1. Ocean Acidification and the Effects on Marine Trace Gas Production
Alison Webb
University of East Anglia
Norwich, UK
Principal Supervisor: Professor Peter Liss 1

2. Effects of Acidification
Pre-industrial
Present
2100
Turley & Findlay (2009) pH
Increasing atmospheric ρCO2 results in lowered ocean pH.
Resulting effects may include:
Changes in oceanic primary production
Decreasing biogenic calcification rates
Effects on phytoplankton physiology
Subsequent changes in important biogeochemical cycles, including sulphur
Some background to the project here: Regular increases in pCO2 in the oceans,m as indicated by the lecture by David Kyle, has the effect of decreasing the pH of the surface oceans. The diagram is from Turley and Findlay in 2009, and shows the changes in pCO2 from pre industrial times, through present day and up to the year 2100, which is the year most of the models and the IPCC scenarios work towards.
The changes in pCO2 will likely have wide ranging effects on primary productivity, calcification, physiology and changes to the cycling of elements, oth biologically and chemically mediated. Most of this cycling is carried out by the proiduiction of trace gases: DMS for sulphur, a wide range of halocarbons for bromine, iodine and chlorine.
Previous field experiments on DMS and DMSP have shown significant decreases in concentration under high ρCO2 2

3. Aim of the Project
To study the changes in seawater DMS (Dimethylsulphide) and DMSP (Dimethylsulphoniopropionate) concentrations under increasing ρCO2 and decreasing pH
Community studies in-situ
Laboratory studies with individual organisms
The project is two fold. The trace gases we are interested in are produced by many different species, and are involved in some complex cycling. The effects of CO2 on the entire community has been studied for many years using mesocosms, leading to the development of the KOSMOS mesocosms, of which two major campaigns using these have been sampled for trace gas production. Two fieldexperiments have been studied: an open coastal environment in Bergen, Norway, and a nitrogen-fixing cyanobacterial habitat in the Baltic Sea in Finland.
A series of laboratory experiments have been carried out to focus on the effect of high CO2 on the growth and DMSP/ DMS production of E huxleyi RCC1229. These experiments have been both batch culture and semi-continuous culture, and aim to reproduce the effects seen in Bergen and to try and tease out the results further.
The lab experiments are now focussed solely on Ehux but there are some plans to try the same with cyanobacteria to see what effect this will have. This will be much more focussed on the halocarbons than just DMS the way the Ehux experiments are.

4. KOSMOS Mesocosm Experiments
Nine mesocosms with ρCO2 treatments ranging from 280 – 3000ppm
Sampling performed daily over 6 week periods
Trace Gas Samples analysed daily by GC-MS
DMSP samples fixed and analysed later by GC-FPD
Overall mesocosm experiment description 4

5. Mesocosm Locations Bergen 2011: Open Coastal Environment
Salinity: 30-35
Target Organism: Emiliania huxleyi
Nutrients: Mid-low nitrate and phosphate
Tvarminne 2012: Baltic Sea
Salinity: 5-8
Target Organism: Diazotrophic cyanobacteria
Nutrients: nitrate deplete, low phosphate

6. Total DMS and DMSP in an Open Coastal Environment
DMS showed significantly reduced concentration under increased ρCO2.
DMSP showed significantly lower concentrations in the high ρCO2 mesocosms
Conclusions from Bergen

7. But…
On a per cell basis, DMS and DMSP show opposite trends

8. Total DMS: Baltic Sea No DMSP data!
Conclusions from finland, the dataset and further work
No DMSP data!
DMS has very low correlations with the cell groups counted on the flow cytometer: no way to calculate DMS on a per cell basis.

9. DMS comparison
Concentrations as measured in situ, for directly comparable mesocosms
Comparison of the two experiments based upon the trace gas data.

10. So, where to from here?
Overview of the lab experiments with E.hux: previous experiments including those done down in Essex
Methods used and time of culturing, ie the semi continuous culoture over the same time period as the Bergen Experiment

11. Emiliania huxleyi lab culturing
The results of the experiments showing no significant difference between treatments, albeit with problems with the pH
Semi-continuous culture, DMSP and DMSP samples taken daily.
Air Control
840ppm CO2

12. DMS and DMSP Production
DMS and DMSP show no significant differences under high CO2 when normalised per cell.
Further studies will concentrate on the DMSP issues under low salinity, further development of the semi-continuous cultures, under daily reinoculations, and studies of Aphanizomenon cyanobacteria for DMS emissions
The results of the experiments showing no significant difference between treatments, albeit with problems with the pH

13. In Conclusion
In these studies, CO2 has little impact on DMS or DMSP production in the lab or in the field.
In lab experiments it has no effect on E.huxleyi growth.
What is causing the decrease in growth in the field, and why are there many studies showing a reduction in DMS/ DMSP under high CO2?

14. Acknowledgements
This project was funded by the UK Ocean Acidification Research Programme, under the Natural Environment Research Council.
The field studies presented here were part of the SOPRAN 2 Mesocosm experiment organised and performed by the Heimholtz Centre for Ocean Research (Geomar), Kiel, Germany.
The research leading to these results has received funding from the European Union Seventh Framework Program (FP7/ ) under grant agreement n° , MESOAQUA.