Epilithic diatoms and biological quality of Stratonikon mountain creeks, Chalkidiki (Greece).

During two sampling periods (lowflow and highflow) epilithic diatoms were c ollected in two hydrographic sectors of Stratonikon mountain. In the study 162 taxa were identified from which 42 species, one sub-species and nine va rieties are first records for the Creek flora. Running waters present a hig h species richness and most of the dominant species found in the study area are cosmopolitan, alkaliphilous, prefering well oxygenated waters. The spe cies Achnanthes minutissima var. minutissima, Amphora pediculus, Cocconeis placentula, Rhoicosphenia abbreviata and Nitzschia dissipata var. dissipata were dominant during both sampling periods. Under highflow conditions, the species Gomphonema olivaceum var. olivaceum and G. tergestinum became also dominant. The Shannon's index values varied from 0.6 to 5.0 and evenness f rom 0.15 to 0.86. Dendrograms and MDS plots showed the floristic particular ities of sites due to human activities and environmental conditions. The va lues of IFS diatomic index showed that the biological quality of the water was very good during the study period. (C) ADAC / Elsevier, Paris.