Seaweed is considered any of the red, green or brown marine algae. They need seawater or at least brackish water and enough light for photo synthesis. They have blades (leaf like structures) where photosynthesis takes place. Stipes (stem like structure but does not transport nutrients like land plants) main function is support of the blades, floats that to keep blades near the surface close to light, and a holdfast a basal structure to attach to a surface.

Kelp is one of the photosynthetic brown algae. Photosynthesis is the use of captured energy in sunlight to convert water into hydrogen t hat is combined with carbon dioxide to produce food with oxygen being a byproduct. Nutrients are supplied by the moving water passing the kelp. Water flowing by the blades mixing is increased by the Kelp blades’ serrated edges resulting in more nutrients passing the kelp plant. All parts of the kelp participate in absorbing these nutrients. Tiny floats, pneumatocysts, keep the blades near the surface closest to sunlight allowing photosynthesis to occur. Both top and bottom surfaces of the blades perform photosynthesis.

Seaweeds are foraged for food and medicinal purposes. Also for the extraction of the hydrocolloids alginate, agar and carrageenan, used in the food industry for their gelling, water retention, emulsifying properties and preservation proper ties. Seaweeds are also used as fertilizer, compost or to combat beach erosion by burying it in beach dunes. It is used in toothpaste, cosmetics and paints as well.