@article{BissingerJanderTittel2000,
  author    = {Bissinger, Vera and Jander, J{\"o}rn and Tittel, J{\"o}rg},
  title     = {A new medium free of organic carbon to cultivate organisms from extremely acidic mining lakes (pH 2.7)},
  year      = {2000},
  abstract  = {An algal culture medium was developed which reflects the extreme chemical conditions of acidic mining lakes (pH 2.7, high concentrations of iron and sulfate) and remains stable without addition of organic carbon sources. It enables controlled experiments e.g. on the heterotrophic potential of pigmented flagellates in the laboratory. Various plankton organisms isolated from acidic lakes were successfully cultivated in this medium. The growth rates of an Chlamydomonas- isolate from acidic mining lakes were assessed by measuring cell densities under pure autotrophic and heterotrophic conditions (with glucose as organic C-source) and showed values of 0.74 and 0.40, respectively.},
  language  = {en}
}
@article{KoschorreckTittel2002,
  author    = {Koschorreck, Matthias and Tittel, J{\"o}rg},
  title     = {Benthic photosynthesis in an acidic mining lake (pH 2.6).},
  year      = {2002},
  language  = {en}
}
@article{KlapperBoehrerPackroffetal.2001,
  author    = {Klapper, H. and Boehrer, Bertram and Packroff, G. and Schultze, M. and Tittel, J{\"o}rg and Wendt-Potthoff, Katrin},
  title     = {Bergbaufolgegew{\"a}sser},
  year      = {2001},
  language  = {de}
}
@article{KoschorreckFroemmichenHerzsprungetal.2002,
  author    = {Koschorreck, Matthias and Fr{\"o}mmichen, Ren{\´e} and Herzsprung, Peter and Tittel, J{\"o}rg and Wendt-Potthoff, Katrin},
  title     = {Function of straw for in situ remediation of acidic mining lakes},
  issn      = {0049-6979},
  year      = {2002},
  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{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{TittelKamjunke2004,
  author    = {Tittel, J{\"o}rg and Kamjunke, Norbert},
  title     = {Metabolism of dissolved organic carbon by planktonic bacteria and mixotrophic algae in lake neutralisation experiments},
  year      = {2004},
  abstract  = {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.},
  language  = {en}
}
@article{TittelBissingerZippeletal.2003,
  author    = {Tittel, J{\"o}rg and Bissinger, Vera and Zippel, Barbara and Gaedke, Ursula and Bell, Elanor M. and Lorke, Andreas and Kamjunke, Norbert},
  title     = {Mixotrophs combine resource use to outcompete specialists: Implications for aquatic food webs},
  year      = {2003},
  abstract  = {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.},
  language  = {en}
}
@article{WoelflTittelZippeletal.2000,
  author    = {W{\"o}lfl, S. and Tittel, J{\"o}rg and Zippel, Barbara and Kringel, R.},
  title     = {Occurrence of an algal mass development in an acidic (pH 2.5), iron and aluminium-rich coal mining pond},
  year      = {2000},
  language  = {en}
}
@article{BissingerTittel2000,
  author    = {Bissinger, Vera and Tittel, J{\"o}rg},
  title     = {Process rates and growth limiting factors of planktonic algae (Chlamydomonas sp.) from extremely acidic (pH 2,5 3) mining lakes in Germany},
  year      = {2000},
  language  = {en}
}