Honors Thesis Defense, Prisca Lim

Survey of epiphytic microalgae to evaluate risk of ciguatera fish poisoning across natural and artificial reefs in North Carolina

Epiphytic microalgae are important contributors to the carbon and nutrient cycles, yet are often overlooked during ecological surveys. In reef habitats, epiphytes are often found living on host organisms, including seaweeds or corals, and can influence community composition of higher trophic level taxa. Hence, understanding how epiphytes respond to different reef substrate materials can help inform artificial reef designs that encourage high biodiversity and ecological functioning. One such epiphyte, Gambierdiscus spp., is a harmful benthic dinoflagellate which produces toxins that bioaccumulate and cause ciguatera fish poisoning (CFP) when contaminated fish is consumed by humans. CFP is one of the most frequently reported seafood-associated illness around the world, occurring most often near tropical reefs. Given that rising sea temperature is predicted to expand the range and abundance of Gambierdiscus spp., we investigated the prevalence of Gambierdiscus spp. among artificial reefs of different materials located off the coast of North Carolina through field observations and ex situ experiments. Although no Gambierdiscus spp. were detected among the sampled reefs, experimental results indicated that Gambierdiscus spp. grew fastest in the presence of marl and density decreased significantly when exposed to steel. However, steel artificial reefs had the highest average epiphyte biomass and species richness. 18s rRNA analysis revealed that natural reefs were more likely to be dominated by dinoflagellates, whereas steel and concrete reefs were dominated by diatoms. These findings suggest that CFP risk is relatively low on the reefs studied but natural reefs would likely be preferentially colonized by Gambierdiscus spp. should temperatures become appropriate.