Spatial variation in polyphenolic content of Ascophyllum nodosum (Fucales,Phaeophyta)

Spatial variation in polyphenolic content in annual shoots of the brown alga Ascophyllum nodosum was quantified using a hierarchical sampling design. Three sampling levels, covering distances of 10⁰–10⁶ m, were used. Comparisons were made between two areas, Tjärnö on the Swedish west-coast and the Isle of Man in the Irish Sea, with very different types of environmental conditions. No significant differences in mean polyphenolic levels were found between the two study areas (6.6% of dry mass at Tjärnö and 9.2% at the Isle of Man), whereas significant and substantial differences were found among sites within areas (range 5.7%–11.4%) and among quadrats within sites (range 3.7%–13.1 %). The extensive variation at the smaller spatial scales points out the importance of using thorough sampling procedures at all levels in large-scale studies on algal polyphenolics, e.g. biogeographical comparisons, which have been neglected in several previous studies. Moreover, the results imply that experiments on causal factors of polyphenolic variation should be designed to explain the spatial scales on which the factors are impportant. This study also investigated the relationship between polyphenolic concentration and both plant size and mean area of annual shoots. The mean area was used as an estimate of the mean growth rate of the annual shoots within an individual. No significant relationships were found between shoot growth rate, or plant size, and polyphenolic levels in annual shoots at any of the three spatial scales that were investigated.