RNA/DNA ratios for the estimation of metabolic and functional traits in diatom species from the northwestern Adriatic Sea, a possible impact on quality of mussel populations

Abstract

The aim of this study was to evaluate if the RNA/DNA and taxon-specific 18S rRNA/rDNA ratios could be used to assess the metabolic activity of marine phytoplankton. Indeed, traditional biomass indicators such as abundance and chlorophyll a are able to measure population size without reflecting phytoplankton functional activity. Two diatom species, namely Skeletonema marinoi and Chaetoceros socialis, commonly found in the northwestern Adriatic Sea were selected to perform individual and co-cultured growth experiments. The RNA/DNA and 18S rRNA/rDNA ratios were calculated and were found to peak in the early stages of growth followed by a sharp decline. These evidence suggested that these ratios could be useful indicators of phytoplankton metabolic dynamics and, since phytoplankton represent an important source of food for filter feeding animals, they may be useful to understand the potential impact on mussels growth.