DISTRIBUTION AND ORIGIN OF DISSOLVED DNA IN LAKES OF DIFFERENT TROPHIC STATES

Concentrations and origin of dissolved DNA (dDNA) were studied in 14 l akes in the Mazurian Lake District (Northern Poland) and 7 lakes in So uthern Germany during the summer stratification period. dDNA concentra tion varied markedly (from 0.5 to 70 mu g l(-1)) in the studied lakes. We suggest that this dissolved organic matter fraction can be potenti ally one of the most important P and N sources for planktonic microorg anisms. Laboratory experiments and field observations suggested that e ukaryotic microorganisms (algae) are the most important sources of dDN A in lake water, whereas bacteria mainly decompose the dDNA pool.