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Ascophyllum Distribution Knotted Wrack Is

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Ascophyllum Distribution Knotted Wrack Is This is easily seen along the shoreline throughout Ascophyllum nodosum the year round. Class: Phaeophyceae common on Order: Fucales the shoreline all year round Family: Fucaceae Genus: Ascophyllum Distribution Knotted Wrack is seaweed It is common on the north-western coast of Europe (from of the northern Atlantic northern Norway to Portugal) as well as the east Greenland and extending as far north as the north-eastern coast of North America. It occurs in the Bay the Arctic Ocean. Its of Fundy, Nova Scotia, Prince Edward Island, Baffin Island, southern distribution Hudson Strait, Labrador and Newfoundland. It has been extends as far south as recorded as an accidental introduction to San Francisco, northern Portugal in the California, and as a potentially invasive species eradicated. east and New Jersey on the As well as Knotted Wrack it is known as Rockweed, Norwegian west side of the Atlantic. Kelp, Knotted Kelp, or Egg Wrack. Habitat The species attaches itself to rocks and stones in the middle of It is most abundant on the tidal region. It is found in a range of coastal habitats from sheltered rocky shores in sheltered estuaries to moderately exposed coasts. Often it the mid-intertidal zone (the dominates the inter-tidal zone. Sub-tidal populations are known area that is fully covered to exist in very clear waters such as those of Rhode Island, USA. and uncovered each day) However, an intertidal habitat is more usual. Reproduction Receptacles begin to develop in response to seasonal variations Knotted Wrack is in late spring and early summer. They are oval pods that are dioecious; each plant is initially flat and become inflated, changing from olive green to either male or female. The orange or dark brown. One or more receptacles become visible reproductive receptacles are on the main fronds in the fall. As they mature the sex can be on each separate plant. determined. Mature male receptacles have little orange dots (sperm masses); whereas females have green dots (egg masses). Development Receptacles grow larger by The zygote germinates rapidly, within ten days, putting out a spring. Gametes (eggs and primary rhizoid (root like filament). The tip exudes material sperm) are now ready to be which spreads out into an adhesive foot when contact is made released. Fertilization takes with a solid substrate. It penetrates microscopic crevices. A place externally and they holdfast or anchor is formed. Fronds grow upwards from this Become zygotes – fertilized solid attachment. Growth is year round with no resting period eggs. however the rate of growth varies seasonally. Characteristics The long fronds are flexible, thick and leathery. A number of fronds grow The large, sturdy, single bladders filled with air from each basal holdfast. in the middle of the fronds look like large knots They do not have a mid-rib. hence the name Knotted Wrack. Bladders keep Fronds, as they lengthen, plants suspended upright in the water during develop air bladders. These high tide. They hang downwards draping bladders are egg-shaped themselves over intertidal rocks in thick tangles and occur at regular during low tide. In areas where they are intervals. Fronds can reach abundant incoming tides gradually refloat large 2 metres in length and are groups of these plants creating an expansive olive-brown in colour. swaying undersea forest. Adaptations The species grows slowly and can live to be The large air bladders take decades old in wave-sheltered locations of it towards the light for temperate waters. It does have the capability maximum photosynthesis. to survive low temperatures. Rhizoid Frond flexibility decreases production continues for the life of the plan. possible breakage from These holdfasts (anchors) last for several strong wave action. years. In dense populations they frequently Individual fronds can last coalesce. Fronds which do break off from the 15 years before breakage base during storms form mats which float and the plant regenerates around on the surface. These can last for a new fronds from the base long time. A unique attribute to Ascophyllum is when one of the larger it repeatedly sloughs its entire outer epidermis fronds is damaged. (outermost layer of cells), a phenomenon not exhibited by other related seaweeds. Ecological Aspects It is an indicator of good All sorts of other seaweed species grow underneath knotted water quality. It provides wrack, species that without protection would normally dry out food, shelter, and spawning during ebbing water. In providing shelter for small marine habitat for a variety of animals these in turn provide a food source for animals, including small seabirds and shoreline birds. Large beds, in a crustaceans, juvenile sense becomes a marine habitat. mussels, snails, whelks, Biomass density in southwestern Nova Scotia is periwinkles, barnacles, among the highest in the world. It is harvested limpets, sponges, and fish. by individuals (as a fertilizer) and commercially. It is used to produce liquid fertilizers, soil Status/Threats conditioners, nutritional supplements, skin and Wave action is a major hair care products and for animal fodder etc. source of mortality to Permits are issued to commercial enterprises recently settled zygotes and to individuals. Strategies are in place to ensure environmentally safe and sustainable harvesting of this Sightings in Nova Scotia provincial resource. Harvesting techniques have reverted back It is very common in and from being mechanical to gathering by hand using cutting tools around Nova Scotian and rakes. A benefit to this is providing employment for Nova waters and shorelines. Scotians as well as being less destructive to the Knotted Wrack beds. Refer to the Fisheries and Coastal Resources Act .
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