Teen Sci with WinK

Algal Bloom Causes Red Tides

Posted in Uncategorized by wink on November 25, 2005

There are millions of microscopic algae in the sea water. They photosynthesise/use sun to make food. To trap the necessary sunlight, they use pigments/colours eg green cholrophyll.

In summer/warmer water and also when minerals are available, algae Bloom/grow in number. In favorable times, just one alga can replicate (process of reproducing offsprings) a million times in 1 or 2 weeks!

With increasing numbers, there is competition for light so other pigments which are better adapted at collecting sunlight than green chlorophyll is used by algae. These coloured pigments may discolour the water to red, pink, orange, yellow, blue, green, brown or sometimes violet. This is Red Tide, (red because it is most common coloured pigment used)

Some algal species causing red tide can be very toxic to other organisms including humans. However, algae are very important in the sea because they are at the start of food chains. They may be eaten by shellfish (not harmed by red tide), then humans may eat the shellfish, but the toxins from the algae which are in the shellfish are fatal to humans. So, red tides are usually harmful to humans.


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