@article{KamjunkeMendoncaHardewigetal.2002, author = {Kamjunke, Norbert and Mendonca, Rebeca and Hardewig, Iris and Mehner, Thomas}, title = {Assimilation of different cyanobacteria as food and the consequences for internal energy stores of juvenile roach}, year = {2002}, abstract = {Juvenile roach (Rutilus rutilus L.) fed on the cyanobacterium Aphanizomenon were able to maintain liver glycogen and muscle protein concentrations. In contrast, internal energy stores of fish fed on the cyanobacterium Microcystis were degraded. However, liver glycogen was higher than in starved fish, suggesting that roach was able to obtain some nutrients (probably carbohydrates) from the mucus cover of Microcystis. Weak assimilation of radiolabeled Microcystis by roach was detectable, and assimilation rates increased with increasing proportion of Aphanizomenon in a mixture of both cyanobacteria. We conclude that the incomplete digestion of Microcystis was the main reason for the negative growth rates of roach when fed on this cyanobacterium species.}, language = {en} } @article{KamjunkeSchmidtPflugmacheretal.2002, author = {Kamjunke, Norbert and Schmidt, Katja and Pflugmacher, Stephan and Mehner, Thomas}, title = {Consumption of cyanobacteria by roach (Rutilus rutilus) : useful or harmful to the fish?}, year = {2002}, abstract = {1. The ability of roach to use cyanobacterial food is generally believed to be one reason for the dominance of roach over perch in eutrophic European lakes. The aim of this study was to test whether cyanobacteria really are a suitable food for juvenile roach. Special attention was paid to differences between the two cyanobacteria species Aphanizomenon and Microcystis which are common in eutrophic lakes and are ingested by roach there. 2. We performed growth and behaviour experiments with juvenile roach fed with zooplankton and the different cyanobacteria. Growth rate with Aphanizomenon was lower than with Daphnia but significantly higher than without food, whereas growth rate with Microcystis was as low as without food. 3. In cultivation experiments of roach faeces, Microcystis was found not to have been digested and grew exponentially after passing through the gut whereas Aphanizomenon stayed at low biomass. Differences in growth were not related to the toxin content of cyanobacteria. Investigations of roach motility showed no differences whether fed Aphanizomenon or Microcystis. 4. In contrast to Microcystis, Aphanizomenon can be regarded as a suitable food source for juvenile roach probably due to its better digestability. We conclude that the ability to feed on cyanobacteria is not a general competitive advantage for roach, but the outcome depends on the species composition of the cyanobacteria.}, language = {en} } @article{KamjunkeMehner2001, author = {Kamjunke, Norbert and Mehner, Thomas}, title = {Coupling the microbial food web with fish : are bacteria attached to cyanobacteria an important food source for underyearling roach?}, year = {2001}, abstract = {1. After observing that juvenile roach fed intensively on cyanobacteria and that cyanobacteria were densely colonized by heterotrophic bacteria, we tested whether the bacteria are used by underyearling roach and the extent to which they contribute to the energy requirements of the fish. 2. We radiolabeled attached bacteria in a natural cyanobacterial suspension, fed the fish with these particles, and estimated their assimilation by roach. Biomass of attached bacteria on cyanobacteria increased with the proportion of the cyanobacterium Microcystis in total cyanobacteria. Biomass-specific thymidine incorporation of attached bacteria was higher than that of free bacteria. 3. In feeding experiments, we detected assimilation of bacterial biomass into muscle tissue of underyearling roach. Fish consumed Microcystis to a lesser extent compared to Aphanizomenon but assimilation of attached bacteria was higher when roach fed on Microcystis due to the higher biomass of epibacteria on this cyanobacterium. However, biomass of attached bacteria was too low to be an important food source for underyearling roach. 4. We conclude that assimilation of epibacteria from cyanobacteria cannot explain the success of roach in eutrophic lakes.}, language = {en} } @article{AttermeyerTittelAllgaieretal.2015, author = {Attermeyer, Katrin and Tittel, Joerg and Allgaier, Martin and Frindte, Katharina and Wurzbacher, Christian and Hilt, Sabine and Kamjunke, Norbert and Grossart, Hans-Peter}, title = {Effects of Light and Autochthonous Carbon Additions on Microbial Turnover of Allochthonous Organic Carbon and Community Composition}, series = {Microbial ecology}, volume = {69}, journal = {Microbial ecology}, number = {2}, publisher = {Springer}, address = {New York}, issn = {0095-3628}, doi = {10.1007/s00248-014-0549-4}, pages = {361 -- 371}, year = {2015}, abstract = {The fate of allochthonous dissolved organic carbon (DOC) in aquatic systems is primarily controlled by the turnover of heterotrophic bacteria. However, the roles that abiotic and biotic factors such as light and DOC release by aquatic primary producers play in the microbial decomposition of allochthonous DOC is not well understood. We therefore tested if light and autochthonous DOC additions would increase allochthonous DOC decomposition rates and change bacterial growth efficiencies and community composition (BCC). We established continuous growth cultures with different inocula of natural bacterial communities and alder leaf leachates (DOCleaf) with and without light exposure before amendment. Furthermore, we incubated DOCleaf together with autochthonous DOC from lysed phytoplankton cultures (DOCphyto). Our results revealed that pretreatments of DOCleaf with light resulted in a doubling of bacterial growth efficiency (BGE), whereas additions of DOCphyto or combined additions of DOCphyto and light had no effect on BGE. The change in BGE was not accompanied by shifts in the phylogenetic structure of the BCC, but BCC was influenced by the DOC source. Our results highlight that a doubling of BGE is not necessarily accompanied by a shift in BCC and that BCC is more strongly affected by resource properties.}, language = {en} } @article{KamjunkeTittelKrumbecketal.2005, author = {Kamjunke, Norbert and Tittel, J{\"o}rg and Krumbeck, H. and Beulker, Camilla and Poerschmann, J.}, title = {High heterotrophic bacterial production in acidic, iron-rich mining lakes}, issn = {0095-3628}, year = {2005}, abstract = {The acidic mining lakes of Eastern Germany are characterized by their extremely low pH and high iron concentrations. Low concentrations of CO2 in the epilimnion due to the low pH and reduced light transmission due to dissolved ferric iron potentially limit phytoplankton primary production (PP), whereas dissolved organic carbon (DOC) may promote heterotrophic production of bacteria (HP). We, therefore, tested whether HP exceeds PP in three lakes differing in pH and iron concentration (mean pH 2.3-3.0, 23-500 mg Fe L-1). Bacterial biomass and HP achieved highest values in the most acidic, most iron-rich lake, whereas PP was highest in the least acidic lake. HP was often higher than PP (ratio HP/PP up to 11), indicating that planktonic PP was not the main carbon source for the bacteria. HP was not related to PP and DOC, but HP as well as bacterial biomass increased with decreasing pH. Light stimulated the formation of ferrous iron, changed the DOC composition, and increased the HP in laboratory experiments, suggesting that iron photoreduction caused DOC degradation. This may explain why we found the highest HP in the most acidic and most rich lake. Overall, the importance of bacteria in the cycling of matter and as a basis for the whole food web seemed to increase in more acidic lakes with higher iron concentrations}, language = {en} } @article{KamjunkeRodeBaborowskietal.2021, author = {Kamjunke, Norbert and Rode, Michael and Baborowski, Martina and Kunz, Julia Vanessa and Zehner, Jakob and Borchardt, Dietrich and Weitere, Markus}, title = {High irradiation and low discharge promote the dominant role of phytoplankton in riverine nutrient dynamics}, series = {Limnology and oceanography / American Society of Limnology and Oceanography}, volume = {66}, journal = {Limnology and oceanography / American Society of Limnology and Oceanography}, number = {7}, publisher = {Wiley}, address = {Hoboken}, issn = {0024-3590}, doi = {10.1002/lno.11778}, pages = {2648 -- 2660}, year = {2021}, abstract = {Rivers play a relevant role in the nutrient turnover during the transport from land to ocean. Here, highly dynamic planktonic processes are more important compared to streams making it necessary to link the dynamics of nutrient turnover to control mechanisms of phytoplankton. We investigated the basic conditions leading to high phytoplankton biomass and corresponding nutrient dynamics in eutrophic, 8th order River Elbe (Germany). In a first step, we performed six Lagrangian sampling campaigns in the lower river section at different hydrological conditions. While nutrient concentrations remained high at low algal densities in autumn and at moderate discharge in summer, high algal concentrations occurred at low discharge in summer. Under these conditions, concentrations of silica and nitrate decreased and rates of nitrate assimilation were high. Soluble reactive phosphorus was depleted and particulate phosphorus increased inversely. Rising molar C:P ratios of seston indicated a phosphorus limitation of phytoplankton, so far rarely observed in eutrophic large rivers. Global radiation combined with mixing depth had a strong predictive power to explain maximum chlorophyll concentration. In a second step, we estimated nutrient turnover exemplarily for N during the campaign with the lowest discharge based on mass balances and metabolism-based process measurements. Mass balance calculations revealed a total nitrate uptake of 423 mg N m(-2)d(-1). Increasing phytoplankton density dominantly explained whole river gross primary production and related assimilatory nutrient uptake. In conclusion, riverine nutrient uptake strongly depends on the growth conditions for phytoplankton, which are favored at high irradiation and low discharge.}, language = {en} } @article{TittelBissingerGaedkeetal.2005, author = {Tittel, J{\"o}rg and Bissinger, Vera and Gaedke, Ursula and Kamjunke, Norbert}, title = {Inorganic carbon limitation and mixotrophic growth in Chlamydomonas from an acidic mining lake}, issn = {1434-4610}, year = {2005}, abstract = {Plankton communities in acidic mining lakes (pH 2.5-3.3) are species-poor because they face extreme environmental conditions, e.g. 150 mg l(-1) Fe2++Fe3+. We investigated the growth characteristics of the dominant pigmented species, the flagellate Chlamydomonas acidophila, in semi-continuous culture experiments under in situ conditions. The following hypotheses were tested: (1) Low inorganic carbon (IC) concentrations in the epilimnion (e.g. 0.3 mg l(-1)) arising from the low pH limit phototrophic growth (H-1); (2) the additional use of dissolved organic carbon (mixotrophy) leads to higher growth rates under IC-limitation (H-2), and (3) phagotrophy is not relevant (H-3). H- 1 was supported as the culture experiments, in situ PAR and IC concentrations indicated that IC potentially limited phototrophic growth in the mixed surface layers. H-2 was also supported: mixotrophic growth always exceeded pure phototrophic growth even when photosynthesis was saturated. Dark growth in filtered lake water illuminated prior to inoculation provided evidence that Chlamydomonas was able to use the natural DOC. The alga did not grow on bacteria, thus confirming H-3. Chlamydomonas exhibited a remarkable resistance to starvation in the dark. The compensation light intensity (ca. 20 mu mol photons m(-2) s(-1)) and the maximum phototrophic growth (1.50 d(-1)) fell within the range of algae from non-acidic waters. Overall, Chlamydomonas, a typical r-strategist in circum-neutral systems, showed characteristics of a K-strategist in the stable, acidic lake environment in achieving moderate growth rates and minimizing metabolic losses. (c) 2005 Elsevier GmbH. All rights reserved}, language = {en} } @article{KamjunkeBeckersHerzsprungetal.2022, author = {Kamjunke, Norbert and Beckers, Liza-Marie and Herzsprung, Peter and von T{\"u}mpling, Wolf and Lechtenfeld, Oliver and Tittel, J{\"o}rg and Risse-Buhl, Ute and Rode, Michael and Wachholz, Alexander and Kallies, Rene and Schulze, Tobias and Krauss, Martin and Brack, Werner and Comero, Sara and Gawlik, Bernd Manfred and Skejo, Hello and Tavazzi, Simona and Mariani, Giulio and Borchardt, Dietrich and Weitere, Markus}, title = {Lagrangian profiles of riverine autotrophy, organic matter transformation, and micropollutants at extreme drought}, series = {The science of the total environment : an international journal for scientific research into the environment and its relationship with man}, volume = {828}, journal = {The science of the total environment : an international journal for scientific research into the environment and its relationship with man}, publisher = {Elsevier}, address = {Amsterdam}, issn = {0048-9697}, doi = {10.1016/j.scitotenv.2022.154243}, pages = {14}, year = {2022}, abstract = {On their way from inland to the ocean, flowing water bodies, their constituents and their biotic communities are ex-posed to complex transport and transformation processes. However, detailed process knowledge as revealed by La-grangian measurements adjusted to travel time is rare in large rivers, in particular at hydrological extremes. To fill this gap, we investigated autotrophic processes, heterotrophic carbon utilization, and micropollutant concentrations applying a Lagrangian sampling design in a 600 km section of the River Elbe (Germany) at historically low discharge. Under base flow conditions, we expect the maximum intensity of instream processes and of point source impacts. Phy-toplankton biomass and photosynthesis increased from upstream to downstream sites but maximum chlorophyll con-centration was lower than at mean discharge. Concentrations of dissolved macronutrients decreased to almost complete phosphate depletion and low nitrate values. The longitudinal increase of bacterial abundance and production was less pronounced than in wetter years and bacterial community composition changed downstream. Molecular analyses revealed a longitudinal increase of many DOM components due to microbial production, whereas saturated lipid-like DOM, unsaturated aromatics and polyphenols, and some CHOS surfactants declined. In decomposition exper-iments, DOM components with high O/C ratios and high masses decreased whereas those with low O/C ratios, low masses, and high nitrogen content increased at all sites. Radiocarbon age analyses showed that DOC was relatively old (890-1870 years B.P.), whereas the mineralized fraction was much younger suggesting predominant oxidation of algal lysis products and exudates particularly at downstream sites. Micropollutants determining toxicity for algae (terbuthylazine, terbutryn, isoproturon and lenacil), hexachlorocyclohexanes and DDTs showed higher concentrations from the middle towards the downstream part but calculated toxicity was not negatively correlated to phytoplankton. Overall, autotrophic and heterotrophic process rates and micropollutant concentrations increased from up-to down-stream reaches, but their magnitudes were not distinctly different to conditions at medium discharges.}, language = {en} } @article{WeithoffMoserKamjunkeetal.2010, author = {Weithoff, Guntram and Moser, Michael and Kamjunke, Norbert and Gaedke, Ursula and Weisse, Thomas}, title = {Lake morphometry and wind exposure may shape the plankton community structure in acidic mining lakes}, issn = {0075-9511}, doi = {10.1016/j.limno.2009.11.002}, year = {2010}, abstract = {Acidic mining lakes (pH <3) are specific habitats exhibiting particular chemical and biological characteristics. The species richness is low and mixotrophy and omnivory are common features of the plankton food web in such lakes. The plankton community structure of mining lakes of different morphometry and mixing type but similar chemical characteristics (Lake 130, Germany and Lake Langau, Austria) was investigated. The focus was laid on the species composition, the trophic relationship between the phago-mixotrophic flagellate Ochromonas sp. and bacteria and the formation of a deep chlorophyll maximum along a vertical pH-gradient. The shallow wind-exposed Lake 130 exhibited a higher species richness than Lake Langau. This increase in species richness was made up mainly by mero-planktic species, suggesting a strong benthic/littoral - pelagic coupling. Based on the field data from both lakes, a nonlinear, negative relation between bacteria and Ochromonas biomass was found, suggesting that at an Ochromonas biomass below 50 mu g CL-1. the grazing pressure on bacteria is low and with increasing Ochromonas biomass bacteria decline. Furthermore, in Lake Langau, a prominent deep chlorophyll maximum was found with chlorophyll concentrations ca. 50 times higher than in the epilimnion which was build up by the euglenophyte Lepocinclis sp. We conclude that lake morphometry, and specific abiotic characteristics such as mixing behaviour influence the community structure in these mining lakes.}, language = {en} } @article{KamjunkeJaehnichen2000, author = {Kamjunke, Norbert and J{\"a}hnichen, Sabine}, title = {Leucine incorporation by Microcystis aeruginosa}, year = {2000}, abstract = {In experiments with axenic cultures of Microcystis aeruginosa, we tested whether this cyanobacterium incorporates leucine, a compound that is often used for the measurement of heterotrophic bacterioplankton production. Microcystis showed significant leucine incorporation, and the uptake of exponentially growing cells was higher than the uptake of cells in stationary growth phase. Therefore, the leucine method may not be suitable for measuring bacterial production in highly eutrophic waters with a dominance of cyanobacteria.}, language = {en} }