Deployment Period Research Articles

Comparative wave measurements at a wave energy site with a recently developed low-cost wave buoy (Spotter), ADCP and pressure loggers

AbstractWave measurements from a new, low-cost, real-time wave buoy (Spotter) are investigated in a comparative study as part of a site characterization study at a wave energy candidate site at King Island, Tasmania, Australia. Measurements from the Sofar Ocean Spotter buoy are compared with concurrent measurements from a Teledyne RD Instrument (RDI) 1200 kHz Work Horse ADCP and two RBRsolo3 D wave16 pressure loggers. The comparison period between 8th August – 12th October 2019 provides both the shallowest and longest continuous published comparison undertaken with the Spotter buoy.Strong agreement was evident between the Spotter buoy and RDI ADCP of key wave parameters including the significant wave height, peak wave period, and mean wave direction, with the mean values of those parameters across the full deployment period agreeing within 3%. Surface wave spectra and directional spectra are also analyzed with good agreement observed over the majority of the frequency domain, although the Spotter buoy records approximately 17% less energy within a narrow frequency band near the peak frequency when compared to the RDI ADCP. Measurements derived from the pressure loggers routinely underestimated the significant wave height and overestimated the mean wave period over the deployment period. The comparison highlights the suitability of the Spotter buoy for low-cost wave resource studies, with accurate measurements of key parameters and spectra observed.

Seasonal marine carbon system processes in an Arctic coastal landfast sea ice environment observed with an innovative underwater sensor platform

Studying carbon dioxide in the ocean helps to understand how the ocean will be impacted by climate change and respond to increasing fossil fuel emissions. The marine carbonate system is not well characterized in the Arctic, where challenging logistics and extreme conditions limit observations of atmospheric CO2 flux and ocean acidification. Here, we present a high-resolution marine carbon system data set covering the complete cycle of sea-ice growth and melt in an Arctic estuary (Nunavut, Canada). This data set was collected through three consecutive yearlong deployments of sensors for pH and partial pressure of CO2 in seawater (pCO2sw) on a cabled underwater observatory. The sensors were remarkably stable compared to discrete samples: While corrections for offsets were required in some instances, we did not observe significant drift over the deployment periods. Our observations revealed a strong seasonality in this marine carbon system. Prior to sea-ice formation, air–sea gas exchange and respiration were the dominant processes, leading to increasing pCO2sw and reduced aragonite saturation state (ΩAr). During sea-ice growth, water column respiration and brine rejection (possibly enriched in dissolved inorganic carbon, relative to alkalinity, due to ikaite precipitation in sea ice) drove pCO2sw to supersaturation and lowered ΩAr to < 1. Shortly after polar sunrise, the ecosystem became net autotrophic, returning pCO2sw to undersaturation. The biological community responsible for this early switch to autotrophy (well before ice algae or phytoplankton blooms) requires further investigation. After sea-ice melt initiated, an under-ice phytoplankton bloom strongly reduced aqueous carbon (chlorophyll-a max of 2.4 µg L–1), returning ΩAr to > 1 after 4.5 months of undersaturation. Based on simple extrapolations of anthropogenic carbon inventories, we suspect that this seasonal undersaturation would not have occurred naturally. At ice breakup, the sensor platform recorded low pCO2sw (230 µatm), suggesting a strong CO2 sink during the open water season.

Hybrid optimization for virtual machine migration of utilizing healthcare text in the cloud

Cloud computing as the modern technology that generates, processing, storing, and sharing of medical data has evolved significantly. The health industry has made a lot of progress in transforming its data management activities, from regular storage to the digitalization of health care data. Cloud computing impacting based on lowering of costs, availability of resources, and power. moreover patient has the right or ownership of data in-the-cloud virtualization technology. Keeping the data of the patient in the cloud also facilitates interoperability between the various sectors of the health-care sector-pharmacy, insurance, and payments. Cloud offers virtual hardware, runtime settings, and facilities for those with a credit card. Cloud infrastructure has become a common term for reference to various devices, resources, and concepts. The proposed framework provides a simulated migration approach that is complex and energy-intensive. By activating idle physical machinery mode, this mechanism reduces the power to conserve electricity. This study suggests a modern cloud-based Health care services paradigm for optimizing VM migration utilizing Parallel Particle Swarm Optimization (PPSO). To measure the performance of our VMs model, a new model for health care service is also provided. The findings reveal that, in the overall deployment period, the new model approaches 60% of the state-of-the-art implementations. Furthermore, device performance is increased by 6.2% for demanded data in real-time. Furthermore, the accuracy of the smart hybrid model of resource utilization is 96.8%. In all associated activities, the suggested model is 67% better than other referred versions.

Optimal deployment durations for baited underwater video systems sampling temperate, subtropical and tropical reef fish assemblages

Baited remote underwater stereo-video systems (BRUVs) are being adopted globally as a sampling method for surveying fish assemblages. The literature demonstrates that researchers are using different deployment times, rarely with justification for the time chosen. We aimed to determine the optimal deployment time of BRUVs to sample reef fish assemblages in temperate, sub-tropical and tropical locations along the west coast of Australia. Observations of fish species richness and abundance were compared between deployment periods of 0–15, 15–30, 30–45 and 45–60 min duration. Within the subtropical and tropical locations there was no significant difference in the composition of the fish assemblage beyond 15–30 and 30–45 min respectively, suggesting 30 and 45 min would be suitable. Whereas within the warm temperate location, fish assemblages differed across all deployment periods with at least 60 min required to best characterise the fish assemblage. Most species (60–71%) and individuals (50–75%) were observed within 15 min at all locations and trends in the arrival times of individual species proved to be variable and species-specific. Critically, some larger-bodied target species continued to arrive in high proportions up to 45–60 min at all locations. Despite differences in optimal deployment durations between locations, we recommend that 60 min of imagery be collected as the cost of collecting, storing and annotating the extra imagery is minimal in comparison to the full costs of a program or recollecting imagery. Researchers may choose to analyse the first 30 or 45 min of imagery if sampling subtropical or tropical fish assemblages, yet the full 60 min is available should there be a need for standardised soak times to address questions involving spatial and temporal data collected by different users.

Cloud Data Center Network Construction Based on Virtualization Technology

With the rapid development of information technology, the IT infrastructure in traditional data centers has high investment costs, low utilization rate, long application deployment period, and the difficulty of operation and maintenance increases with the increase of system and energy consumption. In order to solve the above problems, the article analyzes the current network virtualization technology and systematically studies the application scenarios of network virtualization technology, and proposes a cloud computing data center network construction scheme based on network virtualization technology.

Influence of various water quality parameters on passive sampler accumulation kinetics of different metal valencies in freshwater.

Stabilized liquid membrane devices (SLMDs) have been used for passive integrative sampling of metals in freshwater systems. Field measurements of metal accumulation on SLMDs can provide a time-weighted average mass of labile metals over the deployment period. We exposed SLMDs in the laboratory to 0.5μM solutions of silver, zinc, or aluminum as nitrate salts at three levels of water hardness, measuring metal accumulation every 4days for 32days. We saw linear accumulation in all experimental treatments, except for silver in high hardness (345.9mg/L as CaCO3). The time-accumulation relationships indicated that metal sorption rates vary across valency with the lower valency metals generally accumulating at greater rates. Water hardness also affected accumulation rates and accumulated mass with greater rates as hardness increased for zinc and aluminum. The accumulated zinc mass at 32days in soft water was 78% of the mass in hard water for zinc, and accumulated aluminum mass was 29% of the mass in hard water. Factors such as oleate formation on the SLMD surface and solution chemistry, including pH and chemical speciation, were evaluated in explaining our results. Our work supports that SLMDs have utility for sampling metals in freshwater over extended time periods, which may be beneficial when there is limited access to sites; it also provide important interpretive guidance for the use of SLMDs.

Partitioning between polyurethane foam and the gas phase: data compilation, uncertainty estimation and implications for air sampling.

Polyurethane foam (PUF) is frequently applied for sampling semi-volatile organic compounds (SVOCs) in the gas phase. Equilibrium partition coefficients (KPUF/G) often are used to estimate the potential for breakthrough during active air sampling (AAS) and to correct for non-linear uptake during passive air sampling (PAS). KPUF/G is either determined experimentally or estimated, in both cases incurring uncertainties that can be carried over to other parameters. Here, a dataset of 547 measured KPUF/G values and chemical information for 281 distinct chemicals was compiled from the peer reviewed literature. Measured log KPUF/G were compared with predicted values to identify potential bias in data generated with a particular experimental approach. An analysis of the measured data suggests that the uncertainty of unbiased log KPUF/G values is at best 0.2 log units at 15 °C (e.g. for hexachlorobenzene and fluoranthene), but most likely much higher. This implies that inherent passive air sampling rates obtained from the loss of a depuration compound (SR) and breakthrough volumes during AAS can presently not be known with an uncertainty of less than ca. 50%. During short PAS deployment periods, the uncertainty in the effective sampling volume (Vair) derives mainly from the uncertainty in the SR, whereas the uncertainty in KPUF/G of the target compound will become important and even the main source of uncertainty for Vair if deployments are long or target chemicals are relatively volatile. This in turn implies that the uncertainty of Vair cannot be smaller than the uncertainty of SR and KPUF/G and therefore again is at least ca. 50%. We strongly recommend that the uncertainty of air concentrations obtained by non-linear PAS is quantified and reported and we outline a procedure on how to do that. Because the uncertainty in KPUF/G of target and depuration chemicals generally exceeds 30%, it may often be necessary to conduct Monte Carlo simulation.

Condensation corrosion alters the oxygen and carbon isotope ratios of speleothem and limestone surfaces

Condensation corrosion is a natural process which enhances the chemical weathering of limestone cave chambers and speleothems. We evaluated the use of carbonate tablets for detecting condensation corrosion in Glowworm Cave, New Zealand, using local limestone and speleothem as experimental substrates (herein tablets). Evidence for condensation corrosion was assessed via three methods: gravimetric (mass wasting), microscopic (surface pitting, recrystallization) and isotopic (δ13C and δ18O changes). Our results show little evidence of tablet mass loss throughout a 6-month deployment period. However, SEM imaging and isotope analysis (δ13C and δ18O) of the upper ~50 μm layer of the tablets, suggest that condensation corrosion operates in the cave, especially in sectors affected by large diurnal microclimate variations.Most notably, condensation water altered the tablet surface δ13C and δ18O values. Small, positive shifts in surface δ13C and δ18O values are considered to reflect pure dissolution (where dissolution favours the removal of lighter isotopologues). In contrast, tablets that exhibited large positive shifts in δ13C in tandem with large negative shifts in δ18O values, are interpreted as showing calcite recrystallization and the inheritance of higher DIC δ13C values (13C fractionation by CO2 degassing), lighter water δ18O values and/or kinetic fractionation of δ18O. This study therefore demonstrates that stable isotopes could be applied to detect paleoclimatic episodes of condensation corrosion in speleothems.

Spatial and temporal variations of halogenated flame retardants and organophosphate esters in landfill air: Potential linkages with gull exposure.

Landfills represent important sources of local emissions of organic contaminants, including halogenated (HFR) and organophosphate ester (OPE) flame retardants used in a large variety of consumer products. Gulls foraging in landfills may be exposed to elevated atmospheric concentrations of HFRs and OPEs that may vary spatially and temporally within a landfill site, thus modulating their exposure. The objective of the present study was to investigate the spatial and temporal variability of HFR and OPE concentrations in air samples collected from a major landfill in the Montreal area (QC, Canada) that is frequently visited by gulls for foraging. Miniature stationary passive air samplers (PASs) and high-volume active air samplers (AASs) were deployed in six different areas within this landfill site for 34 days to collect HFRs and OPEs in air. During the same period, wild-caught ring-billed gulls (Larus delawarensis) were equipped on their back with a similar miniature PAS that was deployed in the landfill along with a GPS datalogger to monitor their movements for ten days. Elevated concentrations of certain OPEs (e.g., tris(2-chloroethyl) phosphate and tris(2-chloroisopropyl) phosphate) and brominated diphenyl ether (BDE)-209 were measured in stationary PASs and AASs, although they were homogenously distributed within this landfill site. Temporal variability was observed for concentrations of BDE-209, -99 and -47 measured in AASs as well as tributyl phosphate during the 34-day deployment period. Moreover, air concentrations of BDE-209, -207 and -206 and selected OPEs (tris(1,3-dichloro-2-propyl) phosphate and tris(methylphenyl) phosphate) determined using AASs were positively correlated with ambient air temperatures. Gulls that visited a landfill at least once exhibited significantly greater concentrations of BDE-47 measured in PASs they carried on their back, suggesting that landfill air may represent a source of exposure to PBDEs for these birds, and potentially other urban-adapted wildlife using these sites for foraging.

Residential movements of top predators in Chile’s most isolated marine protected area: Implications for the conservation of the Galapagos shark, Carcharhinus galapagensis, and the yellowtail amberjack, Seriola lalandi

Abstract Marine protected areas (MPAs) are becoming a widely used tool for the conservation of biodiversity and for fishery management; however, most of these areas are designed without prior knowledge of the basic ecological aspects of the species that they are trying to protect. This study investigated the movement of two top predators: the Galapagos shark, Carcharhinus galapagensis, and the yellowtail amberjack, Seriola lalandi, in and around the Motu Motiro Hiva Marine Park (MMHMP) using MiniPAT satellite tags to determine the effectiveness of this MPA for the protection of these species. The Galapagos sharks (n = 4) spent most of their tag deployment periods inside the MMHMP. However, high intraspecific variability was observed in their movement dynamics. Daily individual maximum movements ranged from 17 to 58 km and the maximum distance from Salas y Gómez Island, the only emergent island within the MMHMP, ranged from 31 to 139 km. The maximum linear distance travelled for a female juvenile Galapagos shark (152 cm total length) was 236 km, which is greater than the maximum distance previously documented for juveniles of this species (<50 km). For the yellowtail amberjack (n = 1), 91% of the satellite geolocations were within the MMHMP, with a maximum daily distance travelled of 6 km. The maximum distance travelled between points was 111 km and the maximum distance from Salas y Gómez Island was 62 km. All archival tagged fish spent most of their time at depths of <50 m and never left the epipelagic zone. Daytime versus night‐time differences were pronounced in all individuals but showed high interindividual variability. This study provides a baseline on the movement of these two top predators in the MMHMP and provides valuable insights for the creation of MPAs in the region and elsewhere.

Possible Linkages between Microseisms in the Andaman-Nicobar Region and Swells in the South Indian Ocean

AbstractMicroseism source characterization and its genesis play a key role in linking microseism records to prevailing atmospheric and oceanic conditions. In the present study, we analyzed the spatial and temporal distribution of microseisms in the Andaman-Nicobar region using ocean-bottom seismometers and nearby continental stations data for the deployment period of January–April 2014. We attempted to establish a linkage between microseisms and ocean wave parameters derived from the ERA5 dataset. The short-period secondary microseisms (2–5 s) show a marked difference compared with long-period secondary microseisms (6–10 s) and are associated with local climatology and geomorphology. In contrast, long-period microseisms are related to distant sources in the South Indian Ocean. The primary microseisms (11–20 s) are weak in the Andaman region and do not correlate with any ocean wave parameters.

Implementing the Health Early Warning System based on syndromic and event-based surveillance at the 2019 Hajj.

During the 2019 Hajj, the Ministry of Health in Saudi Arabia implemented for the first time a health early warning system for rapid detection and response to health threats. This study aimed to describe the early warning findings at the Hajj to highlight the pattern of health risks and the potential benefits of the disease surveillance system. Using syndromic surveillance and event-based surveillance data, the health early warning system generated automated alarms for public health events, triggered alerts for rapid epidemiological investigations and facilitated the monitoring of health events. During the deployment period (4 July-31 August 2019), a total of 121 automated alarms were generated, of which 2 events (heat-related illnesses and injuries/trauma) were confirmed by the response teams. The surveillance system potentially improved the timeliness and situational awareness for health events, including non-infectious threats. In the context of the current COVID-19 pandemic, a health early warning system could enhance case detection and facilitate monitoring of the disease geographical spread and the effectiveness of control measures.

Dynamics Modelling and Simulation for Deployment Characteristics of Mesh Reflector Antennas

The dynamics of mesh reflectors are characterized by large deformation when antennas undergo a large motion in the deployment process. In this work, absolute node coordinate formulation (ANCF), with the merit of precise description of large deformation, is employed to consider the flexibility of the reflector net. From a practical perspective, the effect of the torsional spring is incorporated into the dynamic governing equations by an equivalent mechanical model. Deployment simulation of the mesh reflector antennas is performed by a numerical procedure. It can be found that with the action of a degenerative driven force caused by the friction effect, the deployed process of antennas exhibits a character of asynchronous deployment. Additionally, a significant increase in tension during the final period of deployment has an intense influence on smooth deployment.

Application of Photo-Identification and Lengthened Deployment Periods to Baited Remote Underwater Video Stations (BRUVS) Abundance Estimates of Coral Reef Sharks

Baited Remote Underwater Video Stations (BRUVS) are widely used for monitoring relative abundances of fishes, especially sharks, but only the maximum number of individuals seen at any one time (MaxN) is usually recorded. In both the Cayman Islands and the Amirante Islands, Seychelles, we used photo-ID to recognise individual sharks recorded on BRUVS videos. This revealed that for most species the actual numbers of separate individuals (IndN) visiting the BRUVS were significantly higher than MaxN, with, for example, ratios of IndN to MaxN being 1.17 and 1.24 for Caribbean reef, Carcharhinus perezi, and nurse, Ginglymostoma cirratum, sharks in the Cayman Islands, and 2.46 and 1.37 for blacktip reef, C. melanopterus, and grey reef, C. amblyrhynchos, sharks, respectively, in the Amirantes. Further, for most species, increasing the BRUVS deployment period beyond the 60 min normally used increased the observed IndN, with more than twice as many individuals in the Cayman Islands and >1.4 times as many individuals in the Amirantes being recorded after 120 min as after 60 min. For most species, MaxN and IndN rose exponentially with time, so data from different deployment periods cannot reliably be compared using catch-per-unit-effort (CPUE) calculated as catch-per-unit-time. In both study areas, the time of first arrival of individuals varied with species from <1 min to >2 h. Individually identifiable sharks were re-sighted after up to 429 days over 10 km away in the Cayman Islands and 814 days over 23 km away in the Amirantes, demonstrating that many individuals range over considerable distances. Analysis of Cayman re-sightings data yielded mean population estimates of 76 ± 23 (SE) and 199 ± 42 (SE) for C. perezi and G. cirratum, respectively. The results demonstrate that, for sharks, the application of both photo-identification and longer deployment periods to BRUVS can improve the precision of abundance estimates and provide knowledge of population size and ranging behaviour.

Time-Integrative Passive Sampling of Very Hydrophilic Chemicals in Wastewater Influent

Passive sampling of very hydrophilic chemicals is challenging due to the weak adsorption affinity to commonly used sorbent phases. Here we present a technique for the passive time-integrative sampling of highly water-soluble chemicals in wastewater influent, using a new diffusion-based sampling device. The sampler is a sealed chamber covered at one end by a porous polyethylene membrane, allowing chemicals to diffuse through the water-filled pores into the receiving phase of water. When submerged, the concentration gradient drives diffusion into the sampler, increasing the concentration of analytes in the receiving phase over time. To calibrate and test sampler performance, the sampler was deployed in wastewater influent for 31 d. The accumulation of acesulfame, ethyl sulfate, methamphetamine, and benzoylecgonine into the sampler was modeled using simultaneously collected 24 h composite samples. The four chemicals are typically monitored in wastewater-based surveillance programs and ranged in log Kow from -2.49 (ethyl sulfate) to 2.22 (methamphetamine). In situ calibration showed linear increases in concentration over the deployment period, and calculated sampling rates ranged from 2.2 mL d-1 (methamphetamine) to 4.0 mL d-1 (ethyl sulfate). This technique is useful for the time-integrative sampling of a range of hydrophilic chemicals in wastewater and shows potential for other aquatic matrices.

Remote video methods for studying juvenile fish populations in challenging environments

Understanding the dynamics of juvenile fish populations is a key component to understanding variation in adult populations, however, juvenile fish are frequently found in a variety of structurally complex habitats which are often not easily sampled. The use of baited (BRUV) and unbaited (RUV) remote underwater stereo-video to study juvenile fish populations is uncommon and thus far, no study has directly compared the efficacy of these two methods solely for juvenile fish assemblages.The macro-tidal Kimberley region in the north-west of Australia is challenging to sample using diver-based methods due to the strong currents and prevalence of saltwater crocodiles (Crocodylus porosus). We sampled 60 Stereo-RUVs and 60 Stereo-BRUVs across four shallow-water (1-6 m) benthic habitats: coral, mangrove, macroalgae, and seagrass, to contrast the effect of the presence or absence of bait, deployment period, in-water visibility and tidally driven water speed on estimates of relative total abundance, species richness, and composition of the juvenile fish assemblage.No difference was detected in the ability of stereo-BRUV or stereo-RUV to quantify the relative total abundance, species richness, or assemblage composition of juvenile fish. We also found little effect of in-water visibility or tidally driven water speed, likely as a result of stratifying our sampling to slack water periods.We found that a deployment period of 10 min for Stereo-BRUVs and 15 min for Stereo-RUVs was optimum for sampling the juvenile fish assemblage across all four contrasting habitats. Since no statistical significance was observed between 10 and 15 min, we recommend that Stereo-RUVs deployed for 15 min during tidal slack water conditions are an optimum way to provide consistent results for comparisons of juvenile fish assemblage metrics across the benthic habitats studied within this region.The controlled video methodologies described here provided an opportunity to access un-sampled juvenile fish habitats and assemblages where traditional diver-based methodologies are impossible. Applying these methods broadly can help to improve our understanding of the status of juvenile fish and infer the reproductive success and viability of their populations across a range of habitat and environments.

Acoustic seasonality, behaviour and detection ranges of Antarctic blue and fin whales under different sea ice conditions off Antarctica

Descriptions of seasonal occurrence and behaviour of Antarctic blue and fin whales in the Southern Ocean are of pivotal importance for the effective conservation and management of these endangered species. We used an autonomous acoustic recorder to collect bioacoustic data from January through September 2014 to describe the seasonal occurrence, behaviour and detection ranges of Antarctic blue and fin whale calls off the Maud Rise, Antarctica. From 2479 h of recordings, we detected D- and Z-calls plus the 27 Hz chorus of blue whales, the 20 and 99 Hz pulses of fin whales and the 18-28 Hz chorus of blue and fin whales. Blue whale calls were detected throughout the hydrophone deployment period with a peak occurrence in February, indicating continuous presence of whales in a broad Southern Ocean area (given the modelled detection ranges). Fin whale calls were detected from January through July when sea ice was present on the latter dates. No temporal segregation in peaks of diel calling rates of blue and fin whales was observed in autumn, but a clear temporal segregation was apparent in summer. Acoustic propagation models suggest that blue and fin whale calls can be heard as far as 1700 km from the hydrophone position in spring. Random forest models ranked month of the year as the most important predictor of call occurrence and call rates (i.e. behaviour) for these whales. Our work highlights areas around the Maud Rise as important habitats for blue and fin whales in the Southern Ocean.

Sediment resuspension in winter in an exceptional low suspended sediment concentration area off Qinhuangdao in the Bohai Sea

Seawater with low suspended sediment concentration (SSC) and high salinity dominates the sea area off Qinhuangdao all year round, especially in winter, which is an exceptional case since most of the coastal waters in the Bohai Sea are turbid. Being one of the most famous coastal tourist resorts in the area, it is crucial to keep the seawater around Qinhuangdao clear and unpolluted. Three bottom-mooring systems were deployed in the low SSC region from February to March 2017 for up to 22 days to reveal the processes and mechanisms of local sediment resuspension. The observation results showed that during the strongest wind of the whole deployment period, the sediment resuspension process included a turbulent resuspension event that occurred in the high turbulent kinetic energy period, and a continuous resuspension event when the bed shear stress (BSS) was larger than critical. The turbulent resuspension event was characterised by high-turbidity resuspension of sediments near the bed in the form of pulsation, with a depth of influence not more than the thickness of the bottom boundary layer. It was found to be triggered by strong turbulence driven by storm winds. In contrast the continuous resuspension could be attributed to high wave-dominated BSS. During storm winds, high concentrations of suspended sediment in the upper and middle layers appeared to lag the wind speed by about 8–10 h. In contrast, the turbulent resuspension event occurred at the same time as the strong winds. In-situ measurements from all three moorings indicate that it is the local weak sediment resuspension, even under the influence of storm winds in winter, that causes the formation of the low SSC area off Qinhuangdao.

Compaction of the Groningen gas reservoir investigated with train noise

SummaryInduced seismicity in the Groningen gas field in the Netherlands has been related to reservoir compaction caused by gas pressure depletion. In situ measurement of compaction is therefore relevant for seismic hazard assessment. In this study, we investigated the potential of passively recorded deep borehole noise data to detect temporal variations in the Groningen reservoir. Train signals recorded by an array of 10 geophones at reservoir depth were selected from the continuous noise data for two 5-month deployments in 2015. Interferometry by deconvolution was applied to the high-frequency train signals that acted as stable, repetitive noise sources. Direct intergeophone P and S wave traveltimes were then used to construct the P- and S-wave velocity structure along the geophone array. The resulting models agree with independently obtained velocity profiles and have very small errors. Most intergeophone P wave traveltimes showed decreasing traveltimes per deployment period, suggestive of compaction. However, the retrieved traveltime changes are very small, up to tens of microseconds per deployment period, with uncertainties that are of similar size, about 10 microseconds. An unambiguous interpretation in terms of compaction is therefore not warranted, although the 10 μs error per 5-month period is probably smaller than can be achieved from active time-lapse seismic surveys that are commonly used to measure reservoir compaction. The direct P-wave amplitudes of the train-signal deconvolutions were investigated for additional imprints of compaction. Whereas the P-wave amplitudes consistently increased during the second deployment, suggestive of compaction, no such trend was observed for the first deployment, rendering the interpretation of compaction inconclusive. Our results therefore present hints, but no obvious effects of compaction in the Groningen reservoir. Yet, this study demonstrates that the approach of deconvolution interferometry applied to deep borehole data allows monitoring of small temporal changes in the subsurface for stable repetitive noise sources such as trains.

Movements, habitat utilization, and post-release survival of cobia (Rachycentron canadum) that summer in Virginia waters assessed using pop-up satellite archival tags

BackgroundCobia (Rachycentron canadum) is a cosmopolitan marine fish that inhabits tropical, sub-tropical, and temperate marine and estuarine waters and supports a major recreational fishery along the U.S. Atlantic and Gulf of Mexico coasts. Recent changes in U.S. cobia management have sparked controversy and highlighted limitations in our understanding of the species’ biology. This study utilized pop-up satellite archival tags (PSATs) to assess the movements, habitat utilization, and post-release survival of cobia that summer in Virginia waters.ResultsPSATs were deployed on 36 cobia caught in Virginia state waters using standard recreational techniques in August 2016 and August–September 2017. All fish larger than 37-in total length were tagged, and several of these were hooked deeply. No mortalities were inferred for the 20 cobia whose PSATs reported and remained attached for at least 10 days. Premature release of tags was an issue, and only five PSATs remained attached for the full 180-day deployment period. Some fish undertook long seasonal movements, with one individual entering Florida waters well beyond the current stock demarcation boundary. Several fish overwintered in waters offshore of North Carolina near the continental shelf break. Cobia demonstrated a strong affinity for waters ≥ 20 °C, even in the coldest months. They displayed distinct seasonal differences in habitat utilization, spending high proportions of their time near the surface during the summer months and extended periods at depths ≥ 20 m in the winter months.ConclusionsCobia are hardy fish with low post-release mortality when handled respectfully. Their migratory patterns are clearly temperature driven, and seasonal changes in habitat utilization means varied vulnerability to fishing gears. Further understanding of cobia migratory patterns, particularly in conjunction with spawning activity, is needed to best manage this species.