Ancient shells transform into thriving oyster reef in Caloosahatchee River

LEE COUNTY, Fla. —

The Sanibel Captiva Conservation Foundation has built a three-acre oyster reef at the mouth of the Caloosahatchee River, using ancient shells to enhance water quality and support marine life.

Located about a mile off the coast of Shell Point, where the Caloosahatchee meets San Carlos Bay, the reef was constructed by marine scientists.

"It's working right, exactly, because they are foraging. They are finding small crabs," Doctor Eric Milbrandt with the SCCF said.

The project aims to address the loss of oyster reefs, with 90% of them having been destroyed, often used for roadways.

"We've lost 90% of our oyster reefs, and a lot of those reefs were just put on barges and used for roadways," Milbrandt said. "It's like if we can replace them, we have a lot of work to do obviously, but this is one step towards that."

In just six months, the reef has become a hub for various marine species.

"So right now the birds are using it. They are finding nooks and crannies but as you can imagine, as the tide comes back in, all the fish that are in the surrounding area or maybe finding small pools to hide under the smaller fish, the crabs that all come out and start foraging on the surface and then eventually the larger fish will come and so it's kind of like a smorgasbord for juvenile redfish," Milbrandt said. "They come in, they've been able to go downstream of and just sit and heat whatever is coming off the reef."

Oysters play a crucial role in filtering water, with each oyster capable of filtering 50 gallons of water per day.

"So the amazing thing about oysters is that they filter 50 gallons of water per oyster per day and right now you probably have 200 oysters per square meter, about half your dinner table but in two years, we'll have a thousand oysters per square meter and that has a tremendous benefit in terms of clearing the water and helping to remove nutrients from the water," Milbrandt said.

The shells used for the reef were sourced from a former orange grove on the Lee-Charlotte line.

"See that ledge right there. That's where your shell starts. So that layer down here, that is probably 12-13 feet of shell to get to this level. This is where those shells were that you saw in the restoration," said Joe Rice with Bermont Materials, which provided the shells.

The shells, buried for centuries, are now helping to filter and feed marine life once again.

"You can see today even, over the reef where there is water, how clear the water is, and that's because the filtration process is already occurring," Milbrandt said.

However, the impact on the whole bay is limited, highlighting the need for more reefs. "In terms of the whole bay, it's only going to have a very small impact on the area around the reef, which is why we need to build more reefs," Milbrandt said.

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