Influence of N/P ratio on competitive abilities for nitrogen and phosphorus by <Emphasis Type="Italic">Microcystis aeruginosa</Emphasis> and <Emphasis Type="Italic">Aulacoseira distans</Emphasis> |
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Authors: | Marcelo Manzi Marinho Sandra Maria Feliciano de Oliveira e Azevedo |
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Institution: | 1.Laboratório de Ecologia e Taxonomia de Algas – DBV/IBRAG,Universidade do Estado do Rio de Janeiro,Rio de Janeiro,Brasil;2.Laboratório de Ecofisiologia e Toxicologia de Cianobactérias (LETC), Instituto de Biofísica Carlos Chagas Filho,Universidade Federal do Rio de Janeiro,Rio de Janeiro,Brasil |
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Abstract: | Microcystis aeruginosa and Aulacoseira distans strains were grown in batch cultures to investigate the consequences of N/P ratio on the growth of these species and on their
abilities to take up nitrogen and phosphorus. N/P ratio did not influence the growth rates, which were similar under all the
experimental conditions. However, exponential growth lasted longer in Microcystis than in Aulacoseira, especially under low N/P ratio conditions. Distinct patterns of nutrient uptake for Aulacoseira and Microcystis were observed. N-uptake was higher in Microcystis, but not influenced by N/P ratio. However, the amount absorbed was proportional to the concentration in the culture medium
for both strains studied. Although Microcystis showed lower uptake of N per biomass unit, a greater yield of Microcystis growth relative to the diatom was observed. This could have resulted from its ability to produce biomass using less nitrogen
per unit of biomass. A variation of N/P ratio in the culture medium during the growth of both species was observed. This owed
to the uptake of nutrients, with Microcystis showing greater potential than Aulacoseira to influence the N/P ratio. Thus, in contrast to what has been stated in the literature, our results indicated that a low
N/P ratio could be a consequence of the capacities and rates of cyanobacterial uptake of nitrogen and phosphorus. |
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Keywords: | Competition Cyanobacteria Diatoms Growth N and P uptake Batch cultures |
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