Marine algae are important components of the marine ecosystems, contributing to increase their biodiversity. They are composed of avascular and photosynthetic plants (consuming carbone dioxide and producing oxygen) and are at the base of the trophic chain as food for fish, molluscs, sponges, etc. Most marine algae occur attached to the rocks in the intertidal and subtidal, zones, however, it may grow associated with other plants or substrates.
They often form associations amog themselves, protecting the coastline by acting has "wave breakers". Algae may have several shapes: leaf-like, tree-like, filamentous, and branched. Although it only exists in small quantities, in the Madeira Archipelago there are approximately 359 identified species of algae. Most of these species (about 64%) belong to the Phylum Rhodophyta (red algae). The remaining species belong to the Phylum Chlorophyta (green algae) and Chromophyta.