Thebiological system of the lower salinity ponds in Kalloni Saltworks (NE. Aegean Sea, Greece): phytoplankton and macrobenthic invertebrates

Abstract

1 - Spatial and seasonal variations of two important biological quality elements (phytoplankton and macrobenthic invertebrates) in Transitional Water (TW) ecosystems were studied in Kalloni Saltworks, located at the island of Lesvos (NE. Aegean Sea, Greece). 2 - A total of 36 phytoplankton taxa, belonging to 5 classes, were collected in the study area during both seasonal samplings. Many of the species found in the study area are coastal/brackish waters species that are commonly encountered in transitional waters ecosystems. A substantial seasonal change in species composition, as well as in the observed trends in density and biomass variations along the salinity gradient was revealed. Blooms of Euglena acusformis, Mesodinium rubrum and phytoflagellates were recorded in the study area. 3 - A total of 43 macrobenthic invertebrates taxa, belonging to 6 major groups, were collected in the study area during both seasonal samplings. Most of the abundant macrobenthic invertebrate species in the study area were typical lagoonal or marine/estuarine species commonly occuring in coastal lagoons, whereas typical marine species gradually disappeared downstream the pond sequence. The patterns of variation of macrobenthic invertebrates' density and biomass along the salinity gradient were different between seasons, partly due to the strong dominance of Hydrobia acuta in autumn, while species richness declined along the salinity gradient in both seasons.