ALBERT

Beschreibung: Author Posting. © The Oceanography Society, 2012. This article is posted here by permission of The Oceanography Society for personal use, not for redistribution. The definitive version was published in Oceanography 25, no. 1 (2012): 62–77, doi:10.5670/oceanog.2012.04.

Beschreibung: The Lau Integrated Study Site (ISS) has provided unique opportunities for study of ridge processes because of its back-arc setting in the southwestern Pacific. Its location allows study of a biogeographical province distinct from those of eastern Pacific and mid-Atlantic ridges, and crustal compositions along the ridge lie outside the range of mid-ocean ridge crustal compositions. The Lau ISS is located above a subduction zone, at an oblique angle. The underlying mantle receives water and other elements derived from the downgoing lithospheric slab, with an increase in slab influence from north to south. Water lowers the mantle melting temperature and leads to greater melt production where the water flux is greater, and to distinctive regional-scale gradients along the ridge. There are deeper faulted axial valleys with basaltic volcanism in the north and inflated axial highs with andesites in the south. Differences in igneous rock composition and release of magmatic volatiles affect compositions of vent fluids and deposits. Differences in vent fluid compositions and small-scale diffuse-flow regimes correlate with regional-scale patterns in microbial and megafaunal distributions. The interdisciplinary research effort at the Lau ISS has successfully identified linkages between subsurface processes and deep-sea biological communities, from mantle to microbe to megafauna.

Beschreibung: Support was provided by National Science Foundation grants OCE-1038135 to MKT, OCE-0732369 and OCE-0240985 to CRF, OCE-0732369 and OCE-0838107 to PRG, OCE-0242618 to CHL, OCE-0242902 and OCE-0752256 to PJM, OCE-0728391 and OCE-0937404 to A-LR, and a GRFP to RB.

Beschreibung: Author Posting. © The Oceanography Society, 2012. This article is posted here by permission of The Oceanography Society for personal use, not for redistribution. The definitive version was published in Oceanography 25, no. 1 (2012): 234–245, doi:10.5670/oceanog.2012.22.

Beschreibung: Diffuse-flow, low-temperature areas near hydrothermal vents support life via chemosynthesis: hydrogen sulfide (and other reduced chemical compounds) emanating from the subsurface is oxidized with bottom-water oxygen through bacterial mediation to fix carbon dioxide and produce biomass. This article reviews the in situ diffuse-flow chemistry (mainly H2S and O2) and temperature data collected in 2006 and 2009 along the Eastern Lau Spreading Center (ELSC), and from 2004 to 2008 at 9°N along the East Pacific Rise (9 N EPR), predominantly around macrofauna that contain endosymbionts at these two hydrothermal vent regions. More than 48,000 and 20,000 distinct chemical and temperature data points were collected with a multi-analyte electrochemical analyzer in the diffuse-flow waters at 9 N EPR and the ELSC, respectively. Despite their different geological settings and different macrofauna (two different species of snails and mussels at the ELSC versus two different species of tubeworms and mussels at 9 N EPR), there are similarities in the temperature and chemistry data, as well as in the distributions of organisms. The pattern of water chemistry preferred by the provannid snails (Alviniconcha spp., Ifremeria nautilei) and Bathymodiolus brevior at the ELSC is similar to the water chemistry pattern found for the siboglinid tubeworms (Tevnia jerichonana, Riftia pachyptila) and the Bathymodiolus thermophilus mussels at 9 N EPR. The eruptions at 9 N EPR in 2005 and 2006 resulted in increased H2S concentrations, increased H2S/T ratios, and an initial change in the dominant tubeworm species from Riftia pachyptila to Tevnia jerichonana after the eruption created new vent habitats. In 2005, two sites at 9 N EPR showed major increases in the H2S/T ratio from 2004, which suggested a probable eruption in this basalt-dominated system. At the ELSC, there was a decrease in the H2S/T ratio from northern to southern sites, which reflects the change in geological setting from basalt to andesite and the shallower water depths at the southern sites.

Beschreibung: This work was supported by NSF grants OCE-0240896, OCE-073243 (ELSC), OCE-0308398 (OTIC), OCE-0326434, and OCE-0937324 (EPR) to GWL; ESI-0087679, OCE-9529819, and OCE-0327353 to RAL; OCE-0327261, OCE-0328117, OCE-0451983 to TMS; and OCE 0240985 and OCE 0732333 to CRF.