Community Structure of Benthic Invertebrates on Necker Ridge in the North Pacific

In shallow water the Hawaiian Archipelago is one of the most isolated archipelagos in the world, but at depth it may be connected to the vastly understudied seamount-rich region of the central and western Pacific by Necker Ridge, an elongated seamount approximately 600 km west of Honolulu. We hypothesize that if Necker Ridge has acted as a conduit for larval dispersal to and from the Hawaiian Archipelago and the Mid-Pacific Mountains, then similar fauna should be found on Necker Ridge as in Hawaii. During explorations of Necker Ridge using the Pisces IV submersible in 2011, HD video transects were taken and voucher samples were collected for morphological identifications and genetic determination of species identifications. The Ridge was characterized by hard substrates and strong currents and was dominated by suspension feeders, including corals, sponges, and crinoids. The north and south pinnacles on the ridge demonstrate significantly different community structures (p < 0.001), with the northern sites heavily dominated by corals while the southern sites are dominated by two species of crinoid. Morphological data shows few differences between species found on Necker and in Hawaii, but preliminary genetic data shows 34% of octocoral samples have sequences unique to Necker Ridge. These data so far suggest that Necker Ridge does not have a strong overlap in community structure with the Hawaiian Archipelago.