Variations in the alginate content and composition of Durvillaea antarctica and D-willana from southern New Zealand

The brown seaweeds Durvillaea antarctica and D. willana are dominant compon ents of the lower littoral and upper sublittoral of exposed rocky shores in southern New Zealand. Tissue samples of both species, harvested from a sit e on the south-east coast of South Island over a period of 2 years, were an alysed for alginate content and composition. Individuals of both species we re further separated into different blade (lamina and palm) and stipe (cort ex and medulla) fractions to assess variation within the thallus. On averag e the alginate content and frequency of mannuronic acid (F-m) was higher in D. antarctica than in D. willana. Blades contained more alginate than stip es, laminae and stipes were rich in mannuronic acid whereas holdfasts were rich in guluronic acid. Variations in composition are considered to reflect the functional differences of the tissue, giving flexibility to blade and stipe and rigidity to the holdfast. Despite fluctuations in content and com position between collection times no seasonal trends in either component we re apparent.