EMILY ANTHES and CURTIS KRUEGER
A giant patch of the algal bloom is sucking oxygen from waters off Pinellas and Pasco counties, killing sea life and wreaking environmental harm.
Fishing and diving off Pinellas and Pasco counties could be disrupted for more than a year because huge numbers of fish are dying in an oxygen-starved zone of the Gulf of Mexico.
Data released Tuesday show oxygen in the gulf has dropped to severely low levels in an area that begins about 10 miles off the coast of mid Pinellas County and extends north to Pasco County.
Scientists say it appears the phenomenon was brought on by an especially long-lived episode of Red Tide, which has been blooming in the gulf since January.
Wayne Genthner, captain of Wolfmouth Charters and an avid scuba diver, calls it "one of the greatest environmental disasters in the history of Florida."
Most scientists won't go that far. But all agree it's a serious problem that hurts diving, angling and tourism, along with the environment itself.
The newest scientific evidence, from the state Fish and Wildlife Research Institute, confirms what divers and fisherman have been saying for weeks: The oxygen-depleted areas have turned into fish graveyards.
Boaters have found goliath grouper bobbing dead on the gulf's surface and sea turtles too weakened to dive. Divers have searched the sea floor, only to find dead sponges and coral and shells of crabs with no living animal inside.
"It's been devastating ... there's just massive fish kills," said Dave Mistretta, captain of the Jaws Too fishing boat in Indian Rocks Beach.
Cynthia Heil, senior research scientist at the institute, said the effect on marine life on the sea floor is the worst since a massive Red Tide bloom in 1971.
Longtime beachgoers along the Suncoast are familiar with Red Tide, a toxic growth of algae that can kill fish. Outbreaks also can cause respiratory problems in humans.
But this episode is much more severe, Heil said, and unusual because it came so early in the season. Red Tide is most common in the fall. This outbreak began in January and has lasted through summer.
This summer bloom is occurring when the gulf has a strong "thermocline," a layer of water where the temperature changes quickly.
The thermocline, which separates the warmer surface water from the cooler bottom water, traps the toxic bloom near the bottom of the gulf, worsening its effects there, Heil said. When the algae's toxins kill fish, bacteria breaking down the dead matter rob the water of oxygen.
The strong thermocline also prevents oxygen produced near the surface from descending. Both the depleted oxygen levels and the Red Tide can kill fish.
Many anglers and divers have seen the evidence firsthand.
Genthner, the scuba diver, said he saw fish die before his eyes, dropping to the bottom of the ocean like dead leaves. Big and ancient conch shells that Genthner had watched for years have vanished.
"The worst part is what you feel when you see what used to be a cornucopia of beauty and grace, beautiful tropical fish and coral and big strong grouper, and all of that is eliminated," he said. "It draws the life out of you. That stuff really hurts."
He said he used to do about $3,000 a week in charter business. Some weeks this summer he only earned $300, he said.
Herman Maddox, captain of the Sea Fox dive boat in Dunedin, said he sailed out through Hurricane Pass on Sunday and saw dead fish bobbing about 7 miles off shore. He stopped 10 miles out and dove, but the water was "a milky greenish color with about 3 feet of visibility down to about 25." At 40 feet below, visibility was only 1 foot.
Later, they sailed 12 to 14 miles off shore and dove again. "At 38 feet it went black," he said.
He said he also came upon a sea turtle Sunday, but it was too weak to dive away, as they normally do when a boat approaches. He said he took it to the Clearwater Marine Aquarium.
Sea turtles are facing problems because of the Red Tide, which is forcing them to swim through a "sea of death" to lay their eggs on shore, said Joe Murphy, coastal protection campaign coordinator for the Sierra Club. And the young turtles have to swim back out through it, he said.
The Mote Marine Laboratory has documented an unusually high number of sea turtle deaths the past three months, which it says can likely be attributed to Red Tide. Between Aug. 1 and Monday, the lab recovered 33 dead turtles. During the entire month of August, the lab typically recovers between five and nine. An additional 21 dead turtles were reported in July, and 18 in June.
Although oxygen-starved zones like this can occur naturally as an outgrowth of Red Tide, some environmentalists say longstanding pollution in the area has made the ecosystem more fragile. They say that could make it more difficult for marine life in the gulf waters to recover.
"If we had healthy coastlines, occasional natural blips wouldn't be as concerning as they are today," Murphy said. In the past few years, he said, coastline health has deteriorated from pollution, hurricane damage, other Red Tide outbreaks and additional factors.
Larry Brand, a marine researcher at the University of Miami, said most scientists agree that Red Tides in many parts of the world are getting worse.
It's unclear why, he said.
Brand said it's likely increased pollution, wastewater and other runoff from land in the past few decades could be exacerbating Red Tide blooms.
"My guess is that the increased nutrients from land runoff are having an effect," Brand said at a Sierra Club news conference Tuesday. "Maybe it's just a coincidence. We need to do more research."
The good news is that recovery is possible. The 1971 Red Tide created oxygen-starved zones similar to those observed this year, Heil said. That year, scientists also documented mass deaths of marine life and coral reef inhabitants in roughly the same area as this year's zones.
But in about 18 months, fish had come back. And within five years, their populations had been restored to normal levels, according to the Research Institute.
"This presents us with an opportunity to actually examine how those communities did recover," Heil said. She said more study also is needed to learn how and why the Red Tide and the oxygen-depleted zones developed.
There already is evidence of improvement. In certain sites that the institute has been testing weekly for over a month, oxygen levels have been increasing, she said.
But some are skeptical about how much recovery is possible. Genthner said he does not expect a full recovery even in five years, because the water quality is poorer now than it was in 1971 and the damage is so great.
"This is not like some goldfish dying in your tank and you shed a tear and flush him down the toilet," Genthner said. "This is the tank. This is everything."
Times staff writer Curtis Krueger can be reached at email@example.com or at 727 893-8232. Times staff writer Graham Brink and Times researcher Angie Holan contributed to this report.