ILPLA   05424
INSTITUTO DE LIMNOLOGIA "DR. RAUL A. RINGUELET"
Unidad Ejecutora - UE
congresos y reuniones científicas
Título:
PLANKTON RELATIONSHIPS UNDER MINIMUM WATER LEVEL
Autor/es:
MACDONAGH, M. E.; CASCO MA,; CLAPS, M. C.
Lugar:
Joao Pessoa, Brasil
Reunión:
Simposio; Plankton Symposium IV; 2007
Institución organizadora:
Association for Plankton Research
Resumen:
The management politics implemented in the Río Tercero reservoir since 1983 have promoted a reduced range of water level fluctuations, in order to ensure the availability of water for cooling a nuclear power plant, by maintaining a minimum-security level. The main effect of this measure has been the anticipation of the spillway outflow period. Rainfall was strongly seasonal and its duration has influenced the extension of the spill outflow period. As a result, the monthly renovation was variable, ranging from 0.5 to 0.08 per month. Based on this parameter, during the period February 1999 – February 2000, two phases could be distinguished with significant differences (t= 2.48; p = 0.01; n= 15/11) between them. A positive correlation (r= 0.62; p = 0.002) was found between the densities of phytoplankton and zooplankton during the first period (when the turnover rate was high) and a negative, but insignificant correlation (r= -0.4 to -0.7, depending on the sampling station considered) during the second period (when the turnover rate was low). During the second period, minimum phytoplankton diversity values and highest phytoplankton density were recorded, Actinocyclus normanii being the dominant species. Among the zooplankton, populations of different cladoceran species developed, instead of common species of rotifers and copepoda present during the first period. The PCA analyses showed that both, phytoplankton and zooplankton, were negatively influenced by higher monthly replacement rates during the period of stronger spillway outflow, whereas an opposite relationship was found between phytoplankton and zooplankton densities during more stable conditions.p = 0.01; n= 15/11) between them. A positive correlation (r= 0.62; p = 0.002) was found between the densities of phytoplankton and zooplankton during the first period (when the turnover rate was high) and a negative, but insignificant correlation (r= -0.4 to -0.7, depending on the sampling station considered) during the second period (when the turnover rate was low). During the second period, minimum phytoplankton diversity values and highest phytoplankton density were recorded, Actinocyclus normanii being the dominant species. Among the zooplankton, populations of different cladoceran species developed, instead of common species of rotifers and copepoda present during the first period. The PCA analyses showed that both, phytoplankton and zooplankton, were negatively influenced by higher monthly replacement rates during the period of stronger spillway outflow, whereas an opposite relationship was found between phytoplankton and zooplankton densities during more stable conditions.