Variación temporal de la biomasa del perifiton de Egeria densa Planch. en un arroyo pampeano.

ADONIS GIORGI; CLAUDIA FEIJOÓ

LIMNETICA

ASOC ESPAN LIMNOL-MISLATA

Año: 2010 vol. 29 p. 269 - 278

0213-8409

The variation of the periphyton biomass descriptors (dry weight, organic weight, and chlorophyll-a) on Egeria densa is analyzed during 21 months of sampling at the Las Flores stream, a pampean stream that ows into the Lujan River. The percentage of organic matter in the periphyton samples varies between 10 and 80 %. The percentage of chlorophyll-a in relation to dry weight ranges from 0.10 to 3, and between 0.6 and 32 in relation to the dry organic weight. The spatial variation inside the E. densa stand was higher than the temporal variation. The changes in the periphytic biomass are also associated with the factors that affect the development of autotrophs and heterotrophs, such as precipitations, water velocity, temperature, and macrophyte biomass. The periphyton is dominated by autotrophs in almost all of the cases, except after heavy rains when the proportion of heterotrophs or detritic material increases. The autotrophic component of the periphyton is reduced in high temperature months by the shading produced by the oating macrophytes on E. densa. The predominance of autotrophs throughout the year would allow the support of the high number of herbivorous found in the stream in other studies.