anna maria island





  • Nancy McAleer

Red Tide - Everything You Need To Know

Red Tide FAQ's

Facts, resources & health information related to red tide.

What to do when an algae bloom hits the shore and how to salvage a vacation on the beach. Specifically this article relates to the Karenia Brevis phytoplankton that forms in the Gulf of Mexico off of Florida, Texas, Alabama, Louisiana, and Mexico.

What is red tide?

Red tide is the common name for a toxic algae bloom formed by a phytoplankton called Karenia Brevis. It forms in the off-shore in the ocean and Gulf of Mexico waters. This type of algae cannot survive in freshwater.

Karen Brevis

How does red tide grow?

Karenia Brevis is commonly present in the Gulf of Mexico. It blooms when water temperatures range between 72 - 82° F and salinities range between 31 - 37% (Steideinger et al. 1998). Sunlight and lack of water nutrients also play a role.


Why is red tide red?

Large concentrations can discolour water giving it a red or brown shade. Water may be discoloured from clear to dark hues.

Red Tide

Where does red tide form?

Red tide is believed to initiate offshore at depth before migrating to the surface. It is a slow developing phytoplankton compared to other phytoplankton species. The wind, currents, and weather are factors in transporting red tide inshore.

P.Schmidt, Charlotte Sun

Does red tide only occur in Florida?

No. Red tide is not a local occurrence. It can be found in other oceanic coastal areas throughout the world produced by different types of phytoplankton (Australia, South America, North America, Asia, etc…)

Recorded incidents of Red Tide

Is red tide a new phenomenon?

No. The first recorded case of Red Tide was in 1530 off the Florida Gulf Coast. According to Florida Wildlife Commission, fish kills near Tampa Bay were included in records of early Spanish explorers. In the 1700’s the first recorded case was in British Columbia, Canada. Other cases have been recorded in the 1800's and the first scientific recording in the U.S.A. was in 1947. It has been monitored and studied by scientists rigorously ever since throughout the world.

How long does red tide last?

A red tide bloom can last a few days, weeks or in rare cases months depending on the environmental conditions that influence the life cycle of an algae algae bloom. Onshore winds bring red tide near the shore and offshore winds drive it out to sea. The dissipation of red tide depends on sunlight, water temperature, nutrients, and water salinity, as well as wind, water currents and the weather. Red tide can dissipate and return towards he end of its life cycle due to these elements.

Clock on Beach

Can red tide live when it's washed up on the beach?

Karenia Brevis is a single celled marine algae which can only survive in marine waters (and has a pretty narrow range of tolerance for things like salinity). However, when waves are crashing onshore, the cells break open allowing the brevetoxin cells produced to become airborne, which is why (when winds are blowing onshore) humans can breathe in the toxins resulting in itchy eyes, runny noses, and scratchy throats.

Can we predict where red tide will occur?

No. Once red tide has been identified its movements can be predicted by monitoring the data. You can access Florida information by visiting Data is taken each Wednesday and Friday or more often in areas of high concentrations. The updated data can help people make decisions regarding their beach activities.

How can I navigate a safe holiday with my family during red tide?

Although we are not experts, we have spoken with the experts at Mote Marine Laboratory and Manatee County to help our guests and visitors safely enjoy a trip to Anna Maria Island during a red tide break-out. There are 3 great digital tools you can use to check daily conditions. is a Mote Marine Laboratory website that conducts daily water samples throughout the state of Florida. This interactive map can help you by zooming into your closest beach and clicking on the map marker. A pop up of the daily samples will appear. The Mote Marine Lab employees instructed us to look at the following criteria:

  1. DATE REPORTED - ensure the date and time are current, the report is posted daily.

  2. FLAG - safety conditions determined by the lifeguard stations. Not specifically red tide related but helps determine safety as well rip currents For more Red Flag and Rip Current information visit our Beach Safety Page here.

  3. WATER COLOR - Red Tide affects water clarity, the more dark it is the more intense red tide is.

  4. RED DRIFT - is not the same thing as red tide.

  5. RESPIRATORY IRRITATION - reported if people have been coughing while on the beach

  6. DEAD FISH - usually related to red tide

  7. WIND DIRECTION - if the wind is blowing inward towards the land, the more opportunity for Karenia Brevis cells to break and become airborne. In our case on Anna Maria Island inland would be towards the east.

  8. SURF - If the surf is choppy and crashing on the beach this also causes Karenia Brevis cells to break and become airborne, causing respiratory irritation.

Visit the website here for today's conditions.

Example Mote Marine Red Tide Beach Report

FWC - Red Tide Current Tide

The Florida Wildlife Commission has created a new interactive digital map with daily conditions relating to specific presence of the Karenia Brevis algae's daily water samples updated at 5 pm. The legend on the map is very easy to follow by color code of their categories ranging from not present to high concentrations.

Visit the FWC Red Tide Current Map here for today's conditions.

FWC Red Tide Current Map Legend

FWC Red Tide Example Map


The Florida Health website is a government agency dedicated to providing health and safety information for the state of Florida. In addition to red tide information this website also provides information about blue-green algae, etc... Their rating system has categories from Good to Poor with associated dates that the samples were taken. you can also view samples on this website. Be sure to check the dates next to the beach location to ensure you are reading up to the minute accurate data. To search for beaches on Anna Maria Island, Click the Manatee County Beaches button found on page 2.

Visit the Florida Health Government Beach Report website here.

Florida Health Government Beach Report

Are red tides harmful?

Red tides produce toxic chemicals that can affect both marine organisms and humans. Red tides can cause massive fish kills, and mortality in birds and marine mammals who accidentally ingest the algae through grasses and other affected fish. (ie: manatees, dolphins).

Dolphin with fish

What are the health effects of red tide on humans?

Call 1-888-232-8635 for Red Tide Health Questions