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Scuba Science 10 & 11- Chemical Ecology on Coral Reefs...& Chemical Ecology of Marine Macroalgae...

Valerie J. Paul and Raphael Ritson-Williams Smithsonian Marine Station at Fort Pierce bio Natural products can mediate behavioral and ecological interactions among many different species in tropical reef habitats, and several examples of chemically mediated interactions will be presented. Phyllidiid nudibranchs have contrasting color patterns that are thought to be a defensive mechanism, even though their colors make these nudibranchs obvious to visual predators. Feeding assays were conducted on Guam to determine if color patterns and chemical defenses could deter fish separately or in combination. Extracts and four different color patterns significantly deterred fish feeding. Several species of Phyllidia were extracted and tested for chemical defense against predators. While some species consistently deterred predatory fishes in field assays, others did not. The phyllidiid nudibranchs provide a fascinating example of aposematic (warning) coloration. Algal species that have proliferated in reef habitats often contain natural products that deter generalist herbivores. On reefs in Guam and Belize, we determined the palatability of common macroalgae to reef fishes. In Belize, we also studied the feeding preferences of the sea urchin Diadema antillarum. Some macroalgae and cyanobacteria were not eaten by generalist herbivores and are chemically defended. Due to the macroalgal dominance observed on reefs today, competitive interactions between corals and macroalgae are a topic of great interest. Research has shown that adult corals are good competitors with macroalgae, but it is at the early life-history stages, as larvae and new recruits, that corals are thought to be inferior competitors. Some macroalgae and cyanobacteria, as well as extracts of these species, caused either recruitment inhibition or avoidance behavior in coral larvae. On reefs experiencing increased algal abundance, the restocking of coral populations may be slowed due to recruitment inhibition caused by algal natural products. James B. McClintock1, Charles D. Amsler1, and William J. Baker2 1University of Alabama at Birmingham 2University of South Florida bio Fourteen years ago we presented the first survey of the chemical and ecological bioactivity of Antarctic shallow-water marine invertebrates. In essence, we reported that despite theoretical predictions to the contrary the incidence of chemical defenses among sessile and sluggish Antarctic marine invertebrates were widespread. Since that time we and others have greatly expanded upon the knowledge base of Antarctic marine chemical ecology, both from the perspective of examining new distinct geographic regions, including macroalgae which dominate shallow-water communities along the Antarctic Peninsula, as well as broadening the evaluation of the functional and ecological significance of secondary metabolites. Importantly, many of these studies have been framed within established theoretical constructs, particularly the Optimal Defense Theory (ODT). In the present seminar, we provide an overview of the chemical ecology of macroalgae and benthic marine invertebrates that comprise communities along the Antarctic Peninsula, a region of Antarctica that is in many respects both physically and biologically distinct from the rest of the continent.
Length: 32:13


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