The oceanic uptake of anthropogenic CO2 emissions is leading to an alteration of seawater carbonate chemistry, manifested as increasing [H+], falling [CO32-] and a drop in seawater pH. Over the coming centuries this process, termed “ocean acidification”, is expected to negatively impact marine biota, with implications for marine biological and biogeochemical processes. In this thesis, the impact that such changes may have on the net production of a range of climatically- and atmospherically-important marine biogenic trace gases, including halocarbons and dimethyl sulphide (DMS), is assessed through a mesocosm phytoplankton bloom CO2 perturbation experiment, two laboratory CO2 incubation experiments on natural seawater samples, and at a volcanically-acidified shallow marine fieldsite in Italy. Large and significant reductions in DMS and DMSP concentrations under future high CO2 conditions were observed during the mesocosm experiment (mean decreases of 57 percent and 24 percent, respectively), a finding in strong support of a previous study (Avgoustidi 2007). Furthermore, concentrations of iodocarbons showed large decreases, with mean decreases under high CO2 ranging from 59 to 93 percent. Results for the laboratory incubation experiments also showed a reduction in iodocarbon concentrations (when normalised to chlorophyll a) under high CO2. These changes may be the result of shifts in plankton community composition in response to the high CO2 conditions, and/or impacts on dissolved organic matter and the bacterial communities involved in the formation of these compounds. The response of bromocarbons was less clear cut during the experimental studies. Following investigations at a naturally-acidified fieldsite in Italy, it was concluded that this site was a poor natural analogue to the impact of future ocean acidification on marine trace gas production. Taking the results of the mesocosm and laboratory incubations into consideration, a combined decrease in both DMS and iodocarbons in response to ocean acidification may have considerable impacts on future atmospheric chemistry and global climate.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:569312 |
| Date | January 2010 |
| Creators | Hopkins, Frances Elizabeth |
| Publisher | University of East Anglia |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | https://ueaeprints.uea.ac.uk/10582/ |
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