Characterizing epiphytic macroalgae assemblages in understudied Hawaiian mangrove stands

Abstract

The introduction of Rhizophora mangle, red mangrove, to the Hawaiian Islands has created a rare opportunity to investigate the characteristics of the species that assemble within a novel ecosystem. In this thesis, I investigate the effects of mangrove invasion on macroalgal biodiversity by addressing the following questions:

Are the macroalgal assemblages within Hawaiian mangrove forests primarily comprised of localized or more broadly distributed species? Does the introduction of R. mangle to Hawai’i create macroalgal assemblages and richness similar to native mangrove forests?

With the help of the Sherwood Algal Biodiversity Lab, I used morphological and molecular analysis (DNA barcoding) to conduct the most extensive survey of the macroalgal epiphytes of Hawaiian mangrove forests to date. I identified 28 distinct taxa of epiphytic macroalgae within the mangrove forests on the islands of O’ahu and Molokai. The introduction of R. mangle to Hawai’i appears to have dramatically altered the macroalgal composition of the Hawaiian intertidal zone, promoting the dominance of invasive and broadly distributed species. The low rate of endemism and generally cosmopolitan taxa identified in this study suggest that relatively few endemic macroalgae species can tolerate the conditions generated by R. mangle invasion. Hawaiian mangrove stands also appear to support relatively high macroalgal richness and a unique composition of macroalgal taxa compared to native mangrove forests. The novel ecosystem and community of organisms formed by Hawaiian mangrove invasion add to our understanding of how the introduction of new species can affect local biodiversity.