Distribución de los microcrustáceos en lagunas de Castilla-La Mancha. Ciclos estacionales y migración vertical en lagunas cársticas estratificadas

Resumen

This study focuses on the ecological study of planktonic microcrustaceans of lakes. The three main aims are: (1) To relate the distribution of these organisms with the physical and chemical characteristics of their environments and try to establish an habitat typology based on microcrustacean assemblages. The littoral areas of 45 water bodies in Castilla-La Mancha were studied. A total of 82 species were found: 32 copepods, 45 cladocerans and 5 anostraceans. The zooplanktonic assemblages found, whether between the different species were mainly dominated by two factors, salinity and permanence of water. (2) To know the vertical distribution and seasonal cycles of these organisms in a water meromictic lake (La Cruz) with an annual whiting due to calcium carbonate precipitation during three years. A total of 5 planktonic species were found (three cladocerans and two copepods). The marked stratification of this lake results in a strong spatial heterogeneity along the vertical profile. Most of the organisms are located in the metalimnion during the stratified periods. The effect of the whiting was also analysed, but the only population being significantly affected was Diaphanosoma brachyura. Littoral populations were studied at five different points. Seasonal variations are related to lacustrine processes (vertical mixing and whiting). In addition, settling was studied by means of sedimentation traps. Among the collected rests, those of chydorids were the best preserved. (3) To describe diel vertical migrations and the associated changes with respect to the vertical structure of zooplanktonic populations in stratified meromictic karstic lakes (La Cruz and El Tobar). In La Cruz, the study of the vertical migration focuses on the effect of whiting over the planktonic species. The cladoceran species showed a typical pattern but when whiting occurs the populations has a shallower mean residence depth and their migration distance is shorter. The copepods show either normal or reverse migration. In El Tobar was studied at different periods. September and April normal migration patterns were observed for the three cladoceran species and in November showed reverse patterns. In, reverse migration for the copepod Arctodiaptomus salinus in September and no migration pattern was found for Tropocyclops prasinus.