Geographic variation in polyphenolic levels of Northeastern Pacific kelps and rockweeds

Brown algal polyphenolic compounds are secondary metabolites whose function s may include protecting plants from pathogens or damage by UV radiation, a nd deterring feeding by herbivores. We present here the first analysis of s patial variation (at scales from tens of meters to hundreds of kilometers) in concentration of these compounds in two orders of brown algae from the n ortheastern Pacific Ocean. In kelps (order Laminariales), variation among s ites was significant in only 25% of species examined and was consistent wit hin families thigh in the Alariaceae and low in the Laminariaceae and Lesso niaceae). In rockweeds (order Fucales, family Fucaceae), site variation was high in three of four species examined. Both the proportion of high polyph enolic kelp species and the magnitude of spatial variation within species f rom both kelps and rockweeds were much higher than would have been predicte d from previous studies in other regions. In one kelp (Laminaria groenlandi ca), significant differences between sites occurred at scales of only tens of meters, No latitudinal dines were observed. Differences in phenolic conc entrations of kelps spanned nearly an order of magnitude in one species, He dophyllum sessile. Phenolic levels were significantly higher in members of the Fucales than the Laminariales, but showed no significant differences be tween intertidal and subtidal species.