The effects of elevated CO2 and ocean acidification on the production of marine biogenic trace gases

Webb, Alison (2015) The effects of elevated CO2 and ocean acidification on the production of marine biogenic trace gases. Doctoral thesis, University of East Anglia.

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Abstract

The human-induced increases in atmospheric carbon dioxide since the beginning of the
industrial revolution have led to increasing oceanic carbon uptake and changes in seawater
carbonate chemistry, resulting in lowering of surface water pH. To date, surface ocean acidity
has increased by 30% compared with pre-industrial times. The aim of this study was to
investigate the relationship between increasing pCO2, decreasing pH and changes in volatile
dimethylsulphide (DMS) and halocarbon concentrations, through 70,000 litre, high pCO2
mesocosm experiments and laboratory culture studies. DMS is a climatically important trace
gas produced by marine algae: it transfers sulphur into the atmosphere and is a major
influence on biogeochemical climate feedbacks. Halocarbons are also important biogenic trace
gases which undergo atmospheric photochemical degradation, releasing halide radicals to
participate in atmospheric ozone cycling, and transfer halogens from sea to land.
Evidence is presented from a Norwegian coastal study which showed a 60% DMS, 30% DMSP
and 40% iodocarbon reduction in high pCO2 mesocosms, and in the Baltic Sea, known for its
low-salinity, cyanobacterial dominated community, where DMS concentrations showed an
80% reduction under high pCO2 but halocarbon concentrations were unaffected. No decrease
in DMS or DMSP concentrations were identified in high pCO2 laboratory cultures of the DMSproducing
species Emiliania huxleyi RCC1229, and halocarbons were undetectable. Changes in
trace gas concentrations may arise due to pH effects on the interactions between microbial
producers and consumers. Other effects may arise from cell biochemistry due to long-term
adaptation to increased ρCO2 and reduced pH on the enzymatic activity production of the
compounds. Further studies should determine the nature of the pCO2 and pH effect on
bacterial interactions with DMS, DMSP and halocarbon production and breakdown. There
should also be attention given to the DMS source in the cyanobacterial-dominated community
of the Baltic Sea.

Item Type: Thesis (Doctoral)
Faculty \ School: Faculty of Science > School of Environmental Sciences
Depositing User: Mia Reeves
Date Deposited: 30 Jun 2015 13:54
Last Modified: 30 Jun 2015 13:54
URI: https://ueaeprints.uea.ac.uk/id/eprint/53426
DOI:

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