Oyster aquaculture could combat Potomac River pollution
Shellfish raised on the river bottom would remove excess nutrients from the water.
Shellfish raised on the river bottom would remove excess nutrients from the water.
Comments
Oysters can't make any difference in Potomac River water quality. A 1946 paper states “...in the late 1800’s it [the oyster harvest] averaged approximately 1,600,000 bushels." Given 300 market-sized oysters per bushel, for a few years, 480 million oysters were harvested annually. Then the harvest crashed and in recent years it has rarely exceeded 5,000 bushels.
One million market-sized oysters contain at most 150 kilograms of nitrogen (N), with sub-equal amounts in the shell and dry tissue. Even if we could harvest 480 million oysters again, only 72,000 kg of N would be removed (150 kg N / million oysters * 480 million oysters). Today, the Potomac River receives about 30 million kilograms of N each year. So the maximum oyster harvest ever recorded, which can never be reached again, could only remove 0.2% of today’s N load (72,000 / 30,000,000).
Pollution always needs to be reduced at the source and “sop-up” strategies (oysters in this case) are never effective. In the case of the Bay, the only strategy that will significantly improve water quality is to raise the fertilization efficiency of crops from around 65% where it is today to at least 80% by banning the cheap disposal of animal waste (poultry litter, sludge and manure) by land application and replacing conventional fertilizers with controlled- (slow-, timed-) release products. All the money we have spent reducing pollution from wastewater treatment plants hasn't made any significant difference in Bay water quality and more oysters won't either.
Dr. Lynton S. Land, Ophelia VA
www.VaBayBlues.org
Great article - really tells a great story!
Thank you!
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