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Effect of ocean acidification and elevated fCO2 on trace gas production by a Baltic Sea summer phytoplankton community


Webb, AL and Leedham-Elvidge, E and Hughes, C and Hopkins, FE and Malin, G and Bach, LT and Schulz, K and Crawfurd, K and Brussaard, CPD and Stuhr, A and Riebesell, U and Liss, PS, Effect of ocean acidification and elevated fCO2 on trace gas production by a Baltic Sea summer phytoplankton community, Biogeosciences, 13 pp. 4595-4613. ISSN 1726-4170 (2016) [Refereed Article]


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Copyright 2016 the authors. Licensed under Creative Commons Attribution 3.0 Unported (CC BY 3.0)

DOI: doi:10.5194/bg-13-4595-2016


The Baltic Sea is a unique environment as the largest body of brackish water in the world. Acidification of the surface oceans due to absorption of anthropogenic CO2 emissions is an additional stressor facing the pelagic community of the already challenging Baltic Sea. To investigate its impact on trace gas biogeochemistry, a large-scale mesocosm experiment was performed off Tvärminne Research Station, Finland, in summer 2012. During the second half of the experiment, dimethylsulfide (DMS) concentrations in the highest-fCO2 mesocosms (1075–1333µatm) were 34% lower than at ambient CO2 (350µatm). However, the net production (as measured by concentration change) of seven halocarbons analysed was not significantly affected by even the highest CO2 levels after 5 weeks' exposure. Methyl iodide (CH3I) and diiodomethane (CH2I2) showed 15 and 57% increases in mean mesocosm concentration (3.8±0.6 increasing to 4.3±0.4pmolL−1 and 87.4±14.9 increasing to 134.4±24.1pmolL−1 respectively) during Phase II of the experiment, which were unrelated to CO2 and corresponded to 30% lower Chl a concentrations compared to Phase I. No other iodocarbons increased or showed a peak, with mean chloroiodomethane (CH2ClI) concentrations measured at 5.3 (±0.9)pmolL−1 and iodoethane (C2H5I) at 0.5 (±0.1)pmolL−1. Of the concentrations of bromoform (CHBr3; mean 88.1±13.2pmolL−1), dibromomethane (CH2Br2; mean 5.3±0.8pmolL−1), and dibromochloromethane (CHBr2Cl, mean 3.0±0.5pmolL−1), only CH2Br2 showed a decrease of 17% between Phases I and II, with CHBr3 and CHBr2Cl showing similar mean concentrations in both phases. Outside the mesocosms, an upwelling event was responsible for bringing colder, high-CO2, low-pH water to the surface starting on day t16 of the experiment; this variable CO2 system with frequent upwelling events implies that the community of the Baltic Sea is acclimated to regular significant declines in pH caused by up to 800µatm fCO2. After this upwelling, DMS concentrations declined, but halocarbon concentrations remained similar or increased compared to measurements prior to the change in conditions. Based on our findings, with future acidification of Baltic Sea waters, biogenic halocarbon emissions are likely to remain at similar values to today; however, emissions of biogenic sulfur could significantly decrease in this region.

Item Details

Item Type:Refereed Article
Keywords:ocean acidification, trace gas, plankton
Research Division:Earth Sciences
Research Group:Oceanography
Research Field:Biological oceanography
Objective Division:Expanding Knowledge
Objective Group:Expanding knowledge
Objective Field:Expanding knowledge in the earth sciences
UTAS Author:Bach, LT (Dr Lennart Bach)
ID Code:133569
Year Published:2016
Web of Science® Times Cited:19
Deposited By:Ecology and Biodiversity
Deposited On:2019-07-02
Last Modified:2019-08-12
Downloads:18 View Download Statistics

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