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FCGU: Lake O releases likely already harming oysters and seagrass in the Caloosahatchee

Posted at 6:12 PM, Mar 07, 2024

W.P. FRANKLIN LOCK AND DAM, Fla. — We are in week 3 of water releases down the Caloosahatchee from Lake Okeechobee. One of the reasons the U.S. Army Corps is doing these releases now instead of later: oyster spawning season is around the corner.

However, experts are telling Fox 4 these releases are already harming the oysters.

“Right now, the flows are low enough that at the mouth of the estuary down by Shell Point and San Carlos Bay the oysters aren’t getting impacted,” said FGCU Professor Dr. Darren Rumbold. “But some place above that, before you get to Piney Point maybe or Cape Coral Bridge, the salinity is zero or close to zero and the organisms are being impacted.”

Dr. Rumbold has been researching for years how these releases from Lake Okeechobee effect sensitive species in the Caloosahatchee. He says the two species he is most concerned about are our oyster reefs and our sea grasses.

“The reefs are used by all sorts of organisms and when the oysters are killed the reefs breakdown over time, just simply from wave energy,” said Dr. Rumbold. “And when that reef breaks down, that habitat it is no longer available for those organisms.”

And it's not just the low salinity from freshwater releases, but it’s also the "tannings" or dark water that comes with it, like we saw during week 2 of the releases.

“The more colored the water is, it’s not going to reach the bottom and then the sea grasses are going to suffer,” said Dr. Rumbold. “So that more long-term impacts of loss of acre of oysters, filtering the water, is probably a lot better than an acre of storm water treatment areas,” said Dr. Rumbold.

That's because both oysters and sea grass will pull nutrients out of the water.

Nutrients can feed red tide and other harmful algal blooms.

“It’s really sad that we are killing things that could help the water quality,” said Dr. Rumbold.

But, Dr. Rumbold says given the cooler water temperatures right now, pulses like the U.S. Army Corps are doing might be enough to save the adult oysters populations.

However, if these releases continue beyond the current plan of April 1 into the warmer months, those same oysters will struggle.

“You are going to have to reconsider the duration of the stress, because they are already going to be under stress from the heat,” said Dr. Rumbold.

Fox 4 Meteorologist Andrew Shipley asked Dr. Rumbold if he thinks the oyster populations that once thrived in the Caloosahatchee estuary will ever return up the river given where we are at with releases.

“Some people actually want to have oyster gardens up by the City of Fort Myers," he replied. "I'm not sure if they will ever have oysters, they might have for one year, with small newly settled spat, but I don’t think we will ever have the flexibility and the opportunity to have oyster all the way up there.”

Dr. Rumbold says a good goal would be if we could get oysters as far inland as the Cape Coral Bridge.