The Knotted wrack is a common brown algae. Its scientific classification is Ascophyllum nodosum. It is a fairly large seaweed. It is a member of the Fucaceae family. It is the only member in its genus. It grows in the northern Atlantic ocean and off the north western coast of Europe including Greenland. There are several alternative names for this plant include knotted kelp, egg wrack and Norwegian kelp.
The Knotted wrack has long fronds with large leaves that are divided. They have long air bladders that are egg shaped. This are located at regular intervals on the fronds. They have no stalks. The fronds are about two millimeters in length. The fronds are attached by root like structures that act as anchors for aquatic plants. These are called holdfasts. These holdfasts can hold onto rocks and and boulders. The fronds are an olive brown and they have a slightly compressed appearance with no mid rib. The female and male organs form on different individual plants.
The life history is one of the diploid (meaning having two homologous or similar copies of each chromosome) and gametes (fused cells). The gametes are produced in conceptacles or cavities of marine and freshwater algae that contain the reproductive organs. They are embedded in receptacles that have short branches and are yellowish in color.
Periwinkles, along with other lifeforms, will munch on the Knotted wrack for a free lunch.
There are several varieties of the Knotted wrack. They grow on sheltered sites on shorelines and can become a dominant species. They are fond of areas that are protected from waves but still have access to water.They almost always grow in sheltered habitats such as estuaries An estuary is a partially enclosed body of water that has one free runway into the sea and one or more streams and rivers running into it. They can also grow in coasts that are moderately exposed. They are rare in open exposed areas and if they do grow there they are usually scraggly and stunted with very little stability. The life span of the Knotted wrack is usually ten to fifteen years. The Knotted wrack is a very invasive plant and in parts of California it had to be eradicated to prevent it from destroying other species of plant life. This seaweed is said to be the best known and most studied species of seaweed in the scientific community.