The Phytoplankton and Trophic State of Lake Skadar/Shkodra

According to the high number of registered microalgae (1,069 taxa), Lake Skadar represents one of the biodiversity hot spots of Europe. The lake is unstratified, due to its shallowness and vertical mixing caused by the wind-driven hydrodynamics. The main limiting factor for phytoplankton growth in Lake Skadar is the amount of phosphorus. The phytoplankton dynamics and distribution are generally governed by meteorological and hydrological factors that induce distinct temporal and spatial heterogeneity. The central, pelagic zone of the lake is characterized by the dominance of euplanktonic species, mostly centric diatoms, during the whole annual cycle. The western and northwestern, more isolated, and shallower parts of the lake have a greater abundance of greens and blue-greens (that overdominate diatoms during the summer) and a higher percentage of resuspended benthic-epiphytic forms. The average chlorophyll a concentration indicates mesotrophic conditions in Lake Skadar, but during midsummer, when the highest phytoplankton abundance and biomass occurs, the trophic level of the lake increases to eutrophy. Comparison to former phytoplankton data shows distinct differences in terms of the qualitative and quantitative composition of the phytoplankton community of Lake Skadar, which indicate lake eutrophication.