Written by: Clive Wright
During the last few days, a number of reddish brown slicks have been seen in the ocean in St Francis Bay area. This has sometimes been accompanied by a stinky smell. This what is known as a “red tide”.
The bioluminescence, shown in the photographs, is the result of a chemical reaction in these relatively large cells (they can be up to about 1mm in size) in special organelles called scintillons. The reaction involves the action of an enzyme called luciferase on a chemical called luciferin which produces the spectacular light show in the water.
Red by day, but blue by night as the sea turns into fairyland with billions of micro-organisms flashing their blue lights like an oceanic “blue light brigade”. Whenever the organism is disturbed it lets off a tiny burst of light. So when a wave passes them they unite in a flash along the lip of the wave. The resulting lightshow is spectacular. If you walk along the wet sand, the sand around your feet lights up in a celebration of your passing.
According to Dr. Derek Du Preez of Nelson Mandela Metropolitan University (NMMU), the current red tide occurring along our coastline is the result of a bloom of dinoflagellate microalgae called Noctiluca scintillans (commonly known in some parts of the world as “sea sparkle” – for obvious reasons). They are non-photosynthetic, whereas most other dinoflagellates use light energy to produce the sugars that they need for sustenance, and instead feed on other microalgae, usually diatoms. Their colour is determined by what they eat, usually pigments called carotenoids or xanthophylls. I have only ever seen orange-red blooms of this species (when they eat diatoms), but there have been reports of green Noctiluca scintillans blooms when they feed on green microscopic algae. The green colour would be the result of pigments called chlorophylls.
The phenomena have also been observed in the Kromme River, so if you venture out for a swim at night, you will be surprised by a light show all around you.
If you are seeing the bioluminescence for the first time, you will be in awe of what nature can provide for visual entertainment.
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