Effect of elevated pCO2 on trace gas production during an ocean acidification mesocosm experiment

• Published in: Biogeosciences
• Main Authors: Zhang, Sheng-Hui, Yu, Juan, Ding, Qiong-Yao, Yang, Gui-Peng, Gao, Kun-Shan, Zhang, Hong-Hai, Pan, Da-Wei
• Format: Text
• Language: English
• Published: 2019
• Subjects: Ocean acidification
• Online Access: https://doi.org/10.5194/bg-15-6649-2018; https://www.biogeosciences.net/15/6649/2018/

A mesocosm experiment was conducted in Wuyuan Bay (Xiamen), China, to investigate the effects of elevated p CO 2 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 ( CHBrCl 2 ), methyl bromide ( CH 3 Br ), dibromomethane ( CH 2 Br 2 ) and iodomethane ( CH 3 I ). 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 p CO 2 mesocosms (1000 µ atm) was 28 % lower than that in low p CO 2 mesocosms (400 µ atm). Elevated p CO 2 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 p CO 2 treatment. Unlike DMS, the elevated p CO 2 did not affect DMSP production ability of T. weissflogii or P. tricornuntum throughout the 5-week culture. A positive relationship was detected between CH 3 I and T. weissflogii and P. tricornuntum during the experiment, and there was a 40 % reduction in mean CH 3 I concentration in the high p CO 2 mesocosms. CHBrCl 2 , CH 3 Br , and CH 2 Br 2 concentrations did not increase with elevated chlorophyll a (Chl a ) concentrations compared with DMS(P) and CH 3 I , and there were no major peaks both in the high p CO 2 or low p CO 2 mesocosms. In addition, no effect of elevated p CO 2 was identified for any of the three bromocarbons.