Resumo

RAMIREZ C, ANGÉLICA M  e  PLATA-DIAZ, YASMÍN. Perifitic Diatoms in Different Reach of Two Lotic Systems in High Mountain (Páramo de Santurbán, Norte de Santander, Colombia) and Their Relation with Environmental Variables. Acta biol.Colomb. [online]. 2008, vol.13, n.1, pp.199-216. ISSN 0120-548X.

Three sample zones: the headwater zone, the mid flow zone and the stream zone were selected in two lotic system of the Páramo de Santurbán, during rainy and dry season. In each zone the influence of physical, chemical and hydrological variables on the structure of the benthic diatom assemblage were evaluated. A component principal analysis evaluated the environmental variation. A correlation matrix established the importance of the environmental factors in the registered species. Conductivity, redox potential, pH, and flow, were determinant factors on the environmental variation and on the assemblage structure differences between the zones. Acidity allowed the high occurrence of Eunotia species, and organic pollution allowed the abundance of Nitzchia and Navicula species. Six species were abundant: Navicula tantula, Achnanthidium minutissimum, Achnanthidium lanceolatum, Gomphonema parvulum, Navicula cryptocephala and Gomphonema lagenula. The stream zones registered high values of flow and conductivity, which were related with their lower diversity. Low flow and little stress condition on the mid flow zones were correlated with the highest values of diversity and with the similarity found in the dominant species between these zones in the two systems. The assemblage did not register seasonal variation; dissimilarity of diatom assemblages was larger among samples from different reach, compared with samples of different periods of the same reach, indicating that benthic diatom assemblages in the Páramo de Santurbán were mainly affected by habitat differences between zones. Our results highlight the importance of environmental factors in the composition and abundance of benthic diatoms in tropical aquatic systems.

Palavras-chave : periphytic diatoms; lotic systems; Páramo de Santurbán.

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