Seaweed
![Ascophyllum nodosum exposed to the sun in Nova Scotia, Canada](/Images/godic/202501/25/Ascophyllum_nodosum5101.jpg")
![Dead man's fingers (Codium fragile) off the Massachusetts coast in the United States](/Images/godic/202501/25/Codiumfragile5101.jpg")
![The top of a kelp forest in Otago, New Zealand](/Images/godic/202501/25/Kelp_forest_Otago_1s5102.JPG")
![Seaweeds cover this rocky seabed on the east coast of Australia](/Images/godic/202501/25/NSW_seabed_25102.JPG")
Seaweed refers to several species of macroscopic, multicellular, marine algae.
The term includes some members of the red, brown, and green algae. Seaweeds can also be classified by use (as food, medicine, fertilizer, filtration, industrial, etc.).