Journal cover Journal topic
Biogeosciences An interactive open-access journal of the European Geosciences Union
Journal topic
Volume 15, issue 5
Biogeosciences, 15, 1425-1445, 2018
https://doi.org/10.5194/bg-15-1425-2018
© Author(s) 2018. This work is distributed under
the Creative Commons Attribution 3.0 License.
Biogeosciences, 15, 1425-1445, 2018
https://doi.org/10.5194/bg-15-1425-2018
© Author(s) 2018. This work is distributed under
the Creative Commons Attribution 3.0 License.

Research article 08 Mar 2018

Research article | 08 Mar 2018

Effect of temperature rise and ocean acidification on growth of calcifying tubeworm shells (Spirorbis spirorbis): an in situ benthocosm approach

Sha Ni1,a, Isabelle Taubner1, Florian Böhm1, Vera Winde2,b, and Michael E. Böttcher2 Sha Ni et al.
  • 1GEOMAR, Helmholtz Centre for Ocean Research Kiel, 24148 Kiel, Germany
  • 2Geochemistry & Isotope Biogeochemistry Group, Marine Geology Department, Leibniz Institute for Baltic Sea Research (IOW), 18119 Rostock-Warnemünde, Germany
  • apresent address: Department of Geology, Lund University, 22362 Lund, Sweden
  • bpresent address: LUBW, Institute for Lake Research, Langenargen, Germany

Abstract. The calcareous tubeworm Spirorbis spirorbis is a widespread serpulid species in the Baltic Sea, where it commonly grows as an epibiont on brown macroalgae (genus Fucus). It lives within a Mg-calcite shell and could be affected by ocean acidification and temperature rise induced by the predicted future atmospheric CO2 increase. However, Spirorbis tubes grow in a chemically modified boundary layer around the algae, which may mitigate acidification. In order to investigate how increasing temperature and rising pCO2 may influence S. spirorbis shell growth we carried out four seasonal experiments in the Kiel Outdoor Benthocosms at elevated pCO2 and temperature conditions. Compared to laboratory batch culture experiments the benthocosm approach provides a better representation of natural conditions for physical and biological ecosystem parameters, including seasonal variations. We find that growth rates of S. spirorbis are significantly controlled by ontogenetic and seasonal effects. The length of the newly grown tube is inversely related to the initial diameter of the shell. Our study showed no significant difference of the growth rates between ambient atmospheric and elevated (1100ppm) pCO2 conditions. No influence of daily average CaCO3 saturation state on the growth rates of S. spirorbis was observed. We found, however, net growth of the shells even in temporarily undersaturated bulk solutions, under conditions that concurrently favoured selective shell surface dissolution. The results suggest an overall resistance of S. spirorbis growth to acidification levels predicted for the year 2100 in the Baltic Sea. In contrast, S. spirorbis did not survive at mean seasonal temperatures exceeding 24°C during the summer experiments. In the autumn experiments at ambient pCO2, the growth rates of juvenile S. spirorbis were higher under elevated temperature conditions. The results reveal that S. spirorbis may prefer moderately warmer conditions during their early life stages but will suffer from an excessive temperature increase and from increasing shell corrosion as a consequence of progressing ocean acidification.

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Spirorbis tube worms are common epibionts on brown algae in the Baltic Sea. We made experiments with Spirorbis in the Kiel Outdoor Benthocosms at CO2 and temperature conditions predicted for the year 2100. The worms were able to grow tubes even at CO2 levels favouring shell dissolution but did not survive at mean temperatures over 24° C. This indicates that Spirorbis worms will suffer from future excessive ocean warming and from ocean acidification fostering corrosion of their protective tubes.
Spirorbis tube worms are common epibionts on brown algae in the Baltic Sea. We made experiments...
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