Limnology

, Volume 2, Issue 2, pp 65–71 | Cite as

Morphological variability of Aulacoseira granulata (Ehr.) Simonsen (Bacillariophyceae) in the Lower Paraná River (Argentina)

  • I. O'Farrell
  • G. Tell
  • A. Podlejski
RESEARCH PAPER

Abstract

In this paper we consider the morphological variation within a natural population of Aulacoseira granulata (Ehr.) Simonsen in relation to environmental factors. This species was dominant in the phytoplankton of the Lower Paraná River (Argentina) and exhibited seasonal fluctuations of cell dimensions. The mean cell diameter was directly correlated with the river water level and inversely with pH and nitrate concentrations, whereas cell length was directly correlated with transparency and nitrate concentration and inversely with suspended solids. This pattern was similar to that observed for filament length. The cell length : diameter ratio was inversely related to water level and discharge and directly related to pH, transparency, and nitrate concentration. Maximum diameters did not coincide with maximum lengths. A tendency to maintain cell volume throughout the annual cycle was observed, which probably relates to both buoyancy and photosynthetic capacity. These results associate the water ascendancy and the size recovery phases to discharge. Cells become smaller on the ebbing of the flood phase, and the decreasing depth increases the probability that the alga will be disentrained from the turbulent field. The loss during low water would act as a stimulus for auxosporulation, contributing to the production of large cells to start off the next population.

Key wordsAulacoseira granulata Diatoms Cell morphology South America Phytoplankton 

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Copyright information

© The Japanese Society of Limnology 2001

Authors and Affiliations

  • I. O'Farrell
    • 1
  • G. Tell
    • 1
  • A. Podlejski
    • 1
  1. 1.Lab. Limnología, Dpto. Biología, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Ciudad Universitaria, C1428EHA Buenos Aires, Argentina Tel. +54-4576-3300 (int.490); Fax +54-4576-3384 e-mail: ines@bg.fcen.uba.arAR

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