Аскофиллум узловатый: описание и распространение

Species of seaweed

Ascophyllum nodosum is a large, common cold water seaweed or brown alga (Phaeophyceae) in the family Fucaceae. Its common names include knotted wrack, egg wrack, feamainn bhuí, rockweed, knotted kelp and Norwegian kelp. It grows only in the northern Atlantic Ocean, along the north western coast of Europe (from the White Sea to Portugal) including east Greenland and the north eastern coast of North America. Its range further south of these latitudes is limited by warmer ocean waters. It dominates the intertidal zone. Ascophyllum nodosum has been used numerous times in scientific research and has even been found to benefit humans through consumption.

Ascophyllum nodosum is the only species in the genus Ascophyllum. The original name (basionym) was Fucus nodosus Linnaeus 1753. The species was transferred to the genus Ascophyllum (as Ascophylla) by Stackhouse (Papenfuss 1950), under the name Ascophyllum laevigata (Guiry and Guiry 2020). The combination Ascophyllum nodosum was made by Le Jolis (1863).

Ascophyllum nodosum has long tough and leathery fronds, irregularly dichotomously branched fronds with large, egg shaped air bladders set in series at regular intervals along the fronds and not stalked. The air bladders create a way for fronds broken by wave exposure or other causes to be dispersed and regrow in other areas. While the fronds can reach up to 2 m, the length depends on wave exposure: the length increases with water velocity until a certain point, then decreases as waves become more intense. olive brown in color and somewhat compressed, but without a midrib.

Each individual plant is dioecious, either male or female. A year after the plant is fertilized and forms a zygote, the first frond grows, and at the beginning of year 2, an air bladder forms, which creates a way to age the plants. Free floating forms of this species are found in, for example, A. n. mackaii Cotton, which is found at very sheltered locations, such as at the heads of sea lochs in Scotland and Ireland.

Ascophyllum nodosum is found mostly on sheltered sites on shores in the midlittoral, where it can become the dominant species in the littoral zone. It may take approximately five years before becoming fertile. Ascophyllum nodosum is an autotroph, meaning that it makes its own food by photosynthesis, like other plants and algae. The air bladders on A. nodosum serve as a flotation device, which allows sunlight to reach the plant better, aiding photosynthesis. Polysiphonia lanosa (L.) T. A. Christensen is a small red alga, commonly found growing in dense tufts on Ascophyllum whose rhizoids penetrate the host. It is considered by some as parasitic; however, as it only receives structural support from knotted wrack (not parasitically), it acts as an epiphyte.

This species has been recorded in Europe from Ireland, the White Sea, the Faroe Islands, Norway, Britain and Isle of Man, Netherlands, and North America from the Bay of Fundy, Nova Scotia, Baffin Island, Hudson Strait, Labrador, and Newfoundland.