Description:
Plants with olive or yellow-brown fronds to 4 m long and 25 cm wide, more often about 1 m and 7.5 cm wide. Attached by a root-like hold fast at the base from which a narrow flexible stipe arises which continues into the leafy part of the plant as a distinct mid-rib, generally with a yellow-brown colour. The reproductive structures, apparent as dark-brown areas, are confined to unbranched leafy appendages borne on the stipe, usually in two rows.
Habitat:
Generally growing on rock in wave-exposed places, often forming a band at low water and in the shallow sub tidal, but also occurring in tidal pools in the lower shore.
Distinguishing features:
In Alaria, the midrib is more or less terete (circular in cross section), is usually a lighter colour, and the reproductive structures are borne at the base of the frond in special leaflets called sporophylls.
Usage:
Used in the past in both Scotland and Ireland for human consumption, fodder and also as a fertiliser on infertile land. More recently, it has become of economic interest as a foodstuff in aquaculture for herbivorous mollusks, urchins, shrimp and fish (Nakagawa et al. 1997). Contains up to 42% alginic acid (Lewallen & Lewallen 1996).
