Influence of wave action and latitute on morphology and standing crop of New ZealandDurvillaea antarctica(Chamisso) Hariot (Phaeophyta, Durvilleales)

Abstract

Variations in morphology and standing crop of New Zealand Durvillaea antarctica (Chamisso) Hariot are described quantitatively in relation to wave action and latitude. Distinct “thonged” (very strong wave action) and “cape” (moderate wave action) forms are recognised and described. Complete intergradation occurs, but the extent to which a population tends to one form is indicative of the wave forces predominating. Thonged-form plants show increases in overall length, stipe length and diameter, and degree of division and honeycomb development ofthe blade. Cape-form plants show a reduced overall length, stipe length and diameter, and degree of division and honeycombing of the blade. Where the impact force of waves is exceptionally strong plants may become stunted and lack development of a blade base. Generally the species is scarce where wave action is exceptionally strong or where conditions are calm. Regardless of other conditions prevailing the size of stipes increased with latitude. Water turbulence has a much greater influence on population density and standing crop than latitude. Highly or very highly turbulent areas have almost double the population density (22–30/m²) and standing crop (15.0–20.4 kg wet wt/m²) compared with moderately turbulent areas (l0.1–15.1/m²; 9.9–10.9 kg wet wt/m²).