21334865
not annotated - annotated - LINNAEUS only
The outcome of competition between the two chrysomonads Ochromonas sp. and Poterioochromonas malhamensis depends on pH.
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). We performed pairwise growth experiments between these two species at four different pH ranging from 2.5 to 7.0. Heterotrophic bacteria served as food for both flagellates. Results were compared to growth rates measured earlier in single species experiments over the same pH range. We tested the hypothesis that the acidotolerant species benefits from competitive release under conditions of acid stress. The neutrophilic strain numerically dominated over the acidotolerant strain at pH 7.0, but was the inferior competitor at pH 2.5. At pH 3.5 and 5.0 both strains coexisted. Surprisingly, P. malhamensis prevailed over Ochromonas sp. under moderately acidic conditions, i.e. at the pH where growth rates of the latter peaked when grown alone. Since bacterial food was not limiting, resource competition is improbable. It appears more likely that P. malhamensis ingested cells of its slightly smaller competitor. 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.
Ann file
T1 Species 75 104 Poterioochromonas malhamensis
N1 Reference T1 Taxonomy:88167
T2 Species 218 247 Poterioochromonas malhamensis
N2 Reference T2 Taxonomy:88167
T3 Species 969 983 P. malhamensis
N3 Reference T3 Taxonomy:88167
T4 Species 1226 1240 P. malhamensis
N4 Reference T4 Taxonomy:88167