Scientists search for 'smoking gun' in the dead zone of Florida's red tide

Dr. Mike Parsons of Florida Gulf Coast University is looking for evidence far off shore.

ff Sanibel Island, Florida (CNN) — On a good day, a beach trip to Sarasota or a boat trip out of Fort Myers can be a sun-kissed adventure filled with relaxation and anticipation.

These are not good days.

The infamous "red tide" has turned southwest Florida into a tragic dead zone with miles of deserted beaches and boatfuls of dread.

The worst toxic algae bloom in recent memory is plaguing paradise and no one has any idea how long it will last and whether this is the new normal.

Fish are seen washed ashore on Sanibel Island.

"Back in 1994 we had an outbreak and it killed 196 manatee," says Bob Wasno, a marine biologist with Florida Gulf Coast University. "Everybody was just completely outraged. They yelled and jumped up and down and said 'This is not going to happen again.' Here we are 24 years later and this is worse than ever."

The daily sightings of dead dolphins and lifeless sea turtles, beaches covered in rotting fish and the first recorded loss of a massive whale shark are all the result of a tiny organism known as Karenia brevis. It occurs naturally in saltwater, produces a neurotoxin deadly to most fish and marine mammals and is potentially harmful to humans.

But while red tides have broken out in Florida for centuries, scientists believe they may be getting worse after generations of unchecked development, water mismanagement and the new scourge of climate change.

"The real question is exactly what role (human) activity is playing on red tides," says Dr. Mike Parsons, a red tide expert at Florida Gulf Coast University. "Between water discharges, our use of agricultural nutrients, the development of Florida and warming seas -- are we poking the bear?"

I rode along as Parsons and his colleague, Dr. Bill Mitsch, set out to sample water 20 miles off the coast of Fort Myers.

It's where the briny Gulf of Mexico mixes with the fresh water that flows down the Caloosahatchee River from Lake Okeechobee, and Mitsch hopes it will yield an answer. "I'm looking for the smoking gun," he says.

Generations of sugar cane farming has altered the chemistry of Florida's biggest lake and a vast system of dikes and dams built to "drain the swamp" and create a retirement wonderland has killed half of the Everglades and put the rest of this vital wetland on life support.

In the wet season, Florida dumps massive amounts of Okeechobee's nutrient-rich water into the most delicate ecosystems, while in the dry season, that water is diverted to farms and cities.