TAMPA — Dozens of dead crabs were floating in Hillsborough Bay along Bayshore Boulevard on Sunday, centered near Bay to Bay Boulevard.
Though the die-off extended a few hundred feet in both directions, the cause is a mystery.
Until the bay's water is tested, Red Tide can't be ruled out as a possibility, said Robert Weisberg, a professor and oceanographer at the University of South Florida's College of Marine Science.
"For the last several days there have been high concentrations at the mouth of the Tampa Bay on the south side — Holmes Beach, Anna Maria Island," he said. Though Red Tide "could have been transported" to Hillsborough Bay, Weisberg said he had not seen any observations to confirm it.
Ryan Rindone, a biologist with the Gulf of Mexico Fishery Management Council, said he doubts Red Tide has made its way to Tampa Bay waters but advised residents to remain vigilant.
"The bay is a very large and complicated body of water," Rindone said. "Being that Red Tide is knocking on the door, people should be observant about what is going on. But a lot of things could have happened (with the crabs)."
One possibility, Weisberg said, is that "there is a lot of industry in that end of the bay."
Ari Fustukjian, an associate veterinarian with the Florida Aquarium, cited disease as a possibility.
"Different diseases may flare up due to changes to the water temperature," he said.
The Florida Fish and Wildlife Conservation Commission has not tested Hillsborough Bay for Red Tide. The agency said it did not know if the bay's water would be sampled this week.
The wildlife commission's website says invertebrates can be killed by the low-oxygen conditions resulting from a Red Tide bloom.
Red Tide has spread along Florida's gulf coast for months, affecting beaches in Lee, Charlotte, Sarasota and Manatee counties. The microscopic algae Karenia brevis reproduces offshore, then ocean currents deliver it to the beaches.
Though there has been concern that Pinellas County would be next to be affected by Red Tide, Weisberg said Red Tide could bypass Pinellas for Hillsborough through the shipping channels.
Fustukjian said Red Tide could have also killed Hillsborough Bay crabs by poisoning their food supply, which, depending upon the species, includes sea grass or "oysters, clams and mussels that filter feed."
If crabs "eat enough of them, they will get a toxic dose," he said.
The food supply being poisoned could be an issue facing Florida long after the bloom is gone.
"If it gets into the base of the food chain," Fustukjian said, "we will be seeing repercussions of this for several weeks and months down the road."
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Contact Paul Guzzo at firstname.lastname@example.org. Follow @PGuzzoTimes.