Abstract
Abstract. A mesocosm experiment was conducted in Wuyuan Bay (Xiamen), China, to investigate the effects of elevated pCO2 on the phytoplankton species Phaeodactylum tricornutum (P. tricornutum), Thalassiosira weissflogii (T. weissflogii) and Emiliania huxleyi (E. huxleyi) and their production ability of dimethylsulfide (DMS), dimethylsulfoniopropionate (DMSP), as well as four halocarbon compounds, bromodichloromethane (CHBrCl2), methyl bromide (CH3Br), dibromomethane (CH2Br2) and iodomethane (CH3I). Over a period of 5 weeks, P. tricornuntum outcompeted T. weissflogii and E. huxleyi, comprising more than 99 % of the final biomass. During the logarithmic growth phase (phase I), mean DMS concentration in high pCO2 mesocosms (1000 µatm) was 28 % lower than that in low pCO2 mesocosms (400 µatm). Elevated pCO2 led to a delay in DMSP-consuming bacteria concentrations attached to T. weissflogii and P. tricornutum and finally resulted in the delay of DMS concentration in the high pCO2 treatment. Unlike DMS, the elevated pCO2 did not affect DMSP production ability of T. weissflogii or P. tricornuntum throughout the 5-week culture. A positive relationship was detected between CH3I and T. weissflogii and P. tricornuntum during the experiment, and there was a 40 % reduction in mean CH3I concentration in the high pCO2 mesocosms. CHBrCl2, CH3Br, and CH2Br2 concentrations did not increase with elevated chlorophyll a (Chl a) concentrations compared with DMS(P) and CH3I, and there were no major peaks both in the high pCO2 or low pCO2 mesocosms. In addition, no effect of elevated pCO2 was identified for any of the three bromocarbons.
Highlights
Anthropogenic emissions have increased the fugacity of atmospheric carbon dioxide from the pre-industrial value of 280 μatm to the present-day value of over 400 μatm, and these values will further increase to 800–1000 μatm by the end of this century (Gattuso et al, 2015)
DMS is the most important volatile sulfur compound produced from dimethylsulfoniopropionate (DMSP), which is ubiquitous in marine environments, mainly synthesized by marine microalgae (Stefels et al, 2007), a few angiosperms, some corals (Raina et al, 2016), and several heterotrophic bacteria (Curson et al, 2017) through complex biological interactions in marine ecosystems
During the logarithmic growth phase, the elevated pCO2 led to a reduction in mean DMSPconsuming bacteria (29 %) and DMS concentration (28 %) compared with those in the low pCO2 treatment
Summary
Anthropogenic emissions have increased the fugacity of atmospheric carbon dioxide (pCO2) from the pre-industrial value of 280 μatm to the present-day value of over 400 μatm, and these values will further increase to 800–1000 μatm by the end of this century (Gattuso et al, 2015). DMS is the most important volatile sulfur compound produced from dimethylsulfoniopropionate (DMSP), which is ubiquitous in marine environments, mainly synthesized by marine microalgae (Stefels et al, 2007), a few angiosperms, some corals (Raina et al, 2016), and several heterotrophic bacteria (Curson et al, 2017) through complex biological interactions in marine ecosystems. It remains controversial, DMS and its by-products, such as methanesulfonic acid and non-sea-salt sulfate, are suspected of having a prominent part in climate feedback (Charlson et al, 1987; Quinn and Bates, 2011). Several assumptions have been presented to explain these contrasting results and attributed the pH-induced variation in DMSproduction capability to altered physiology of the algae cells or of bacterial DMSP degradation (Vogt et al, 2008; Hopkins et al, 2010, Avgoustidi et al, 2012; Archer et al, 2013; Hopkins and Archer, 2014; Webb et al, 2015)
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