Deep-sea Photographs Research Articles

Notes on cephalopods photographed near the bottom in the Clipperton-Clarion Fracture Zone

Deep-sea photographs from IFREMER dives in the Clipperton-Clarion Fracture Zone included six cephalopods. These are all cirrate (=finned) octopods in two families, Opisthoteuthidae and Cirroteuthidae.

‘Lophenteropneust’ hypothesis refuted by collection and photos of new deep-sea hemichordates

The deep ocean is home to a group of broad-collared hemichordates--the so-called 'lophenteropneusts'--that have been photographed gliding on the sea floor but have not previously been collected. It has been claimed that these worms have collar tentacles and blend morphological features of the two main hemichordate body plans, namely the tentacle-less enteropneusts and the tentacle-bearing pterobranchs. Consequently, lophenteropneusts have been invoked as missing links to suggest that the former evolved into the latter. The most significant aspect of the lophenteropneust hypothesis is its prediction that the fundamental body plan within a basal phylum of deuterostomes was enteropneust-like. The assumption of such an ancestral state influences ideas about the evolution of the vertebrates from the invertebrates. Here we report on the first collected specimen of a broad-collared, deep-sea enteropneust and describe it as a new family, genus and species. The collar, although disproportionately broad, lacks tentacles. In addition, we find no evidence of tentacles in the available deep-sea photographs (published and unpublished) of broad-collared enteropneusts, including those formerly designated as lophenteropneusts. Thus, the lophenteropneust hypothesis was based on misinterpretation of deep-sea photographs of low quality and should no longer be used to support the idea that the enteropneust body plan is basal within the phylum Hemichordata.

Charles Davis Hollister, 1936-1999 A personal scientific appreciation of the father of 'contourites'

Abstract The untimely death of Charley Hollister in a climbing accident robbed the contourite community of the principal originator and proponent of the concept of deep-ocean current-controlled sedimentation. He possessed boundless enthusiasm, a strong belief that science should be and was fun, a wonderful ability to get disparate groups of people to work together and a fine capacity to see connections between varied strands of data. The latter ability in particular allowed him as a graduate student at Lamont Geological Observatory in the 1960s to put together physical oceanography from Georg Wust, early seismic profiler results from the Ewings, deep-sea photographs, stratigraphic and sedimentological data from cores with his supervisor Bruce Heezen, and develop the notion of sedimentation controlled by deep geostrophic flows. Charley was born into a landed Californian family whose fortunes were founded on cattle ranching. Eschewing the role of sedate conformity and leadership normally reserved for elder sons, his boyhood was, by his own account (thoroughly confirmed by his family), happily irresponsible. His schooling was chequered and his undergraduate academic performance at Oregon State University undistinguished. However, although his best developed abilities were as a marksman and mountaineer, late in the day the spark of what he really wanted to do struck. Doc Ewing, director of Lamont was persuaded that Charley's enthusiasm once channelled, could lead to a successful career as a marine geologist and admitted him to the graduate programme in 1960. In the late 1950s ideas about the deep circulation developed rapidly with Wust's (1955) recalculation

Impact of benthic disturbance on megafauna in Central Indian Basin

Abstract Deep-sea photographs and video data were studied to evaluate the effects of benthic disturbance on megafaunal distribution in the Central Indian Basin. Xenophyophores (41%) and holothurians (30%) are the most abundant taxa, followed by other groups in the area before the disturbance. An overall reduction (32%) in the total megafaunal population after disturbance is direct evidence of the impact on benthic environment. Different groups such as xenophyophores, sea anemones, shrimps, starfish, brittle stars, holothurians and fish show different degrees of reduction (21–48%) in their numbers, depending upon their ability to withstand increased turbidity and sedimentation rates due to disturbance. Faunal groups such as protobranch molluscs, polychaete worms, seafans and squids, observed before the disturbance, were not seen after disturbance, whereas populations of some taxa increased after the disturbance. Increased numbers of mobile taxa could be due to increased levels of organic carbon due to resedimentation, whereas increase in sessile taxa may partly reflect the difficulty in distinguishing live from dead specimens. The impact on faunal assemblages is more severe in the disturbed area than the undisturbed area. Our results indicate that monitoring of megafauna can be used effectively to evaluate the potential impacts of large-scale mining or other disturbance on the seafloor, and may therefore help in developing measures for conservation of the benthic environment.

Volcanic Morphology of the East Pacific Rise Crest 9°49′–52′: Implications for volcanic emplacement processes at fast-spreading mid-ocean ridges

Deep sea photographs were collected for several camera-tow transects along and across the axis at the East Pacific Rise crest between 9°49′ and 9°52′ N, covering terrain out to 2 km from the ridge axis. The objective of the surveys was to utilize fine-scale morphology and imagery of seafloor volcanic terrain to aid in interpreting eruptive history and lava emplacement processes along this fast-spreading mid-ocean ridge. The area surveyed corresponds to the region over which seismic layer 2A, believed to correspond to the extrusive oceanic layer, attains full thickness (Christeson et al., 1994a, b, 1996; Hooft et al., 1996; Carbotte et al., 1997). The photographic data are used to identify the different eruptive styles occurring along the ridge crest, map the distribution of the different morphologies, constrain the relative proportions of the three main morphologies and discuss the implications of these results. Morphologic distributions of lava for the area investigated are 66% lobate lava, 20% sheet lava, 10% pillow lava, and 4% transitional morphologies between the other three main types. There are variations in inferred relative lava ages among the different morphological types that do not conform to a simple increase in age versus distance relationship from the spreading axis, suggesting a model in which off-axis transport and volcanism contribute to the accumulation of the extrusive layer. Analysis of the data suggests this ridge crest has experienced three distinctly different types of volcanic emplacement processes: (1) axial summit eruptions within a ∼1 km wide zone centered on the axial summit collapse trough (ASCT); (2) off-axis transport of lava erupted at or near the ASCT through channelized surface flows; and (3) off-axis eruptions and local constructional volcanism at distances of ∼0.5-1.5 km from the axis. Major element analyses of basaltic glasses from lavas collected by Alvin, rock corer and dredging in this area indicate that the most recent magmatic event associated with the present ASCT erupted relatively homogeneous and mafic (>8.25 weight percent wt.% MgO) basalts compared to older, off-axis lavas which tend to be more chemically evolved (Perfit and Chadwick, 1998; Perfit and Fornari, unpublished data). The more primitive lavas have a more extensive distribution within and east of the ASCT. More evolved basalts (MgO ∼500 m from the ASCT suggests that regions of off-axis volcanism may be sourced from older and cooler sections of the axial magma lens. Analysis of these data suggests that this portion of the EPR has not experienced large scale volcanic overprinting in the past ∼30 ka. The predominance of lobate flows (66%) throughout much of the crestal region, and subtle variations in sediment cover and apparent age between flows, suggest that eruptive volumes and effusion rates of individual eruptions have been similar over much of the last 30 ka and that most of the eruptions have been small, probably similar in volume to the 1991 EPR flow which had an estimated volume of ∼1×106 m3 (Gregg et al., 1996).

Photographic evidence of variable bottom-current activity in the Suruga and Sagami Bays, central Japan

Complex patterns of bottom-current behaviour were clarified by studies of sedimentary features and orientations of benthic animals in the deep Suruga and Sagami Bays on the Pacific side of central Honshu, Japan. Both the Suruga and Sagami Bay measure about 60 km in length as well as in width at their mouths and are about 1500 m deep in their central portions. The size of each bay is comparable to that of ancient forearc basins. The bottom sediments are characterized by turbidites and slump deposits. At 32 stations on the bottom of the bays, deep-sea photographs were taken, most of which clearly indicate bottom-current activity. Current-induced bottom features are current-lineations, moat-like scours around resistant objects, crag-and-tail structures behind obstacles, ripple marks, sand ridges and deformed biogenic structures such as burrows, mounds, tracks and faeces. These features are produced by bottom currents with rather high velocities. Other important current indicators are some benthic organisms, which in general show a sensitive response to currents and adopt particular orientations. Typical examples of megabenthos identified in the bottom photographs as effective current indicators are the small deimatid holothurian Peniagone japonica, the benthic shrimp Glyphocrangon hastacauda, sea anemones, and sea pens. Among them, the orientation of Peniagone japonica shows abrupt changes of current direction with time, for example, from N (0°) to SW (240°) during 15 min and from N to S and back to N, a complete rotation during 40 min. The results of these observations indicate that the bottom currents in deep bays tend to fluctuate rapidly in velocity and direction, probably owing to strong internal tidal waves in the very steep embayments. Upslope currents appear to be present at the mouths of submarine canyons. Thus, it should be borne in mind that palaeocurrent analysis of ancient bottom-current deposits or contourites is limited in application.

Contemporary sedimentary processes in the Monterey Canyon-fan system

A study of the Monterey Canyon and fan was conducted to investigate contemporary sedimentary activity using a camera sled, Alvin dives and Sea-Beam bathymetry. Physical characteristics and plan view morphology of the walls, terraces, thalweg floor and levees of the Monterey Canyon and fan, as well as the gullied and non-gullied regions of the adjacent continental slope have been studied. The canyon floor and fan valley thalweg channel from 2900 to 3500 m exhibited properties indicative of moderate to low energy conditions (weak currents, smoothed sea-bed, deposits of disintegrated kelp, bioturbated mud substrate, fecal pellets, absence of scour). Chemosynthetic communities consisting of clams and a pogonophoran, were found in the fan valley from 3000 to 3600 m. Local areas of rockfalls and slumps from the canyon and fan valley walls were not fresh (sedimented, abundantly colonized by benthic biota). Terraces and levee crests were mud-draped and bedrock exposures on canyon walls were encrusted by benthic organisms. Freshest disturbances were found in gullies on the adjacent continental slope where bedrock was scoured clean of sediment and loose debris. A major submarine slide detached from escarpments on the lower slope, and extends across the fan. The slide surface was mud-draped, hummocky, and contained bedforms with wavelengths up to 150 m and up to 10 m relief. The survey was conducted shortly before the Loma Prieta earthquake (October 17, 1989) that caused substantial ground motion in on-shore regions of Monterey Bay. Any substantial sub-sea disturbances generated by the ensuing earthquake should be discernable from the pre-earthquake state by comparison with the deep-sea photographs and observations.

Composition and spatial organization of a cold seep community on the South Barbados accretionary prism: Tectonic, geochemical and sedimentary context

Deep faunal assemblages were observed on cold seeps, between 1000 and 2000m depth, along the southern termination of the Barbados accretionary prism, during the Caracolante II and Diapicar cruises. Faunal composition and microdistribution of a cold seep community were analyzed at one site using deep-sea photographs and seismic (3.5 Kz) profiles. The community is dominated by large mussels up to 20cm long (possibly related to the genus Bathymodiolus), tiny vesicomyid clams, and vestimentiferan clusters in which animals are up to 2m long. There is a high density of sponges (three species), bryozoans and gorgonians. Other taxa occasionally associated with this assemblage include galatheid crabs, anemones, holothurians and possibly pennatulaceans which are numerous at boundaries of the site. A typical deep-sea fauna of fish, asteroids and ophiuroids is also scattered about the vicinity. This seep community is distributed as a band of discontinuous colonies, 40–50m in width and more than 10km in length. Living colonies alternate with accumulations shells and bare areas. The substratum is hard mud covered by a ferrugineous crust and cemented by carbonates. The early diagenetic character of the bottom and the occurrence of biological assemblages indicate that seepages of sulphur and/or methane, which have been revealed along the decollement zone of the Barbados prism, must diffuse through the sea floor. These biological and geological features are located on the crests of NE-SW anticlinal ridges and mud volcanoes which have been built by diaprism.

Deep-sea photographs of the northwestern and central Pacific Ocean: an invitation to deep-sea environment: Fujioka, Kantaro, Masaharu Watanabe and Kazuo Kobayashi, 1989. Bull. Ocean Res. Inst. Univ. Tokyo, 27:214pp

Deep-sea photographs of the northwestern and central Pacific Ocean: an invitation to deep-sea environment: Fujioka, Kantaro, Masaharu Watanabe and Kazuo Kobayashi, 1989. Bull. Ocean Res. Inst. Univ. Tokyo, 27:214pp

The use of a Canadian (perspective) grid in deep-sea photography

The construction and characteristics of a Canadian (perspective) grid as applicable for oblique deep-sea photographs are described. The implementation of such a grid through an automated digitizing system allow fast accurate and precise calculations of sizes and densities of animals and other objects. Changes in the camera's inclination due to “nose up” or “nose down” motion over rough topography can cause erroneous calculations of size. The magnitude of this error increases quasi-exponentially with distance of objects from the lower edge of the image and is particularly large for camera systems with a small angle of inclination. The area in a photograph from which accurate counts can be taken, should be determined a posteriori for each type of object (e.g. species), based on a plot of density vs distance from the camera.

Mapping of hemipelagic versus turbiditic muds by feeding traces observed in deep-sea photographs

Summary The Madeira Abyssal Plain is composed mainly of turbiditic sediments derived from the NW African margin. Through this cover project hills covered with draped pelagic sediments. The surface layers of both sediment types are similar with respect to grain size and mineralogy. Similarly, there is no difference in the distribution of pelagic organisms living in the overlying waters. The foraging behaviour of benthic communities on each sediment type is markedly different, however, so that sediment type can be determined from this parameter alone. It is suggested that the potentially richer food supply available at depth within the turbidites has produced the differences observed.

THE SUPERGIANT AMPHIPOD ALICELLA GIGANTEA CHEVREUX FROM THE NORTH PACIFIC GYRE

Recent collections from the central North Pacific provide evidence that the mysterious supergiant amphipod seen in deep-sea photographs from the North Pacific (Hessler et al., 1972) is Alicella gigantea. These specimens confirm that Alicella gigantea is the only known amphipod from the Pacific that has the same appearance and reaches the size of the supergiant amphipod reported by Hessler et al. (1972). The supergiant specimens from the Pacific differ morphologically in two ways from the Atlantic specimens, heretofore based on two individuals described in 1899. These taxonomic differences, which appear to be due to changes associated with maturation, are described and a key to Atlantic and Pacific specimens is provided. Various aspects of the natural history of A. gigantea are discussed from the results of our morphological analyses and from unpublished observations.

Ichnology of Neritic Turbidite: Silurian Red Mountain Formation, Georgia and Tennessee: ABSTRACT

It has recently been shown by others that two thousand units in the Red Mountain Formation are relatively shallow-water turbidites, water depth roughly 100 to 300 ft (30 to 91 m). The turbidites, probably storm-generated, consist of alternating sandstones and shales in fining-upward sequences with scoured bases; the lower turbidite grades upward into hummocky bedded alternating sandstones and shales. Biogenic structures are dominated by Chondrites gracilis, C. flexuosus, and Trichophycus striatus, which occur through most of the units. Others include Dictyodora, Asterosoma, Planolites spp., ?Megagrapton, as yet unnamed radiating grazing trails, and rare Fraena, Aulichnites, Monocraterion, Halopoa, and ?Bifungites. The traces are preserved largely as sandstone hypichnia, h nce most were the work of mud-dwellers. Deposit-feeding evidently predominated over suspension-feeding; ?Megagrapton is an example of a bacteria-farming network. The ethology of Trichophycus is uncertain; the burrow was partly a dwelling structure but may have been the work of a deposit-feeder, suspension-feeder, or carnivore. Stellate forms of Trichophycus are perhaps analogous to circular patterns of burrow apertures seen in deep-sea photographs. The assemblage is a mixture of genera from Cruziana (shelf) and Zoophycos (slope) ichnofacies, as might be expected in a neritic turbidite. Without recently published stratigraphic evidence, the units could be misinterpreted as bathyal turbidites. End_of_Article - Last_Page 979------------

Feeding Posture of Modern Stalked Crinoids

MOST modern crinoids (Echinodermata) are comatulids, which lack the stalk characteristic of Palaeozoic crinoids. The specialisation and adaptation to different ecological niches made possible by loss of the stalk have resulted in several different ways of spreading the arms and pinnules in an array for suspension feeding. Until the 1960s, most observations were based on specimens in aquaria. These suggested that the comatulids sit on the substratum with the mouth orientated upwards, the arms stretched out in the form of a broad funnel or collecting bowl. The crinoid was thought to wait passively for a rain of its food material from above1. This feeding posture is used by some deep water crinoids2,3. Direct observations of the feeding behaviour of a shallow water comatulid in the Red Sea during the 1960s demonstrated that the arms are withdrawn during the day, but at night are arrayed in a vertical plane to form a filtration fan. This fan is orientated perpendicular to a prevailing weak current, filtering some 40,000 1 of water at a current speed of 2 cm s−1 during one period of activity4. These observations and a review of deep-sea photographs indicated that modern crinoids favour an environment with moderate currents and are to some degree current-seeking (rheophilic)5. Application of these ideas to the palaeocology of Palaeozoic stalked crinoids suggested that most were rheophilic, using the stalk to raise the calyx above the substratum and allowing the arms to be outspread in a planar, circular filtration fan2. The morphology of some ancient forms, however, was considered indicative of a rheophobic mode of life.

Deep Sea Photographs of an Active Seismic Fault Zone near Gibraltar Straits

IN October 1969, the RV Jean Charcot made a geophysical survey of the Horseshoe seamount and abyssal plain west of Gibraltar Straits and south-west of Cape Saint-Vincent, Portugal; this is the eastern end of the Azores–Gibraltar seismic zone1 which is a compressive plate boundary2,3. During this survey a series of deep-sea photographs were obtained near the location of the last major earthquake of February 28, 1969 (magnitude 7.3 to 8.0, location 36.0° N 10.6° W according to the USCGS preliminary report).

Fracture Orientations near Great Abaco Fault

Compass-oriented deep-sea bottom photographs taken on the Blake Escarpment near Great Abaco Canyon reveal that the outcropping Cretaceous limestone is broken by several fracture sets. Three distinguishable trends of what are assumed to be vertical fractures are found. One trending N. 55° W., which corresponds to the strike of Great Abaco fault; another trending N. 25° E., which corresponds to the strike of the prominent linear magnetic anomaly along Blake Escarpment off Great Abaco Island; and a third trend of N. 60° E., which is thought to be a second order shear fracture related to the movements along the first two trends.