Dead Goliath grouper, tarpon, snook, sea turtles, manatees. Fishing guide Chris O'Neill has filmed them all this week while documenting the effects of a strong red tide bloom that's lingering off the Southwest Florida coast. "It's pretty bad, and it smells like massive death," O'Neill said. "I saw a manatee and a sea turtle and six tarpon dead in one small body of water. I only had to look for a couple of hours. It wasn't hard to find. I could see about six Goliaths laying on the beach at Boca Grande." Dead fish have been washing up on Southwest Florida beaches for months now, since a long-lived bloom started in October. But mostly those fish were mullet, which will actually eat the red tide, and small baitfish, which can't swim far distances to escape the toxic algal blooms. Now breeding-age gamefish like snook, grouper and tarpon are dying, a sign that the bloom has become more intense in coastal waters. "I've spent 10 years studying Goliath grouper and tagging them, and I just watched the whole population of Charlotte Harbor die," O'Neill said. "The future of the fishery was cut off at the knees." The bloom has stayed largely in the Lee County area but now stretches from just south of Tampa Bay to the Collier-Monroe border, according to the Florida Department of Environmental Protection. The organism that causes red tide here (Karenia brevis) occurs naturally but can bloom to deadly levels when conditions are right. Excess nutrients from farms and developed areas help fuel the outbreaks, increasing the duration and intensity of the blooms, experts say. Fish kills were reported this week in Captiva, Boca Grande, Gasparilla Island and Useppa Island, according to FWC records. The National Weather Service issued a hazardous beach conditions warning for Lee and Charlotte counties Tuesday. Red tide also causes respiratory issues in humans, with symptoms ranging from a scratchy throat to more severe breathing problems. "There was heavy respiratory irritation and fish kills in the Boca Grande area," said Hayley Rutger, with Mote Marine Laboratory in Sarasota. "A number of areas in Southwest Florida are forecast to get respiratory irritation. Lee has anywhere from low to high depending on where you are." More intense concentrations are being found in Charlotte Harbor and northern Pine Island Sound, according to the University of South Florida's College of Marine Science. USF models show the bloom moving inland over the next three days. Rutger said a state forecast shows the red tide bloom staying in place over next few days."They're looking at varying patterns over the next few days, although minimal movement is expected," Rutger said. "We have some changes and patterns, but the overall movement isn't much." "I'm congested right now," said O'Neill, the fishing guide. "I have breathing issues from the last two days of being out here. Certainly someone with respiratory problems would be in danger."