CECOAL   02625
CENTRO DE ECOLOGIA APLICADA DEL LITORAL
Unidad Ejecutora - UE
artículos
Título:
Abundance and diversity of phytoplankton in the Paraná river (Argentina) 220 km downstream of the Yacyretá reservoir
Autor/es:
ZALOCAR DE DOMITROVIC, Y.; POI DE NEIFF, A.S.G.; CASCO, S.L.
Revista:
BRAZILIAN JOURNAL OF BIOLOGY
Editorial:
RiMA
Referencias:
Año: 2007 vol. 67 p. 53 - 63
ISSN:
1519-6984
Resumen:
Patterns in the temporal composition, abundance and species richness of the phytoplankton community of the Paraná river prior to and after the initial filling phase of the Yacyretá reservoir are analyzed. The study site is located 220 km downstream from the Yacyretá reservoir and 30 km downstream from the confluence with the Paraguay river. Because both rivers waters remain separated and unmixed at the study site, we compared the possible effects of the impoundment on both river banks (left and right banks) during  hydrological periods with similar duration and magnitude of the low and high water phases. Physical and chemical conditions measured at right bank (water from Paraguay river) were similar at both periods (pre and post-impoundment) whereas conductivity, pH and orthophosphate concentration increased at left bank (water from High Paraná river and Yacyretá reservoir) after the impoundment. Changes in phytoplankton density and species composition were observed only in samples collected from waters flowing from the reservoir (left bank). The density of Chlorophyceae (Chloromonas acidophila, Chlamydomonas leptobasis, Choricystis minor, Chlorella vulgaris, Scenedesmus ecornis, Monoraphidium minutum, M. contortum and M. pusillum) and Cryptophyceae (Rhodomonas minuta, Cryptomonas marssonii and C. ovata) increased while Cyanophyceae (Cylindrospermopsis raciborskii, Raphidiopsis mediterranea and Planktolyngbya subtilis) and Bacillariophyceae (Aulacoseira granulata and its bioforms), decreased compared to previous studies conducted on  the left bank of the Paraná river. Phytoplankton collected from the right bank of the river did not differ in pre and post- impoundment samples because they  originate from the Paraguay river, which remains relatively unaffected by human activities.