A scientist is challenging a state report that says there is no clear evidence that toxic red tide is on the rise in the waters off southwest Florida.

“Red tide is more abundant,” said Larry Brand, a professor of marine biology at the University of Miami. “You can count on it getting worse.”

Brand was part of a panel that spoke Sunday to about 170 people at a Sierra Club red tide community forum on St. Pete Beach.

A recent study by Florida’s Fish and Wildlife Research Institute found data collected between 1954 and 2006 was too scattered to show a trend in red tides.

Brand said he was able to filter the results and document an increase in nutrients off Florida shores that has fed a 14-fold increase in red tides since the 1950s.

He said the most likely source of the increase is the state’s fast-growing human population, who are dumping increasing amounts of sewage, fertilizer and other nutrients into Florida’s waters.

Cynthia Heil, a senior research scientist and harmful algae bloom group leader at the institute, disputes Brand’s analysis. Nutrients also come from natural sources and there is no evidence of a single source contributing to increased red tide in Florida, she said.

“We really can’t analyze the data,” Heil said. “Are we seeing an increase in red tide? We can’t really tell from this data set.”

Red tide is formed when a microscopic algae reproduces at an explosive rate. The algae produces a neurotoxin that can paralyze or make breathing difficult for fish, manatees or even humans that inhale or ingest it.

Florida was hammered by a record red tide bloom in 2005. Officials said the financial impact of the 2005 red tide, which expanded at one point cover to about 25,000 square miles in the Gulf of Mexico, is impossible to estimate. Estimates ran from $49 million to $240 million in the Tampa Bay area alone.

Frank Muller-Karger, a professor of oceanography at the University of South Florida, said the red tide this year is less severe, but he said the federal and state governments must devise and pay for a comprehensive study of the problem.

“There is not one technique that is going to work this out,” he said. “I understand the state of Florida is putting some money into this. But the federal government has actually shrunk in terms of red tide funding. We need to fund the science.”

Scientists are now tracking a red tide bloom off southwestern Florida between Sarasota and Collier counties. Dead fish are washing up on some beaches. Some people are complaining of respiratory distress caused by red tide. In July, eleven people in Lee County were hospitalized after contracting neurological shellfish poisoning from scallops they picked illegally from red tide-contaminated waters.

Some southwest Florida business owners, who saw the 2005 tourist season ruined by thousands of dead fish washing up on Florida beaches, want action now.

“I get the impression they’re moving forward, but very slowly,” said Lenne Nicklaus-Ball, vice president of the Sirata Beach Resort on St. Pete Beach. “When they say we can’t prove this and we can’t say that, they’re not giving us the answers we need. The state of Florida needs to wake up.”

Brand said Florida can’t afford to wait for a perfect answer.

“When you’re dealing with a complex ecosystem, there is no such thing as absolute proof,” he said. “If you do something now, it will take years to see the effects.”