Creature of the Month

Return to Main Page




Phytoplankton are one of the major producers of the sea. They are capable of producing energy from sunlight through photosynthesis.  Phytoplankton is not a taxonomic group, but rather a term used to
describe a range of different microscopic plant-like organisms that drift passively on the world's oceans. Phytoplankton include both algae and bacteria.

Phytoplankton are the most numerous producers on the planet. A liter of sea water may contain a million of these organisms. 

Plankton comes from the Greek word planktos, meaning to drift or wander. Any organism that drifts in the the water rather than swimming is considered part of the plankton (including large jellyfish).

Phytoplankton blooms can have a considerable affect on the environment. Dinoflagellates are responsible for a destructive event known as a red tide. They contain a powerful toxin that can kill
fishes, oysters, clams, etc, and even poison humans. During a red tide dinoflagellates bloom in such high numbers, they literally turn the water red. Red tides can stretch for hundreds of kilometers.

During a night dive you might notice millions of tiny flashing lights in the water. These are dinoflagellates. Their ability to glow is known as bioluminescence and can be used to evade predators, attract prey or simply to communicate. The dinoflagellates' flash,
which lasts for only a fraction of a second, is produced by a chemical reaction inside the organism triggered by a disturbance in the water. Even a motion as gentle as passing your hand through the
water can leave a trail of stars in its wake. Most bioluminescence is blue, because this is the color that travels furthest through the water. Red light is quickly absorbed as you descend, which is why
everything appears blue at depth.

Reprinted with permission:
Copyright SCUBA Travel -

Diatoms thru a microscope