Red Tide
Have you ever wondered what causes the different-colored tints in the ocean or freshwater lakes? This colored water – whether red, brown, green or yellow – is commonly known as a “red tide” or a harmful algal bloom. Blooms are formed by single-celled photosynthetic organisms that can sometimes be harmful to humans, wildlife and the environment. Some harmful algae produce toxins that accumulate in shellfish, making them dangerous to eat. These toxins can be so potent that shellfish can become unsafe for human consumption even if the algae are present in concentrations so low that the water is not colored. Since certain weather and climate conditions can favor the development of a red tide, scientists can use forecasts to provide advanced warning of the increased risk of red tide events. Knowing when blooms might occur ahead of time allows health authorities to be proactive in their management decisions.
Viewer Tip: Red tides typically occur on the U.S. west coast in summer and fall when water temperatures are warmer, but shellfish can become toxic at any time of the year. If you want to know whether colored water is toxic in your area or if you are planning a recreational trip to the beach to dig for shellfish and want to know if they will be safe to eat, contact your state’s health department.
This information is provided by the West Coast Center for Oceans and Human Health, a part of NOAA’s Northwest Fisheries Science Center. Learn more at www.nwfsc.noaa.gov/hab/.
