Blood Tides: The science behind Florida’s Red Tides

Depending on where you are in the world, especially if you read or watch the news, you might have heard about the recent disaster to hit the Florida waters. The disaster I’m talking about is Red Tide, which is currently sweeping the Floridian coast, killing wildlife by the masses. Reports are flooding in of marine animals, from turtles, manatees and fish- to even a whale shark, washing up along the shores due to the latest bloom of red tide.

Red tide along the coastline. (Source: Flickr. Credit: P. Alejandro Díaz)

But what is Red Tide and how is it killing so much marine wildlife?

According to the National Oceanic and Atmospheric Administration (NOAA), Red Tide is the term used for a harmful algal bloom. Algae, is the term for photosynthetic organisms that are predominantly aquatic – they aren’t plants. Things such as seaweed, phytoplankton (tiny marine organisms) and dinoflagellates class as algae.

Algal blooms are usually harmless, and in some occasions can be quite beneficial to

Microscopic view of Karenia brevis (Source: Wikicommons)

 marine life as they offer an abundance of food. However, some algae are toxic – toxic enough to kill. These Harmful Algae Blooms (HAB) can be due to a range of algae but in Florida it’s commonly due to Karenia brevis, a dinoflagellate. Karenia brevis produces neurotoxins, known as brevetoxins, that result in neurological and gastrointestinal problems in other organisms that ingest the algae, resulting in death. High concentrations of K. brevis can cause a reddish hue to the water, hence the name Red Tide.

The current blooms in Florida aren’t uncommon, in fact they’re a yearly occurrence in the summer. Navigated by winds and currents to the shores of Florida in high concentrations, the latest bloom is 100 miles long. Since this years blooms began, an estimated 300 tonnes of fish have already washed up dead, with governors declaring a state of emergency for 7 Florida counties. Red Tide proves deadly to already suffering species like the manatee, who’s already dwindling populations are susceptible. Large blooms like the one occurring this year can result in large Red Tide morality events, already surpassing last years death toll.

When organisms accidentally ingest K. brevis their nervous system are affected. Humans can also be affected by Red Tide. Wave action can rupture K. brevis cells releasing them into the air. This makes it possible for K. brevis to affect humans without ingestion by causing respiratory complaints, this can seriously effect those with respiratory issues. The local seafood industry is also affected. Many popular seafoods such as clams and mussels are filter feeders and can accumulate the toxins within their tissues. Usual warning signs for inedible food such as bad taste or cooking methods such as cooking contaminated food on high heat are useless with the brevetoxins. This is because they are difficult to detect, as they are “tasteless, odourless, and heat and acid stable”. This is resulting in local economic effects, with big losses to restaurants, fisheries and tourism.

At present, scientists still don’t know exactly what causes Red Tide on the Florida coasts, theories range from hurricanes to land run off. We’re also struggling to come up with solutions too, but scientists are tirelessly working on ways to save our marine life. For more information about the current red tide issues in Florida visit the Florida Fish and Wildlife Conservation Commission here.

Until next time,

Cate x

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