Do temporary lakes vary from year to year? A comparison of limnological parameters and zooplankton from two consecutive annual cycles in an Argentine temporary saline lake

Document Type: Primary Research paper

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Abstract

Temporary wetlands alternate dry phases with hydroperiods of varying duration. When their salinity is high it becomes one of the abiotic factors more influencing on wetland ecology. Due to the temporary nature of the ecosystem, the physico-chemical and biological parameters exhibit relatively large variation in short time periods; therefore studies limited to short periods cannot record long-term dynamics. Temporary aquatic ecosystems in other latitudes have been well studied; however those in Argentina have received little attention, despite their high frequency; particularly in the semi-arid central-west belt. Given that in La Pampa province (central region of Argentina) data previously collected from different hydroperiods of several temporary saline lakes are available, the aim of this study was to compare and establish relationships between physico-chemical parameters, and zooplankton taxonomic composition, diversity and biomass, recorded in two consecutive annual cycles in a saline lake in the northern of the province. Seasonal water and zooplankton samples were obtained during 2006 and 2007. Salinity differed, and increased from a mean of 23.98 g.L-1 (2006) to 36.71 g.L-1 (2007). Transparency, total phosphorus, chlorophyll-a, and total suspended solid concentrations did not differed. Total species richness was reduced (six and three species in 2006 and 2007, respectively), and was negatively correlated with salinity. Halophilic species, including Boeckella poopoensis, Brachionus plicatilis, and Moina eugeniae were registered during both years. Total zooplankton density and biomass were not significantly distinct, neither those of copepods and rotifers; however cladocerans were negatively affected by salinity, resulting in decreased density and biomass in 2007. The zooplankton species inhabiting this saline lake are halophilic, which can explain the few differences observed in biological parameters between the two annual cycles.

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