@article{TittelWiehleWannickeetal.2009,
  author    = {Tittel, Joerg and Wiehle, Ines and Wannicke, Nicola and Kampe, Heike and Poerschmann, Juergen and Meier, Jutta and Kamjunke, Norbert},
  title     = {Utilisation of terrestrial carbon by osmotrophic algae},
  issn      = {1015-1621},
  doi       = {10.1007/s00027-008-8121-2},
  year      = {2009},
  abstract  = {Terrestrial-derived dissolved organic carbon (DOC) contributes significantly to the energetic basis of many aquatic food webs. Although heterotrophic bacteria are generally considered to be the sole consumers of DOC, algae and cyanobacteria of various taxonomic groups are also capable of exploiting this resource. We tested the hypothesis that algae can utilise DOC in the presence of bacteria if organic resources are supplied in intervals by photolysis of recalcitrant DOC. In short-term uptake experiments, we changed irradiation in the range of minutes. As model substrates, polymers of radiolabelled coumaric acid (PCA) were used, which during photolysis are known to release aromatic compounds comparable to terrestrial-derived and refractory DOC. Three cultured freshwater algae readily assimilated PCA photoproducts equivalent to a biomass-specific uptake of 5-60\% of the bacterial competitors present. Algal substrate acquisition did not depend on whether PCA was photolysed continuously or in intervals. However, the data show that photoproducts of terrestrial DOC can be a significant resource for osmotrophic algae. In long-term growth experiments, interval light was applied one hour per day. We allowed cultured Chlamydomonas to compete for ambient DOC of low concentration. We found higher abundances of Chlamydomonas when cultures were irradiated intermittently rather than continuously. These data suggest that photolysis of DOC supports algal heterotrophy, and potentially facilitates growth, when light fluctuations are large, as during the diurnal light cycle. We concluded that osmotrophic algae can efficiently convert terrestrial carbon into the biomass of larger organisms of aquatic food webs.},
  language  = {en}
}
@article{KamjunkeBohnGrey2006,
  author    = {Kamjunke, Norbert and Bohn, Christiane and Grey, John},
  title     = {Utilisation of dissolved organic carbon from different sources by pelagic bacteria in an acidic mining lake},
  issn      = {0003-9136},
  doi       = {10.1127/0003-9136/2006/0165-0355},
  year      = {2006},
  abstract  = {We compared growth rates and efficiencies of pelagic bacteria from an extremely acidic mining lake (pH 2.6, mean depth 4.6m) supplied with different sources of carbon: (1) excreted by phytoplankton, (2) derived from benthic algae, (3) entering the lake via ground water, and (4) leached from leaf litter. Bacteria exhibited high growth rate and efficiency on exudates of pelagic and benthic algae. In contrast, they showed a lower growth rate and efficiency with organic carbon from ground water, and grew at a very high rate but a very low efficiency on leaf leachate. Results from stable isotope analyses indicate a greater importance of benthic exudates and leaf leachate for bacteria in the epilimnion, and a higher impact of ground water sources in the hypolimnion. Given the magnitude of differential source inputs into the lake, we suggest that benthic primary production was the most important carbon source for pelagic bacteria. The benthic-pelagic coupling seems to be more relevant in this shallow acidic lake with low pelagic carbon dioxide concentrations than in neutral lakes},
  language  = {en}
}
@article{KamjunkeVogtWoelfl2009,
  author    = {Kamjunke, Norbert and Vogt, Bernhard and Woelfl, Stefan},
  title     = {Trophic interactions of the pelagic ciliate Stentor spp. in North Patagonian lakes},
  issn      = {0075-9511},
  doi       = {10.1016/j.limno.2008.08.001},
  year      = {2009},
  abstract  = {The zooplankton of oligotrophic lakes in North Patagonia is often dominated by mixotrophic ciliates, particularly Stentor amethystinus and Stentor araucanus. Therefore, we tested whether Stentor spp. (i) is an important food for juvenile endemic (Cheirodon australe, Galaxias maculatus, Odontesthes mauleanum, Percichthys trucha) and introduced (Oncorhynchus mykiss) fish species, and (ii) represents a remarkable grazer of bacteria. Ingestion rates of fish estimated by disappearance of Stentor in feeding experiments ranged between 8 (G. maculatus) and 53 (C australe) ciliates per fish and day, and assimilation rates measured by using radioactively labelled Stentor ranged between 3 (P. trucha) and 52 (C australe) ciliates per fish and day. However, although we detected the consumption of Stentor by fish, the daily consumption amounted to at most 0.2\% of the fish biomass which can not cover the energy requirement of the fish. Furthermore, the daily consumption was equivalent to a maximum of 1.6\% of the Stentor standing stock so that fish predation does not seem to be an important mortality factor for the ciliates. The clearance rate of Stentor sp. on natural bacteria was on average 3.8 mu l cil(-1) h(-1). The daily ingestion (mean 3.9 ngC cil(-1) d(-1)) was about 3.5\% of the individual biomass of Stentor sp. Therefore, bacteria ingestion might explain a ciliate growth rate of appr. 1\% d(-1), which was about 17\% of the photosynthesis of endosymbiotic algae. The maximum density of Stentor sp. in the take could ingest about 1 mu g C L-1 d(-1) bacteria which is only 3\% of average bacterial production. Thus, grazing by Stentor sp. does not seem to be a main loss factor for the bacteria.},
  language  = {en}
}
@article{GaedkeKamjunke2006,
  author    = {Gaedke, Ursula and Kamjunke, Norbert},
  title     = {Structural and functional properties of low- and high-diversity planktonic food webs},
  issn      = {0142-7873},
  doi       = {10.1093/plankt/fb1003},
  year      = {2006},
  abstract  = {To test the consequences of decreased diversity and exclusion of keystone species, we compared the planktonic food webs in two acidic (pH <= 3), species-poor mining lakes with those in two species-rich, neutral lakes. The ratio of heterotrophic to autotrophic biomass (HIA) 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 predator-prey weight ratios, with small top predators hardly exceeding their pry 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},
  language  = {en}
}
@article{KamjunkeGaedkeTitteletal.2004,
  author    = {Kamjunke, Norbert and Gaedke, Ursula and Tittel, J{\"o}rg and Weithoff, Guntram and Bell, Elanor M.},
  title     = {Strong vertical differences in the plankton composition of an extremely acidic lake},
  year      = {2004},
  abstract  = {Vertical differences in food web structure were examined in an extremely acidic, iron-rich mining lake in Germany (Lake 111; pH 2.6, total Fe 150mg L-1) during the period of stratification. We tested whether or not the seasonal variation of the plankton composition is less pronounced than the differences observed over depth. The lake was strongly stratified in summer, and concentrations of dissolved organic carbon and inorganic carbon were consistently low in the epilimnion but high in the hypolimnion. Oxygen concentrations declined in the hypolimnion but were always above 2mg L-1. Light attenuation did not change over depth and time and was governed by dissolved ferric iron. The plankton consisted mainly of single-celled and filamentous bacteria, the two mixotrophic flagellates Chlamydomonas sp. and Ochromonas sp., the two rotifer species Elosa worallii and Cephalodella hoodi, and Heliozoa as top predators. We observed very few ciliates and rhizopods, and no heterotrophic flagellates, crustaceans or fish. Ochromonas sp., bacterial filaments, Elosa and Heliozoa dominated in the epilimnion whereas Chlamydomonas sp., single-celled bacteria and Cephalodella dominated in the hypolimnion. Single-celled bacteria were controlled by Ochromonas sp. whereas the lack of large consumers favoured a high proportion of bacterial filaments. The primarily phototrophic Chlamydomas sp. was limited by light and CO2 and may have been reduced due to grazing by Ochromonas sp. in the epilimnion. The distribution of the primarily phagotrophic Ochromonas sp. and of the animals seemed to be controlled by prey availability. Differences in the plankton composition were much higher between the epilimnion and hypolimnion than within a particular stratum over time. The food web in Lake 111 was extremely species-poor enabling no functional redundancy. This was attributed to the direct exclusion of species by the harsh environmental conditions and presumably enforced by competitive exclusion. The latter was promoted by the low diversity at the first trophic level which, in turn, was attributed to relatively stable growth conditions and the independence of resource availability (inorganic carbon and light) from algal density. Ecological theory suggests that low functional redundancy promotes low stability in ecosystem processes which was not supported by our data.},
  language  = {en}
}
@article{WeisseBerendonkKamjunkeetal.2011,
  author    = {Weisse, Thomas and Berendonk, Thomas U. and Kamjunke, Norbert and Moser, Michael and Scheffel, U. and Stadler, P. and Weithoff, Guntram},
  title     = {Significant habitat effects influence protist fitness evidence for local adaptation from acidic mining lakes},
  series = {Ecosphere : the magazine of the International Ecology University},
  volume    = {2},
  journal   = {Ecosphere : the magazine of the International Ecology University},
  number    = {12},
  publisher = {Wiley},
  address   = {Washington},
  issn      = {2150-8925},
  doi       = {10.1890/ES11-00157.1},
  pages     = {14},
  year      = {2011},
  abstract  = {It is currently controversially discussed if the same freshwater microorganisms occur worldwide wherever their required habitats are realized, i.e., without any adaptation to local conditions below the species level. We performed laboratory experiments with flagellates and ciliates from three acidic mining lakes (AML, pH similar to 2.7) to investigate if similar habitats may affect similar organisms differently. Such man-made lakes provide suitable ecosystem models to test for the significance of strong habitat selection. To this end, we analyzed the growth response of three protist taxa (three strains of the phytoflagellate Chlamydomonas acidophila, two isolates of the phytoflagellate Ochromonas and two species of the ciliate genus Oxytricha) by exposing them to lake water of their origin and from the two other AML in a cross-factorial design. Population growth rates were measured as a proxy for their fitness. Results revealed significant effects of strain, lake (= habitat), and strain X habitat interaction. In the environmentally most adverse AML, all three protist taxa were locally adapted. In conclusion, our study demonstrates that (1) the same habitat may affect strains of the same species differently and that (2) similar habitats may harbor ecophysiologically different strains or species. These results contradict the 'everything is everywhere' paradigm.},
  language  = {en}
}
@article{KamjunkeStraileGaedke2009,
  author    = {Kamjunke, Norbert and Straile, Dietmar and Gaedke, Ursula},
  title     = {Response of heterotrophic bacteria, autotrophic picoplankton and heterotrophic nanoflagellates to re- oligotrophication},
  issn      = {0142-7873},
  doi       = {10.1093/plankt/fbp037},
  year      = {2009},
  abstract  = {We investigated the response of the microbial components of the pelagic food web to re-oligotrophication of large, deep Lake Constance where total phosphorus concentrations during mixing decreased from a maximum of 2.81 mu mol L- 1 in 1979 via 1.87 mu mol L-1 in 1987 to 0.26 mu mol L-1 in 2007. Measurements of heterotrophic bacteria, autotrophic picoplankton (APP) and heterotrophic nanoflagellates (HNF) in 2006 and 2007 were compared to values from 1987 to 1997. We hypothesized that the biomass and seasonal variability of all groups will decrease under more oligotrophic conditions due to reduced resource availability, particularly for APP and HNF but less for the competitively stronger bacteria. Average bacterial biomass between spring and autumn was unrelated to phosphorus, whereas the ratio of bacterial biomass to chlorophyll a concentration increased with decreasing trophy due to declining chlorophyll concentrations. In contrast, a unimodal relationship was found between APP and phosphorus with low biomass at low and high phosphorus concentrations and maximum biomass in between. Average HNF biomass decreased strongly by a factor of 10-30 with decreasing trophy, and chlorophyll-specific HNF biomass was unimodally related to phosphorus. The relative seasonal biomass variability did not change for any group during re-oligotrophication. To conclude, HNF responded much more strongly and bacteria less so than chlorophyll concentrations to oligotrophication, whereas APP exhibited a more complex pattern.},
  language  = {en}
}
@article{WagnerKamjunke2001,
  author    = {Wagner, Annekatrin and Kamjunke, Norbert},
  title     = {Reduction of the filtration rate of Daphnia galeata by dissolved photosynthetic products of edible phytoplankton},
  year      = {2001},
  abstract  = {The filtration rate of Daphnia galeata was determined in in situ experiments in Bautzen Reservoir and in laboratory experiments, where daphnids were exposed to filtrates that previously contained either natural phytoplankton or cultured eukaryotic algae (Scenedesmus obliquus or Asterionella formosa), respectively. Individual filtration rate (FR) was measured using fluorescent beads, taking into account ingested beads in the gut only. Compared to heated control treatments (100°C), dissolved compounds released by the nutritious cultured algae during the preconditioning phase or by the natural phytoplankton assemblages from Bautzen Reservoir strongly reduced the filtration rate of D. galeata (down to 60 \%). Heating deactivated these dissolved compounds. A significant correlation was found between primary production measured in situ and the reduction of FR in the filtrate of reservoir water, indicating that extra- cellular products released during photosynthesis triggered the reduction of the filtration rate. The ratio of ingested to collected beads was used to quantify the proportion of food, which was not only collected but passed the mouth of D. galeata. The ratio of ingestion to collection was compared between filtered and unfiltered reservoir water both media identical with respect to the concentration of dissolved compounds, whereas other factors (e. g. food concentration, temperature, filtration rate) were different. The changes in this ratio between filtered and unfiltered reservoir water suggest that D. galeata is capable of a chemosensory control of the ingestion behaviour by detecting external metabolites.},
  language  = {en}
}
@phdthesis{Kamjunke2005,
  author    = {Kamjunke, Norbert},
  title     = {Prokaryoten in pelagischen Nahrungsnetzen : Interaktionen zwischen Cyanobakterien und Fischen sowie Bakterien und mixotrophen Flagellaten},
  address   = {Potsdam},
  pages     = {Getr. Z{\"a}hlung},
  year      = {2005},
  language  = {de}
}
@article{LewinKamjunkeMehner2003,
  author    = {Lewin, Wolf-Christian and Kamjunke, Norbert and Mehner, Thomas},
  title     = {Phosphorus uptake by Microcystis during passage through fish guts},
  year      = {2003},
  abstract  = {Herbivorous fish feed on cyanobacteria. Digestability differs, however, between cyanobacteria species without mucous cover and mucilaginous genera such as Microcystis. The latter can pass fish guts almost undamaged, and it has been hypothesized that they can take up nutrients during gut passage. Here we tested whether live Microcystis, as food for juvenile roach labeled with 33P, indeed showed higher radioactivity after gut passage as compared to gut contents in control experiments with fish fed heated Microcystis. Microcystis showed high viability after passage through roach guts, and live colonies had a significantly higher radioactivity than dead ones. We conclude that Microcystis is protected against digestion in roach guts and can directly use the phosphorus supplied in the fish guts during passage.},
  language  = {en}
}