Geographical Variation in the Effects of Brown Algal Secondary Metabolites on Temperate Marine Herbivores

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This research builds on previous findings that qualitative and quantitative differences exist in the secondary metabolites produced by kelp-like plants between the temperate northeast and southwest Pacific regions. The purpose of the research is to: 1) further document variation in the levels and kinds of secondary chemicals among large brown algae from California and New Zealand, and 2) determine behavioral and long term responses of selected marine plant-eating invertebrates to these compounds. Extensive collections will be made from both areas to document variation in concentrations of polyphenolic and lipophilic compounds among the common brown algal species; among individuals and tissues within species; and through time in detached plants. Feeding preferences of common sea urchins and snails from both regions will be tested for the effects of these secondary compounds by measuring variation in consumption rate. Physiological influences of secondary metabolites on various plant-eating invertebrates will be evaluated by measuring absorption efficiencies, growth rates, and gonadal development among experimental treatments in which the kinds and levels of secondary metabolites are varied. Hypothetically interactions between algae and the animals which consume them will differ among these regions in two important ways: 1) the amount and diversity of chemical defenses in New Zealand algae will be greater than in California species; and 2) the algae eaters in New Zealand will be more tolerant of polyphenolics than will similar algal consuming invertebrates from California. Overall, the mechanisms which mediate transfer of energy from the algae which are the dominant primary producers on temperate rocky shores to the invertebrates which consume them are predicted to vary greatly on a biogeographical scale.