LDWF meeting to talk about Big Lake Oysters

[MathGeek]

Originally Posted by Duck Butter

No one is denying the benefits of oysters, they are extremely important as you have pointed out. But oysters are not a magic bullet, nor do they decrease hypoxia to a noticable extent. They will shut down in hypoxic conditions. They can't just uproot and move away from the conditions, so they shut down, therefore no more filtration.

Chesapeake Bay is a much different system than Calcasieu. The water stays in the bay for much longer, and most of the bay is too deep to support oyster reefs. Further, the oysters are in the estuary, whereas, most of the hypoxia is in the Gulf of Mexico.

No one is suggesting that oysters offer complete control or are a magic bullet. The question is whether algae blooms and hypoxia go down when oyster populations go up, and if so, by how much?

Certainly, maintaining a balanced ecosystem requires more than oyster reef restoration. But if oyster reef restoration could reduce the average hypoxia in the near shore Gulf off of Cameron Parish by 50%, wouldn't this be an interesting and relevant finding?

Isn't it worth analyzing the existing data to explore the potential?

[Duck Butter]

Originally Posted by MathGeek

Chesapeake Bay is a much different system than Calcasieu. The water stays in the bay for much longer, and most of the bay is too deep to support oyster reefs. Further, the oysters are in the estuary, whereas, most of the hypoxia is in the Gulf of Mexico.

No one is suggesting that oysters offer complete control or are a magic bullet. The question is whether algae blooms and hypoxia go down when oyster populations go up, and if so, by how much?

Certainly, maintaining a balanced ecosystem requires more than oyster reef restoration. But if oyster reef restoration could reduce the average hypoxia in the near shore Gulf off of Cameron Parish by 50%, wouldn't this be an interesting and relevant finding?

Isn't it worth analyzing the existing data to explore the potential?

it would be very relevant, but it hasn't been found despite decades of oyster research and decades of hypoxic zones

low to no oxygen is low to no oxygen to an oyster whether its in Calcasieu Lake, Sabine Lake, Florida, Delaware, or Japan. Everything else you have been saying is spot on, just leave the hypoxia out of the list of ecosystem services oysters perform is all. You put a fish in a hypoxic zone, it swims away or dies, a shrimp swims away or dies, an oyster does not have that option so it closes up and does not filter feed. There are studies showing oysters get stressed and die during hypoxic conditions, they can't magically filter out phosphorus, nitrogen, and potassium out of the water when they have no oxygen to survive on.

[MathGeek]

Originally Posted by Duck Butter

it would be very relevant, but it hasn't been found despite decades of oyster research and decades of hypoxic zones

low to no oxygen is low to no oxygen to an oyster whether its in Calcasieu Lake, Sabine Lake, Florida, Delaware, or Japan. Everything else you have been saying is spot on, just leave the hypoxia out of the list of ecosystem services oysters perform is all. You put a fish in a hypoxic zone, it swims away or dies, a shrimp swims away or dies, an oyster does not have that option so it closes up and does not filter feed. There are studies showing oysters get stressed and die during hypoxic conditions, they can't magically filter out phosphorus, nitrogen, and potassium out of the water when they have no oxygen to survive on.

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.

[Duck Butter]

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.

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.