RELATIONSHIPS BETWEEN NUCLEIC-ACID CONCENTRATIONS AND PRIMARY PRODUCTION IN THE CATALAN SEA (NORTHWESTERN MEDITERRANEAN)

We explored the relationships between classical estimators of autotrop hic biomass and primary production, such as chlorophyll a concentratio n and C-14-fixation rates, and biochemical indices based on DNA and RN A determinations, which have been proposed as indicators of physiologi cal state in natural plankton populations. The measurements were made during two cruises across the Catalan Front, carried out in May 1989 a nd February 1990, corresponding respectively, to periods of stratifica tion and moderate mixing. DNA and RNA concentrations (measured by a do uble-staining fluorimetric technique) were significantly correlated wi th chlorophyll a in February 1990, but not in May 1989, when a marked deep chlorophyll maximum was present. Significant positive correlation s between RNA concentration and primary production and between RNA:DNA and primary production were found during both surveys, probably refle cting both higher RNA concentrations per cell and enhanced bacterial a nd microheterotrophic growth in high primary production situations. Th e results support the potential usefulness, in biological oceanography , of biochemical indicators based on DNA and RNA concentrations.