A red tide is the phenomenon where the coastal waters turn red. Red tides can be seen all over the world and can potentially have a harmful effect on the environment.

Red tide
Red Tide at Bombay Beach by CEBImagery, licensed under CC BY-NC 2.0


Red tide
Red Tide at the Institute of Ocean Sciences by Chris Willey, licensed under CC BY-NC-ND 2.0

The cause of a red tide is an algal bloom. An algal bloom is rapid increase of algae population. The microscopic marine life-forms responsible for the red color is a phytoplankton called Dinoflagellates.

The cause of this algal bloom is unknown. Scientists have suggested that there could be a link with climate change, but there’s is no real evidence supporting this idea. There also seems to be a link with water polution. Red tides seem to occur more often near coastal areas where sewage is release into the water.

Health effects

Red tides can be harmful to the environment, because the algae produce toxins which can affect the central nervous system of fish, birds and other animals. People eating sea-food contaminated by the red tide can become very ill.

The toxins can also become airborne through the breaking of the waves, or strong winds. When inhaled, it’s possible for some people to start experiencing symptoms as coughing, runny noses and wheezing. Mostly, these symptoms go away when leaving the immediate area of the red tide. But for people already suffering from respiratory conditions such as asthma, these symptoms may last for a couple of days.

Red tide
Red Tide, Dana Passage by charleschandler, licensed under CC BY-NC-ND 2.0

Bioluminescent waves

Bioluminescent waves
Red Tide +1 by Phil Gibbs, licensed under CC BY-NC-ND 2.0

These algae also have a very cool side to them which becomes apparent during nighttime. When they are under physical stress, such as waves breaking on the beach or a a surfboard surfing over them, they give off a bright blue-green glow. Even stepping through the waves will trigger this reaction. The reason why they are able to do this is because of a chemical called lucifrin, which the algae can produce on it’s own. The bright glow serves as a defense mechanism to disorientate predators.

Bioluminescent waves
Red Tide Luminescense by catalano82, licensed under CC BY 2.0