LIMNOLOGY AND OCEANOGRAPHY 34: 543-558

The measurement and distribution of dissolved nucleic acids in aquatic environments

D. M. Karl and M. D. Bailiff

Department of Oceanography and Hawaii Institute of Geophysics, University of Hawaii, Honolulu, Hawaii 96822, USA

Nucleic acids (DNA and RNA) are ubiquitous components of the dissolved organic matter (DOM) pool of all oceanic, neritic, estuarine, and freshwater habitats studied to date. A new method for the quantitative determination of dissolved nucleic acids (DNA and RNA) in water and sediment samples was developed, evaluated, and utilized in a study of various marine and freshwater ecosystems. Under appropriate reaction conditions, dissolved DNA (D-DNA) and dissolved RNA (D-RNA) are efficiently removed from solution with the addition of cetyltrimethylammonium bromide (CTAB) and subsequent formation of insoluble CTA-nucleic acid salts. The insoluable salts are collected, by filtration, onto glass-fiber filters and analyzed for DNA and RNA with fluorometric and clorometric procedures, respectively. The performance of this CTAB method is simple, reliable, and reproducable for measuring dissolved nucleic acids in natural aquatic environments. For the ecosystems investigated herein, D-DNA and D-RNA concentrations ranged from 0.56 to 88 µliter^-1 and 4.03 to 871 µg liter^-1; the ratio of D-RNA to D-DNA ranged from 4.1 to 11.5.