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Oysters continue to face stressors from all angles in Estero Bay

Posted at 11:39 AM, Apr 17, 2024

ESTERO BAY, Fla. — Oyster reefs are critical to our ecosystems here in Southwest Florida. What would happen if we were to lose them? What stresses are they seeing? Fox 4 Meteorologist Andrew Shipley asked a Marine Biologist Melissa May at Florida Gulf Coast University to find out.

"For the last three years we have been trying to understand if the oyster reefs in Estero Bay are healthy, because they filter lots of water,” said May. “They are a sign of ecosystem health."

While studying this reef, two events sparked an additional search for Dr. May. The first of those events being Hurricane Ian.

"When we came out after the hurricane things looked the same as it basically looks now,” said Dr. May. “Other than there were pockets of trash."

Ian's surge submerged the oysters. But that same surge brought concerns of poor water quality post storm.

"So, what we think happened from all the debris deposited was that household chemicals and cars and diesel fuel and paint leached into the water and over time that stuff started to build up in the oyster tissue,” said Dr. May. “So, we found that by November they were starting to so minimal signs of stress."

That has led Dr. May to new experiments to see if these oysters still have contaminants in them from the storm. But while post Ian there was concern, that concern was exponential this past summer.

"So, there was an extreme heat wave last July, where temperatures, even water temperatures, were close to 95,” said Dr. May. “We were recording water temperatures in the shallow parts of the reef of 95 regularly. Which is near the upper limits of what oysters can tolerate."

"So, after Ian there was maybe a two time increase in stress levels and during that heat wave it was like 20 or 30," said Dr. May.

Stress levels in the oysters were so high, Dr. May asked herself what happens if we start to have a large-scale mortality event.

"So, if the oysters were to disappear your water becomes muckier, there is more stuff in it, and usually that has a very negative impact on other organisms," said Dr. May.

"The other species that are not as good with dealing with those stressors have to leave,” said Dr. May. “So, you can get things where only crabs will live here. Your fish populations will go. It really causes large-scale shifts in the ecosystem and make it not as great for ecotourism."

Unfortunately, with a warming planet, heat waves like last summer could become even more common. That heat in combination with those stressors could spell more trouble for the oysters in southwest Florida.

"One thing that can be problematic about multiple stressors is they might be able to handle a temperature range of 70 degrees, but when you add in low salinity that shrinks down to like 50,” said Dr. May. “And if you add in low food that shrinks down even more. The more stress you pile on them the less adapted or less capability they have to actually deal with that stress. So, we start to see morality events happen a lot more quickly."

More deadly events are the last thing oysters need. Globally, 85% of earth's oysters reefs have been lost.