PRELIMINARY RESULTS ON SECONDARY METABOLITES FROM ANTARCTIC BROWN ALGAE AND THEIR ECOLOGICAL RELEVANCE

Abstract

Iken, K. 1, Amsler, C. D.1, Hubbard, J. M.2, McClintock, J. B.1, Baker, B. J.3 1University of Alabama at Birmingham, Dept. of Biology, Birmingham, AL 35294‐1170 USA 2Hanshew Middle School, 10121 Lake Otis Pkwy., Anchorage, AK 99507 USA; 3Dept. of Chemistry, Florida Institute of Technology, Melbourne, FL 32901 USABrown algae (Phaeophyceae) are often dominant members in abundance and biomass of Antarctic macroalgal communities. They are ecologically important in providing habitat structure and shelter to many invertebrates and fish. However, as live algae they often appear to be of little importance as food for herbivores. Palatability of thalli of eight abundant Antarctic brown algae was tested against two sympatric algal grazers, the fish Notothenia coriiceps and the sea star Odontaster validus. Polar and non‐polar organic extracts of six brown algae were also tested against these grazers and against the omnivorous amphipod Gondogeneia antarctica. Almost all thalli and at least one of the extract types per algal species were unpalatable to the grazers, suggesting that chemical defenses are probably present in Antarctic brown algae. We further tested biological activity of brown algal extracts in antimicrobial assays as well as antifouling assays with sympatric bacteria and diatoms, respectively. We chemically screened organic brown algal extracts for the occurrence of secondary metabolites. Acetogeno‐terpenes were detected in Desmarestia menziesii and D. anceps. Phlorotannins were present in all brown algal species analyzed, but at different concentrations between species as well as between different thallus parts within individuals. Phlorotannin extracts were size fractionated to examine distribution and abundance of various size classes between species as well as between different thallus parts within individuals.