For beachgoers in the Tampa Bay area, the last few weeks have been anything but normal. Discolored, soupy waters have been lapping the shore, and the beaches are laden with dead, rotting sea life.

Maya Burke, a lifetime resident of Pinellas County, knows the sights — and smells — at this time of year are anything but normal.

"The bay is really hurting right now," she said. "It's significant numbers of dead fish all up and down the food chain, from small forage fish all the way up to tarpon, manatees, dolphins. ... If it's swimming in the bay, right now it's washing up dead."

The hordes of fish were killed by a red tide, a large "bloom" of toxic algae that appears on Florida's Gulf Coast about once a year. Exposure to blooms can cause respiratory irritation in humans. To fish and other sea animals, they can be deadly. But Burke, who serves as the assistant director of the Tampa Bay Estuary Program, and ocean scientists agree: A bloom of this intensity shouldn't be happening in Tampa Bay right now.

Fish have been washing up on the bay's shore since early June, floating in from massive clumps out at sea where they first collected at the site of blooms, called "fish kills." Possibly because of strong winds created by Tropical Storm Elsa, fish have been piling on shores in much larger and smellier quantities. The worst of it is being seen now in nearby St. Petersburg.

Algal blooms are natural — the timing and severity are not

The microscopic algae that create red tides, known as Karenia brevis, are naturally found in the waters of the Gulf of Mexico. But intense blooms are rarely seen in the summer in the Tampa Bay area, according to Richard Stumpf, an oceanographer at the National Oceanic and Atmospheric Administration.

Blooms typically begin in the fall and go away by January, but summer blooms in the area have occurred a handful of times in more recent history: 1995, 2005 and, most recently, 2018.

"This is not normal," Stumpf said. "The fact that it's been three years since the last one is not good."

Officials have cleaned up 600 tons of dead sea life

St. Petersburg city officials have said the red tide seems even worse than in 2018, when a long-lasting bloom killed sea life as large as manatees and dolphins, caused widespread health effects and drove tourists away from beaches.

Cleanup efforts are ongoing, with no end in sight. Some fish have to be picked up by hand, and crews must quickly remove rotting fish or else the nitrogen-hungry algae will only continue to feed on their nutrients, Burke said.

The Pinellas County solid waste division has reported that since late June, 600 tons of dead sea life have been collected by cleanup crews throughout the county. During a news conference, St. Petersburg's emergency manager, Amber Boulding, said more could wash to shore until the bloom moves away. When that will happen, according to Stumpf, is unknown.

"We scrape the beaches. We get it cleaned up — as soon as those tides change, we have fish right back in," Boulding said. "We don't know the end of it."

The reason for the red tide's severity and location is under debate

Another unknown that Florida faces is what has made this summer's bloom so severe. Rainfall, wind and the amount of phosphorus and nitrogen in the water can all play a part, according to Stumpf, but the cause cannot yet be confirmed.

Tom Frazer, dean and professor at the University of South Florida's College of Marine Science, said at a recent discussion at the Fish and Wildlife Research Institute in St. Petersburg that a wastewater spill at a phosphate plant in April could be fueling the outbreak, but isn't the cause.

No matter the cause, Burke says the untimely results of this summer's red tide are gruesome.

"It's just not the bay that we're used to seeing," she said.

Josie Fischels is an intern on NPR's News Desk.

Copyright 2021 NPR. To see more, visit https://www.npr.org.