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A Marine Focus
Causes: Methane Hydrates - continued

Oxidation the methane would be accomplished though the use of sulfate as all dissolved oxygen would have been consumed in the top few centimeters of sediment. The oxidation of methane would result in sulfide production via the removal of oxygen from the sulfate.  The most notable sulfide products would be pyrite and hydrogen sulfide. Some of the remaining methane escaping into the water column would be consumed by aerobic organisms. This consumption would lead to the production of carbon dioxide. Hence, methane release and oxidation would lead to a draw down in oxygen and an increase in carbon dioxide. Evidence of carbon dioxide enrichment can be seen in anomalous carbonate strata near the end-Permian margin. Carbon dioxide combining with water would have formed bicarbonate ions. These ions would react with dissolved calcium already present in the water to form calcium carbonate. (Knoll, 1996)

A drawdown of oxygen in marine environments leads to dysoxia. If the quantity of methane released was great enough, local or widespread anoxia would occur. This would cause harmful effects in aerobic organisms, ranging from physiological consequences to death. In areas where anoxia became pervasive or enduring, such as the deep ocean, life would have been severely retarded. A rise in anaerobic organisms, including methanogens, would follow the advent of anoxic conditions. The presence of these organisms would further increase methane production. (Knoll, 2006)