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- Title
Interactions between allelopathic properties and growth kynetics in four freshwater phytoplankton species studied by model simulations.
- Authors
Barreiro, Aldo; Vasconcelos, Vitor
- Abstract
We chose four species of freshwater phytoplankton: the chlorophyceans Ankistrodesmus falcatus, Chlamydomonas reinhardtii and Selenastrum capricornutum, and the cyanobacteria Oscillatoria sp. in order to study their competitive abilities for nitrate and their allelopathic properties. We parameterized models of nitrate uptake and growth with laboratory experiments. According to them, the species were ranked (from the best to the worst competitors): S. capricornutum, C. reinhardtii, A. falcatus and Oscillatoria sp. C. reinhardtii and Oscillatoria sp. were previously reported as allelopathic. In the present work, Oscillatoria sp. was allelopathic only against A. falcatus. However, none of our species was sensitive to C. reinhardtii. Additionally, we found an unknown allelopathic effect of A. falcatus against Oscillatoria sp. Our findings point out the high specificity of allelopathic interactions. With these data, we constructed a model of interspecific competition for nitrate, including allelopathic interactions. By performing model simulations, we studied how three factors influence the outcome of competition: relative abundance of competing species, resistance to allelopathy, and nitrate concentration. Our simulations showed that the initial ratio of species abundances will significantly determine the outcome of competition. If the worst competitor was the allelopathic species, the more it needs to outnumber the competing species, unless it is very sensitive to allelopathy (not defended). Nitrate has an important influence, showing a non-intuitive outcome of competition experiments at low nitrate concentrations, where the worst competitor (allelopathic species) wins competition in the majority of cases, whereas at intermediate concentrations, the better competitor dominates except for unfavorable ratios of abundances. With the increased amounts of nitrate, conditions again favor the worst competitor (the stronger allelopathic species). Despite the potential for two species coexistence showed by previous theoretical analysis of systems was similar to ours, our simulations did not detect this outcome. We hypothesized that this is due to the strong allelopathic effect of Oscillatoria sp.
- Subjects
FRESHWATER phytoplankton; ALLELOPATHIC agents; MARINE species diversity; ANKISTRODESMUS falcatus; CHLAMYDOMONAS reinhardtii; SELENASTRUM capricornutum; ALLELOPATHY
- Publication
Aquatic Ecology, 2014, Vol 48, Issue 2, p191
- ISSN
1386-2588
- Publication type
Article
- DOI
10.1007/s10452-014-9475-2