Thursday, September 06, 2007
By Elizabeth Middleton
As Kathy Malaxos recently slid her green kayak into the water near Cooper's Bayou Park in Clearwater, the muck was so thick and so deep that it sucked her shoes off.
"It's slick slime," the Safety Harbor resident said. "Your feet get pulled into it."
That muck - and, more specifically, what is in it - is the subject of a $149,494 environmental study by the Southwest Florida Water Management District, commonly known as Swiftmud. The study will address the accumulation of sediment, silt and mud in the Safety Harbor watershed of Old Tampa Bay.
Researchers hope to determine the source of the muck buildup in the Safety Harbor basin and whether it affects organisms that live and feed in the sediments.
"We don't know at this point if it is causing ecological harm," said Holly Greening, senior scientist with the Tampa Bay Estuary Program, a partnership of federal, state and local environmental agencies and a co-sponsor of the study.
Old Tampa Bay was once home to white beaches, blue crabs and oysters. Over the years, however, the Safety Harbor watershed that flows into the bay has been transformed from rural to residential and industrial uses.
"The perception is that there has been a rapid accumulation of organic sediment in the Safety Harbor water basin," Greening said. "We want to look at the extent and volume of the muck."
Scientists plan first to map the contour and depth of the muck using a side-scan sonar. Then they'll take core samples of sediment and other organic material and analyze them to determine the source of the muck.
"We don't know if it's from plants, animals, algae or man-made materials," Greening said.
Using sophisticated techniques, researchers will measure the levels of nitrogen and phosphorus in the muck, giving them an "isotropic signature" of the muck's origin. Different kinds of organic matter can be identified by their distinct ratios of nitrogen to non-nitrogen molecules. By looking at the muck's chemical fingerprint, scientists will determine whether it's caused by natural land uses or man-made compounds such as lawn fertilizer.
That's important because the nitrogen in fertilizer can cause giant algae blooms in water. As microscopic algae cells die and decompose, they eat up oxygen in the water, choking and killing fish, grasses and shellfish.
Increased development and the paving over of previously grassy areas also affect the watershed. Instead of seeping into the ground, rain flows across concrete and asphalt, picking up pollutants along the way.
Construction of the Lake Tarpon Outfall Canal, which connects Lake Tarpon to Old Tampa Bay, may be a contributor. The Army Corps of Engineers dug the canal in 1968 to prevent flooding around Lake Tarpon after heavy rains.
"We may be able to tell if there is a link between the muck and the change in salinity from freshwater discharge into the watershed," said Lizanne Garcia, Swiftmud's project manager for the study. The amount of silt that flows into the bay from the canal also will be studied.
The study also will look at water clarity and sea grass. Sea grass provides a habitat for shellfish and other animals, making it a sign of a healthy ecosystem, but it needs good, clear water.
Testing will begin next month and is expected to take about a year. The study will be conducted by the University of South Florida's College of Marine Science, Eckerd College and the U.S. Geological Survey. Pinellas County and the cities of Oldsmar, Clearwater and Safety Harbor have also budgeted funds for the project.
Researchers will report their findings to Swiftmud and the partners of the Tampa Bay Estuary Program.
What happens next will depend on the agencies in the estuary program, but it could include removing the muck and educating residents about the impact of their activities on water quality.
"Everyone lives in a watershed," Swiftmud spokeswoman Robyn Hanke said. "How you fertilize, how you dispose of grass clippings - everything you do affects the watershed area."
What will be done?
1. Scientists plan to map the contour and depth of the muck using a side-scan sonar.
2. Then they'll take core samples of sediment and other organic material and analyze them to determine the source of the muck.
3. Using sophisticated techniques, researchers will measure the levels of nitrogen and phosphorus in the muck, giving them an "isotropic signature" of the muck's origin.
4. By looking at the muck's chemical fingerprint, scientists will determine whether it's caused by natural land uses or man-made compounds such as lawn fertilizer.
St. Petersburg Times
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