Abstract
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 largescale 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-f CO2 mesocosms (1075–1333 µatm) were 34 % lower than at ambient CO2 (350 µatm). 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 ± 0.4 pmol L−1 and 87.4 ± 14.9 increasing to 134.4 ± 24.1 pmol L−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) pmol L−1 and iodoethane (C2H5I) at 0.5 (±0.1) pmol L−1. Of the concentrations of
bromoform (CHBr3; mean 88.1 ± 13.2 pmol L−1), dibromomethane (CH2Br2; mean 5.3 ± 0.8 pmol L−1 ), and dibromochloromethane (CHBr2Cl, mean 3.0 ± 0.5 pmol L−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 800 µatm f CO2. 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.
community of the already challenging Baltic Sea. To investigate its impact on trace gas biogeochemistry, a largescale 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-f CO2 mesocosms (1075–1333 µatm) were 34 % lower than at ambient CO2 (350 µatm). 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 ± 0.4 pmol L−1 and 87.4 ± 14.9 increasing to 134.4 ± 24.1 pmol L−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) pmol L−1 and iodoethane (C2H5I) at 0.5 (±0.1) pmol L−1. Of the concentrations of
bromoform (CHBr3; mean 88.1 ± 13.2 pmol L−1), dibromomethane (CH2Br2; mean 5.3 ± 0.8 pmol L−1 ), and dibromochloromethane (CHBr2Cl, mean 3.0 ± 0.5 pmol L−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 800 µatm f CO2. 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.
| Original language | English |
|---|---|
| Pages (from-to) | 4595-4613 |
| Number of pages | 19 |
| Journal | Biogeosciences |
| Volume | 13 |
| DOIs | |
| Publication status | Published - 15 Aug 2016 |
Profiles
-
Peter Liss
- School of Environmental Sciences - Emeritus Professor
- Centre for Ocean and Atmospheric Sciences - Member
- Climatic Research Unit - Member
- ClimateUEA - Steering Committee Member
Person: Honorary, Research Group Member
-
Gill Malin
- Centre for Ocean and Atmospheric Sciences - Member
- School of Environmental Sciences - Emeritus Associate Professor
- Centre for Ecology, Evolution and Conservation - Member
- Marine Knowledge Exchange Network - Member
- Collaborative Centre for Sustainable Use of the Seas - Member
- Environmental Biology - Member
- ClimateUEA - Member
Person: Honorary, Member, Research Group Member, Research Centre Member