TITLE:
The Effects of Ocean Acidity and Elevated Temperature on Bacterioplankton Community Structure and Metabolism
AUTHORS:
Nam Siu, Jude K. Apple, Craig L. Moyer
KEYWORDS:
Ocean Acidification, Climate Change, Bacterioplankton, Community Structure
JOURNAL NAME:
Open Journal of Ecology,
Vol.4 No.8,
May
30,
2014
ABSTRACT: 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 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 ocean acidity and
elevated temperature on bacterioplankton community structure and metabolism.
Terminal-restriction fragment length polymorphism (T-RFLP) of small subunit
ribosomal (SSU) genes 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 SSU clone library analyses. Both ambient and low
pH communities were dominated by Gammaproteobacteria and Alphaproteobacteria,
although abundance of Alphaproteobacteria increased in communities incubated at
lower pH. This was expressed by the gamma to alpha ratio dropping from ~9 to 4,
respectively. In general, the representative taxa from these two classes were
distinctly different between the treatments, with a few taxa found to be
persistent in both 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.