) is the study of algae
. Most algae are eukaryotic
organisms that live in a wet environments. They are distinguished from the higher plants
by a lack of true roots
. Many species are single-celled and microscopic; many others are multicellular
to one degree or another, some of these growing to large size (for example, seaweeds such as kelp
). Algae are important as primary producers
in aquatic ecosystems.