Abstract
A method was developed for the determination of dissolved DNA in aquatic environments. The method is based upon the concentration of dissolved DNA by ethanol precipitation of 0.2-mum-pore-size filtered water. The DNA in concentrated extracts was quantified by the fluorescence of Hoechst 33258-DNA complexes. Fluorescence not attributable to DNA was corrected for by DNase I digestion of the extracts and averaged 25% of the total fluorescence for all samples. The effectiveness of the procedure for concentrating dissolved DNA was demonstrated by the efficient (>90%) recovery of internal standards. Concentrations of dissolved DNA from a variety of marine and freshwater environments ranged from 0.2 to 44 mug/liter, with the highest values being obtained for estuarine and river environments. The method is simple, specific for DNA, and more sensitive than previously described methods for the determination of extracellular DNA.