Sea kelp
Sea kelp are large brown algae (seaweeds), classified in the taxonomic class Phaeophyceae and the order Laminariales. Distributed in nutrient-rich, shallow waters around the world, sea kelp are grouped into about 300 different genera. Some kelp species grow to 200 feet long, at rates of two feet per day, and exist in dense, ecologically important marine habitats known as kelp forests. Kelp is used in human diets, as dietary supplements, and as alternative treatments for medical conditions.
Habitat
Kelp inhabit clear shallow waters along rocky coastlines and are most successful in regions of nutrient upwellings--where cool, nutrient-rich bottom waters are brought to the surface during oceanic mixing-- or areas that are continuously high in nutrients and cold (42 to 72 degrees Fahrenheit). Because kelp require sunlight for photosynthesis, they live in shallow water (depths of six to 90 feet), where sunlight can still penetrate.
Unique Characteristics
Kelp use anchor-like structures called holdfasts to grip onto rocky substrates, rather than typical plant root systems. Kelp also have gas bladders called pneumatocysts to keep blades floating, allowing them to grow towards the water surface, where more sunlight can be harvested.
Life History
Sea kelp can be divided into two life history types, annuals and perennials. Annual species (e.g., bull kelp; Nereocystis leutkeana), complete their life cycle in one year. Perennial species (e.g., giant kelp; Macrocystis pyrifera), can live several years, with their lifespan primarily determined by environmental conditions. However, all kelp have a two-stage life cycle. Parent kelp (known as sporophytes) release millions of spores, which grow into small male and female plants called gametophytes. The male gametophytes produce sperm, which fertilize eggs produced by female gametophytes. Fertilized eggs develop into embryos and eventually grow into mature kelp (sporophytes).
Growth Rate
Sea kelp have tremendous growth rates, making them among the most productive plants in the plant kingdom. For example, giant kelp grow an average of 10 inches per day in the spring, but can grow to 200 feet long, at rates up to 2 feet per day.
Ecological Importance
Kelp forests are among the most biologically productive habitats in the marine environment and form tiered canopies within the ocean. Kelp forests provide vital habitat for a wide variety of invertebrates, fish, birds, and marine mammals, including many charismatic megafauna--California sea lions, harbor seals, sea otters and gray whales, among others--that feed in kelp forests and use them as a refuge from storms and predators.
Human Dietary Uses
According to whfood.com, some of the most popular forms of kelp for cuisine include Nori (used in making sushi rolls), Kelp flakes (used to season food, often as a salt substitute), Kombu (often used to flavor soups), and Wakame (used to make Japanese miso soup). Kelp contains the highest concentrations of iodine in nature and offer a rich supply of important dietary minerals, including magnesium, calcium, iron, and others. Kelp is used as a natural supplement for promoting healthy thyroid function and as an alternative remedy for treating goiters. Kelp also contains phytonutrients called lignans, which are thought to help decrease the risk of breast cancer. In addition, kelp contains significant amounts of the B-vitamin folic acid, which is thought to reduce the risk for colon cancer.
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