Florida Keys News
Wednesday, January 22, 2014
Early signs good for bay

SOUTH FLORIDA -- All signs say that a $26 million project aimed at improving water quality in Florida Bay has already made a difference after one year of operation, researchers at Audubon of Florida's Tavernier Science Center say.

"The short-term goals were higher flow, lower salinity and higher vegetation, which is exactly what we got," Jerry Lorenz, the biologist who heads the Tavernier Science Center, said recently.

But officials with the South Florida Water Management District, which built the C-111 canal and water retention project, are more cautious in their assessment.

"Really, from a scientific standpoint, it is probably way too soon to draw those conclusions," said Terrie Bates, division director of water resources for the water district. "You are just one year into operation of a project that is trying to reverse decades and decades of alteration."

Still, everybody agrees on one thing: Phase 1 of the C-111 project is functioning as intended. As a result, water managers are able to keep more water in Taylor Slough, Florida Bay's main freshwater tributary, rather than having to send it east through the South Florida canal system.

Consequently, more freshwater is now heading into western Florida Bay, where it is most needed. Scientists believe that reducing salt levels in the bay is a key to reviving its ecosystem.

The new retention and pump system went online fully in June 2012. At the time, said Lorenz, the salinity level at the three Florida Bay monitoring stations that Audubon charts in the Taylor Slough vicinity averaged 13 parts per thousand. By last June that number had dropped to three parts per thousand.

That 80 percent drop was much more pronounced than what Audobon found at monitoring stations outside the area where the C-111 project is delivering freshwater. For example, at Audubon's three eastern Florida Bay monitoring stations, salinity dropped less than 50 percent during those 12 months, from 17 to 10 parts per thousand.

Salinity levels, though, routinely vary in Florida Bay, and rainfall patterns have a major impact on how salty the water is at any time. Rainfall differs not only in quantity from year to year but in where it falls. In a particular year, for example, rain can be heavier than usual in the eastern bay and average in the western bay.

In an attempt to ferret whether the salinity drop was due to rainfall or the new restoration system, Audubon compared western Florida Bay salinity levels in June 2013 to the levels in June 2009 -- the end of a 12-month rain cycle that was nearly identical to 2012-13, Lorenz said. Salt content in June 2009 was more than five times as high as it was last June.

Lorenz said the low salinity levels last June have been accompanied by a five-fold increase in the vegetation beneath Taylor Slough. Ultimately, such increases in vegetation should lead to larger population of forage fish and those increases, in turn, should work their way up the food chain to the gamefish and wading birds for which Florida Bay is beloved.

Lorenz acknowledges that one year is too soon to draw a scientifically valid conclusion about the cause of the burgeoning vegetation beneath Taylor Slough and the lower salinity levels in western Florida Bay, but that doesn't mean he's not confident.

"When we see something that is strange and out of place for my 25 years of experience, and coincidentally, we had a $26 million project come on, I go, 'Wow,'" he said.

Lorenz isn't the only one who has documented short-term improvements near Taylor Slough that have coincided with operation of the new canal and water retention system. Florida International University biologist Tom Frankovich, who monitors aquatic vegetation in lakes that separate central and west Florida Bay from the mainland, has made similar observations.

In West Lake on the southern edge of the Everglades National Park mainland, for example, an aquatic grass called chara is viewed by scientists as a sign of good water quality. Chara cover was up throughout the lake last winter compared to the winter of 2011-12, before the project when online.

Another good sign, says Frankovich, is that migrating winter coots and ducks, which feed on chara, have returned to West Lake with a vengeance. Frankovich recently saw what he estimated to be 20,000 coots and ducks on the lake. He said he's never seen more than an estimated 5,000 at one time before.

Still, he's hesitant to attribute the changes to the C-111 project. West Lake's chara cover, for example, was already on a fast rise the winter before the project went live.

He said more will be learned about how the pump and retention system is working when the relatively wet weather of the past 18 months gives way.

"What's going to happen during droughts?" Frankovich said. "That's going to be the key."

Meanwhile, Everglades National Park's lead hydrologist says more time and data will help determine if the project has truly improved water quality in western Florida Bay.

"You can't take any one event or any one year and attribute cause generally," said the park's Kevin Kotun.

rsilk@keysnews.com

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