engleski

Taurine turnover in the north Adriatic Sea

Taurine, a sulfur containing organic acid, is produced by marine metazoans and phytoplankton. Omics studies have revealed that proteins involved in taurine uptake and transformation are widespread among marine prokaryotic communities. However, little is known about the production and turnover of taurine in the marine environment. Concentrations of taurine and leucine were measured by High Performance Liquid Chromatography over a seasonal cycle in the coastal northern Adriatic Sea (off Rovinj, Croatia). Concurrently, the bulk uptake and respiration rates of taurine and uptake of leucine by prokaryotes were assessed using radiolabeled substrates. Taurine release rates by copepod communities were also determined. The maxima taurine concentrations (7.9±5.9 nM), assimilation rates (2.7±0.7 nmol L-1 d-1) and release rates by abundant copepods (8.8±12.1 nmol individual-1 d-1) were determined in November, coinciding with a phytoplankton bloom. In contrast, the maximum leucine incorporation rates occurred in summer (5.3±3.7 nmol L-1 d-1). Turnover times ranged from 2h to 7d for leucine and taurine, respectively. Taurine was taken up by a phylogenetically diverse community of prokaryotes, including SAR11 and Thaumarchaeota, as assessed by microautoradiography combined with fluorescence in situ hybridization. However, the shift in the proportion of taurine respired of the total taurine uptake from spring (72.5±4.8 %) to the fall during the phytoplankton bloom (34.5±7.4 %) suggests a response of the prokaryotic community to the availability of this compound. Taken together, our results indicate that taurine is an important nutrient and energy source for microbial communities in nearshore waters.

taurine ; crustacean zooplankton ; release rates ; prokaryotic uptake ; North Adriatic Sea

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