Hydrological cycle and interannual variability of the aquatic community in a temporary saline lake (Fuente de Piedra, Southern Spain)

Fuente de Piedra is a shallow, temporary saline lake whose seasonal behavior is strongly dependent on the annual hydrological budget. In this study, we outline the characteristics of Fuente de Piedra Lake for two years that had different hydrological budgets. The high precipitations in 1989‐90 caused the lake not to dry as usual, and decreased both salinity and the amplitude of changes. There were also differences in nutrient dynamics, with generally lower concentrations of soluble reactive phosphorus and ammonium, whereas in the more humid year nitrate showed a distinct maximum in winter. Winter bloom chlorophyll a concentrations were also much higher in 1989‐90 ( 600 gl 1 ) but there was also a winter productive phase that was presumably poorly coupled with consumption processes that predominate in spring. Planktonic assemblages were different between years. Highly halotolerant phytoplankton species (Dunaliella salinaand D. viridis) became scarcer, and especially two previously unrecorded diatoms (Cyclotella sp. and Chaetoceros sp.) became dominant in the bloom time in the wet year. The species richness of the zooplankton increased in the wet year, with new species appearing that were not collected during 1987‐88 (Branchinectella media, Daphnia mediterranea, Macrothrixsp., Arctodiaptomus salinus, Cyclopssp., Sigara sp...). There was also a much higher development of macrophytes (Ruppia drepanensis, Althenia orientalis, Lamprothamnium papulosum ) and bird populations, especially flamingoes ( Phoenicopterus ruber). Important interannual variations in this sort of system point to the need for long term studies to observe the whole range of states that define the lake as an entity.