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More scientists are committed to researching ways to control red tide, but it may take some experimental practices to come up with answers, scientists at a public meeting broadcast from Mote Marine Laboratory said Thursday.

Scientists attending the four-day red tide workshop at Mote said they still cannot definitively say that freshwater runoff from rivers, such as the Caloosahatchee, causes harmful red tide blooms, but they have detected some possible remedies.

Red tide is the common name for blooms of microscopic algae, called Karenia brevis. The algae releases a toxin that kills fish and causes coughing, sneezing and watery eyes in some people.

One of the more controversial experimental remedies to the blooms, discussed by about 70 scientists from across the nation who attended the workshop, was a process called clay flocculation, which is to spray tiny clay particles over red tide blooms in the ocean, said John Anderson, the meeting’s moderator.

The microscopic algae clings to the clay, which aggregates to form larger particles, Anderson said. The particles then settle to the bottom of the ocean, he said.

Members of the public who attended the public meeting, which was held in Sarasota and broadcast to St. Petersburg and Florida Gulf Coast University, spoke mostly against the experimental method.

“Things are fragile on the bottom,” said Wayne Guthrey, a fishing charter captain in Sarasota. “One thing it doesn’t need is a coating of clay.”

Scientists have already started researching the effects of clay flocculation. Experiments started in test tubes, then moved to thin bags that hung in the water and finally to a limited application of 200 pounds of clay.

The clay that falls to the bottom can kill shellfish, such as oysters and clams. However, red tide also kills those same organisms, Anderson said.

Guthrey said he also was concerned that initial experiments used clay generated by Florida’s phosphate industry. “I do not trust the phosphate industry to do one thing good for the state of Florida,” Guthrey said. Where the clay ends up after it falls to the bottom is another question, he said.

The amount of clay on the bottom would be very thin — about the size of a raisin, Anderson said, and it would move to places on the ocean bottom where clay and silt typically accumulate.

Experimentation with clay flocculation is still in the very early stages, but, without the public’s support, answers to significant questions, such as those raised by Guthrey, can’t be answered, Anderson said.

“I think you want us to do those bloom studies so we can answer you on a big scale,” he said. Others in the crowd, however, were more concerned about finding a connection between water running off of land and red tide.

There are 24 theories about where red tide comes from: Seven focus on rainfall and river runoff, six focus on substances on the ocean floor, seven focus on substances in the water column and hydrodynamics, and four are chemically based.

Nitrogen, such as the kind found in fertilizer, is known to feed red tide blooms. There are other sources of nitrogen, as well, another scientist said.

Scientists discovered that red tide feeds on nitrogen from the air, deep water and sewage.

None argued with the logic that reducing nutrients, such as those that come from river water, only could help reduce red tide blooms.

“The issue is how much it contributes to red tide and there is not much information on that,” said Kumar Mahadevan, president of Mote.