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Berlin Brandenburg

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  • 1
    In: Journal of Phycology, August 2009, Vol.45(4), pp.807-811
    Description: Algae of various taxonomic groups are capable of assimilating dissolved organic carbon (DOC) from their environments (mixotrophy). Recently, we reported that, with increasing biomass of mixotrophs, heterotrophic bacteria did not increase. We hypothesized that algal uptake of external DOC may outweigh their release of DOC by exudation (H1). Here, we addressed an alternative hypothesis that algae did not assimilate external DOC but constrained the release of DOC (H2). In chemostat experiments, we cultured the mixotrophic Negoro together with heterotrophic bacteria. As external substrates, we used glucose, which was potentially available for both bacteria and algae, or fructose, which was available only for bacteria. We increased the biomass of algae by the stepwise addition of phosphorus. Bacterial biomass did not increase in experiments using glucose or when fructose was offered, suggesting that mechanisms other than algal mixotrophy (H1) kept concentrations of bacteria low. Measured exudation rates (percent extracellular release, PER) of mixotrophic algae ( W. Krüger) were very low and ranged between 1.0% and 3.5% at low and moderately high phosphorus concentrations. In contrast, an obligately phototrophic alga ( H. Ettl) showed higher exudation rates, particularly under phosphorus limitation (70%). The results support H2. If mixotrophy is considered as a mechanism to recycle organic exudates from near the cell surface, this would explain why algae retained mixotrophic capabilities although they cannot compete with bacteria for external organic carbon.
    Keywords: Algae ; Bacteria ; Chemostat ; Competition ; Doc ; Exudation ; Mixotroph
    ISSN: 0022-3646
    E-ISSN: 1529-8817
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  • 2
    Language: English
    In: Hydrobiologia, 2010, Vol.649(1), pp.379-383
    Description: To investigate the consequences of increased temperature and enhanced input of dissolved organic matter (DOM) into lakes for heterotrophicic bacteria and for mixotrophic algae which use DOM in addition to photosynthesis, the hypotheses were tested whether (1) both bacteria and mixotrophic algae benefit from increased input of DOM, or (2) increased DOM input enhances bacterial biomass and thereby decreases algal biomass. Growth experiments in batch cultures, exudation measurements, and competition experiments in chemostats were performed at two temperature levels. Increased temperature stimulated the autotrophic growth rate of Chlorella protothecoides . Bacteria and Chlorella increased their heterotrophic growth rates at higher DOM concentration at lower temperature whereas enhanced DOM concentration hardly stimulated their growth at higher temperature. In chemostats, enhanced input of soil extract increased both bacterial and algal biomass at lower temperature whereas bacterial biomass increased only slightly and algal biomass decreased at higher temperature. Thus, the temperature determines the response of microorganisms to enhanced DOM concentration.
    Keywords: Bacteria ; Mixotrophic algae ; Temperature ; DOM ; Climate change ; Chemostat
    ISSN: 0018-8158
    E-ISSN: 1573-5117
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  • 3
    Language: English
    In: Science of the Total Environment, 01 April 2016, Vol.548-549, pp.51-59
    Description: Enhanced concentrations of dissolved organic matter (DOM) in freshwaters are an increasing problem in drinking water reservoirs. In this study we investigated bacterial DOM degradation rates in the tributaries of the reservoirs and tested the hypotheses that (1) DOM degradation is high enough to decrease DOM loads to reservoirs considerably, (2) DOM degradation is affected by stream hydrology, and (3) phosphorus addition may stimulate bacterial DOM degradation. Bacterial biomass production, which was used as a measure of DOM degradation, was highest in summer, and was usually lower at upstream than at downstream sites. An important proportion of bacterial production was realized in epilithic biofilms. Production of planktonic and biofilm bacteria was related to water temperature. Planktonic production weakly correlated to DOM quality and to total phosphorus concentration. Addition of soluble reactive phosphorus did not stimulate bacterial DOM degradation. Overall, DOM was considerably degraded in summer at low discharge levels, whereas degradation was negligible during flood events (when DOM load in reservoirs was high). The ratio of DOM degradation to total DOM release was negatively related to discharge. On annual average, only 0.6–12% of total DOM released by the catchments was degraded within the tributaries.
    Keywords: Bacterial Production ; Doc ; Freshness Index ; Humification Index ; Phosphorus ; Environmental Sciences ; Biology ; Public Health
    ISSN: 0048-9697
    E-ISSN: 1879-1026
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  • 4
    In: Journal of Plankton Research, 2012, Vol. 34(10), pp.922-927
    Description: Ingestion of the large pelagic ciliates Stentor araucanus and S. amethystinus by the cyclopoid copepod Mesocyclops araucanus was independent of light conditions and copepod sex, but rates were twice as high on S. araucanus as on S. amethystinus . Copepods consumed 44–183% of their biomass daily. Absorption efficiency was 5–40%, while 20–30% of the ingested food was found in the faeces. In field samples, 32–93% of Mesocyclops had ingested Stentor, indicating the importance of this food source.
    Keywords: Predation ; Cyclopoid Copepods ; Mixotrophic Ciliates ; 〈Kwd〉〈Italic〉Stentor〈/Italic〉〈/Kwd〉 ; North Patagonian Lakes
    ISSN: 0142-7873
    E-ISSN: 1464-3774
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  • 5
    Language: English
    In: Journal of Microbiological Methods, February 2016, Vol.121, pp.8-10
    Description: A method for recovering CO respired by bacterioplankton for analysis of carbon isotopes was adapted for use with standard laboratory equipment without a technically demanding harvest line. The recovered CO was more depleted in C than the dissolved organic carbon (DOC) source, which suggests a selective respiration of older carbon.
    Keywords: Dissolved Organic Carbon (Doc) ; Inorganic Carbon (Ic) ; Degradation ; Carbon Isotopes ; Reservoir ; Biology
    ISSN: 0167-7012
    E-ISSN: 1872-8359
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  • 6
    In: Journal of Plankton Research, 2012, Vol. 34(2), pp.102-112
    Description: Aquatic bacteria are considered to exhibit a paradoxical behaviour. They luxuriously consume phosphorus, the element often restricting the abundance of algae, which provide the organic substrates maintaining bacterial growth. Here, we test the hypothesis that bacteria can limit their uptake of phosphorus and increase the availability of phosphorus to algae. The physiological costs for bacteria must be compensated for by a surplus of photosynthetic exudates facilitating higher biomass production. To test the potential of such an economic behaviour, we used a new differential equation model that was parameterized by independent experiments. Model results indicate that this potential does exist. As a consequence, we conducted continuous growth chemostat experiments. Bacteria did not leave more phosphorus to, “high exudation” algae compared with algae with low release. Therefore, the hypothesis was not supported by the experiments. However, bacteria significantly increased production 1.4–1.8-fold in cultures with “high exudation” algae. This was explained by an increase in conversion of organic carbon from growth medium into bacteria biomass. Algal exudates were quantitatively negligible but could act as growth factors. The results show that biomass of algae and bacteria cannot be predicted solely by mineral nutrients and carbon as assumed by the classical theory.
    Keywords: Bacteria ; Phytoplankton ; Exudation ; Phosphorus ; Differential Equation Model
    ISSN: 0142-7873
    E-ISSN: 1464-3774
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  • 7
    In: Freshwater Biology, August 2004, Vol.49(8), pp.1062-1071
    Description: 1. Lakes formed in mining pits often contain high concentrations of dissolved ferric iron and sulphate (e.g. 2 and 16 mmol L, respectively) and the pH is buffered between 2.5 and 3.5. Efforts to neutralise their water are based on the stimulation of lake internal, bacterial iron‐ and sulphate reduction. Electron donors may be supplied by organic carbon compounds or indirectly by enhancement of primary production. Here, we investigated the function of mixotrophic algae, which can potentially supplement or deplete the organic carbon pool, in the carbon metabolism and alkalinity budget of an acidic mining lake. 2. Two weeks after organic substrates had been added in a large mesocosm of 30 m diameter, a bloom of occurred, reaching a biovolume of 80 mm L. Growth experiments using filtered lake water showed that the alga reduced the overall dissolved organic carbon (DOC) concentration despite significant photosynthetic activity. However, when were grown together with natural bacterioplankton, net DOC consumption did not increase. 3. Uptake experiments using [C]‐glucose indicated that bacteria dominated glucose uptake and remineralisation. Therefore, the DOC leached in the water column was processed mainly by planktonic bacteria. Leached DOC must be regarded as loss, not transferred by larger organisms to the sediment, where reduction processes take place. 4. From phytoplankton biomass and production 2 years after fertilisation we estimated that pelagic photosynthesis does not supply an electron donor capacity capable of reducing more than 2% of actual stock of acidity per year. We estimated that only the benthic primary production was in a range to compensate for ongoing inputs of iron and sulphate.
    Keywords: Acidic ; Chlamydomonas ; Mining Lakes ; Mixotrophic ; Organic Carbon
    ISSN: 0046-5070
    E-ISSN: 1365-2427
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  • 8
    Language: English
    In: Environmental Monitoring and Assessment, 2015, Vol.187(7), pp.1-13
    Description: As benthic biofilms mediate essential functions in stream ecosystems (e.g., carbon flux, storage of nutrients and other substances), the element-specific regulation of the biofilm composition is of great interest. We tested whether (1) the elemental composition of biofilms is related to that of the water column and (2) there are different accumulation patterns from the dissolved phase (adsorption) and the particulate phase (incorporation of suspended matter). We analysed biomass parameters, nutrients and metals in biofilms and surface waters at 28 sites within a stream network (Bode catchment, Germany). Algal biomass in biofilms was dominated by diatoms. The P/C ratio in biofilms was positively related to total phosphorus of surface water (and to the proportion of agricultural area in the catchment) indicating phosphorus limitation of biofilms, whereas the N/C ratio was not related to nitrate levels of surface water, and neither the P/C nor the N/C ratio to the concentration of dissolved organic carbon (DOC) of surface water. Biofilms were enriched in metals compared to their concentrations in water. The metals in biofilms were positively related to the concentration of dissolved metals in surface water for iron and strontium (but not for manganese, copper, zinc, arsenic or lead) and to the concentrations of particle-associated metals of surface waters for strontium and lead. Manganese and arsenic were the metals with a negative effect on the biomasses of biofilm diatoms and cyanobacteria. Overall, we observed element-specific accumulation patterns in biofilms with selected elements being related to the water column while others were probably subject to biofilm-internal processes.
    Keywords: Nutrients ; Stoichiometry ; Heavy metals ; Total reflection X-ray fluorescence spectrometry (TXRF) ; Stream biofilms ; River Bode
    ISSN: 0167-6369
    E-ISSN: 1573-2959
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  • 9
    In: Journal of Plankton Research, 2006, Vol.28(7), pp.707-718
    Description: To test the consequences of decreased diversity and exclusion of keystone species, we compared the planktonic food webs in two acidic (pH3), species-poor mining lakes with those in two species-rich, neutral lakes. The ratio of heterotrophic to autotrophic biomass (H/A) was similar in acidic and neutral lakes with comparable productivity. However, food webs in both acidic lakes were largely restricted to two trophic levels in contrast to the four levels found in neutral lakes. This restriction in food chain length was attributed to the absence of efficient secondary consumers, rather than to productivity or lake size which resulted in unusually low predatorprey weight ratios, with small top predators hardly exceeding their prey in size. In contrast to the neutral lakes, plankton biomass size spectra of acidic lakes were discontinuous due to a lack of major functional groups. The unique size-dependence of feeding modes in pelagic food webs, with bacteria in the smallest size classes followed by autotrophs, herbivores and carnivores, was maintained for bacteria but the other feeding modes strongly overlapped in size. Thus, their characteristic succession along the size gradient was roughly preserved under extreme conditions but the flow of energy along the size gradient was truncated in the acidic lakes. For most but not all attributes studied, differences were larger between acidic and neutral lakes than between neutral lakes of different trophic state.
    Keywords: Feeding ; Plankton Surveys ; Food Chains ; Predation ; Carnivores ; Predators ; Biomass ; Trophic Levels ; Lakes ; Herbivores ; Interspecific Relationships ; Predator Prey Interactions ; Species Diversity ; Consumers ; Mining ; Prey ; Plankton ; Food Webs ; Plankton Surveys ; Feeding ; Food Chains ; Predation ; Carnivores ; Predators ; Biomass ; Succession ; Trophic Levels ; Keystone Species ; Predator-Prey Interactions ; Lakes ; Herbivores ; Interspecific Relationships ; Structure-Function Relationships ; Species Diversity ; Consumers ; Mining ; Prey ; Plankton ; Food Webs ; Freshwater ; Ecosystems and Energetics ; Effects on Organisms ; Ecosystem and Ecology Studies ; Ecology;
    ISSN: 0142-7873
    E-ISSN: 1464-3774
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  • 10
    Language: English
    In: International Biodeterioration & Biodegradation, April 2012, Vol.69, pp.17-22
    Description: To investigate biofilm growth on paints under field conditions, we developed a modified approach enabling subsequent Confocal Laser Scanning Microscopy (CLSM) for the three-dimensional analysis of undisturbed samples. Painted polycarbonate slides were glued on polycarbonate panels mounted on a test raft in a harbour, and one slide per paint and depth was used on each of the five sampling dates over three months. On seven out of ten paints, biomass dry weight and chlorophyll a of biofilms increased nearly linearly over time whereas biofilm development was inhibited on three paints. Quantitative CLSM results revealed that extracellular polymeric substances were the dominating component of the biofilms. Since top-view CLSM did not enable the complete observation of thick biofilms, cryosections were prepared to determine biofilm thickness. Results of biofilm thickness were comparable to those of biomass and chlorophyll. The vertical extension of CLSM top-view images was not related to biomass dry weight and to biofilm thickness from cryosections and was, therefore, no suitable measure for biofilm characterisation. In contrast, biofilm thickness measured from cryosections was positively related to biomass dry weight indicating the need of cryosections for thick biofilms. ► Painted polycarbonate slides enabled CLSM analyses of undisturbed biofilms. ► Extracellular polymeric substances were the dominating biofilm component. ► Biofilm thickness from cryosections was positively related to biomass dry weight. ► The preparation of cryosections is necessary to investigate thick biofilms. ► CLSM is a suitable method for investigating biofilms on paints in the field.
    Keywords: Bacteria ; Diatoms ; EPS ; Confocal Laser Scanning Microscopy ; Paint ; Cryosection ; Engineering ; Biology ; Anatomy & Physiology
    ISSN: 0964-8305
    E-ISSN: 1879-0208
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