Community structure of hermatypic corals at Layson Island and Lisianski Island/Neva Shoal in the Northwestern Hawaiian Islands: a new layer of scientific exploration

Abstract

The distribution and abundance of scleractinian corals at Laysan Island and Lisianski Island/Neva Shoal in the Northwestern Hawaiian Islands were determined by georeferenced towed-diver surveys that covered more than 56,000 m2 of benthic habitat and site-specific surveys at 33 sites during 2000 2004. Three complementary methods (towed-diver surveys, videotransects, and photoquadrats) were used to quantify percent cover of corals by genus or species at each bank and determine relative abundance. Colony counts within belt transects at fixed sites were used to assess colony density and size-class distribution. Significant differences were found between the two banks at comparable depths (7-18 m) in percent coral cover, relative abundance of the three primary genera (Porites, Montipora, and Pocillopora), and size class distributions of these genera. The coral community at Lisianski/Neva Shoal was characterized by higher percent cover, higher colony density, and a tendency towards larger colonies than the coral community at Laysan. Porites was the dominant genus at both locations, but the relative abundance of Pocillopora and Montipora differed between the banks, with Pocillopora more common at Laysan than at Lisianski/Neva Shoal, and Montipora more common at Lisiansksi/Neva Shoal than at Laysan. Notable differences were also found in the distribution of the three primary genera at the two banks. These demographic data are discussed in the context of the known history of exposure of these remote reefs to salient factors influencing the condition of coral communities including marine debris, bleaching, and disease. They provide a detailed baseline of the composition of these shallow-water communities in the early years of the 21st century that will serve as a comparative benchmark for examining long-term change. _____________________________ 1Joint Institute for Marine and Atmospheric Research and NOAA Pacific Islands Fisheries Science Center, 1125B Ala Moana Blvd., Honolulu, HI 96814 USA, Email: Jean.Kenyon@noaa.gov 2Hawaii Institute of Marine Biology, P.O. Box 1346, Kaneohe, HI 96744 USA 3 3University of Hawaii, 200 3Kawili St., Hilo, HI 96720 USA Manuscript received 23 October 2007; revised 09 November 2007.