A toxic algae bloom is spreading along the Texas Gulf coast, killing millions of fish and fouling beaches with their remains.
State environmental regulators call the red tide concentrations the largest since 1986 when a strain passed through the region, killing more than 22 million fish in a four-month period.
The latest growth over the weekend has resulted in enough concentrations to be seen by the naked eye and cause respiratory irritation in humans.
Texas Parks and Wildlife Department biologists observed red tide on Sunday in the Corpus Christi Bay near downtown. Red tide was also spotted in the Oso Bay and near the Port Aransas jetties.
"We do not have an accurate number yet. But we are estimating several million fish have been killed so far," Dave Buzan, spokesman for the TPWD Kills and Spills Team, told the Corpus Christi Caller-Times in Monday's editions.
He said one visible bloom off Matagorda Bay appeared on Sept. 18.
"It is so big it can be detected on satellite imagery," he said.
In the Houston area, officials said Sunday that the tide that had infected Gulf of Mexico waters was dispersing into inland waters, including Galveston Bay.
"It's terrible," Richard Napoli, co-owner of Capt. Nap's Marina along the Texas City Dike. told the Houston Chronicle.
He said a shrimper pulled in a net half-filled with dead fish Saturday. On Friday, nearly a dozen three-pound flounders and trout were found along the dike.
A high concentration of microscopic algae producing a toxin, red tide affects the central nervous system of fish and kills them. While the fish kills usually consist of schooling species, such as mullet and menhaden, the algae has a domino effect on other marine life.
For humans eating contaminated fish or shellfish, the toxin can cause numbness, dizziness, nausea, fever and muscle paralysis. The most serious cases can result in respiratory arrest and death.
Health risks to humans who swim in affected waters include breathing irritation, scratchy throat and itchy, red eyes. People with asthma or other health problems could be sensitive to toxins released by the algae.
Red tide earlier this month was discovered in the waters off Galveston Island for the first time since 1986. It killed tens of thousands of fish.
"Some (fish) do not die from red tide," said Wes Tunnell, director of the Center for Coastal Studies at Texas A&M University-Corpus Christi. "They die from lack of oxygen."
Commercial harvesting of oysters in Galveston Bay has been shut down since Sept. 5 because of red tide. Officials with the Texas Department of Health's Seafood Safety Division are reviewing whether similar restrictions need to be issued in the Coastal Bend. Oyster season doesn't open in Corpus Christi until November.