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General Biology of Ascophyllum nodosum Ascophyllum
nodosum
is a Stramenopile. It generally grows upward in the
water column anchoring to hard substrates using a holdfast. Upward growth
promotes the maximum absorption of sunlight for photosynthesis (Lobban 1985).
Ascophyllum nodosum grows with an apical tip resulting in the newest
tissue being farthest from the holdfast, and the oldest tissue closest to
the hold fast. It gro Ascophyllum produces a noxious secondary chemical that is meant to repel herbivores that will damage the seaweed (Norton and Manley 1990; Norton et al. 1990; Williams and Seed; John et al. 1992). Ascophyllum also regularly sheds its epidermis to remove any unwanted organisms from the surface of the plant. This is a characteristic shared by Fucoids and is an important mechanism in controlling damage caused by epiphytes. Distribution in the Rocky Inter-tidal Ascophyllum nodosum is found at sites with low, moderate and high wave action. At Nahant, Massachusetts there is moderate wave action and Ascophyllum is found predominately in the mid to upper tidal heights. At this site there are a number of other seaweeds present that may compete with Ascophyllum for space. They include Fucus spiralis and Fucus vesiculosus which are found above the Ascophyllum zone, and Mastocarpus stellatus and Chondrus crispus which are found below the Ascophyllum zone (Vadas and Elner; John et al 1992). The upper limit is set by physiological factors such as air exposure, desiccation, or overheating. The lower limit is controlled by biological factors such as competition between seaweed species or predation of Ascophyllum gametes by marine organisms present in the lower inter-tidal (Knox, George 2001) .
Ecological Importance Ascophyllum
is a foundation
species in the rocky inter-tidal because it provides A variety of organisms including amphipods, isopods, crabs, and gastropods feed in the upper inter-tidal during high tide. These organisms migrate further up in the inter-tidal by using Ascophyllum to protect them from desiccation (Menge 1978; Hacker and Steneck 1990; John et al. 1985). Living on Ascophyllum is beneficial to many sessile organisms because it elevates them from the surface of the rocks increasing the flow water which supplies more oxygen and food. It also aids in the prompt removal of wastes (Williams & Seed; John et al. 1992). Invertebrates may use Ascophyllum, or other macro algae, to increase the survival and dispersal of off spring by laying egg masses directly on the algae (Williams & Seed; John et al. 1992). RELATED LINKS
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all year round, and has no resting period (Lobban 1985). In order to support a long and
continually growing stipe, Ascophyllum utilizes specialized gas
bladders called pnuematocysts that give buoyancy to the seaweed and keep
it lifted in the water column. These pnuematocysts are easily seen by the naked eye are a good indication of
the aproximate age of the
Ascophyllum stipe (Robertson pers. com.) The thalus of this seaweed is flexible to
decrease breakage that may result from strong wave action. 
organisms with a sturdy substrate to attach to. Ascophyllum also
provides protection from desiccation and predation. It has been
experimentally shown to reduce the temperature by 10 degrees Celsius on a
sunny day, increase humidity by 100% and decrease light intensity by 99% (Vadas and Elner; John
et al 1992).
In addition to habitat amelioration, Ascophyllum provides nutrients in the form of dissolved and particulate organic
carbon that supports detrivors and filter feeding organisms (Lobban, et al
1985).