Contrasting effects of acidification and warming on dimethylsulfide concentrations during a temperate estuarine fall bloom mesocosm experiment
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Published:2019-03-21
Issue:6
Volume:16
Page:1167-1185
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ISSN:1726-4189
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Container-title:Biogeosciences
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language:en
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Short-container-title:Biogeosciences
Author:
Bénard RobinORCID, Levasseur Maurice, Scarratt Michael, Michaud Sonia, Starr Michel, Mucci AlfonsoORCID, Ferreyra Gustavo, Gosselin MichelORCID, Tremblay Jean-Éric, Lizotte MartineORCID, Yang Gui-Peng
Abstract
Abstract. The effects of ocean acidification and warming on the concentrations of
dimethylsulfoniopropionate (DMSP) and dimethylsulfide (DMS) were investigated
during a mesocosm experiment in the Lower St. Lawrence Estuary (LSLE) in the
fall of 2014. Twelve mesocosms covering a range of pHT (pH on the
total hydrogen ion concentration scale) from 8.0 to 7.2, corresponding to a
range of CO2 partial pressures (pCO2) from 440
to 2900 µatm, at two temperatures (in situ and +5 ∘C; 10
and 15 ∘C) were monitored during 13 days. All mesocosms were
characterized by the rapid development of a diatom bloom dominated by
Skeletonema costatum, followed by its decline upon the exhaustion of
nitrate and silicic acid. Neither the acidification nor the warming resulted
in a significant impact on the abundance of bacteria over the experiment.
However, warming the water by 5 ∘C resulted in a significant
increase in the average bacterial production (BP) in all 15 ∘C
mesocosms as compared to 10 ∘C, with no detectable effect of
pCO2 on BP. Variations in total DMSP
(DMSPt = particulate + dissolved DMSP) concentrations
tracked the development of the bloom, although the rise in DMSPt
persisted for a few days after the peaks in chlorophyll a. Average
concentrations of DMSPt were not affected by acidification or
warming. Initially low concentrations of DMS (<1 nmol L−1)
increased to reach peak values ranging from 30 to 130 nmol L−1 towards
the end of the experiment. Increasing the pCO2 reduced the
averaged DMS concentrations by 66 % and 69 % at 10 and
15 ∘C, respectively, over the duration of the experiment. On the
other hand, a 5 ∘C warming increased DMS concentrations by an
average of 240 % as compared to in situ temperature, resulting in a
positive offset of the adverse pCO2 impact. Significant
positive correlations found between bacterial production and concentrations
of DMS throughout our experiment point towards temperature-associated
enhancement of bacterial DMSP metabolism as a likely driver of the mitigating
effect of warming on the negative impact of acidification on the net
production of DMS in the LSLE and potentially the global ocean.
Funder
Fonds de recherche du Québec – Nature et technologies Natural Sciences and Engineering Research Council of Canada
Publisher
Copernicus GmbH
Subject
Earth-Surface Processes,Ecology, Evolution, Behavior and Systematics
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