Limnetica 30

Five populations of freshwater red algae were investigated between February 2008 and September 2009 in four segments of the Jarama River Basin (Tajo Basin), Iberian Peninsula, between 40-41◦ N, 3-4◦ W, at 700 to 1200 m altitude. Three species were documented (Batrachospermum gelatinosum, Lemanea fluviatilis and Paralemanea catenata) and information was collected about includes their morphology and the physical and chemical characteristics of the water. All the taxa have been reported previously, but the present work includes the first detailed morphological description of red algae in the region and their ecological preferences. The waters in these study sites are cool to temperate (5-17 ^oC), acid to circumneutral (pH 6.3-7.5) and with a low ion concentration (specific conductivity 77-270 µS cm⁻¹). Two groups were distinguished on the basis of nutrient concentration. The first group, which included B. gelatinosum and L. fluviatilis, is found in clean water with low nutrient concentration, while the second group, which included P. catenata, occurred in nutrient-rich water. Gametophytes of L. fluviatilis and P. catenata were present in all seasons, with the highest percentage cover in autumn and winter corresponding to high current velocity and low water temperature. However, gametophytes were longest, and spermatangial sori and carposporophytes were most abundant in spring when current velocity was low and water temperature was high. The distribution of Batrachosermales from the Jarama Basin showed a strong affinity with temperate regions of central Europe and floras of other continents.