Red Tide FAQ: What to know about the bloom impacting Tampa Bay

TAMPA, Fla. (WFLA) – The red tide is back along Florida’s Gulf Coast, according to the Florida Fish and Wildlife Conservation Commission – and it’s back with a vengeance. As memories of a severe bloom from several years ago linger, coupled with concerns about a sewage breach at Piney Point in Manatee County earlier this year, people living along the coast are worried.

If you’re new to Florida or can’t remember the 2018 bloom, here’s what to know about the Red Tide:

What is the red tide?

The FWC describes the red tide – also known as the nuisance algal bloom – in the form of a higher than normal concentration of microscopic algae. An overgrowth occurs when there are large concentrations of cells, which can discolor the water – making it reddish or brown.

The species that causes most red tides in Florida and the Gulf of Mexico is Karenia brevis or K. brevis.

How often do red tides occur and how long do they last?

Red tides occur naturally in Florida. According to the FWC, “K.brief is found year-round at background concentrations 1000 cells per liter or less. Blooms occur in the Gulf of Mexico almost every year and usually occur in late summer or early fall.

However, according to Mote Marine, human-made nutrients and nutrient pollution can fuel red tide growth, making them more severe.

“Yes, the scientific data available so far suggests that it is possible that nutrients flowing from land to sea – including natural AND human-made nutrients carried by stormwater runoff and input from rivers – serve as additional ‘food’ for the growth of Karenia brevis red tide blooms that have moved inshore,” Mote explains on his website.

The FWC says most blooms last between three and five months, but some can persist for over a year. Mote adds on its site that the duration of a bloom depends on the “physical, chemical, biological and ecological conditions that influence its growth and persistence, including sunlight, nutrients and salinity, as well as speed and direction of the wind and water currents”.

What does the red tide do to marine life?

K. brevis produces brevetoxins capable of killing fish and other marine species, as well as birds. Killed fish can be a noticeable impact of a bloom and are tracked by the FWC.

“Red tides can also lead to the death of invertebrates, including shrimp, sponges, sea urchins, crabs and some crustaceans,” the FWC says on its website. “In most cases, it is unclear whether invertebrate death occurs due to exposure to toxins or low oxygen conditions resulting from blooms.”

The FWC explains that mass bird deaths are also common during a red tide because the birds eat contaminated fish and shellfish.

Dolphins and manatees can also be impacted by red tide.

Can the red tide harm humans?

The brevetoxins produced by the red tide can cause respiratory or eye irritation. According to the FWC, this is because the toxins become airborne when wave action breaks up the cells. The FWC warns that the red tide can cause “serious illness” for people who already suffer from serious or chronic respiratory conditions such as emphysema or asthma.

A study is underway at Roskamp Institute in Sarasota to examine whether or not the red tide has long-term impacts on humans.

Can I swim in water affected by the red tide?

According to the FWC, most people will swim well. However, red tide can kill fish and you should not swim near dead fish as they may be associated with harmful bacteria, experts say.

While most people should be able to swim during a bloom, the FWC says some may experience skin irritation, eye burn or respiratory irritation.

“Use common sense,” advises the FWC. “If you are particularly susceptible to irritation from plant products, avoid an area with a red tide bloom. If you experience irritation, get out of the water and rinse thoroughly.

Can I eat seafood during a red tide?

Humans can suffer from neurotoxic shellfish poisoning if they eat shellfish – such as clams, oysters or mussels – that are contaminated with brevetoxins, have no taste, smell or color and cannot be destroyed by cooking. This is why the harvesting of shellfish in restricted areas is prohibited during red tides.

“Fish are safe to eat as long as they are caught alive and only the muscle is eaten”, the FWC says on its website. “The muscle of shellfish, including crab, shrimp and lobster, is unaffected by red tide toxins and can be eaten.”

The FWC adds that store-bought shellfish, as well as shellfish served in restaurants, are safe to eat as they are monitored for safety by the government and are generally not harvested locally. If harvested locally, the FWC says the shells are tested for red tide toxins before being sold.

Local finfish are also safe to eat during a red tide, as long as they are filleted, according to the FWC.

“Although toxins can accumulate in the guts of fish, these areas are removed when the fish are filleted,” the FWC site explains. “However, it is never a good idea to eat dead or distressed animals, especially in a red tide area, because the reason for the strange behavior or death of the animal cannot be absolutely known.”

How do you know if a beach is affected by the red tide?

The FWC tracks the red tide year-round and regularly releases water samples that are made public online. You can find the last eight days of sampling on a interactive map on the commission’s website. A red tide status update is published on the FWC website every Wednesday and Friday.

Mote Marine Laboratory also monitors the condition of beaches and has a interactive map set up online which you can check before you go.

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