Algologie

Algologie is the branch of botany that studies algae, a diverse group of photosynthetic organisms that ranges from microscopic phytoplankton to large macroalgae such as seaweeds. In many French-language sources, algologie is used interchangeably with phycology, the science of algae; some authors distinguish the terms by historical tradition or scope. Algologie encompasses taxonomy and systematics, morphology, physiology, ecology, and biogeography of algae, as well as their life cycles, reproduction, and pigments.

Algal groups commonly studied include green algae (Chlorophyta), red algae (Rhodophyta), and brown algae (Phaeophyceae), along with numerous microscopic lineages such as diatoms and dinoflagellates. Depending on the author, cyanobacteria may be included or treated as a separate field. Methods combine traditional microscopy with molecular techniques, cultivation, and ecological fieldwork.

Ecologically, algae form the base of many aquatic ecosystems, contribute to primary production, shape habitats, and drive nutrient cycles. They can also form blooms, some of which have environmental and economic impacts. Algae have industrial relevance for food and feed, pharmaceuticals and nutraceuticals, pigments, biofuels, and wastewater treatment processes.

Historically, algologie developed from early natural history and taxonomy in the 18th and 19th centuries and has been strengthened by advances in molecular biology and genomics. It intersects with marine biology, limnology, ecology, and biotechnology and informs conservation, resource management, and environmental monitoring.