Mesozooplankton taurine production and prokaryotic uptake in the northern Adriatic Sea

Elisabeth L Clifford,Mirjana Najdek,Victor Ortiz,Paolo Paliaga,Chie Amano,Eva Sintes,Gerhard J Herndl,Daniele De Corte,Ingrid Ivančić

doi:10.1002/lno.11544

Abstract

Dissolved free taurine, an important osmolyte in phytoplankton and metazoans, has been shown to be a significant carbon and energy source for prokaryotes in the North Atlantic throughout the water column. However, the extent of the coupling between taurine production and consumption over a seasonal cycle has not been examined yet. We determined taurine production by abundant crustacean zooplankton and its role as a carbon and energy source for several prokaryotic taxa in the northern Adriatic Sea over a seasonal cycle. Taurine concentrations were generally in the low nanomolar range, reaching a maximum of 22 nmol L−1 in fall during a Pseudonitzschia bloom and coinciding with the highest zooplankton taurine release rates. Taurine accounted for up to 5% of the carbon, 11% of the nitrogen, and up to 71% of the sulfur requirements of heterotrophic prokaryotes. Members of the Roseobacter clade, Alteromonas, Thaumarchaeota, and Euryarchaeota exhibited higher cell‐specific taurine assimilation rates than SAR11 cells. However, cell‐specific taurine and leucine assimilation were highly variable in all taxa, suggesting species and/or ecotype specific utilization patterns of taurine and dissolved free amino acids. Copepods were able to cover the bulk taurine requirements of the prokaryotic communities in fall and winter and partly in the spring–summer period. Overall, our study emphasizes the significance of taurine as a carbon and energy source for the prokaryotic community in the northern Adriatic Sea and the importance of crustacean zooplankton as a significant source of taurine and other organic compounds for the heterotrophic prokaryotic community.

Highlights

To elucidate the link between taurine release by crustacean zooplankton and uptake by prominent prokaryotic taxa, we investigated taurine production and utilization dynamics over a seasonal cycle in the northern Adriatic Sea
Physicochemical characteristics of the water column Water temperature showed typical seasonal dynamics for the northern Adriatic Sea, with winter temperatures of $ 10C increasing during spring and reaching in the stratified water column in summer 23C at the sea surface (Fig. 1a)
The northern Adriatic Sea is a highly dynamic system influenced by riverine freshwater discharge and the oligotrophic central Adriatic waters (Kraus et al 2016)

Summary

Introduction

Members of SAR11 and Rhodobacteraceae are often present in high abundances during bloom events (Alonso and Pernthaler 2006; Choi et al 2018), utilizing taurine and other low-molecular weight organic compounds (Li et al 2018). Toward the decline of a bloom, other prokaryotic groups dominate the community, such as Bacteroidetes, degrading high-molecular weight organic compounds (Alonso and Pernthaler 2006; Choi et al 2018). To elucidate the link between taurine release by crustacean zooplankton and uptake by prominent prokaryotic taxa, we investigated taurine production and utilization dynamics over a seasonal cycle in the northern Adriatic Sea

Methods

Results

Conclusion