Search

Recent surface ship multibeam surveys of the Sur Pockmark Field, offshore Central California, reveal >5,000 pockmarks in an area that is slated to host a wind farm, between 500‐ and 1,500‐m water depth. Extensive fieldwork was conducted to characterize the seafloor environment and its recent geologic history, including visual observations with remotely operated vehicles, sediment core sampling, and high‐resolution, near‐bottom Chirp and multibeam surveys collected with autonomous underwater vehicles to capture the morphology and stratigraphy of the pockmarks. No evidence of high methane concentrations in sediments, chemosynthetic biological communities, or methane‐derived diagenetic byproducts was found. Chirp data and sediment cores showed alternating layers of slowly accumulating hemipelagic drapes interrupted by more reflective turbidite horizons that extend throughout the pockmark field and beyond. Chirp data showed multiple episodes of lateral migration over time in some of the pockmarks in association with erosion and infilling events. Laterally continuous turbidite horizons that overlay erosional surfaces indicated that pockmark migration occurred synchronously in multiple pockmarks separated by tens of kilometers. These shifts are presumed to be the result of asymmetrical erosion of the pockmark flanks caused by passing sediment gravity flows. While some pockmarks occur in chains, most are not clustered or randomly spaced but are regularly dispersed within the pockmark field. We hypothesize that intermittent, unconfined sediment gravity flows occurring over at least the last 280,000 years are the source of the regionally continuous turbidite deposits and the mechanism that maintained the regularly dispersed pockmarks. Plain Language Summary: Over 5,000 pockmarks were mapped in water depths between 500 and 1,500 m offshore Central California in an area slated to host a wind farm. Pockmarks are large circular seafloor depressions commonly believed to be formed and maintained by methane flux. Video footage from the pockmark field, detailed maps of the seafloor, sediment cores, and images of the subsurface were collected. Importantly, no significant evidence of methane gas was found in any of the collected data sets. Instead, the subsurface profiles and sediment samples indicated that the pockmarks contain layers of fine sediment deposited slowly over time alternating with sandy layers deposited by large sediment flows. These flows appear to erode the pockmark centers, and leave behind regionally continuous sandy deposits (turbidites). Some sediment flows have caused sufficient erosion to the pockmarks flanks to simultaneously shift the position of multiple pockmarks, 10s of kilometers apart. Most of the pockmarks are not randomly scattered or clustered on the seafloor but are distributed in a regular, equally spaced pattern. We hypothesize that intermittent, unconfined sediment gravity flows occurring over at least the last 280,000 years are the source of the regionally continuous turbidites and the mechanism that maintained the regularly spaced pockmarks over time. Key Points: No evidence of methane venting was found in the Sur PockmarksThe persistence and lateral migration of the Sur Pockmarks are attributed to erosion and deposition during unconfined sediment gravity flowsRecurrent, regional, and unconfined sediment gravity flows have occurred in the Sur Pockmark Field for at least ∼280,000 years [ABSTRACT FROM AUTHOR]

Here we show how ultra‐high resolution seabed mapping using new technology can help to understand processes that sculpt submarine canyons. Time‐lapse seafloor surveys were conducted in the axis of Monterey Canyon, ∼50 km from the canyon head (∼1,840 m water depth) over an 18‐month period. These surveys comprised 5‐cm resolution multibeam bathymetry, 1‐cm resolution lidar bathymetry, and 2‐mm resolution stereophotographic imagery. Bathymetry data reveal centimeter‐scale textures that would be undetectable by more traditional survey methods. Upward‐looking Acoustic Doppler Current Profilers at the site recorded the flow character of internal tides and the passage of three turbidity currents, while sediment cores collected from the site record flow deposits. Combined with flow and core data, the bathymetry shows how turbidity currents and internal tides modify the seabed. The turbidity currents drape sediment across the site, infilling bedform troughs and smoothing erosional features carved by the internal tides (e.g., rippled scours). Turbidity currents with speeds of 0.9–3.3 m/s failed to cause notable bedform movement, which is surprising given that flows with similar speeds produced rapid bedform migration elsewhere, including the upper Monterey Canyon. The lack of migration may be related to the character of the underlying substrate or indicate that turbidity currents at the site lack dense, near‐bed layers. The scale of scours produced by the internal tides (≤0.7 m/s) approaches the scale of features recorded in the ancient rock record. Thus, these results illustrate how the scale gap between seabed mapping technology and the rock record may eventually be bridged. Plain Language Summary: This study presents the highest resolution repeat seafloor mapping surveys to date in a submarine canyon. Centimeter‐scale seafloor surveys were conducted over an 18‐month period at a location ∼50 km from the head of Monterey Canyon. Turbidity currents (rapid, down‐slope density‐driven flows of water) and internal tides (tidal currents that flow along the seabed) were recorded by a seafloor instrument node deployed in the study area. Turbidity currents drape sediment across the bedforms, infill troughs, and smooth out erosional features carved by internal tides. While the turbidity currents caused considerable migration of bedforms in the upper canyon, there was surprisingly no notable migration at the study site. The lack of migration may be related to the relatively coarse nature of the seafloor underlying the bedforms and suggests that the turbidity currents at the site lacked a dense near‐bed layer characteristic of flows farther up‐canyon. The internal tides carved centimeter‐scale scours in the seabed, a scale that approaches that of features preserved in the rock record. This study, therefore, shows how new mapping technology may eventually bridge the scale gap between modern seafloor surveys and the ancient rock record. Key Points: Ultra‐high resolution time‐lapse mapping is combined with flow monitoring and sediment cores to document submarine canyon activityFast turbidity currents fail to cause notable bedform migration, though flows with similar speeds cause significant migration up‐canyonSub‐meter to meter‐scale scours, likely carved by internal tides, approach the scale of features preserved in the rock record [ABSTRACT FROM AUTHOR]

A significant amount of illness has origins in oral microorganisms. The current SARS-CoV-2 (severe acute respiratory syndrome coronavirus 2) pandemic has reduced the general population's access to and use of routine and nonemergency dental care. This creates a dangerous situation in which oral bacteria, fungi, and viruses may remain unchecked and allowed to flourish, which in turn increases risks for several systemic diseases as well as negative outcomes for pregnancies and surgical patients. This situation presents opportunities for health maintenance and disease prevention by individuals as well as for dental health professionals to use anti-infective treatments and procedures. Lifestyle medicine professionals have a chance to encourage behaviors that individuals can undertake to promote good oral health outside of the dentist's office as well as shaping public perceptions about and reinforcing the importance of resuming dental visits as governmental restrictions allow. [ABSTRACT FROM AUTHOR]

The near‐bed section of submarine gravity flows travels at the highest and most destructive speeds making direct measurements of this region of the flow difficult. Here results are presented from "boulder‐like" Benthic Event Detectors (BEDs) that measured their own rotation, depth and temperature while carried within the near‐bed region of gravity flows. BEDs were deployed in Monterey Canyon from 200 to 500 m water depth for 18 months (2016–2017) during the Coordinated Canyon Experiment. BEDs moved in 10 out of 14 gravity flows that transited the upper canyon. BEDs moved within the body of the flow because the initial velocities of the BEDs were 66 ± 16% (1 SD) of the flow transit velocities. BEDs rotated freely during most of their first moves and gained depth faster than in later moves, when their motion was more random and wobblier. The differences in BED motions between first and later moves suggest BEDs moved at different depths within the flow. The inferred near‐bed flow structure is strongly stratified with a fast, less‐dense layer moving above a slower and denser layer. Coherent changes between pressure and acceleration indicate that BEDs rode a crescent shaped bedform (CSB) morphology that persisted throughout flow events. The variability in BED speeds while riding the CSB morphology indicates a fluid‐like nature of the near‐bed layer. BED motions ended after being caught in the trough of a CSB. Based on recorded temperature decay rates after flow events, the thickness of redeposited sediment is 2–3 m. Plain Language Summary: A large portion of the sediment discharged by rivers to the ocean is carried to the deep sea as sediment‐laden currents, called sediment gravity flows, that are routed along submarine canyons carved on the continental slope. Because these flows are very energetic, episodic and occur in relatively inaccessible environments it has been challenging to document their velocity, sediment load, the thickness of the flow and internal structure, and the flow runout distance and duration. Boulder‐shaped, motion‐sensing devices, called Benthic Event Detectors (BEDs), were developed to better understand these flows. BEDs are capable of recording their own motion while being carried within sediment gravity flows. BEDs placed in Monterey Canyon for 18 months were carried by 10 sediment gravity flows. Based on the type of motion the BEDs experienced while being transported, it is inferred that the flows remobilize the seafloor down to 2–3 m and that the body of the flow behind the flow front consists of a very dense slow moving layer overridden by a fast less dense layer. Knowledge about the nature of these flows is important for evaluating the extent they constitute a geohazard to seafloor‐resting infrastructure such as pipelines and seabed cables. Key Points: Boulder‐like detectors were developed to document the internal dynamics of sediment gravity flowsDetectors were transported in 10 out of 14 sediment gravity flows that transited their locations in Monterey CanyonIn each case, the body of the gravity flow consists of a faster dilute layer that overlies a slower denser basal layer [ABSTRACT FROM AUTHOR]

Bemisia tabaci (Gennadius) (Hemiptera: Aleyrodidae) is a pest species complex that causes widespread damage to cassava, a staple food crop for millions of households in East Africa. Species in the complex cause direct feeding damage to cassava and are the vectors of multiple plant viruses. Whilst significant work has gone into developing virus-resistant cassava cultivars, there has been little research effort aimed at understanding the ecology of these insect vectors. Here we assess critically the knowledge base relating to factors that may lead to high population densities of sub-Saharan African (SSA) B. tabaci species in cassava production landscapes of East Africa. We focus first on empirical studies that have examined biotic or abiotic factors that may lead to high populations. We then identify knowledge gaps that need to be filled to deliver sustainable management solutions. We found that whilst many hypotheses have been put forward to explain the increases in abundance witnessed since the early 1990s, there are little published data and these tend to have been collected in a piecemeal manner. The most critical knowledge gaps identified were: (i) understanding how cassava cultivars and alternative host plants impact population dynamics and natural enemies; (ii) the impact of natural enemies in terms of reducing the frequency of outbreaks and (iii) the use and management of insecticides to delay the development of resistance. In addition, there are several fundamental methodologies that need to be developed and deployed in East Africa to address some of the more challenging knowledge gaps. [ABSTRACT FROM AUTHOR]

Long‐term warming of the continental shelf of the Canadian Beaufort Sea caused by the transgression associated with the last deglaciation may be causing decomposition of relict offshore subsea permafrost and gas hydrates. To evaluate this possibility, pore waters from 118 sediment cores up to 7.3‐m long were taken on the shelf and slope and analyzed for chloride concentrations and δ180 and δD composition. We observed downcore decreases in pore waters Cl− concentration in sediments from all sites from the inner shelf (<20‐m water depth), from the shelf edge, from the outer slope (down to 1,000‐m water depths), and from localized shelf features such as midshelf pingo‐like features and inner shelf pockmarks. In contrast, pore water freshening is absent from all investigated cores of the Mackenzie Trough. Downcore pore waters Cl− concentration decreases indicate regional widespread freshwater seepage. Extrapolations to zero Cl− of pore water Cl− versus δ180 regression lines indicate that freshwaters in these environments carry different isotope signatures and thus are sourced from different reservoirs. These isotopic signatures indicate that freshening of shelf sediments pore waters is a result of downward infiltration of Mackenzie River water, freshening of shelf edge sediments is due to relict submarine permafrost degradation or gas hydrate decomposition under the shelf, and freshening of slope sediments is consistent with regional groundwater flow and submarine groundwater discharge as far as 150 km from shore. These results confirm ongoing decomposition of offshore permafrost and suggest extensive current groundwater discharge far from the coast. Plain Language Summary: The continental shelves around the Arctic Ocean were exposed to very low temperatures during the last glacial period more than 12,000 years ago. Precipitation that infiltrated these areas froze in the soils as permafrost. When climate warmed at the end of the glacial period, sea level rose and inundated the shelves warming them up. The warming may be reaching the now submarine permafrost and inducing its melting. This permafrost decomposition may be detected as freshwater seeping into the seafloor. In this study, we found evidence that in the Canadian Beaufort Sea not only permafrost is decomposing and seeping into the seafloor but also current groundwater discharge into the seafloor occurs at distances as far as 150 km from the current shore, likely routed by the permafrost presence in the shelf as a frozen lid. Active water discharge onto sediments may induce sediment instabilities that result in landslides, which can trigger tsunamis. In addition, sediment instabilities are a geohazard for sea‐based infrastructure. Key Points: Freshening was observed in near‐seabed sediment pore waters in the shelf, shelf edge, and continental slope of the Canadian Beaufort Sea but not in the Mackenzie TroughThe source of freshwater in shelf sediments is top‐down infiltration of seawater mixed with Mackenzie River water in the water columnThe source of freshwater in shelf edge sediments is degradation of relict terrestrial submarine permafrost or gas hydrates under the shelf, whereas in the slope the source is submarine groundwater discharge [ABSTRACT FROM AUTHOR]

High-resolution multibeam bathymetry data collected with an autonomous underwater vehicle (AUV) complemented by compressed high-intensity radar pulse (Chirp) profi les and remotely operated vehicle (ROV) observations and sediment sampling reveal a distinctive rough topography associated with seafl oor gas venting and/or near-subsurface gas hydrate accumulations. The surveys provide 1 m bathymetric grids of deep-water gas venting sites along the best-known gas venting areas along the Pacifi c margin of North America, which is an unprecedented level of resolution. Patches of conspicuously rough seafl oor that are tens of meters to hundreds of meters across and occur on larger seafl oor topographic highs characterize seepage areas. Some patches are composed of multiple depressions that range from 1 to 100 m in diameter and are commonly up to 10 m deeper than the adjacent seafl oor. Elevated mounds with relief of >10 m and fractured surfaces suggest that seafl oor expansion also occurs. Ground truth observations show that these areas contain broken pavements of methane-derived authigenic carbonates with intervening topographic lows. Patterns seen in Chirp profi les, ROV observations, and core data suggest that the rough topography is produced by a combination of diagenetic alteration, focused erosion, and infl ation of the seafl oor. This characteristic texture allows previously unknown gas venting areas to be identifi ed within these surveys. A conceptual model for the evolution of these features suggests that these morphologies develop slowly over protracted periods of slow seepage and shows the impact of gas venting and gas hydrate development on the seafl oor morphology. [ABSTRACT FROM AUTHOR]

The purpose of this study was to compare displacement behavior of cyclically loaded cadaveric human intervertebral discs as measured noninvasively on a clinical 3.0 T and a research 9.4 T MRI system. Intervertebral discs were cyclically compressed at physiologically relevant levels with the same MRIcompatible loading device in the clinical and research systems. Displacement-encoded imaging was synchronized to cyclic loading to measure displacements under applied loading with MRI (dualMRI). Displacements from the two systems were compared individually using linear regression and, across all specimens, using Bland-Altman analysis. In-plane displacement patterns measured at 3.0 T and 9.4 T were qualitatively comparable and well correlated. Bland-Altman analyses showed that over 90% of displacement values within the intervertebral disc regions of interest lay within the limits of agreement. Measurement of displacement using dualMRI using a 3.0 T clinical system is comparable to that of a 9.4 T research system. Additional refinements of software, technique implementation, and image processing have potential to improve agreement between different MRI systems. Despite differences in MRI systems in this initial implementation, this work demonstrates that dualMRI can be reliably implemented at multiple magnetic field strengths, permitting translation of dualMRI for a variety of applications in the study of tissue and biomaterial biomechanics. [ABSTRACT FROM AUTHOR]

While submarine canyons are the major conduits through which sediments are transported from the continents out into the deep sea, the time it takes for sediment to pass down through a submarine canyon system is poorly constrained. Here we report on the first study to couple optically stimulated luminescence (OSL) ages of quartz sand deposits and accelerator mass spectrometry 14C ages measured on benthic foraminifera to examine the timing of sediment transport through the axial channel of Monterey Submarine Canyon and Fan, offshore California. The OSL ages date the timing of sediment entry into the canyon head while the 14C ages of benthic foraminifera record the deposition of hemipelagic sediments that bound the sand horizons. We use both single-grain and small (~2 mm area) single-aliquot regeneration approaches on vibracore samples from fining-upward sequences at various water depths to demonstrate relatively rapid, decadal-scale sand transport to at least 1.1 km depth and more variable decadal- to millennial-scale transport to a least 3.5 km depth on the fan. Significant differences between the time sand was last exposed at the canyon head (OSL age) and the timing of deposition of the sand (from 14C ages of benthic foraminifera in bracketing hemipelagic sediments) are interpreted as indicating that the sand does not pass through the entire canyon instantly in large individual events, but rather moves multiple times before emerging onto the fan. The increased spread in single-grain OSL dates with water depth provides evidence of mixing and temporary storage of sediment as it moves through the canyon system. The ages also indicate that the frequency of sediment transport events decreases with distance down the canyon channel system. The amalgamated sands near the canyon head yield OSL ages that are consistent with a sub-decadal recurrence frequency while the fining-upward sand sequences on the fan indicate that the channel is still experiencing events with a 150-250 year recurrence frequency out to 3.5 km water depths. [ABSTRACT FROM AUTHOR]

In this article, the term ' churn' is used not only because of the degree of change to staffing, but also because some of the reasons for staff movement are not classified as voluntary turnover. The difficulties for the nurse managing a unit with the degree of ' churn' should not be under- estimated. Changes to skill mix and the proportions of full-time, agency, and tempora ry staff present challenges in providing clinical leadership, scheduling staff, perfo rmance management, and supervision. Perhaps more importantly, it is likely that there is an impact on the continuity of care provided in the absence of continuity of staffing. A greater understanding of the human and financial costs and consequences, and a willingness to change established practices at the institutional and ward level, are needed. [ABSTRACT FROM AUTHOR]

Aim. To find that changes in models of service delivery together with the dynamic nature of the contemporary health care context have changed the direction and focus of nurses' work. The aim of this paper is to explore some of the drivers for change and their impact and recommend a way forward to optimising nurses' work in the hospital environment. Background. The healthcare workplace has been transformed over the past 20 years in response to economic and service pressures. However, some of these reforms have had undesirable consequences for nurses' work in hospitals and the use of their time and skills. Results. As the pace and complexity of hospital care increases, nursing work is expanding at both ends of the complexity continuum. Nurses often undertake tasks which less qualified staff could do while at the other end of the continuum, are unable to use their high level skills and expertise. This inefficiency in the use of nursing time may also impact negatively on patient outcomes. Conclusions. Nurses' work that does not directly contribute to patient care, engage higher order cognitive skills or provide opportunity for role expansion may decrease retention of well-qualified and highly skilled nurses in the health workforce. Relevance to clinical practice. In this climate of nursing shortages, we need to use nurses in a cost-effective but also, intellectually satisfying manner, to achieve a sustainable nursing workforce. [ABSTRACT FROM AUTHOR]

Recent investigations using the Monterey Bay Aquarium Research Institutes (MBARI) Remotely Operated Vehicles (ROVs) "Ventana" and "Tiburon" and interpretation of MBARI's EM 300 30 kHz multibeam bathymetric data show that the northern flank of the Santa Barbara Basin has experienced massive slope failures. Of particular concern is the large (130 km²) Goleta landslide complex located off Coal Oil Point near the town of Goleta, that measures 14.6-km long extending from a depth of 90m to nearly 574m deep and is 10.5 km wide. We estimate that approximately 1.75 km³ has been displaced by this slide during the Holocene. This feature is a complex compound submarine landslide that contains both surfical slump blocks and mud flows in three distinct segments. Each segment is composed of a distinct head scarp, down-dropped head block and a slide debris lobe. The debris lobes exhibit hummocky topography in the central areas that appear to result from compression during down slope movement. The toes of the western and eastern lobes are well defined in the multibeam image, whereas the toe of the central lobe is less distinct. Continuous seismic reflection profiles show that many buried slide debris lobes exist and comparison of the deformed reflectors with ODP Drill Site 149, Hole 893 suggest that at least 200 000 years of failure have occurred in the area (Fisher et al., 2005a). Based on our interpretation of the multibeam bathymetry and seismic reflection profiles we modeled the potential tsunami that may have been produced from one of the three surfical lobes of the Goleta slide. This model shows that a 10m high wave could have run ashore along the cliffs of the Goleta shoreline. Several other smaller (2 km² and 4 km²) slides are located on the northern flank of the Santa Barbara Basin, both to the west and east of Goleta slide and on the Conception fan along the western flank of the basin. One slide, named the Gaviota slide, is 3.8 km², 2.6 km long and 1.7 km wide. A distinct narrow scar extends from near the eastern head wall of this slide for over 2 km eastward toward the Goleta slide and may represent either an incipient failure or a remnant of a previous failure. Push cores collected within the main head scar of this slide consisted of hydrogen sulfide bearing mud, possibly suggesting active fluid seepage and a vibra-core penetrated ∼ 50 cm of recent sediment overlying colluvium or landslide debris confirming the age of ∼300 years as proposed by Lee et al. (2004). However, no seeps or indications of recent movement were observed during our ROV investigation within this narrow head scar indicating that seafloor in the scar is draped with mud. [ABSTRACT FROM AUTHOR]

A sediment gravity flow descended through the axis of Monterey Canyon on 20 December 2001 at 13:35 Pacific standard time. The timing of this event is documented by a current-meter package which recorded an 11.9-dbar pressure increase in less than 10 min and was found 550 m down-canyon from its deployment site, buried completely within a >70-cm-thick gravity flow deposit. This event is believed to have started in less than 290 m of water because an instrument at this location was also lost at the same time. A 178-cm core collected after the event from the axis of the canyon at 1,297-m water depth contained fresh, greenish, chlorophyll-rich organic material at 32-cm sub-bottom depth, suggesting the event extended to this water depth. The only trigger identified for this mass movement event appears to be moderate sea and surf conditions. Thus, gravity flow events of this magnitude do not require an exceptional triggering event. [ABSTRACT FROM AUTHOR]

Transform faults have anomalously low rates of seismicity, but it's not clear whether this reflects persistent earthquake-generating fault patches surrounded by creep, or the presence of creep and earthquakes at different times along the same patch. We use new, autonomous underwater vehicle high-resolution seafloor mapping to image the morphology of and offsets along transform fault segments in the Gulf of California, offshore Mexico. Fault zone structure imaged in this study shows evidence for the initiation and cessation of activity along individual fault splays over geologic time. A series of six identically offset depositional fans evidence 21-23 m of slip along the main transform fault, which could not have been produced by a single earthquake given the length of the transform. Rather, the lack of smaller-magnitude offsets indicates synchronous deposition and an absence of multiple slope failure-inducing earthquakes, which is consistent with the idea that creep and/or small-magnitude events occur asynchronously with large earthquakes in the slip history of a given transform fault segment. [ABSTRACT FROM AUTHOR]