Brown algae are a group of marine organisms belonging to the phylum Ochrophyta. They are primarily found in cold coastal waters and can vary in size from small filaments to large seaweeds, such as kelp. Brown algae contain chlorophyll and other pigments, giving them their characteristic brown color. These organisms play a crucial role in marine ecosystems, providing habitat and food for various marine life. They also contribute to the production of oxygen and help in carbon fixation. Brown algae are important for human use as well, being harvested for food, fertilizers, and various industrial applications.