5.3 Economic importance and applications of marine algae

Marine algae are more than just slimy seaweed. They're economic powerhouses, used in food, cosmetics, and medicine. From nori in sushi to carrageenan in ice cream, these versatile organisms have countless applications.

Cultivating and harvesting seaweeds is big business. Farmers grow nori on nets, kelp on longlines, and harvest wild seaweed beds. These algae are packed with nutrients, have medicinal properties, and even help fight climate change.

Economic Importance and Applications of Marine Algae

Commercial species of marine algae

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• Red algae (Rhodophyta)
  • Nori (Porphyra) used in sushi and as a seasoning
  • Carrageenan (Chondrus crispus, Kappaphycus alvarezii, Eucheuma denticulatum) acts as a thickening agent in food products, cosmetics, and pharmaceuticals
• Brown algae (Phaeophyceae)
  • Kelp (Laminaria, Saccharina, Macrocystis) used in food products, fertilizers, and animal feed
  • Wakame (Undaria pinnatifida) consumed as a vegetable in soups and salads
  • Alginate (Ascophyllum nodosum, Laminaria hyperborea, Macrocystis pyrifera) serves as a thickening and stabilizing agent in food, textiles, and pharmaceuticals
• Green algae (Chlorophyta)
  • Sea lettuce (Ulva lactuca) used in salads, soups, and as a nutritional supplement
  • Chlorella (Chlorella vulgaris, Chlorella pyrenoidosa) used as a dietary supplement and in animal feed

Cultivation and harvesting of seaweeds

• Nori cultivation involves seeding nets or ropes with spores and suspending them in seawater, then harvesting mature blades
• Kelp cultivation uses longlines seeded with juvenile sporophytes suspended in seawater, harvested by cutting mature blades
• Carrageenan and alginate production through wild harvesting from natural seaweed beds or cultivation on nets, ropes, or rafts in seawater, harvested by hand or mechanically depending on the scale of operation

Properties and applications of marine algae

• Nutritional properties include being rich in vitamins (A, B, C, E, K), high in minerals (iodine, calcium, iron, magnesium), containing essential fatty acids (omega-3 and omega-6), and being a good source of dietary fiber
• Medicinal properties:
  1. Antioxidant compounds (polyphenols, carotenoids) have potential in preventing chronic diseases and cancer
  2. Antiviral and antibacterial properties show potential in treating infections and boosting the immune system
  3. Anti-inflammatory compounds (fucoidan, phlorotannins) demonstrate potential in treating arthritis and other inflammatory conditions

Management of marine algal resources

• Challenges include overharvesting of wild seaweed populations, habitat degradation due to pollution and coastal development, climate change impacts on seaweed growth and distribution, and invasive species competing with native seaweeds
• Opportunities:
  • Sustainable cultivation practices such as integrated multi-trophic aquaculture (IMTA) and offshore and land-based seaweed farming
  • Ecosystem services provided by seaweed beds include carbon sequestration, nutrient cycling, and habitat provision for marine life
  • Development of new products and applications in areas like biofuels and bioplastics, wastewater treatment and bioremediation, and animal feed and agricultural fertilizers