Oysters on the decline in Cedar Key and Big Bend

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Mollusks important ecologically and for fishing industry

By Mark Scohier

 Reduced freshwater flow from the Suwannee River into the Gulf is responsible for a 66-percent decline in oyster populations in Cedar Key and the Big Bend area, according to scientists from the University of Florida.

“We have not seen evidence of oysters on sandbars coming back to a healthy reef,” said Jennifer Seavy, a UF ecologist who has been studying the area since 2009.
Seavy told a group of more than 50 people in Cedar Key Saturday that aerial photography in the last 30 years, combined with two years of site surveys at oyster beds show a decline in reefs at Horseshoe Cove, Lone Cabbage, Corrigan’s and Suwannee reefs.
Worldwide, scientists say oysters are disappearing because of over-harvesting. A study published last year by the American Institute of Biological Sciences states that 85 percent of oyster reefs are gone.
But in the Big Bend, according to Seavy, the decline can be attributed to higher levels of salinity resulting from years of low flow coming out of the Suwannee. Higher salinity levels, coupled with warmer temperatures, increase disease and predation, which weakens reefs and causes them to be broken up by waves, Seavy explained.
Rising sea levels, attributed to climate change, is also a factor contributing to high salinity levels, she said. Oysters have been dealing with gradually rising sea levels for thousands of years, but not on the scale seen in the last 30.
“So, it’s kind of like a one-two punch,” she said.
A 66-percent loss in 30 years is a “fundamental change to the system,” she said, adding that some of the reefs are estimated to be thousands of years old. “This is a huge loss for ecological services.”
Seavy said the disappearing mollusks are important for a number of reasons. “Oysters are called environmental engineers,” she said.  They help protect coastlines by dissipating wave energy, they create habitat for other species and are “renown for their ability to filter water,” something that helps support the fishing industry that brings millions of dollars in economic benefit to the region each year.
Ricky Cooke, president of the Cedar Key Oysterman’s Association in attendance at Saturday’s meeting, said the findings of the study were, in his experience, accurate.
“The day a group sucks water out of the Suwannee, it (the fishing industry) will all be gone,” he added.
Recently, Florida’s water districts, under policies set by Gov. Rick Scott, have come under fire for granting huge water withdrawal permits to large cities and the agricultural industry. David Still, who was director for the Suwannee River Water Management District before he resigned last week, says groundwater in several basins in the district could be tapped out in 20 years. Still is one of four water district directors to resign from Florida’s five districts since Scott became governor.
Also in attendance at Saturday’s meeting, Andrew Gude, director of the Lower Suwannee National Wildlife Refuge, said, “Our biggest challenge right now comes from outside.”
Water quality and quantity are both being affected by agriculture and municipalities outside of the area’s watershed, he said.
Agriculture, attributed to most of the high nitrate pollution in area springs and rivers, is the biggest user of water in the tri-county area, though studies show densely populated cities like Jacksonville and even Gainesville, to a lesser extent, are having an effect on the water table in areas like Levy County. Scientists say water withdrawal from Jacksonville is so strong it has changed the geological contours that once diverted more of the water filtering down from Georgia to wells, springs and rivers in the 14 counties managed by SRWMD.
“Any straw you stick in the ground is going to have an effect,” Still said in a recent phone interview.
Couple large withdrawals with record-breaking drought and the most visible result is the trickle that the Suwannee River and some of its springs have been reduced to in some parts of the district. Area wells have set records for all-time lows, and flow levels in some places are lower than they have been in almost a century. Some springs along the middle Suwannee have completely ceased flowing.
But there’s still hope for oysters, Seavy said.
“If you build it, they, the spat, will come. And then they will go and come back again. The reef is dynamic.”
Spat, as Seavy calls it, is the term for the larvae that later become mature oysters. And it’s abundant, but because oysters are not re-colonizing historical reefs, added measures, in the form of artificial reefs, need to be considered, she said.
A few years ago, at the suggestion of UF aquaculture extension agent Leslie Sturmer, a manmade reef made from spat- laden clam bags was constructed near Atsena Otie Key.
“This reef is growing,” Sturmer, also at the meeting, said. About 4,500 hundred bags, each containing up to 8,000 oyster larvae, were purchased from clammers to construct the reef. Clammers consider the spat filled bags fouled, she said. “But an oyster person sees this and sees treasure.”
Seavy said the Big Bend area, despite suffering from decreased fresh water flow, has lots of advantages for oysters. The area is not heavily developed, and oysters have been shown to grow faster in the Gulf, maturing about three times faster than they would in other areas. And inland oyster populations, those living in the marsh, continue to do well and make up about 30 percent of current oyster numbers.
Seavy said there are plans to continue monitoring the reefs, working at restoration and studying associated issues, such as the impact the decline might have on other species like the American Oyster Catcher bird, a species whose highest density in breeding season is found in the Big Bend area.
“There’s a huge impact on other species,” she said.