Almost every summer in Florida, you hear news about red tide.
But what exactly is it, and why is it so talked about?
Red tide in Florida, which often occurs along the state's
Gulf coast, is caused by the accumulation of
Karenia brevis, a type of single-celled organism
called a dinoflagellate.
Red tides occur around the world and are not all
caused by the same species, nor are they always red.
In fact, most dinoflagellates are harmless, but some
including K. Brevis, produce neurotoxins that can cause
respiratory problems in humans and attack the central
nervous systems of fish and other wildlife.
Red tide in Florida is designated as a "harmful algal bloom"
or "HAB," due to the impacts it can have on the environment,
humans, and our coastal economies.
Red tides occur almost annually in the Gulf, particularly
in the Tampa Bay and Charlotte Harbor region.
The first scientifically documented red tide bloom
in Florida dates back to 1844, predating extensive human development.
Florida's red tides can appear throughout the year,
though they usually peak late summer to early fall
and can last from a few days to months.
Red tide blooms in Florida begin 10 to 40 miles offshore
in the bottom waters of the Gulf of Mexico
where K. Brevis is almost always present at
low and harmless concentrations.
K. Brevis cells that hang out at the bottom are brought
to the surface by a phenomenon known as upwelling,
a process in which deep, cold, and nutrient-rich water rises
to the surface.
K. Brevis, like all algae, requires three things to grow and
survive. Optimal light, temperature, and nutrients,
specifically nitrogen and phosphorous.
Winds and ocean currents then bring the bloom
inshore, where it has an impact on our coast.
In fact, these currents play the biggest role in determining
which parts of our coastline will be affected.
Once the bloom moves near shore, nutrients associated with
decaying red tide and fish kill biomass are among
the most significant nutrients sources for blooms.
So much so, that red tide has been considered nearly self-sustaining.
Nearshore red tide blooms can also obtain nutrients from
air pollution, water releases from rivers and estuaries,
and estuarine flux, or the exchange of nutrients to and from the estuary.
K. Brevis produces neurotoxic brevetoxins
Through inhalation, direct contact, or ingestion,
these toxins, in high enough concentration, can harm
and kill fish, birds, and marine mammals.
Exposure to brevetoxins occur through inhalation or ingestion.
People in coastal areas can experience varying degrees of
eye, nose, and throat irritation.
Eating contaminated shellfish can also lead to Neurotoxic Shellfish Poisoning.
However, keep in mind that store-bought seafood
or seafood served in restaurants are safe to eat.
Each year, red tides are estimated to cost Florida more than
$20 million in tourism-related losses.
The 2015-16 red tide event caused a $1.3 million
sales loss to the hard clam aquaculture industry.
Health costs and lost work days associated with HABS cost
the U.S. $22 million annually.
Water samples are collected from over 100 locations throughout Florida
on a weekly, bi-monthly, or monthly basis through partnerships
with state agencies, county governments, and community members.
The Florida Fish and Wildlife Conservation Commission maintains
a daily sample map that shows results from the last 8 days
of red tide sampling. During a harmful algae bloom
event, the National Oceanic and Atmospheric Administration,
also issues twice-weekly forecasts using satellite
imagery and other data to monitor blooms and
the potential for impacts.
Red tide blooms feed on excess nitrogen and phosphorous
once they make their way to our coasts.
These excess nutrients come from a variety of sources,
such as stormwater runoff, fertilizer runoff,
septic tanks, and/or faulty wastewater systems.
These excess nutrients play a role in the extent
and duration of large bloom events.
For more information on red tide, you can visit
the FWC's website and the Florida Department of Health.
The information in this video was provided by the
National Ocean Service, Florida Sea Grant, and the Florida Fish and Wildlife Conservation Commission.