Collaborative Research: The Chemical Ecology of Shallow-water Marine Macroalgae and Invertebrates on the Antarctic Peninsula

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0125152Amsler/Baker/McClintockThe benthic marine ecosystem near Palmer Station, Antarctica provides an excellent site for the study of the function and evolution of chemical defenses in marine organisms. Antarctica is unique in that sea stars and other invertebrates are the major predators on benthic animals. Sea stars are quite different from other, biting predators because they often feed by extruding their cardiac stomach over their prey for external digestion. This feeding pattern should be a particularly strong selective force for surface-sequestration of chemical defenses, especially in Antarctica where sea stars are the major sponge predator and biting spongivores are relatively uncommon. Antarctic sea stars are slow moving predators that feed on individual sponges for long periods of time and can have patchy distributions. However, they are much larger than the small grazers thought to be important in inducing chemical defenses at lower latitudes. Previous studies by the investigators have established the presence and ecological role of secondary metabolites in a wide variety of sessile and sluggish antarctic marine invertebrates and in marine macroalgae. The current project focus on two sets of questions concerning the function and evolution of chemical defenses. First, the predictions of the Optimal Defense Theory and the Induced Defense Model of plant and animal chemical defenses will be tested. The former theory predicts that chemical defenses will be differentially sequestered in tissues that are most susceptible to predation. The latter theory predicts that such predators should select for inducible defenses and these Antarctic predator-prey relationships provide the opportunity to separate the issue of predator size from the basic predictions of the model. Second, the investigators propose to utilize the ecologically dominant members of the Antarctic Peninsula's rich macroalgal flora and the distinctive nutrient environment of coastal Antarctica to test predictions of multiple, interactive roles for secondary metabolites in brown macroalgae including predictions of the Induced Defense Model. An additional test will examine whether increased ultraviolet radiation in shallow water benthic communities caused by atmospheric ozone depletion might be affecting secondary metabolite production. Because of the dominance of these macroalgae in their communities, understanding factors that influence their trophic relationships are important for understanding community dynamics as a whole. The investigators plan to continue to vigorously pursue and foster opportunities to integrate their scientific research with a variety of educational activities, including supporting undergraduate, as well as graduate and postgraduate research; and science teachers through the NSF Teachers Experiencing Antarctica program.