THE BEGINNINGS OF ANTARCTIC MACROALGAL CHEMICAL ECOLOGY: DEFENSES AGAINST HERBIVORES IN A NITROGEN REPLETE, CARBON LIMITED OCEAN

• Published in: Journal of Phycology
• Format: Article in Journal/Newspaper
• Language: English
• Published: Wiley 2001
• Subjects: Alabama; Antarctic; Antarctic Peninsula; Iken; McClintock; Antarc*
• Online Access: http://dx.doi.org/10.1111/j.1529-8817.2001.jpy37303-4.x; https://api.wiley.com/onlinelibrary/tdm/v1/articles/10.1111%2Fj.1529-8817.2001.jpy37303-4.x; https://onlinelibrary.wiley.com/doi/pdf/10.1111/j.1529-8817.2001.jpy37303-4.x

Amsler, C. D. 1 , Iken, K. B. 1 , McClintock, J. B. 1 , Furrow, F. B. 2 , & Baker, B. J. 2 1 Department of Biology, University of Alabama at Birmingham, Birmingham AL 35294‐1170 USA; 2 Department of Chemistry, Florida Institute of Technology, Melbourne, FL 32901 USA We examined palatability of Antarctic Peninsula macroalgae in feeding bioassays with three common, sympatric macroalgal‐consuming omnivores (amphipod, fish, sea star). Antarctic macroalgae have low C:N ratios, high nitrogen contents, and are usually growth limited by carbon (light). The Carbon Nutrient Balance Hypothesis (CNBH) predicts that macroalgae would produce nitrogenous secondary metabolites for defense rather than high levels of non‐nitrogenous defenses under these conditions. To date, feeding bioassays have been performed on fragments of thallus from 26 macroalgal species and 21 (81%) were rejected by at least one omnivore. Organic extracts from 13 macroalgal species rejected as thallus were used in feeding bioassays. At least one extract from 12 species (92%) was rejected by at least one omnivore, suggesting that chemical defenses against herbivores probably are present in at least some of the macroalgal species. We have identified a number of specific, non‐nitrogenous secondary metabolites in these extracts and previous workers have also reported non‐nitrogenous secondary metabolites from antarctic macroalgae. Additional extracts targeting nitrogenous metabolites from 25 species were subjected to thin layer chromatography and visualized by stains specific for nitrogenous compounds. No nitrogenous secondary metabolites were identified by this or other methods. Nitrogenous secondary metabolites are also extremely rare in macroalgae from other areas of the world. Consequently, although our bioassays suggest that chemical defenses probably do occur, our data cast doubt on the applicability of the CNBH for predicting the chemical composition of macroalgal defenses under carbon limited conditions. (NSF OPP9814538, OPP9901076)