Red tide is a pretty daunting and ominous phenomenon whereby the water changes color and takes on a deep red hue. This crimson tide may look like a harbinger of doom but it’s actually a natural and not entirely uncommon event.
But that doesn’t mean it’s harmless, as red tides can actually be seriously harmful and detrimental to humans and marine life.
What Causes Red Tides?
Red tides are also known as harmful algal blooms. They are caused by a type of algae. These organisms are commonly found in the water but their numbers are usually so low that they can’t be seen with the naked eye. During a red tide, the numbers increase and become so dense that the water appears to change color.
The organisms that cause red tides have been around for a long time, longer than humans in fact, but they are becoming more frequent due to human interaction.
It’s believed that sewage treatment plants and pollution from agriculture flows into the ocean and causes the algae to breed faster, triggering a resulting red tide bloom.
Are Red Tides Dangerous?
Some of the organisms that cause a red tide bloom produce toxins that can harm humans and sea life. Not only can direct contact lead to serious health implications, but humans can also ingest potentially harmful toxins by consuming fish and shellfish that have consumed or been in contact with these algae.
To prevent such issues, seafood is often tested for toxins, although it’s not unheard of for contaminated seafood to make it into the supply chain.
During harmful algal blooms, it’s not uncommon to see dead marine animals wash up on the shore.
When and Where do Red Tides Occur?
In the United States, red tides are often seen in the Gulf of Mexico, where an organism known as karenia brevis (K. brevis) causes “Florida red tides” and has been known to spread as far north as the Carolinas.
They are also seen in the Gulf of Maine, where a species known as alexandrium fundyense is the culprit.