Seaweeds are excellent sources of polysaccharides. Commercially, seaweed extracts produce the food thickener carrageenan, agar for food and biological research uses, docosahexaenoic acid, fertilizer, vitamins, and other products. One of the most profitable marine aquaculture products is nori (the red alga Porphyra), used for wrapping the near-ubiquitous sushi. This market exceeds $1.61 billion a year.
More reasons exist to grow seaweed than just profit from seaweed itself. Aquaculture is growing in popularity, as evidence accumulates that the ocean alone cannot supply enough finfish, crustaceans, and mollusks to the world. But with fish farming comes pollution, especially increases in nitrogen and phosphorus. Seaweeds can help control these byproducts. Christina Halling, a doctoral student in the department of systems ecology at Stockholm University, Sweden, explains, "In an intensive salmon farm, less than one-third of the added nutrients [provided] through feed is removed through the fish harvest. Two-thirds of the nutrients are released ...
