______ is a marine algae used as food.

Sargassum :

1. Sargassum is a genus of large brown algae that floats in island-like masses and never attaches to the sea.
2. Marine algae, also known as seaweed, provides food and shelter for marine life
3. Sargassum seaweed contains a lot of carotene, cellulose, protein, and amino acids like aspartic and glutamic acid.

Final Answer: Sargassum is a marine algae used as food.