Assessment of physicochemical and biological characteristics of La Salada shallow lake (Argentina) using high frequency buoy data

ALFONSO, M.B.; VITALE, A.J.; MENENDEZ, M.C.; PERILLO, V.L.; PICCOLO, M.C.; PERILLO, G.M.E.

Bahia Blanca

Workshop; GLEON 15; 2013

Instituto Argentino de Oceanografía

Argentinian Pampean lakes are shallow and naturally eutrophic. Because of their great area/volume ratio they respond to environmental, hydrological and anthropogenic changes modifying their water characteristics. La Salada is a saline shallow lake located in the South of Buenos Aires Province (Argentina). Water Authority maintains its water level discharging water from the Colorado River. A buoy installed on the lake since October 2012 provides high frequency water and meteorological data. The purpose of the investigation is to analyze the physico-chemical water characteristics and the presence of zooplankton. The study period is from October 2012 to September 2013. Monthly measurements with an HORIBA U10 meter and zooplankton samples (47 μm mesh pore size net) were taken. Transparency was measured with a Secchi disk. Monthly chlorophyll-a values ranged between 16.6-54.7 μg L-1, classifying as a mesotrophic to eutrophic lake. The Chlorophyll-a/Phaeopigments ratio was always >1, indicating a good status of phytoplankton population. This lake is classified as mesosaline (34.5) and turbid (Zm/Zp >1). Precipitation influenced water pH, Secchi depth and chlorophyll-a values (p = 0.03, p = 0.004 and p = 0.04 respectively). Water level showed a significant correlation with electrical conductivity (p= 0.0018) and chlorophyll-a (p = 0.0317). Chlorophyll-a correlated to air temperature (p = 0.006) and conductivity (p = 0.01). These results show the impact of water discharge from human management on the structure and dynamics of the biologic community. Typical halophytic Rotifera species, Brachionus plicatilis and the large predatory pleurotosmatid Paradileptus elephantinus were registered. This study presents the first scientific basis for further studies in La Salada shallow lake.