The outcome of competition between the two chrysomonads Ochromonas sp. and Poterioochromonas malhamensis depends on pH.
Bottom Line: We investigated the effect of pH on the competition of two closely related chrysomonad species, Poterioochromonas malhamensis originating from circumneutral Lake Constance, and Ochromonas sp. isolated from a highly acidic mining lake in Austria (pH ∼2.6).Results were compared to growth rates measured earlier in single species experiments over the same pH range.Adverse effects mediated via allelopathy, either directly on the competing flagellate or indirectly by affecting its bacterial food, might also have affected the outcome of competition.
Affiliation: Institute for Limnology of the Austrian Academy of Sciences, Herzog Odilostraße. email@example.comShow MeSH
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Mentions: Irrespective of pH, cell numbers of both flagellate species decreased during the first 24 h of the experiments. In the experiment conducted at pH 2.5, cell numbers of both strains were similar and relatively constant during the initial 4 days (Fig. 1A), ranging from 40,000 to 65,000 cells ml−1. Beginning on day 4 of the experiment, the abundance of Ochromonas sp. increased exponentially until the end of the experiment. The slope of the regression line corresponded to an average μ of 0.39 d−1 during days 3–8, i.e. growth of Ochromonas sp. in the competition experiment was not statistically different from when grown alone at pH 2.5 (Fig. 2A). The final abundance of Ochromonas sp. was close to 300,000 cells ml−1, while the final abundance of P. malhamensis was lower than at the beginning of the experiment.
Affiliation: Institute for Limnology of the Austrian Academy of Sciences, Herzog Odilostraße. firstname.lastname@example.org