Meeting Abstract
Tropical island ecosystems and their human residents depend on the multiple stable-state reef community that provides food, protection from storms and income via tourism. Worldwide, overfishing and eutrophication via urbanization of nearby lands have led to record losses of coral dominated reefs. On so-called urban reefs, impacts of eutrophication push algal growth rates above rates of herbivore grazing. In most cases, few grazers or their guilds are left. Such appears to be the case for the Waikīkī reef region, where the marine plant community is dominated by the invasive species Acanthophora spicifera, Avrainvillea amadelpha, and Gracilaria salicornia. In an effort to identify ways to restore this reef to a better balance, feeding preferences of the native urchin Tripneustes gratilla were examined to establish feeding preferences on native vs. introduced seaweeds found in the Waikīkī region. Urchins were placed in tanks with continuous flow and offered a pair-wise combination of a native and an invasive algal species over a 24 hour period at the Anuenue Fisheries Research Center. In total, 15 urchins were used and three replicate runs were conducted between Oct. 25th and Nov. 15th, 2014. In most cases, the urchins grazed the invasive species A. spicifera and G. salicornia more readily than native species with the exception of native Microdictyon setchellianum and Gracilaria cornopifolia. Future work will include caging experiments in areas of mixed plant assemblages to test the outcomes of our previous studies. Such tests are important to validate the use of urchins as biocontrol agents for regions with mixed native and invasive algal assemblages.
