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Date Permissions Signed


Date of Award


Document Type

Masters Thesis

Degree Name

Master of Science (MS)



First Advisor

Moyer, Craig L.

Second Advisor

Apple, Jude K.

Third Advisor

Schwarz, Dietmar, 1974-


By the end of the 21st century, mean sea surface temperatures are expected to increase 4°C, while atmospheric CO2 concentrations are predicted to triple causing seawater to become more acidic. These compounding effects will undoubtedly have major consequences for the organisms and processes in the oceans. Bacterioplankton play a vital role in the marine carbon cycle and the oceans' ability to sequester CO2. We utilized pCO2 perturbation experiments to investigate the effects of elevated temperature and acidity on bacterioplankton community structure and metabolism. Terminalrestriction fragment length polymorphism (T-RFLP) revealed that bacterioplankton incubated in lower pH conditions exhibited a reduction of species richness, evenness, and overall diversity, relative to those incubated in ambient pH conditions. Non-metric multidimensional scaling (MDS) of T-RFLP data resulted in clustering by pH suggesting that pH influenced the structure of these communities. Shifts in the dominant members of bacterioplankton communities incubated under different pH were observed in both T-RFLP and clone library analyses. Both ambient and low pH communities were dominated by sequences of γ-proteobacteria and α-proteobacteria, although abundance of α-proteobacteria increased in communities incubated at lower pH. Although the representatives from these two classes were distinctly different between the treatments, a few taxa were found to be persistent in all treatments. Changes in the structure of bacterioplankton communities coincided with significant changes to their overall metabolism. Bacterial production rates decreased, while bacterial respiration increased under lower pH conditions. This study highlights the ability of bacterioplankton communities to respond to ocean acidification both structurally and metabolically, which may have significant implications for their ecological function in the marine carbon cycle and the ocean's response to global climate change.





Western Washington University

OCLC Number


Subject – LCSH

Marine bacteria--Effect of high temperatures on; Marine bacteria--Metabolism--Effect of high temperatures on; Marine bacteria--Effect of water acidification on; Marine bacteria--Metabolism--Effect of water acidificaiton on; Marine microbial ecology




masters theses




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