The University of Southampton
University of Southampton Institutional Repository

No observed effect of ocean acidification on nitrogen biogeochemistry in a summer Baltic Sea plankton community

No observed effect of ocean acidification on nitrogen biogeochemistry in a summer Baltic Sea plankton community
No observed effect of ocean acidification on nitrogen biogeochemistry in a summer Baltic Sea plankton community
Nitrogen fixation by filamentous cyanobacteria supplies significant amounts of new nitrogen (N) to the Baltic Sea. This balances N loss processes such as denitrification and anammox, and forms an important N source supporting primary and secondary production in N-limited post-spring bloom plankton communities. Laboratory studies suggest that filamentous diazotrophic cyanobacteria growth and N2-fixation rates are sensitive to ocean acidification, with potential implications for new N supply to the Baltic Sea. In this study, our aim was to assess the effect of ocean acidification on diazotroph growth and activity as well as the contribution of diazotrophically fixed N to N supply in a natural plankton assemblage. We enclosed a natural plankton community in a summer season in the Baltic Sea near the entrance to the Gulf of Finland in six large-scale mesocosms (volume ??55?m3) and manipulated fCO2 over a range relevant for projected ocean acidification by the end of this century (average treatment fCO2: 365–1231?µatm). The direct response of diazotroph growth and activity was followed in the mesocosms over a 47 day study period during N-limited growth in the summer plankton community. Diazotrophic filamentous cyanobacteria abundance throughout the study period and N2-fixation rates (determined only until day 21 due to subsequent use of contaminated commercial 15N-N2 gas stocks) remained low. Thus estimated new N inputs from diazotrophy were too low to relieve N limitation and stimulate a summer phytoplankton bloom. Instead, regeneration of organic N sources likely sustained growth in the plankton community. We could not detect significant CO2-related differences in neither inorganic nor organic N pool sizes, or particulate matter N?:?P stoichiometry. Additionally, no significant effect of elevated CO2 on diazotroph activity was observed. Therefore, ocean acidification had no observable impact on N cycling or biogeochemistry in this N-limited, post-spring bloom plankton assemblage in the Baltic Sea.
1726-4170
3901-3913
Paul, Allanah J.
283178fb-6cdb-4faf-971a-58259be87313
Achterberg, Eric P.
685ce961-8c45-4503-9f03-50f6561202b9
Bach, Lennart T.
d1390da7-06d0-4e3f-998c-3b925c9a3a19
Boxhammer, Tim
c628351d-64e5-4299-a0dd-2ac32a3f1fe3
Czerny, Jan
8f08fb1e-1e69-4e8b-bb64-cd8d4ce7fb8b
Haunost, Mathias
953ed65e-7369-4465-b39f-08cfc9ad8951
Schulz, Kai-Georg
4436e85e-fcc8-4483-b21a-96bffa8adc22
Stuhr, Annegret
00949e63-66ea-4f29-9db3-1117771cdc66
Riebesell, Ulf
2218bcf4-b444-4a1a-b268-9875762de458
Paul, Allanah J.
283178fb-6cdb-4faf-971a-58259be87313
Achterberg, Eric P.
685ce961-8c45-4503-9f03-50f6561202b9
Bach, Lennart T.
d1390da7-06d0-4e3f-998c-3b925c9a3a19
Boxhammer, Tim
c628351d-64e5-4299-a0dd-2ac32a3f1fe3
Czerny, Jan
8f08fb1e-1e69-4e8b-bb64-cd8d4ce7fb8b
Haunost, Mathias
953ed65e-7369-4465-b39f-08cfc9ad8951
Schulz, Kai-Georg
4436e85e-fcc8-4483-b21a-96bffa8adc22
Stuhr, Annegret
00949e63-66ea-4f29-9db3-1117771cdc66
Riebesell, Ulf
2218bcf4-b444-4a1a-b268-9875762de458

Paul, Allanah J., Achterberg, Eric P., Bach, Lennart T., Boxhammer, Tim, Czerny, Jan, Haunost, Mathias, Schulz, Kai-Georg, Stuhr, Annegret and Riebesell, Ulf (2016) No observed effect of ocean acidification on nitrogen biogeochemistry in a summer Baltic Sea plankton community. Biogeosciences, 13 (13), 3901-3913. (doi:10.5194/bg-13-3901-2016).

Record type: Article

Abstract

Nitrogen fixation by filamentous cyanobacteria supplies significant amounts of new nitrogen (N) to the Baltic Sea. This balances N loss processes such as denitrification and anammox, and forms an important N source supporting primary and secondary production in N-limited post-spring bloom plankton communities. Laboratory studies suggest that filamentous diazotrophic cyanobacteria growth and N2-fixation rates are sensitive to ocean acidification, with potential implications for new N supply to the Baltic Sea. In this study, our aim was to assess the effect of ocean acidification on diazotroph growth and activity as well as the contribution of diazotrophically fixed N to N supply in a natural plankton assemblage. We enclosed a natural plankton community in a summer season in the Baltic Sea near the entrance to the Gulf of Finland in six large-scale mesocosms (volume ??55?m3) and manipulated fCO2 over a range relevant for projected ocean acidification by the end of this century (average treatment fCO2: 365–1231?µatm). The direct response of diazotroph growth and activity was followed in the mesocosms over a 47 day study period during N-limited growth in the summer plankton community. Diazotrophic filamentous cyanobacteria abundance throughout the study period and N2-fixation rates (determined only until day 21 due to subsequent use of contaminated commercial 15N-N2 gas stocks) remained low. Thus estimated new N inputs from diazotrophy were too low to relieve N limitation and stimulate a summer phytoplankton bloom. Instead, regeneration of organic N sources likely sustained growth in the plankton community. We could not detect significant CO2-related differences in neither inorganic nor organic N pool sizes, or particulate matter N?:?P stoichiometry. Additionally, no significant effect of elevated CO2 on diazotroph activity was observed. Therefore, ocean acidification had no observable impact on N cycling or biogeochemistry in this N-limited, post-spring bloom plankton assemblage in the Baltic Sea.

Text
bg-13-3901-2016.pdf - Version of Record
Available under License Creative Commons Attribution.
Download (272kB)
Text
bg-13-3901-2016-supplement.pdf - Version of Record
Available under License Other.
Download (371kB)

More information

Accepted/In Press date: 29 May 2016
e-pub ahead of print date: 7 July 2016
Organisations: Ocean and Earth Science

Identifiers

Local EPrints ID: 401873
URI: http://eprints.soton.ac.uk/id/eprint/401873
ISSN: 1726-4170
PURE UUID: 4c26565d-9cac-49bc-b732-378f49ff9b71

Catalogue record

Date deposited: 20 Oct 2016 15:32
Last modified: 27 Apr 2022 05:19

Export record

Altmetrics

Contributors

Author: Allanah J. Paul
Author: Lennart T. Bach
Author: Tim Boxhammer
Author: Jan Czerny
Author: Mathias Haunost
Author: Kai-Georg Schulz
Author: Annegret Stuhr
Author: Ulf Riebesell

Download statistics

Downloads from ePrints over the past year. Other digital versions may also be available to download e.g. from the publisher's website.

View more statistics

Atom RSS 1.0 RSS 2.0

Contact ePrints Soton: eprints@soton.ac.uk

ePrints Soton supports OAI 2.0 with a base URL of http://eprints.soton.ac.uk/cgi/oai2

This repository has been built using EPrints software, developed at the University of Southampton, but available to everyone to use.

We use cookies to ensure that we give you the best experience on our website. If you continue without changing your settings, we will assume that you are happy to receive cookies on the University of Southampton website.

×