Seaweed is usually used as a loose term for different algae that live in the sea or brackish water. They can be grouped into three types: Green, brown and red.
Overall there are around 10,000 species of seaweeds. Roughly 6,000 are red algae, 1,200 greens and 1,750 browns.
Reds and browns are usually found in the sea, whilst green algae are also common to brackish water. All contain the light absorbing pigment chlorophyll, which is essential for photosynthesis.
Seaweeds are usually found close to the shore and then more frequently in rocky areas rather than sand or shingle. They are important ecologically as they cover polar and temperate regions as well as the shores of most oceans.
In some oceans with clear waters they are found to depths of 250m and several miles out to sea. The availability of sunlight limits the extent to which they can survive from shore.
Seaweed in Fertilizers
Seaweed has been used for centuries in coastal regions to supplement nutrients in plants.
Fertilizers with seaweed contain the trace elements magnesium, nitrogen potassium, zinc and iron. Nitrogen is required for the production of nitrate, which is a vital component needed by plants during photosynthesis.
Many people now brew organic tea from seaweed for use as a fertilizer.
Other uses for seaweed
Seaweed is used in medicine and also in industrial products as diverse as explosives, dyes and paper coatings.
Probably the most well known use of seaweed in food is in Asian cooking. It serves as a wrap for sushi and as a healthy addition to a multitude of recipes.
Lesser known uses are that compounds extracted from seaweed are added to gel and stabilise certain types of foods, pharmaceuticals and cosmetics. Alginates from brown seaweed are beneficial to a variety of water-based products, including stabilisation during extreme differences in temperature, time and pH. They are used in ice-cream manufacture, to prevent ice crystals forming, and for brewing some German beers to name but two.