Members of the Phycology Section of the German Botanical Society who conduct research on algae nominate the seaweed Laminaria as ‘Alga of the year’: the kelp Laminaria can reach lengths of several metres. It forms, together with other macroalgal species, large underwater forests in the sea (so-called ‘kelp forests’). Kelps contain alginic acid which has several applications as stabilising agents in many food and cosmetic products. In contrast to other plants, kelps grow mainly in winter when sunlight is sparse. Algae take up the greenhouse gas carbon dioxide and are the most important oxygen producers of the world.