ASSESSMENT OF TROPHIC STATE IN THE WATER ECOSYSTEM OF GJIROKASTRA DISTRICT, ALBANIA

The assessments of water and sediment qualities are considered as the best indicators for monitoring eutrophication in water ecosystems. Viroi Lake, in Gjirokastra district (south part of Albania) was selected to evaluate eutrophication conditions during the years 2011-2013. The water and sediment samples were collected for quality evaluation. The following physico-chemical indicators of water: pH, temperature, conductivity, dissolved oxygen, biological oxygen demand, chemical oxygen demand, nitrates (N-NO sub(3) super(-)), nitrites (N-NO sub(2) super(-)), ammonium (N-NH sub(4) super(+)), total phosphor (TP), and the presence of microorganisms as Fecal sp. were estimated. Also, the texture, pH, CEC, carbonates (CaCO sub(3)), total nitrogen, total phosphor and humus of sediment samples were assessed. Furthermore, the concentration of heavy metals, such as Cu, Cr, Ni, Pb and Cd, were measured in sediment samples, as sensitive indicators of water ecosystems. Background values of heavy metals, given as 90 super(th) percentile, were used to evaluate the sediment pollution from heavy metals. Based on the obtained results, this ecosystem presented a trophic degree from oligotrophy to eutrophy. Microbiological analyses showed that Viroi Lake was polluted with microorganisms (fecal streptococci and fecal coliforms). The sediments can be classified, using sediment quality guideline (SQG) of USEPA, as non-polluted or heavily polluted according to the occurrence of specific heavy metals.