Red Tide spreading across Atlantic coast

Miami-Dade, Broward, Palm Beach, Martin and St. Lucie counties all show signs of the toxic algae in water samples.

Double red flags fly at Lake Worth Beach in Palm Beach County on Oct. 2, 2018. Red Tide has spread into the Atlantic Ocean. [Wilfredo Lee | Associated Press photo]
Double red flags fly at Lake Worth Beach in Palm Beach County on Oct. 2, 2018. Red Tide has spread into the Atlantic Ocean. [Wilfredo Lee | Associated Press photo]

This article was updated at 6:15 p.m. on Oct. 5, 2018.

Red Tide continued to spread across South Florida, with the state confirming that the toxic algae was present in water samples in Miami-Dade, Martin and St. Lucie counties, after originally finding it in Palm Beach County.

Miami-Dade officials closed beaches north of Haulover Inlet, north of Bal Harbour, early Thursday morning after tests for Red Tide organisms were positive, the Miami Herald reported. The tests showed medium concentrations of the microscopic algae Karenia brevis, the organism responsible for Red Tide. Those beaches reopened on Friday.

Further tests in Miami Beach and Key Biscayne also tested positive, but in lower concentrations that did not warrant closing the beaches.

The action in Miami-Dade came after the Florida Fish and Wildlife Conservation Commission’s Red Tide status update for Oct. 3 showed up to medium concentrations of Karenia brevis in Palm Beach County. Beachgoers in Palm Beach County began complaining about respiratory distress and throat and eye irritation on Sept. 28, prompting beach closures countywide.

Palm Beach County beaches, like Miami-Dade, reopened on Friday.

Lower concentrations also were confirmed in Martin and St. Lucie counties on Wednesday. The commission reported fish kills in South Florida over the course of the week.

READ MORE: Answers to questions about Red Tide.

Background and low concentrations of the algae were found in Broward County, according to Friday's Red Tide status update. The state typically revises its Red Tide updates on Wednesdays and Fridays.

The FWC this week also began posting daily updates to its Red Tide data, which are updated at 5 p.m. The map and further information is available here.

When conditions are right, Karenia brevis algae multiplies rapidly and causes a bloom that sickens and kills fish and marine wildlife. The bloom can make the water rust-colored, giving the phenomenon its Red Tide name.

No one knows for sure what causes Red Tide blooms, although factors ranging from nutrient-rich runoff to Mississippi River pollution to dust from the Sahara Desert may contribute.

READ MORE: Is Red Tide affecting Florida's seafood? It's best to ask before you eat.

Red Tide is different from the blue-green algae that is plaguing southern Florida currently. The blue-green algae is a freshwater species, while Karenia brevis is a saltwater species. It’s unusual for Red Tide to occur in the Atlantic, although it can happen when currents carry the algae in from the Gulf of Mexico.

The East Coast has had Red Tide problems eight times since the 1950s, the South Florida Sun-Sentinel reported. The most recent case was in 2007. The newspaper said each time the microscopic algae drifted in from the Gulf of Mexico.

READ MORE: Red Tide can affect birds along the shore.

The Gulf Coast, meanwhile, has been experiencing ill effects from a Red Tide bloom that first formed in fall 2017. Beaches from Pasco to Collier counties have tested positive for the toxic algae, as have several counties in the Panhandle.

Concentrations in Bay and Walton counties, especially, were on the increase, as of the latest state update. Southwest Florida counties were experiencing an overall decrease in Karenia brevis concentrations, but concentrations remained high in several locations.

This article was originally published on Oct. 3, 2018.

This article was written by one or more Florida Beach Insider staff members.