TY - JOUR A1 - Spijkerman, Elly A1 - Bissinger, Vera A1 - Gaedke, Ursula T1 - Low potassium and inorganic carbon concentrations influence a possible phosphorus limitation in Chlamydomonas acidophila N2 - Chlamydomonas acidophila, a dominant phytoplankton species in the very acidic Lake 111 (pH 2.7) situated in Germany, faces low concentrations of inorganic phosphorus (P-i), inorganic carbon (C-i) and potassium (K+) in its environment, which may lead to a complex colimitation by these nutrients. We performed laboratory and field investigations to test for P-i limitation and its dependence on C-i and K+ concentrations. The minimum cell quota for phosphorus (Q(0)) and phosphatase enzyme activity were similar to those for neutrophilic algae, despite the low pH and high concentrations of iron and aluminium, indicating no extra metabolic costs or inhibition of enzymes by the extreme environment. The threshold concentration of soluble reactive phosphorus for growth (SRPt), the algal C:P ratio and the alkaline phosphatase enzyme activity all suggested a moderate P-i limitation of C. acidophila in Lake 111. SRPt and Q(0) were higher at low CO2 and K+ concentrations in culture, showing a relationship between C-i and P-i acquisition. Furthermore, SRPt and Q(0) were higher under K+/P-i-colimiting conditions than under P-i-limiting conditions alone, suggesting that K+ concentrations influence P-i limitation in C. acidophila as well. Our results show that a limitation by one macronutrient requires consideration of the availability of the others as their uptake mechanisms depend on each other. Notwithstanding these interactions, C-i or K+ concentrations had no clear influence on the P-i limitation of C. acidophila in Lake 111. Y1 - 2007 UR - http://www.tandfonline.com/doi/full/10.1080/09670260701529596 U6 - https://doi.org/10.1080/09670260701529596 ER - TY - JOUR A1 - Bissinger, Vera A1 - Jander, Jörn A1 - Tittel, Jörg T1 - A new medium free of organic carbon to cultivate organisms from extremely acidic mining lakes (pH 2.7) N2 - 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. Y1 - 2000 ER - TY - JOUR A1 - Tittel, Jörg A1 - Weithoff, Guntram A1 - Bissinger, Vera A1 - Gaedke, Ursula T1 - Ressourcennutzung und -weitergabe im planktischen Nahrungsnetz eines extrem sauren (pH 2,7) Tagebausees Y1 - 2000 ER - TY - JOUR A1 - Bissinger, Vera A1 - Tittel, Jörg T1 - Process rates and growth limiting factors of planktonic algae (Chlamydomonas sp.) from extremely acidic (pH 2,5 3) mining lakes in Germany Y1 - 2000 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 - 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 -