Background Information about the Algae
Microscopic unicellular algae comprise the phytoplankton in salt and freshwater biotopes. The word Plankton is derived from the Greek verb meaning to drift, and this describes the passive floating movements of the algae in water currents.
Microalgae are cosmopolitan and can be found in coastal as well as oceanic waters. Some species are even found in Arctic snow. A rapid spurt of growth can bring about a mass development of algae cells, discoloring surface waters. Such an "algal bloom" may cause skin irritation to swimmers. Some algae produce toxic substances which are harmful to fish. A sudden breakdown of an algal bloom and the resulting oxygen depletion during bacterial decomposition is also a danger to sea life.
Most microalgae require sunlight and nutrients dissolved in the water for their growth. A few members of the Dinoflagellates are luminescent, i.e. they are able to glow in the dark similar to "glow-worms" in the insect world.
The algae are most frequently found in surface waters during the warmer months. The species shown in the photos here were collected from the seawater near the island of Helgoland, Germany, and represent typical North Sea phytoplankton.
For more information on the fascinating organisms we recommend the book (in English)
"Coastal Plankton. Photo Guide for European Seas" by Otto Larink and Wilfried Westheide, Verlag Dr. Friedrich Pfeil, Munich 2006.