Abnormal forms of Cocconeis placentula (Ehrenberg) in a eutrophic shallow lake (Buenos Aires Province, Argentina).

ESQUIUS, K.S.; S.M. ALTAMIRANO & A.H. ESCALANTE

Mar del Plata

Congreso; I Congreso Internacional de Ciencia y Tecnología Ambiental; 2012

Asociación Argentina para el Progreso de las Ciencias

The aims of the present study were to describe the types of deformations present in the valves of Cocconeis placentula (Ehrenberg) and try to correlate the occurrence of these anomalies with some environmental variables estimated in Los Padres Lake (Buenos Aires Province, Argentina). Abnormal forms of C. placentula were observed in periphyton samples on Schoenoplectus californicus (C. A. Meyer) Soják, the dominant marshy macrophyte in this wetland. Monthly samples were collected during a year at two sites: Los Padres Stream inflow area and near the dam built at La Tapera headwaters. Simultaneously, water samples to determine DO, BOD5, pH, conductivity, hardness, solid residue and nutrients were obtained. Cocconeis placentula is a diatom species frequently found in periphyton from Los Padres Lake, but with relative densities lower than 1 %. Abnormal forms of C. placentula were observed, mainly in samples from Los Padres Stream, exhibiting deformities in the outline of their valves. In the abnormal specimens, the occurrence of wide valve was the unique unusual feature, while the valve-length and its striae pattern remained conservative. This work constitutes the first report of diatom abnormal forms from Los Padres Lake.