1,680 research outputs found
Deep-water observation of scalloped hammerhead Sphyrna lewini in the western Indian Ocean off Tanzania
No full textA scalloped hammerhead Sphyrna lewini was observed opportunistically from a remotely operated vehicle 1 m off the seabed at 1042 m depth, during hydrocarbon exploration activities in the Ruvuma Basin off Tanzania. The observation, which occurred during night hours, is the deepest accurately recorded for this species and the first deep-water record for the Indian Ocean. The record adds support for the occurrence in deep water during night hours being a widespread and possibly common behaviour in this species, and further expands a small but growing literature that meso- and bathypelagic environments may be of greater importance to elasmobranchs previously considered to be primarily epipelagic
Recovery of benthic megafauna from anthropogenic disturbance at a hydrocarbon drilling well (380m depth in the Norwegian Sea)
No full textRecovery from disturbance in deep water is poorly understood, but as anthropogenic impacts increase in deeper water it is important to quantify the process. Exploratory hydrocarbon drilling causes physical disturbance, smothering the seabed near the well. Video transects obtained by remotely operated vehicles were used to assess the change in invertebrate megafaunal density and diversity caused by drilling a well at 380 m depth in the Norwegian Sea in 2006. Transects were carried out one day before drilling commenced and 27 days, 76 days, and three years later. A background survey, further from the well, was also carried out in 2009. Porifera (45% of observations) and Cnidaria (40%) dominated the megafauna. Porifera accounted for 94% of hard-substratum organisms and cnidarians (Pennatulacea) dominated on the soft sediment (78%). Twenty seven and 76 days after drilling commenced, drill cuttings were visible, extending over 100 m from the well. In this area there were low invertebrate megafaunal densities (0.08 and 0.10 individuals m?2) in comparison to pre-drill conditions (0.21 individuals m?2). Three years later the visible extent of the cuttings had reduced, reaching 60 m from the well. Within this area the megafaunal density (0.05 individuals m?2) was lower than pre-drill and reference transects (0.23 individuals m?2). There was a significant increase in total megafaunal invertebrate densities with both distance from drilling and time since drilling although no significant interaction. Beyond the visible disturbance there were similar megafaunal densities (0.14 individuals m?2) to pre-drilling and background surveys. Species richness, Shannon-Weiner diversity and multivariate techniques showed similar patterns to density. At this site the effects of exploratory drilling on megafaunal invertebrate density and diversity seem confined to the extent of the visible cuttings pile. However, elevated Barium concentration and reduced sediment grain size suggest persistence of disturbance for three years, with unclear consequences for other components of the benthic fauna
Techniques for monitoring the recovery of deep, cold-qater habitats following physical disturbance from drilling discharges
No full textRecovery of deep, cold-water benthic habitats following physical disturbance caused by discharges of cuttings and water-based mud (WBM) from drilling have been measured using Remotely Operated Vehicle (ROV) sampling techniques. Video data were collected from a well site in the Laggan field in the Faroe-Shetland channel immediately after discharge and again two years after discharge. Data were also collected on baseline conditions and from a nearby well site to provide data on recovery ten years after discharge. Faunal abundance and diversity parameters were quantified from the video and used to assess the community-level disturbance and recovery. Initial disturbance resulted in a reduction in faunal diversity and density from baseline levels close to drilling activity (<100 m). After two years and within 100 m of the drilling activity assemblages were still significantly different in composition and lower in diversity and density. Recovery was observed after ten years as increases in faunal density and diversity close to the site of previous drilling activity. In the area completely covered by cuttings (approx. 30 m radius), there were few megafauna observed in any survey. This work was carried out opportunistically as part of an environmental impact assessment and in stand-by time from a drilling rig. The use of existing technology in stand-by time provides oil and gas operators with opportunities to integrate routine environmental monitoring into normal operations providing a cost-effective and scientifically robust monitoring method
Blood Groups and Physiognomy of British Columbia Coastal Indians:
No full textby R. Ruggles Gates, and Geo. E. Darby.Reprinted from the Journal of the Royal Anthropological Institute, vol. LXIV, Jan.-June 1934
Changes in deep-water epibenthic megafaunal assemblages in relation to seabed slope on the Nigerian margin
No full textLocal-scale habitat heterogeneity associated with changes in slope is a ubiquitous feature of bathyal continental margins. The response of deep-sea species to high habitat heterogeneity is poorly known and slope can be used as a proxy for many important ecological variables, such as current flow, sedimentation and substratum type. This study determines how slope angle effects megafaunal species density and diversity at the Usan field, offshore Nigeria, between 740 and 760 m depth. This deep-water area is increasingly exploited for hydrocarbons, yet lacking in baseline biological information. Replicated remotely operated vehicle video transect surveys were carried out using industry infrastructure (through the SERPENT Project) at a representative range of slopes (1°, 3°, 11° and 29°). Twenty-four species of benthic megafaunal invertebrate were found, numerically dominated by the echinoid Phormosoma placenta, and nine species of fish were observed. Megafaunal invertebrate deposit feeder density decreased significantly with increasing slope (density range 0.503–0.081 individuals m−2). Densities of megafaunal suspension feeders were very low except at the highest slope site (mean density 0.17 m−2). Overall species richness was greater on steeper slopes, although the richness of deposit feeders was not affected. Reduced labile organic matter in sediments on steeper slopes likely reduced deposit feeder densities, but increased current flow at higher slopes allowed both increased richness and density of suspension feeders
Scalloped hammerhead
No full textSwimming at the seabed at >1000 m depthA scalloped hammerhead seen with a Remotely Operated Vehicle (ROV) at over 1000 m depth. At the time of publication this is the deepest record of this species. The observation is described in the SERPENT Project publication:
Alec B.M. Moore and Andrew R. Gates (2015). Deep-water observation of scalloped hammerhead Sphyrna lewini in the western Indian Ocean off Tanzania. Marine Biodiversity Records, 8, e91
http://dx.doi.org/10.1017/S175526721500062
Fish Food in the Deep Sea: Revisiting the Role of Large Food-Falls
No full textThe carcasses of large pelagic vertebrates that sink to the seafloor represent a bounty of food to the deep-sea benthos, but natural food-falls have been rarely observed. Here were report on the first observations of three large ‘fish-falls’ on the deep-sea floor: a whale shark (Rhincodon typus) and three mobulid rays (genus Mobula). These observations come from industrial remotely operated vehicle video surveys of the seafloor on the Angola continental margin. The carcasses supported moderate communities of scavenging fish (up to 50 individuals per carcass), mostly from the family Zoarcidae, which appeared to be resident on or around the remains. Based on a global dataset of scavenging rates, we estimate that the elasmobranch carcasses provided food for mobile scavengers over extended time periods from weeks to months. No evidence of whale-fall type communities was observed on or around the carcasses, with the exception of putative sulphide-oxidising bacterial mats that outlined one of the mobulid carcasses. Using best estimates of carcass mass, we calculate that the carcasses reported here represent an average supply of carbon to the local seafloor of 0.4 mg m−2d−1, equivalent to ~4% of the normal particulate organic carbon flux. Rapid flux of high-quality labile organic carbon in fish carcasses increases the transfer efficiency of the biological pump of carbon from the surface oceans to the deep sea. We postulate that these food-falls are the result of a local concentration of large marine vertebrates, linked to the high surface primary productivity in the study area
Observations of sedimentation near a hydrocarbon drilling site and impacts on a sponge specimen
No full textThe data consist of hourly observations of sedimentation impacts located approximately 31 m southwest of the drilling location, including measurements of proxies of suspended material in the water column, along with observations of the lamellate desmosponge specimen. Acoustic backscatter (1.9-2.0 MHz) and current speed were measured using a Seaguard RCM DW. A time-lapse camera was also deployed: the Nikon E995 camera was set to F 6.0, ISO 200, exposure 1/60, with photos of 2048 x 1536 pixels. As another estimate of suspended material in the water column, brightness (as mean RGB) was calculated for top corners (256 x 256 pixels) in photos, where the corners were not obscured by fish. Settlement of sediment on the sponge specimen was estimated as brightness of a portion of it (approximately 3600 pixels2) in the images. Movement of the sponge was estimated as the distance between successive xy-positions of the apex of the sponge in images. Mean values (6- and 12-hourly) centred on the hourly data, and sums of distance over 6- and 12-h periods were also calculated
Girders of Hydraulic Gates Optimal Design
No full textAbstractMetal gates of hydraulic structures are supplied with load bearing girders. Girders, crossbeams and gates require much steel when being manufactured. Girders of hydraulic gates rational design leads to considerable cost savings. The paper describes steel hydraulic girders optimal design. Steel hydraulic girders optimal design is based on the strength theory introduced by M. Huber, R. Mises, H. Hencky and on the theory of mirror functions. With the help of out-form volume we can either calculate the optimal form for a girder with variable cross-section or the optimal height for a girder of uniform cross-section. The paper introduces hydraulic girders calculations according to the authors’ methodology
Figure 5 in Behaviour and habitat of Neohela monstrosa (Boeck, 1861) (Amphipoda: Corophiida) in Norwegian Sea deep water
No full textFigure 5. Typical distribution of Neohela monstrosa burrows in a densely populated area. The photo from a video transect at station 301 at 1935 m depth shows ~15 burrows made by small (white arrows) and large (black arrows) individuals. Scale is indicated by two laser spots that are 10 cm apart.Published as part of Buhl-Mortensen, Lene, Tandberg, Anne Helene S., Buhl-Mortensen, Pål & Gates, Andrew R., 2015, Behaviour and habitat of Neohela monstrosa (Boeck, 1861) (Amphipoda: Corophiida) in Norwegian Sea deep water, pp. 323-337 in Journal of Natural History 50 on page 331, DOI: 10.1080/00222933.2015.1062152, http://zenodo.org/record/398335
- …
