Meeting Abstract
P1.36 Thursday, Jan. 3 Sea Urchin Herbivory in Hawaiian Shallow Water Ecosystems: Echinothrix as Allies with Tripneustes JESSOP, H.*; TAKABAYASHI, M.; DEMAINTENON, M.J.; BARNETT, C.; OLSON, N.; University of Hawai’i at Hilo; University of Hawai’i at Hilo; University of Hawai’i at Hilo; University of Hawai’i at Hilo; University of Hawai’i at Hilo hollyjessop@yahoo.com
A great deal of research has already been done to investigate sea urchin herbivory in Hawai�i, particularly focusing on the species Tripneustes gratilla. This work has demonstrated that T. gratilla urchins are important grazers on Hawaiian coral reefs, helping to prevent overgrowth of algae and also significantly consuming invasive algal species that have become problematic in Hawai�i. However, sea urchins of the genus Echinothrix co-exist with T. gratilla and are also prevalent on Hawaiian reefs, but as yet they�ve been relatively little studied. We have initiated studies of Hawaiian Echinothrix herbivory by conducting laboratory feeding trials and ecological field surveys, with a focus on elucidating interspecific ecological differences between T. gratilla and Echinothrix, and with a goal of assessing their comparative potential grazing impacts on invasive algal populations. Our experimental data support the hypothesis that T. gratilla and Echinothrix species exhibit similar feeding rates on the Hawaiian invasive algae Gracilaria salicornia, under no-choice experimental conditions. Additionally, our field surveys documenting urchin abundances and distribution patterns reveal habitat partitioning between Echinothrix species and T. gratilla. With grazing rates that are significant and similar, and with differences in spatial distributions on reefs, our results suggest that Echinothrix species may be important allies with T. gratilla in the control of both native and invasive algae in Hawai`i. These results should be useful to conservation managers working to understand and prevent coral reef degradation and macroalgal phase shifts in Hawai�i.
