DETERMINATION OF DISSOLVED DEOXYRIBONUCLEIC-ACID CONCENTRATION IN LAKE WATER

In this paper we discuss the suitability of the cetyltrimethylammonium bromide (CTAB) precipitation method for the determination of dissolve d DNA (dDNA) in lake water. Factors affecting dDNA recovery from the p recipitate and further DAPI fluorometric assay were also examined. The proposed method was particularly suitable for routine determination o f dDNA concentration in low and moderately eutrophicated freshwater en vironments. The detection limit of the method varied from 1.5 mu g dDN A l(-1) for mesotrophic waters to 2.5 mu g dDNA l(-1) for eutrophic la kes. Preliminary observations on the concentration of dDNA in the surf ace water of 8 southern German lakes showed that dDNA concentrations w ere generally related to their trophic status and varied between 2.5 a nd 46.0 mu g l(-1) in mesotrophic and from 11.5 to 72 mu g l(-1) in eu trophic waters.