Quote:
Originally Posted by MathGeek
How many cases have been tested where the oysters are upstream of where the hypoxic zone forms (not actually in it)?
You must have missed this essential feature of the Calcasieu system because you keep mentioning how oysters shut down when oxygen levels drop. The hypoxic zone off of Cameron was not there in late June when Texas A&M scientists measured oxygen levels. It was there in late July when LUMCON scientists sampled the area again. At no time where the waters in the main Calcasieu Estuary hypoxic this summer, but it may be that N, P, C, and algae flowing into the Gulf from the estuary contributed to the size of the hypoxic zone.
Further, it has been estimated that at their peak historical levels, oysters in the Chesapeake Bay completely filtered the water in the bay every 3-4 days.
Since some oyster reefs have been restored, the complete water filtration time is estimated at 300-400 days. Drawing conclusions on the potential to mitigate hypoxia in the Chesapeake Bay seems ill advised when the water filtration by the oysters is only 1% of what is possible.
Calcasieu Lake is much shallower than Chesapeake Bay. The potential exists for oysters in Calcasieu Lake to completely filter the water once per day or more if the oyster reef potential were optimized. Sabine drains a much larger area and inevitably has higher levels of agricultural runoff than Calcasieu. Yet, there is very seldom any hypoxic zone there.
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The hypoxic zone is typically most noticeable during July and August, not June. The whole process takes awhile. Spring rains and snow melt come down the river (carrying fertilizer) and the phytoplankton bloom takes place. Takes 4 - 8 weeks (July-August) after that before maximum phytoplankton die off occurs resulting in the hypoxic conditions
Filtration:
If you took an aquarium of Calcasieu lake water and let oysters filter it, there would still be suspended particles. Oysters can't filter every particle in there, if they could, then they would filter out the salt and you would be left with nothing but pure freshwater. I would definitely advise against drinking the water still after the filtration process as you may end up sick from fecal coliform
You are reaching for cause and effect and that is all I am commenting on, everything else about oysters is great. Just leave out the hypoxia stuff. Oysters are wonderful creatures and every estuary should try and find a balance of having enough of them to perform the ecosystem services they provide and still be able to harvest enough for consumption commercially BUT oysters are not a magic bullet.