Changes in the diatom community in the great lake (Lurë National Park, Albania) from 2005 to 2017 and first steps towards assessment the water quality

Great Lake is the largest of 14 lakes situated in Lurë National Park, in the eastern part of the Lurë Mountains, Albania. To characterize lake ecological status, epiphytic and epilithic diatom samples were collected from the lakeshore in summer 2005, 2013, and 2017. However, in 2017 no macrophytes were present, such that only epilithic diatom samples could be collected. After laboratory analysis, 52 diatom taxa were identified in July 2005, 67 in June 2013, 111 in August 2013, and 126 in August 2017. The genera Diatoma, Epithemia, Fragilaria, and Surirella were not recorded in 2017, contrary to previous years.We applied two diatom indices to asses the ecological status of the Great Lake, IPS (Indice de Polluo–sensibilité), and TDIL (Trophic Diatom Index for lakes). The IPS index indicated very good water quality in all years, while the TDIL indicated moderate water quality in 2005 and 2013 and good water quality in 2017. Because more species have indicator values for calculating the IPS than the TDIL (valve number used to calculate the IPS was above 95%, while for TDIL was below 50% of 400 counted valves), the IPS may be a more promising tool for bioindication of lakes in Albania according to the demands of the Water Framework Directive