Kelp is a type of brown seaweed or algae that grows in regions of the world with cold coastlines. There are different sorts of kelp including: true kelp, giant kelp, and bladder kelp. Kelp is in the order Laminariales and it is debated whether kelp should be classified with Chromista or Protista. They usually grow from holdfasts that anchor to rocky surfaces and the plants themselves are very long, slimy, and have blade-like leaves that branch off the central root or core body.
The body is called the thallus, which runs from top to bottom and has branches growing off of it. The stipes are the stem-like configurations that make up the blade-like leaves. There is a root-like structure called the holdfast that helps fasten the kelp to the ocean floor. The blades contain gas-filled bladders called pneumatocysts, which enable them to float close to the surface of the water to receive more sunlight for photosynthesis.
A strange thing about kelp is that they have a heteromorphic alteration of generations, so the two generations look and develop differently. This means there can be a diploid sporophyte generation of large leafy plants, which constructs spores that become microscopic haploid gametophytes, creating male and female microscopic plants. These microscopic plants on the seafloor fertilize to give rise to the leafy sporophytes. The spores grow in the sori located on the blades, right next to some special blades called sporophylls that are at the foundation of the plant. These in turn latch on to the stipes directly atop the holdfast. One adult by itself can produce numerous sporophylls, with each sporophyll containing billions of minuscule spores.
Kelp usually grow in really cold environments and are able to withstand the harsh and unforgiving sea. It can stay where it first grew or move with the ocean's flow. Kelp forests, just like regular forests on land, have their own seasons or time periods when they undergo extra growth and other changes. Kelp habitat, the areas where the kelp lives, is determined by physical factors such as nutrients, warm or cool temperatures of ocean currents, and occurrences of storms. The Giant kelp's standard of living needs to be met, so it needs a hard base to grow on which is close enough to the surface for sunlight. They also demand an area that has high concentration of nutrients, not too much water motion, with cool, clean, and clear water for first-rate growth. It mainly grows on the west coasts of North and South America, South Africa and Australia. 
Different Uses of Kelp
There are many different uses of kelp for everything from soaps to glass production. They can be used as a thickening agent in ice cream, jelly, salad dressing, toothpaste, and many more things produced by man. Kelp is very popular among many herbalists, and naturopathic applications because of its high, varied mineral content. It has been known to heal, prevent, and help many ailments and illnesses, being grown in Japan for this starting from the eighteenth century. Some of the food recipes where kelp is used include soups, salads, beans, snacks, garnishes, sushi, and broth. 
- Kelp Encyclopedia of Alternative Medicine information about kelp on Answers.com. Encyclopedia of Alternative Medicine Copyright © 2005 by The Gale Group, Inc. Published by The Gale Group, Inc.
- Kelp Wikipedia information about kelp on Answers.com. Wikipedia Copyright © 2007 by Wikipedia. Published by Wikipedia.
- 'KelpWatch' by University of Tasmania
- Kelp Recipes by Vestula Hall