Red tide algae levels growing stronger in some Manatee waters, recent samples show

The latest batch of water samples from around Manatee County shows that levels of the red tide-causing algae, Karenia brevis, are increasing in strength in some areas.

Low concentrations of K. brevis have been detected at sampling points around Anna Maria Island and lower Tampa Bay for the last several weeks. This week, levels dropped around Anna Maria Island and Longboat Key but intensified farther north.

And one sample gathered near Joe Island in the Terra Ceia Aquatic Preserve showed a medium count of K. brevis cells, according to the Florida Fish and Wildlife Conservation Commission, the state agency responsible for monitoring red tide.

Scientists consider medium counts of K. brevis cells “bloom level.” At bloom level, harmful impacts including respiratory irritation and fish kills are more likely.

The medium sample and one low-level sample west of Little Redfish Creek were both collected within just a few miles of where contaminated wastewater from the Piney Point industrial site was discharged into Port Manatee and Bishop Harbor in April. The water contained nutrients, including nitrogen and phosphorous, that can fuel a red tide bloom.

However, researchers with the University of South Florida said this week that it is too soon to tell whether the Piney Point wastewater might be to blame for worsening local red tide conditions. K. brevis is naturally occurring in Gulf Coast waters, and bloom conditions already existed south of Manatee County before the Piney Point discharge.

Complete details of the week’s water sampling results will be released on Friday. Data available on Wednesday showed that low levels of K. brevis were recently recorded around School Key north of Anna Maria Island; at Terra Ceia Point; around the Sunshine Skyway Bridge; and near Little Redfish Creek. Very low levels were observed at Mead Key and around the Skyway Bridge.

Samples taken directly off of Anna Maria Island and Longboat Key showed that K. brevis was at trace levels or not present in those areas.

As of Wednesday evening, local beaches on Anna Maria Island and Longboat Key were free of fish kills and respiratory irritation, according to Mote Marine Laboratory’s live beach conditions tracker.

K. brevis was also found at elevated levels in this week water samples off of Pinellas County and Hillsborough County waters to the north and in Sarasota, Charlotte, Lee and Collier counties to the south. Lee and Collier are currently experiencing high concentrations of the algae, according to FWC.

FWC will issue its next red tide report on Friday.

Fish kills can be reported to FWC at 800-636-0511 or online at myfwc.com/research/saltwater/health/fish-kills-hotline.

This story was originally published May 26, 2021 at 6:11 PM.