Many Forms

More than 100.000 species of algae are on our planet, in many sizes, shapes and colors. They live in oceans, in freshwater, on wet surfaces and soil. We can distinguish between unicellular algae like diatoms or dinoflagellates, and macro algae with structures that remind of leaves, stems and roots. Macro algae can form up to 50 m long seaweeds like giant kelp, forming extensive submerse forests.


Algae are photosynthetically active organisms, but their body plan is simpler when compared to higher plants. Together with the even more simple blue-green algae, strictly spoken Cyanobacteria, they produced considerable amounts of atmospheric oxygen. Millions of years ago Cyanobacteria were exclusively responsible for increasing the atmospheric oxygen. Today, algae produce a significant part of oxygen and are responsible for fixation of about half of the carbon dioxide. They play a central role for life and climate of the world. Algae form the basis of the food chain, as either phytoplankton or microphytobenthos and are crucial for all aquatic ecosystems.

Evolutionary Steps

The evolutionary history of algae is manifold. Some, like green- and red algae or glaucophytes, derive from a primary endosymbiosis like higher plants. One eukaryotic cell engulfed one cyanobacterium. In other groups (like brown algae, diatoms, chrysophytes, cryptophytes, dinoflagellates and euglophytes), an eukaryotic red or green alga was incorporated, leading to a secondary endosymbiosis.

Use and Potential

Thickener, gelling agents, or coating deriving from macro algae are part of food and cosmetic products. Microalgae are potential candidates for biofuel production. Due to the biological differences between algae, algae have many qualities that are relevant not only for biologists but also for geochemists and for the industry. Applicators investigate the siliceous cell walls of diatoms for lightweight construction, the calcareous scales of haptophytes; moreover, the production of neurotoxins in cyanobacteria and bioluminescence in dinoflagellates are investigated.

Algal Portraits

To demonstrate the positive qualities of algae, the Phycology Section nominates the ‘Alga of the year’ that is presented to the public.