Red Tide

By Melynda Hole

During this time of year, when you go to the beach you may see some dead animals wash up on shore. Why is that? This is due to the phenomenon called red tide. Red tide is a type of algal bloom that is free-floating through the water. Since algae only need sunlight and nutrients to thrive, the population will dramatically increase. Algal blooms typically occur when there is an abundance of nutrients in the water. Most of the excess nutrients come from terrestrial runoff from our fertilizers after a long rainy season. It can also happen naturally from freshwater river input, bringing the nutrients from the soil to the bay. 

There are a few different types of species of algae involved in  red tide. The most well-known  is Karenia brevis, which is a type of dinoflagellate phytoplankton. It is a single cell organism, so it is invisible to the naked eye. However, they are visible in mass amounts on the ocean’s surface due to their red color, which is where the red tide gets its name. On occasions it can also display itself as more of a brown color or be entirely colorless and cannot be seen. Not only does red tide suffocate the benthic plants, but it also produces a harmful neurotoxin that disrupts the firing of the nerve cells, which can kill smaller fish, which are then consumed by larger fish,, allowing it to travel up the food chain. When mass amounts of algae dies and starts to decompose, the chemical reaction depletes the oxygen in the water, which also contributes to the suffocation of the larger fish and other marine life. This is the main reason why you  see all the dead animals on the beach. During times when red tide is active, filter feeders are not the safest to eat since they filter out all the harmful algae. It is also harmful to humans. When swimming or being near red tide affected water, people and other land animals may get sick from the exposure to the water or breathing  the toxins in the air. 

Over the years, red tide has gotten more frequent due climate change and consistent nutrient pollution from farming and landscaping. However, there are ways we can help! By reporting whenever you see red tide, or feel any symptoms of red tide (itchy skin and  respiratory irritation around saltwater), it can help scientists at Mote Marine Laboratory and Florida Fish and Wildlife Conservation Commission (FWC) to document red tide data. You can contact the FWC by calling them if you see a dead, sick or injured manatee or sea turtle ((888) 404-3922) or any dead fish washed ashore ((800) 636-0511).