How does the amount of oxygen in water affect the oyster population

At

one time, oysters were so abundant in the Chesapeake Bay that their reefs

defined the major river channels. The reefs extended to near the water surface;

to stray out of the center channel often posed a navigational hazard to ships

sailing up the Bay. Now, after decades of damage to reefs from harvest,

increased disease, falling salinity due to the increased runoff that

accompanies increased impervious surface, and increased sedimentation from

runoff, a significant amount of hard bottom habitat has been lost. The oyster

population in the Bay is less than 1% of what it once was.

    Degrading water quality is both a cause

and an effect of the oyster decline, because fewer oysters means less

filtration capacity. But oysters, as hardy as they are, can be killed by

prolonged periods of low dissolved oxygen at the Bay's bottom. 

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the ratio of the conjugate base to the acid required to attain the desired ph.