The worst red tide in a decade in southwest Florida continues to grow, decimating fish and bird populations, and prompting businesses to close. In addition to fish and birds, manatees and even a whale shark have died in local waters, according to a Miami Herald story.

The paper reported that dead fish have clogged inlets and canals, and 10 dead Goliath grouper — a species that can live four decades or more — have surfaced. On Tuesday, as hundreds of residents gathered at a Cape Coral yacht club to hear federal officials talk about efforts to deal with water conditions, a dead manatee washed up at a boat ramp nearby.

The extreme conditions have forced some marine businesses to close. Sanibel Island, known for the thousands of shells on its beaches, has started issuing residents a daily status report. It said there are six dead fish for every foot of beach.

In nearby Englewood, Paige Bakhaus shut down her paddleboard business and laid off five employees. “It affects us all when something like this happens,” Bakhaus, who founded her company in 2011, told the Herald. “And my company’s really small, so imagine what it’s like for some of the bigger businesses.”

Sportfishing captains, boat-rental services and sightseeing boats have had to shut down in the midst of fish kills and filthy beaches.

“This is horrific what we’re enduring now, but it needs to be a wake-up call to people that clean water is important to more than just wildlife,” said Heather Barron, a veterinarian and research director at Sanibel’s CROW Clinic wildlife rescue center, which began treating poisoned birds last October. “As the person dealing with all these hundreds of dying animals, I’m upset.”

Red tide is a type of algae that produces toxins. It typically occurs off Florida’s southwest coast each year between later summer and spring. This year’s tide is the worst since the last episode in 2006, which lasted more than a year and killed 250 manatees. Weather forecasters expect hazardous beach conditions to last through the weekend.

Sanibel Mayor Kevin Ruane blamed the red tide on a perfect storm of coastal pollution and a hot Gulf of Mexico ignited by flushing nutrient-laden water from Lake Okeechobee. “All they do is obviously fuel the red tide. So it’s a catalyst in making the problem worse,” Ruane said.

Red tide has been associated with a massive blue-green algae bloom that spread across Lake Okeechobee and moved down the Caloosahatchee River into the Gulf of Mexico.

It is unclear how long the red tide will last. Cold fronts in the winter can flush red tides away from the coast. But Florida still has many hot months ahead. “We’ve had all this rain, and now all these dead fish,” said Rick Bartleson, a research scientist with the Sanibel-Captiva Conservation Foundation. “So we’re not running out of nutrients any time soon.”

“Wildlife is the canary in the coal mine,” Barron added. “It’s the thing telling us your environment is very unhealthy and as a human species you need to do something about it.”