Diel patterns of total suspended solids, turbidity, and water transparency in a highly turbid, shallow lake (Laguna Chascomús, Argentina)
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The effects of external physical forcing variables (solar radiation and winds) on short-term dynamics of total suspended solids (TSS), Chlorophyll-a (Chl-a), turbidity levels, and water transparency were studied during 15 days in a highly turbid, shallow lake (Laguna Chascomús, Argentina). Water samples were taken three times per day (8, 14 and 20 h.). Solar radiation and wind velocity showed a repeatedly bell-shaped diurnal pattern, with significant higher values during morning and afternoon, respectively. TSS and turbidity displayed a general decreasing trend during the sampling period, while water transparency showed the opposite trend. Also Chl-a displayed a decreasing trend and was closely correlated to TSS levels. We assayed a first-order kinetics model to detrend the series, obtaining the rate of change during the night, morning, and afternoon. We observed higher values on afternoon compared to morning for TSS, Chl-a, and turbidity levels and the opposite pattern for water transparency. We conclude that this pattern may result from a combination of biological activity, as it took place after a period of intense photosynthetic activity, together with resuspension by winds during the afternoon, (windiest time of the day).
KeywordsShallow turbid lake Physical forcing Total suspended solids Turbidity Water transparency
We thank Ana Torremorell, Paulina Fermani, Fernando Unrein, Maria Llames, and Gonzalo Pérez for assistance in field and laboratory, and Gladys Salcedo Echeverry for statistical assistance. This work was supported by The Argentine network for the assessment and monitoring of Pampean shallow lakes (PAMPA2), by Consejo Nacional de Investigaciones Científicas y Técnicas, PIP-01301 and by Agencia Nacional de Promoción Científica y Tecnológica, PICT 2005-25325.
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