Red tide bloom intensifies off SWFL

A lingering red tide got a boost over the past few days as concentrations rocketed off the coast of Sarasota County this week.

Some of the highest measurements taken were less than 10 miles north of the Lee County line.

Red tide blooms typically start off Sarasota and work their way south toward Fort Myers, Naples and Marco Island.

Karenia brevis is the organism that causes red tides in this region, and concentrations have grown from patchy Friday to 1 million cells per liter and higher Wednesday, according to Florida Fish and Wildlife Conservation Commission reports. Fish kills can occur when levels reach 10,000 cells per liter, which is often enough to make the blooms visible from outer space.

Seafood served commercially must past state tests designed to trace the neurotoxin, so it is safe to buy some fillets at the grocery or have a grouper sandwich.

The organism occurs naturally in this part of the Gulf of Mexico but can be fed by excessive nutrients running off the Southwest Florida landscape. The nutrients don't cause Karenia brevis to form but can extend the frequency and duration of the harmful algal blooms.