Topography, substratum and benthic macrofaunal relationships on a tropical mesophotic shelf margin, central Great Barrier Reef, Australia

Habitats and ecological communities occurring in the mesophotic region of the central Great Barrier Reef (GBR), Australia, were investigated using autonomous underwater vehicle (AUV) from 51 to 145 m. High-resolution multibeam bathymetry of the outer-shelf at Hydrographers Passage in the central GBR revealed submerged linear reefs with tops at 50, 55, 80, 90, 100 and 130 m separated by flat, sandy inter-reefal areas punctuated by limestone pinnacles. Cluster analysis of AUV images yielded five distinct site groups based on their benthic macrofauna, with rugosity and the presence of limestone reef identified as the most significant abiotic factors explaining the distribution of macrofaunal communities. Reef-associated macrofaunal communities occurred in three distinct depth zones: (1) a shallow (75 m). The effects of depth and microhabitat topography on irradiance most likely play a critical role in controlling vertical zonation on reef substrates. The lower depth limits of zooxanthellate corals are significantly shallower than that observed in many other mesophotic coral ecosystems. This may be a result of resuspension of sediments from the sand sheets by strong currents and/or a consequence of cold water upwelling

The Great Barrier Reef margin revealed: implications for deep-water biodiversity distribution

We present new high-resolution multibeam bathymetry datasets from the Great Barrier Reef (GBR) margin. Analysis of these data, combined with sub-bottom profiles and rock dredge samples, provides a fresh insight into the detailed morphology and spatial distribution of GBR margin geomorphic features to 2000 metres depth. The multibeam and seismic data reveal a spectacular network of submarine canyons, slump scars and landslide deposits on the continental slope and upper basin. These data provide a unique insight into the fundamental processes that have shaped the evolution of the GBR margin. Numerous V-shaped canyons incise the slope suggesting active erosion is taking place. Tension cracks and smaller feeder canyons around the heads of the canyons are observed in about 250 m. The canyons often terminate in the Queensland Trough as slide scarps and debris fields where progressive upslope erosion has reduced the stability of the parent margin sediments. We also investigated a cluster of eight knolls in the Queensland Trough up to two km long and over 100 m high in depths of about 1100 m. Sub-bottom profiles across the knolls reveal they are discrete, seismically-opaque blocks capped by about 15 m of soft sediments. A rock dredge recovered evidence of a cold-water coral community, comprising abundant live and dead colonial corals, barnacles, gastropods and manganese-coated concretions, within a matrix of muddy carbonate sediment. These findings suggest the blocks may have broken off the GBR margin as catastrophic landslides, moving down the lower slope and coming to rest in the basin where they now form a habitat for a deep, cold-water coral community. These new observations reveal a diverse picture of the deep margin of the GBR, which will provide important baseline seabed physical data as proxies for benthic habitats and biodiversity distribution in the GBR World Heritage Area (GBRWHA). In particular, slope gradient variation, surficial sediment distribution and any active sedimentation pathways are likely to be important controlling factors in the habitat relationships with assemblages of deep-water biodiversity. Post-cruise analyses of the marine geophysical, geological and biological data will now focus on precise age dating and quantitative analysis of samples, and sedimentary facies and geomorphic mapping to provide new information about the spatial relationships between seabed physical data and deep-water benthic habitats of the GBRWHA

The Tasmantid Seamounts: Window Into the Structural Inheritance of Ocean Floor Fabric

The extinct Tasman Sea spreading centre, active from 84-53Ma, is intersected at a number of locations by the Tasmantid Seamount Chain. The chain, which extends for over 2000km off the east coast of Australia, progressively increases in age from south to north with ages ranging between 6Ma and ~50Ma. While thick sediment ~1,km) obscures much of the northern Tasman Sea basement, detailed morphological and geophysical analyses of the seamounts reveal a strong correlation between tectonic setting, seamount orientation, and volcanicstructure, despite the 20Ma offset between spreading cessation and initial seamount emplacement. Morphologically, structural inheritance is evidenced by the contrast between two volcanic styles: 1) the rugged, predominantly fissure-fed, fabrics characterizing seamounts emplaced at inside corners of spreading segment-transform intersections; and 2) the conical seamounts with summit craters and isolated dyke-fed flank cones that develop off-axis.Furthermore, volcanic fabrics align closely with the principal stress directions expected for a spreading ridge system in which strong mechanical coupling occurs across transform faults. This suggests that the lithosphere is dissected by numerous deep faults, allowing magma to be channelled away from the site of melting along pre-existing structural trends. The generally low effective elastic thickness, Te (<15 km) and lack of a plate age-Te relationship along the chain indicate that structural inheritance is also the major control on lithospheric strength near the extinct spreading centre. While the importance of structural inheritance in controlling magmatic behaviour is commonly acknowledged in continental settings, these results clearly demonstrate the need to also consider it in the oceanic realm

The Tasmantid Seamounts: Window Into the Structural Inheritance of Ocean Floor Fabric

The extinct Tasman Sea spreading centre, active from 84-53Ma, is intersected at a number of locations by the Tasmantid Seamount Chain. The chain, which extends for over 2000km off the east coast of Australia, progressively increases in age from south to north with ages ranging between 6Ma and ~50Ma. While thick sediment ~1,km) obscures much of the northern Tasman Sea basement, detailed morphological and geophysical analyses of the seamounts reveal a strong correlation between tectonic setting, seamount orientation, and volcanicstructure, despite the 20Ma offset between spreading cessation and initial seamount emplacement. Morphologically, structural inheritance is evidenced by the contrast between two volcanic styles: 1) the rugged, predominantly fissure-fed, fabrics characterizing seamounts emplaced at inside corners of spreading segment-transform intersections; and 2) the conical seamounts with summit craters and isolated dyke-fed flank cones that develop off-axis.Furthermore, volcanic fabrics align closely with the principal stress directions expected for a spreading ridge system in which strong mechanical coupling occurs across transform faults. This suggests that the lithosphere is dissected by numerous deep faults, allowing magma to be channelled away from the site of melting along pre-existing structural trends. The generally low effective elastic thickness, Te (<15 km) and lack of a plate age-Te relationship along the chain indicate that structural inheritance is also the major control on lithospheric strength near the extinct spreading centre. While the importance of structural inheritance in controlling magmatic behaviour is commonly acknowledged in continental settings, these results clearly demonstrate the need to also consider it in the oceanic realm

Mesophotic coral ecosystems on the walls of Coral Sea atolls

A research cruise was undertaken in October 2010 to explore potential mesophotic coral communities (30–150 m) in the recently established Coral Sea Conservation Zone (CSCZ). The CSCZ covers an area of almost one million square kilometres east of the Great Barrier Reef (Australia), with its reefs and atolls located hundreds of kilometres from the nearest landmass and surrounded by deep oceanic water. Three of the atolls in the CSCZ (West Holmes Reef [16.243°S, 147.874°E], East Holmes Reef [16.459°S, 148.024°E] and Flora Reef [16.755°S, 147.738°E]) were assessed using SCUBA and a Seabotix ROV. Shallow reef areas (<30 m) consisted largely of bare substrate with predominantly juvenile corals and very low coral cover due to past cyclone damage and thermal bleaching events. In contrast, the steep walls in 40–100 m depth were covered by extensive Halimeda curtains (Fig. 1a), which harboured diverse scleractinian coral communities, including Acropora, Astreopora, Fungia, Galaxea, Goniastrea, Porites, Mycedium (Fig. 1c), Seriatopora and Turbinaria spp., with Pachyseris (Fig. 1d), Leptoseris and Montipora spp. recorded to 102 m depth. At least one of the collected specimens represents a new species record for Australia: Echino- morpha nishihirai (Fig. 1b). Diverse communities of azooxanthellate octocorals were also observed to 150 m, the maximum depth of the ROV. These observations confirm the presence of mesophotic coral ecosystems (MCEs) along the walls of Coral Sea atolls and indicate that MCEs may form extensive features in the CSCZ. The deep-water coral communities may play an important role in the recovery of shallow reef areas on these isolated atolls by functioning as refugia from the repeated disturbances that have affected these reefs

Predicting habitat preferences for Anthometrina adriani (Echinodermata) on the East Antarctic continental shelf

The comatulid crinoid Anthometrina adriani is well represented among the suspension-feeding megaepibenthos from the continental shelf of the Dumont D'Urville Sea, Antarctica. Nearly 500 specimens were sampled during the Collaborative East Antarctic Marine Census expedition onboard the RV 'Aurora Australis' (December 2007 to January 2008), from 50 of the 87 stations over a 400 km2 area. Abiotic environmental factors were measured and an ocean circulation model was used to generate near-bottom parameters. The ecological niche of A. adriani was described by using ecological-niche factor analysis and Mahalanobis distances factor analysis. An environmental suitability map (ESM) was developed to map the optimal habitat. A. adriani prefers moderately deep and relatively cold waters with moderate current velocity, and a substrate with low gravel content and biogenic carbonate. The ESM shows 4 optimal regions: the eastern side of the George V Basin, the eastern side of the Adélie Basin, the southern part of the Adélie Bank, and the coastal area between the Astrolabe and Mertz glaciers. The ecological niche for A. adriani appears very narrow, but the species is widely distributed across the Antarctic shelf. It suggests that local changes in limiting factors have a strong local effect on the distribution of this species and that a total eradication of this species from the shelf would need an Antarctic-wide and synchronic change in these essential parameters. Modeling modifications in environmental conditions under different climate change scenarios could help predict the effect of such changes on the distribution of this selective species

Issues in Modeling Repeat Leisure Consumption: Markov Modeling Examples

Models should be used to facilitate understanding structure in data. This article is about using models that are adequate approximations to reality if models are used. A theory and research context for Markov modeling is given for repeat holiday travel and the examination of destination loyalty. A simple Markov model based on the literature and an expanded state space Markov model based on repeat travel related concepts in the literature are presented. Analysis of travel to Turkey from the UK and to the USA from Australia, Japan and the UK confirms Oppermann's (1998a) claim that simple Markov models result in a poor approximation to reality. It is shown that expanded state space models can accommodate realism. Models producing hypothetical behavior or behavior that mirrors reality are discussed both generally and regarding repeat travel, specifically. Application of the ideas and methods presented to leisure research on matters other than travel is discussed

Cutaneous Nocardia asteroides infection of nontraumatic origin Infecção cutânea de origem não traumática por Nocardia asteroides

This paper reports a case of cutaneous infection of nontraumatic origin caused by Nocardia asteroides in a hospitalized patient with chronic obstructive pulmonary disease. Diagnosis was established by direct and histological examination, cultures from exudate and biopsy specimen. We discuss the classification of clinical forms of Nocardia infections affecting the skin.<br>É relatado um caso de infecção cutânea de origem não traumática por Nocardia asteroides em paciente hospitalizado com doença broncopulmonar obstrutiva crônica. O diagnóstico foi feito pelo exame direto e histológico e culturas do exsudato e fragmento de biópsia. É discutida a classificação das formas clínicas das infecções por Nocardia que afetam a pele