TY - JOUR A1 - Kamjunke, Norbert A1 - Bohn, Christiane A1 - Grey, John T1 - Utilisation of dissolved organic carbon from different sources by pelagic bacteria in an acidic mining lake N2 - 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 Y1 - 2006 UR - http://www.schweizerbart.de/j/archiv-hydrobiologie/ U6 - https://doi.org/10.1127/0003-9136/2006/0165-0355 SN - 0003-9136 ER - TY - THES A1 - Kamjunke, Norbert T1 - Prokaryoten in pelagischen Nahrungsnetzen : Interaktionen zwischen Cyanobakterien und Fischen sowie Bakterien und mixotrophen Flagellaten Y1 - 2005 CY - Potsdam ER - TY - JOUR A1 - Kamjunke, Norbert A1 - Tittel, Jörg A1 - Krumbeck, H. A1 - Beulker, Camilla A1 - Poerschmann, J. T1 - High heterotrophic bacterial production in acidic, iron-rich mining lakes N2 - 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 Y1 - 2005 SN - 0095-3628 ER - TY - JOUR A1 - Tittel, Jörg A1 - Bissinger, Vera A1 - Gaedke, Ursula A1 - Kamjunke, Norbert T1 - Inorganic carbon limitation and mixotrophic growth in Chlamydomonas from an acidic mining lake N2 - 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 Y1 - 2005 SN - 1434-4610 ER - TY - JOUR A1 - Tittel, Jörg A1 - Kamjunke, Norbert T1 - Metabolism of dissolved organic carbon by planktonic bacteria and mixotrophic algae in lake neutralisation experiments N2 - 1. Lakes formed in mining pits often contain high concentrations of dissolved ferric iron and sulphate (e.g. 2 and 16 mmol L)1, 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 in situ mesocosm of 30 m diameter, a bloom of Chlamydomonas occurred, reaching a biovolume of 80 mm3 L)1. Growth experiments using filtered lake water showed that the alga reduced the overall dissolved organic carbon (DOC) concentration despite significant photosynthetic activity. However, when Chlamydomonas were grown together with natural bacterioplankton, net DOC consumption did not increase. 3. Uptake experiments using [14C]-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. Y1 - 2004 ER - TY - JOUR A1 - Kamjunke, Norbert A1 - Gaedke, Ursula A1 - Tittel, Jörg A1 - Weithoff, Guntram A1 - Bell, Elanor M. T1 - Strong vertical differences in the plankton composition of an extremely acidic lake N2 - 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. Y1 - 2004 ER - TY - JOUR A1 - Tittel, Jörg A1 - Bissinger, Vera A1 - Zippel, Barbara A1 - Gaedke, Ursula A1 - Bell, Elanor M. A1 - Lorke, Andreas A1 - Kamjunke, Norbert T1 - Mixotrophs combine resource use to outcompete specialists: Implications for aquatic food webs N2 - The majority of species can be grouped into those relying solely on photosynthesis (phototrophy) or those relying solely on the assimilation of organic substances (heterotrophy) to meet their requirements for energy and carbon. However, a special life history trait exists in which organisms combine both phototrophy and heterotrophy. Such 'mixotrophy' is a widespread phenomenon in aquatic habitats and is observed in many protozoan and metazoan organisms. The strategy requires investment in both photosynthetic and heterotrophic cellular apparatus, but the benefits must outweigh these costs. In accordance with the mechanistic resource competition theory, laboratory experiments revealed that pigmented mixotrophs combined light and prey as substitutable resources. Thereby, they reduced prey abundance below the critical food concentration of competing specialist grazers [Rothhaupt, K. O. (1996) Ecology 77, 716-724]. Here, we demonstrate for the first time the important consequences of this strategy for an aquatic community. In the illuminated surface strata of a lake, mixotrophs reduced prey abundance so steeply that grazers from higher trophic levels, consuming both the mixotrophs and their prey, could not persist. Thus, the mixotrophs escaped from both competition and grazing, and remained dominant. Furthermore, the mixotrophs structured the prey abundance along the vertical light gradient creating low densities near the surface and a pronounced maximum of their algal prey at depth. Such deep algal accumulations are typical features of nutrient poor aquatic habitats, previously explained by resource availability. We hypothesize instead that the mixotrophic grazing strategy is responsible for deep algal accumulations in many aquatic environments. Y1 - 2003 UR - www.pnas.org/cgi/doi/10.1073/pnas.2130696100 ER - TY - JOUR A1 - Lewin, Wolf-Christian A1 - Kamjunke, Norbert A1 - Mehner, Thomas T1 - Phosphorus uptake by Microcystis during passage through fish guts N2 - 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. Y1 - 2003 UR - http://aslo.org/lo/toc/vol_48/issue_6/2392.pdf ER - TY - JOUR A1 - Kamjunke, Norbert A1 - Schmidt, Katja A1 - Pflugmacher, Stephan A1 - Mehner, Thomas T1 - Consumption of cyanobacteria by roach (Rutilus rutilus) : useful or harmful to the fish? N2 - 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. Y1 - 2002 ER - TY - JOUR A1 - Kamjunke, Norbert A1 - Mendonca, Rebeca A1 - Hardewig, Iris A1 - Mehner, Thomas T1 - Assimilation of different cyanobacteria as food and the consequences for internal energy stores of juvenile roach N2 - 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. Y1 - 2002 ER - TY - JOUR A1 - Weithoff, Guntram A1 - Moser, Michael A1 - Kamjunke, Norbert A1 - Gaedke, Ursula A1 - Weisse, Thomas T1 - Lake morphometry and wind exposure may shape the plankton community structure in acidic mining lakes N2 - 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. Y1 - 2010 UR - http://www.sciencedirect.com/science/journal/00759511 U6 - https://doi.org/10.1016/j.limno.2009.11.002 SN - 0075-9511 ER - TY - JOUR A1 - Kamjunke, Norbert A1 - Gaedke, Ursula T1 - Phosphorus gain by bacterivory promotes the mixotrophic flagellate Dinobryon spp. during re-oligotrophication N2 - Bacterivory by mixotrophic flagellates may contribute to their nutrient supply, providing a competitive advantage in oligotrophic waters. We hypothesized an increase in Dinobryon biomass during the re-oligotrophication process in the large and deep Lake Constance. To estimate whether bacterivory contributed substantially to the flagellates' phosphorus supply, we determined ingestion rates. Dinobryon biomass increased with decreasing total phosphorus concentrations in the lake over a period of 17 years (P = 0.0005). The promotion of Dinobryon biomass during re-oligotrophication may be explained by the increasing light availability due to the decreasing biomass of other phytoplankton yielding a release from competition. The date of the Dinobryon abundance maximum shifted to earlier time points in the year, probably because a smaller phosphorus pool was depleted more quickly. Ingestion rates of Dinobryon ranged between 0.5 and 13 bacteria cell(-1) h(-1) (0.2-5.4 fg C pg C-1 h(-1)), and clearance rates varied between 0.2 and 3.2 nL cell(-1) h(-1) (4-78 pL pg C-1 h(-1)), leading to bacterial losses of up to 30% day(-1) of bacterial standing stock. The ingestion of bacteria covered 77% of the phosphorus need of the flagellate during the period of maximum growth in 1996 (net growth rate 0.34 day(-1)), and it fully covered the need at all other times. Y1 - 2007 UR - http://plankt.oxfordjournals.org/ U6 - https://doi.org/10.1093/plankt/fb1054 SN - 0142-7873 ER - TY - JOUR A1 - Tittel, Joerg A1 - Wiehle, Ines A1 - Wannicke, Nicola A1 - Kampe, Heike A1 - Poerschmann, Juergen A1 - Meier, Jutta A1 - Kamjunke, Norbert T1 - Utilisation of terrestrial carbon by osmotrophic algae N2 - 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. Y1 - 2009 UR - http://www.springerlink.com/content/101191 U6 - https://doi.org/10.1007/s00027-008-8121-2 SN - 1015-1621 ER - TY - JOUR A1 - Kamjunke, Norbert A1 - Straile, Dietmar A1 - Gaedke, Ursula T1 - Response of heterotrophic bacteria, autotrophic picoplankton and heterotrophic nanoflagellates to re- oligotrophication N2 - 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. Y1 - 2009 UR - http://plankt.oxfordjournals.org/ U6 - https://doi.org/10.1093/plankt/fbp037 SN - 0142-7873 ER - TY - JOUR A1 - Kamjunke, Norbert A1 - Vogt, Bernhard A1 - Woelfl, Stefan T1 - Trophic interactions of the pelagic ciliate Stentor spp. in North Patagonian lakes N2 - 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. Y1 - 2009 UR - http://www.sciencedirect.com/science/journal/00759511 U6 - https://doi.org/10.1016/j.limno.2008.08.001 SN - 0075-9511 ER - TY - JOUR A1 - Gaedke, Ursula A1 - Kamjunke, Norbert T1 - Structural and functional properties of low- and high-diversity planktonic food webs N2 - 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 Y1 - 2006 UR - http://plankt.oxfordjournals.org/ U6 - https://doi.org/10.1093/plankt/fb1003 SN - 0142-7873 ER - TY - JOUR A1 - Weisse, Thomas A1 - Berendonk, Thomas U. A1 - Kamjunke, Norbert A1 - Moser, Michael A1 - Scheffel, U. A1 - Stadler, P. A1 - Weithoff, Guntram T1 - Significant habitat effects influence protist fitness evidence for local adaptation from acidic mining lakes JF - Ecosphere : the magazine of the International Ecology University N2 - 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. KW - allopatric speciation KW - Chlamydomonas acidophila KW - ciliates KW - everything is everywhere KW - flagellates KW - freshwater microbes KW - habitat-species interaction KW - local adaptation KW - Ochromonas spp. KW - Oxytricha spp. Y1 - 2011 U6 - https://doi.org/10.1890/ES11-00157.1 SN - 2150-8925 VL - 2 IS - 12 PB - Wiley CY - Washington ER - TY - JOUR A1 - Kamjunke, Norbert A1 - Mehner, Thomas T1 - Coupling the microbial food web with fish : are bacteria attached to cyanobacteria an important food source for underyearling roach? N2 - 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. Y1 - 2001 ER - TY - JOUR A1 - Wagner, Annekatrin A1 - Kamjunke, Norbert T1 - Reduction of the filtration rate of Daphnia galeata by dissolved photosynthetic products of edible phytoplankton N2 - 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. Y1 - 2001 ER - TY - JOUR A1 - Kamjunke, Norbert A1 - Jähnichen, Sabine T1 - Leucine incorporation by Microcystis aeruginosa N2 - 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. Y1 - 2000 ER - TY - JOUR A1 - Attermeyer, Katrin A1 - Tittel, Joerg A1 - Allgaier, Martin A1 - Frindte, Katharina A1 - Wurzbacher, Christian A1 - Hilt, Sabine A1 - Kamjunke, Norbert A1 - Grossart, Hans-Peter T1 - Effects of Light and Autochthonous Carbon Additions on Microbial Turnover of Allochthonous Organic Carbon and Community Composition JF - Microbial ecology N2 - 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. KW - Bacterial growth efficiency KW - Continuous cultures KW - Carbon decomposition KW - Leaf litter KW - Photolysis Y1 - 2015 U6 - https://doi.org/10.1007/s00248-014-0549-4 SN - 0095-3628 SN - 1432-184X VL - 69 IS - 2 SP - 361 EP - 371 PB - Springer CY - New York ER - TY - JOUR A1 - Kamjunke, Norbert A1 - Rode, Michael A1 - Baborowski, Martina A1 - Kunz, Julia Vanessa A1 - Zehner, Jakob A1 - Borchardt, Dietrich A1 - Weitere, Markus T1 - High irradiation and low discharge promote the dominant role of phytoplankton in riverine nutrient dynamics JF - Limnology and oceanography / American Society of Limnology and Oceanography N2 - 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. Y1 - 2021 U6 - https://doi.org/10.1002/lno.11778 SN - 0024-3590 SN - 1939-5590 VL - 66 IS - 7 SP - 2648 EP - 2660 PB - Wiley CY - Hoboken ER -