Scientists monitor red tide increase off southwest Florida

Scientists monitor red tide increase off southwest Florida

The public can enhance monitoring using Mote’s smartphone app

Researchers are monitoring elevated levels of the naturally occurring Florida red tide algae, Karenia brevis, along southwest Florida. The public can follow online updates from multiple monitoring partners and even report coastal conditions using Mote Marine Laboratory’s new smartphone app.

Red tide monitoring and prediction in Florida is accomplished through a unique collaboration between the Florida Fish and Wildlife Conservation Commission’s (FWC’s) Fish and Wildlife Research Institute, the Florida Department of Agriculture and Consumer Services (FDACS), the Florida Department of Health, Mote Marine Laboratory, the University of South Florida, National Oceanic and Atmospheric Administration (NOAA), county agencies, other private non-profit agencies, and citizen volunteers. The FWC-Mote Red Tide Cooperative Program leads joint research, monitoring and public education efforts focused on K. brevis red tide.

The single-celled K. brevis alga occurs naturally in the Gulf of Mexico and is observed throughout the year at concentrations considered to be “background.” Higher-than-normal concentrations of K. brevis can include “very low,” “low,” “medium,” and “high” levels. (Below is a table describing these concentrations and their possible effects.*)

During the past two weeks, water samples confirmed a bloom of K. brevis along Lee County, with several samples observed to contain high concentrations of K. brevis. Also during the past two weeks, background to low concentrations were observed in Charlotte County, background to very low concentrations in Sarasota County, and background concentrations in Manatee and Hillsborough counties, according weekly reports issued Nov. 18 and 22 by FWC, which gathers and analyzes red tide data and compiles data from partners statewide, including Mote in Sarasota County.  

Red tide concentrations elevated to levels low or above can cause respiratory irritation in humans and may also kill fish. Many factors, including algae distribution, currents and winds, can determine whether effects are noticeable. When a person leaves an area with a red tide, symptoms usually go away. People with asthma, COPD or other chronic respiratory conditions are cautioned to avoid areas with active red tides.

Blooms of Florida red tide can be very patchy, with background to high concentrations occurring in close proximity to one another. Therefore, effects may be noticeable on one beach but not on a nearby beach.

Monitoring results and tips from Sarasota County scientists

In Sarasota County, water samples are collected weekly at 16 locations by the Sarasota Healthy Beaches program of the Florida Department of Health and analyzed for K. brevis cells by Mote, which contributes its local data to FWC’s statewide reports.  In addition, Mote operates the Beach Conditions Reporting System (, which provides daily condition updates for multiple Gulf Coast beaches.

Smartphone users can also download Mote’s free app, Citizen Science Information Collaboration (CSIC), from the App Store or Google Play. The app allows users to report when and where they experience respiratory irritation or see discolored water or dead fish — all potential indications of Florida red tide.
Water samples collected by the Florida Department of Health on Nov. 20 along Sarasota County and analyzed by Mote contained no K. brevis cells.  This week’s results from local to statewide partners will be included in FWC’s upcoming statewide report expected Friday, Dec. 1, at

As of Monday evening, Nov. 27, Mote’s Beach Conditions Reporting System ( — which provides updates as often as twice daily from multiple Gulf Coast beaches — showed a report of slight respiratory irritation at the Causeway Islands site between Sanibel and Punta Rassa. No other sites reported respiratory irritation or dead fish at that time.
Florida-wide red tide resources:

*Karenia brevis cell counts and meanings

Source: FWC/FWRI: