ILPLA   05424
INSTITUTO DE LIMNOLOGIA "DR. RAUL A. RINGUELET"
Unidad Ejecutora - UE
congresos y reuniones científicas
Título:
Structural differences of phytoplankton in four shallow lakes with different connection to the Salado River (Argentina).
Autor/es:
SOLARI LÍA CRISTINA; MAC DONAGH, MARÍA ELICIA; GABELLONE, N A; RUIZ, GONZALO; QUAINI, KARINA
Lugar:
PUNTA DEL ESTE URUGUAY
Reunión:
Congreso; SHALLOW LAKES 2008; 2008
Institución organizadora:
Universidad de la República Faculty of Sciences
Resumen:
Phytoplankton assemblages were analyzed in four shallow lakes with different degree of connection to the saline Salado River: The San Miguel Lake is a backwater connected directly to the lower course of Salado River by a natural channel; the San Miguel del Monte Lake is connected to the Salado River during flooding; the Lacombe and La Rosita Lakes are seepage lakes with different impact of human activities. Some of these shallow lakes presented different development of submerged and emergent macrophytes. Phytoplankton and water samples were obtained monthly during an annual cycle in each environment. Water temperature, pH, conductivity, dissolved oxygen and turbidity were measured with Horiba multimeter. Transparency was estimated with Secchi disc. Phosphorus concentration and total suspended solids were measured in laboratory.  Phytoplankton was enumerated using the settling technique. Maximum mean conductivity was observed in the San Miguel Lake (8116 µS cm -1) whereas the minimum in the San Miguel del Monte Lake (1742 µS cm -1). Similar mean phosphorus concentrations were recorded in the four shallow lakes. Specific richness was higher in one shallow lake connected with the Salado River (248 species in San Miguel del Monte Lake) than to the recorded in Lacombe (170 species) and San Miguel (165 species). In La Rosita Lake the specific richness was high (218) due to the incorporation of epiphytic algae from the permanent submerged macrophytes bed. Mean phytoplankton density was five times higher in those lakes associated to the Salado River than the seepage lakes. Cyanobacteria were dominated in San Miguel del Monte and in Lacombe Lakes during extensive periods whereas chlorophytes, diatoms and cryptophytes were important during macrophyte colonization or related to flooding of the Salado River. In the San Miguel Lake, cyanobacteria prevailed during flooding periods, diatoms during isolation periods and chlorophytes during steady stable. In the La Rosita Lake phytoplankton dominance changed seasonally (cryptomonadals overcome during autumn and winter whereas chlophytes in spring and summer. Differences on phytoplankton structure in the four shallow lakes are related to hydrological events, to the incorporation of riverine inocula, to the colonization of submerged macrophytes and geomorphologic hydrologic features.