Flowing with the Tide:Epiphytic Host-Specificity and Phenotypic Plasticity of the Brown Alga Padina boryana

Epiphytic algae form complex communities on their macroalgae hosts. The brown algaPadina boryanaacts as a host for epiphytic algal communities, yet no studies have determined whether the community is host-specific. To test for epiphytic host-specificity, four substrates were placed in Cook’s Bay for a three-week period and examined for epiphytic communities. My findings demonstrate that there is host-specificity and that substrate may influence the construction of epiphytic communities.In addition to hosting epiphytes,P. boryanaexhibits phenotypic plasticity – it adopts different morphs in response to environmental conditions. In order to understand howP. boryanaresponds to its environment, I observed where the distinct morphs occurred and attempted a transplant experiment to induce morph change. Furthermore, I compared the epiphytic communities on both morphs. My results support the hypothesis that the foliose morph occurs in shallower waters, while the turf morph is present in deeper water. These results provide evidence thatP. boryanautilizes its phenotypic plasticity as a defense mechanism against predators. Moreover, the morphs affect the epiphytic communities that colonizeP. boryana, substantiating the findings that substrate texture plays a role in the establishment of epiphytic communities