constance (Bodensee)

Shortly before and shortly after the onset of the spring clear-water phase, we took plankton samples from the epilimnion of Lake Constance and incubated them in the laboratory under in situ conditions. In three duplicated treatments, mesozooplankton gt 100 mu-m were removed, left at natural densities or enriched nine-fold. Before the clear-water phase, cyclopoid copepods dominated the mesozooplankton, bacteria probably were controlled by high heterotrophic flagellate densities, and the most important phytoplankton grazers apparently were in the fraction lt 100 mu (ciliates, rotifers). In the copepod enrichments, these small grazers were decimated and chlorophyll a and autotrophic picoplankton reached the highest concentrations. Heterotrophic flagellates did not respond clearly to the different treatments. After the onset of the clear-water phase, Daphnia dominated the mesozooplankton and controlled most components of the microbial food web as well as the phytoplankton. All biomass parameters of the phytoplankton, autotrophic picoplankton, heterotrophic flagellates, and ciliates increased when Daphnia were removed. Bacterial abundances did not respond clearly to the removal of mesozooplankton, because protozoans became important bacterial grazers when they were released from the control by Daphni

Allochthonous contribution to seasonal and spatial variability of organic matter sedimentation in a deep oligotrophic lake (Lake Constance)

Previous studies analysing the chemical composition of profundal sediments of Lake Constance suggest a overall large contribution of allochthonous material to total sedimentation but also a large spatial variability in the relative importance of allochthonous versus autochthonous sedimentation. Here we analyse sedimenting particulate organic matter (POM sed) during an annual cycle at two sites differing in their position relative to the major inflow and thus in their proposed contribution of allochthonous matter to the sedimentary flux, i.e., site [AL] characterised by a more allochthonous contribution und the site [AU] characterised by a more autochthonous contribution