Diurnal variation of rates of denitrification and nitrogen fixation of periphyton associated with Oryza glumaepatula Steud in an Amazonian Lake |
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Authors: | Enrich-Prast A Esteves F A |
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Institution: | (1) Depto. Ecologia, Lab. Limnologia, CCS, Ilha do Fundao, Universidade Federal do Rio de Janeiro, 21941-540 Rio de Janeiro, R. J., Brazil |
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Abstract: | The rates of denitrification and biological nitrogen fixation of the periphyton communities associated with the culms and
adventitious root of Oryza glumaepatula in Lake Batata, State of Pará, Brazilian Amazonia, were investigated over the course
of 24 h. N2O was not detected during the period, demonstrating that denitrification was not occurring. The low concentration of nitrate
in the water column was indicated as the main factor limiting the denitrification process. The rates of biological nitrogen
fixation (BNF) in culms were lowest at night and early morning, while the highest values were measured at 1200 h. BNF rates
in periphyton associated with adventitious roots were lowest during the morning, while highest values were measured at 1600
h. The difference in the daily patterns of BNF rates in the periphyton of culms and roots of O. glumaepatula in the euphotic
zone was attributed to defferences in the availability of organic carbon which supports this process. In the periphyton of
the culms, the BNF process was carried out by heterocystous cyanobacteria, which was photoautotrophs. In the periphyton of
the adventitious roots, BNF was carried out by periphytic bacteria, and is heterotrophically mediated.
This revised version was published online in July 2006 with corrections to the Cover Date. |
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Keywords: | amazonia biological nitrogen fixation denitrification Oryza glumaepatula periphyton |
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