THE EFFECT OF ARCHEAN OCEANS ON CYANOBACTERIA, GREEN SULFUR BACTERIA AND THE RISE OF OXYGEN

Open Access
Author:
Baumann, Beth Anne
Graduate Program:
Geosciences
Degree:
Master of Science
Document Type:
Master Thesis
Date of Defense:
August 21, 2008
Committee Members:
  • Christopher Howard House, Thesis Advisor
Keywords:
  • Archean
  • early earth
  • anoxic atmosphere
  • rise of oxygen
  • early atmsophere
Abstract:
Growth of a common marine cyanobacterium, freshwater cyanobacterium, and a green sulfur bacterium was examined under different oxygen, sulfide, and ferrous iron concentrations. The goal of this study was to explore how early Archean oceans might have affected cyanobacterial proliferation and the response of major preexisting phototrophs to increasing oxygenation in order to better constrain the timing of the rise of oxygen. The results of this study illustrate that cyanobacteria are very negatively affected by reduced iron and to a lesser degree by sulfide. In addition, increasing oxygen provides no discernable advantage to cyanobacteria, suggesting it is unlikely cyanobacteria evolved and proliferated in Fe+2-rich oceans. Archean oceans rich in Fe+2 would likely have confined cyanobacteria to local Fe+2-poor environments, prevented their immediate global propagation, and led to a significant lag time between cyanobacterial evolution and the rise in O2. Sulfur-rich Archean oceans are more likely to have allowed for rapid widespread proliferation of cyanobacteria and an earlier rise in atmospheric O2. Furthermore, the negative response of green sulfur bacteria to slight decreases in reducing power supports early O2 accumulation in H2S-rich Archean oceans.