The toxic red tide bloom that has plagued Florida since November of 2017 seems to finally have dissipated. Last week, the Florida Fish and Wildlife Conservation Commission reported that the red tide organism, Karenia brevis or K. brevis, is no longer present in water samples.
The outbreak was responsible for the deaths of hundreds of manatees and sea turtles and thousands of fish over the last 13 months, as well as the loss of tens of millions in tourist dollars. Unfortunately, scientists say that in the years ahead we are likely to lose many more.
According to the Fourth National Climate Assessment, a report produced by 300 scientists and 13 federal agencies, warming ocean temperatures will increase the intensity and frequency of red tide events.
What is Red Tide?
Microscopic plants called algae fill the ocean. When excess nutrients flow from inland areas into the ocean, algae multiply uncontrollably, creating a “bloom.” These blooms can last from a few weeks to over a year.
Warm ocean temperatures, low salinity, high nutrient levels, calm seas, and sunny days after rain can also trigger these blooms. Wind, currents, storms, and ships can carry them across long distances.
Most algal blooms benefit the environment since algae serve as food for ocean animals. However, a red tide occurs when algae grow out of control and produce toxic effects on people and animals. Some algae species, like K. brevis, turn the ocean’s surface deep red, which leads to the term “red tide.”
Red tide is deadly to marine life and can cause skin and respiratory problems in humans.
What are the effects of Red Tide?
K. brevis produces brevetoxin, which can affect the central nervous system of fish and other vertebrates, causing them to die. These toxins can also accumulate in shellfish and cause neurotoxic shellfish poisoning in people who eat them.
Commercially caught seafood, found in grocery stores and most restaurants, is generally safe to eat during a bloom because monitoring for K. brevis occurs regularly. However, caution is urged when eating recreationally caught fish, as cooking does not destroy red tide toxins.
Swimming during a red tide event is safe for most people, though it may cause skin and eye irritation. Avoid swimming near dead fish, as they can harbor harmful bacteria and create an unpleasant experience.
Waves can break apart K. brevis cells, releasing toxins into the air. This can cause respiratory issues like coughing, sneezing, and itchy, watery eyes. These symptoms usually disappear within a few hours after leaving the beach. However, people with severe respiratory conditions, such as emphysema and asthma, should avoid the beach entirely during red tide.
How can we mitigate Red Tide?
Researchers are working on an antidote to red tide toxins, but slowing climate change is crucial to reducing the frequency and intensity of harmful algae blooms.
In the meantime, our best course of action is to closely monitor red tide outbreaks via water sampling and satellite imagery to mitigate its effects. The sooner red tide algae is detected, the sooner people in the area can receive warning not to eat infected shellfish or swim in contaminated waters.
“The key is observation,” said Robert Weisberg, a physical oceanography professor at the University of South Florida College of Marine Science, “but without observation we are flying blind.”
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