Microscopic plants that live in the surface layers of the seabed, particularly in shallow water and intertidal areas. (https://www.eea.europa.eu/help/glossary/eea-glossary)
Phytochemistry is the study of phytochemicals, which are chemicals derived from plants. (Wikipedia. 2024. Phytochemistry. https://en.wikipedia.org/wiki/Phytochemistry)