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  • 1
    In: Geochemistry, Geophysics, Geosystems, American Geophysical Union (AGU), Vol. 23, No. 1 ( 2022-01)
    Abstract: Extensive methane bubble plumes have been discovered on the Puget Sound seafloor The emission sites of these plumes are associated with major fault zones that penetrate the Cascadia forearc Dissolved methane arising from the plumes is mixed throughout the estuary by tides and local mixing
    Type of Medium: Online Resource
    ISSN: 1525-2027 , 1525-2027
    Language: English
    Publisher: American Geophysical Union (AGU)
    Publication Date: 2022
    detail.hit.zdb_id: 2027201-7
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  • 2
    Online Resource
    Online Resource
    Frontiers Media SA ; 2023
    In:  Frontiers in Marine Science Vol. 10 ( 2023-1-19)
    In: Frontiers in Marine Science, Frontiers Media SA, Vol. 10 ( 2023-1-19)
    Abstract: Volcanic eruptions provide rare opportunities to witness the biological recolonization of areas covered by new lava flows by effectively resetting the ecological succession clock to zero. The role of submarine volcanic eruptions as disturbance events and the resulting patterns of ecological succession have mainly been studied in hydrothermal vent ecosystems. However, the effects of submarine volcanic eruptions as disturbance forces have rarely been studied in non-vent ecosystems, particularly on seamounts. Here, we document the early stages of ecological succession of non-vent benthic communities inhabiting the summit caldera of the active Vailulu’u submarine volcano in American Samoa. Sitting above the Samoan volcanic hotspot, Vailulu’u is the youngest volcano of the Samoan chain. Repeated mapping of Vailulu’u in 1999, 2005, 2006, 2012, and 2017 revealed the progressive growth of a new cone named Nafanua. In 18 years, the cone grew & gt;300 meters in height from a starting depth of ~1000 meters below sea level (mbsl). The differential analyses of this time-series bathymetry dataset enabled the assignment of maximum age ranges to different portions of the new cone. High-definition ROV imagery collected in 2017 revealed patterns of community structuring consistent with ecological succession: newly erupted seafloor contained a subset of the benthic species found on older seafloor. Furthermore, individual animal sizes in the younger seafloor zones were smaller than in the older zones. This unusual interdisciplinary combination of geological and biological observations provides constraints on which deep-sea animals recolonize new seafloor after a major disturbance event and how quickly. This knowledge could be applied to identify signs and states of recovery from anthropogenic disturbances by a deep seamount ecosystem.
    Type of Medium: Online Resource
    ISSN: 2296-7745
    Language: Unknown
    Publisher: Frontiers Media SA
    Publication Date: 2023
    detail.hit.zdb_id: 2757748-X
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  • 3
    Online Resource
    Online Resource
    Frontiers Media SA ; 2021
    In:  Frontiers in Earth Science Vol. 9 ( 2021-3-24)
    In: Frontiers in Earth Science, Frontiers Media SA, Vol. 9 ( 2021-3-24)
    Abstract: Nearly 3,500 methane bubble streams, clustered into more than 1,300 methane emission sites, have been identified along the US Cascadia margin, derived both from archived published data and 2011, 2016–2018 dedicated multibeam surveys using co-registered seafloor and water column data. In this study, new multibeam sonar surveys systematically mapped nearly 40% of the US Cascadia margin, extending from the Strait of Juan de Fuca in the north to the Mendocino fracture zone in the south, and bounded East–West by the coast and the base of the accretionary prism. The frequency-depth histogram of the bubble emission sites has a dominant peak at the 500 m isobar, which extends laterally along much of the Cascadia margin off Oregon and Washington. Comparisons with published seismic data on the distribution of bottom simulating reflectors (BSR), which is the acoustic impedance boundary between methane hydrate (solid phase) and free gas phase below, correlates the bottom simulating reflectors upward termination of the feather edge of methane hydrate stability (FEMHS) zone and the newly identified bubble emission sites off Oregon and Washington. The Cascadia margin off northern California, where the BSR ends seaward of the FEMHS, has fewer sites centered on the 500 m isobaths, although data are more limited there. We propose that the peak in bubble emission sites observed near the 500 m isobath results from migration of free gas from beneath the solid phase of the BSR upslope to the FEMHS termination zone, and suggest that this boundary will be useful to monitor for a change in methane release rate potentially related to a warming ocean.
    Type of Medium: Online Resource
    ISSN: 2296-6463
    Language: Unknown
    Publisher: Frontiers Media SA
    Publication Date: 2021
    detail.hit.zdb_id: 2741235-0
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  • 4
    Online Resource
    Online Resource
    Society of Exploration Geophysicists ; 2022
    In:  Interpretation Vol. 10, No. 1 ( 2022-02-01), p. SB93-SB106
    In: Interpretation, Society of Exploration Geophysicists, Vol. 10, No. 1 ( 2022-02-01), p. SB93-SB106
    Abstract: Acoustic echosounding systems are increasingly used to image water-column backscatter in addition to mapping the seafloor. We have imaged an acoustic flare generated by methane bubbles emanating from a vent sourced at 1840 m water depth offshore northern California using a shipboard Kongsberg EM122. Data include five transits over the flare and approximately 11 h of continuous observation when the ship held station. Shipboard observations showed a strong flare splitting into multiple smaller, intermittent flares at a water depth of 800–1200 m and pronounced temporal variability. We introduce a new approach to processing the data in which we correct the backscatter data for ship motion and bin the data into voxels with dimensions of 20 m in X and Y and 40 m in Z for a transit over the flare and into vertical slices with dimensions of 15 m in X and Z and 4 min in time when the ship was stationary. The processed data indicate that the signal is dominated by bubbles emanating from a source region with a diameter of approximately 40 m located on the southern edge of what is likely a ring of sources with a diameter of approximately 600 m. When the ship was stationary, we were able to track an individual pulse rising at a rate of 8–10 m/min. Our results illustrate the limitations of monitoring temporal variation in gas flux using multibeam echosounders because of the trade-off between imaging the entire flare by averaging over tens of minutes to hours and observing a slice through the flare to capture short-lived pulses of gas expulsion. Nevertheless, because echosounders are widely available, they can continue to provide valuable data on the spatial and temporal distribution of gas emissions on continental margins that can be used to frame hypotheses and plan more comprehensive follow-up experiments.
    Type of Medium: Online Resource
    ISSN: 2324-8858 , 2324-8866
    Language: English
    Publisher: Society of Exploration Geophysicists
    Publication Date: 2022
    detail.hit.zdb_id: 2741968-X
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  • 5
    Online Resource
    Online Resource
    Copernicus GmbH ; 2021
    In:  Natural Hazards and Earth System Sciences Vol. 21, No. 6 ( 2021-06-30), p. 1971-1982
    In: Natural Hazards and Earth System Sciences, Copernicus GmbH, Vol. 21, No. 6 ( 2021-06-30), p. 1971-1982
    Abstract: Abstract. We present an investigation of the disturbance history of an old-growth Douglas-fir (Pseudotsuga menziesii) stand in South Beach, Oregon, for possible growth changes due to tsunami inundation caused by the 1700 CE Cascadia Subduction Zone (CSZ) earthquake. A high-resolution model of the 1700 tsunami run-up heights at South Beach, assuming an “L”-sized earthquake, is also presented to better estimate the inundation levels several kilometers inland at the old-growth site. This tsunami model indicates the South Beach fir stand would have been subjected to local inundation depths from 0 to 10 m. Growth chronologies collected from the Douglas-fir stand shows that trees experienced a significant growth reductions in the year 1700 relative to nearby Douglas-fir stands, consistent with the tsunami inundation estimates. The ±1–3-year timing of the South Beach disturbances are also consistent with disturbances previously observed at a Washington state coastal forest ∼220 km to the north. Moreover, the 1700 South Beach growth reductions were not the largest over the 〉321-year tree chronology at this location, with other disturbances likely caused by climate drivers (e.g., drought or windstorms). Our study represents a first step in using tree growth history to ground truth tsunami inundation models by providing site-specific physical evidence.
    Type of Medium: Online Resource
    ISSN: 1684-9981
    Language: English
    Publisher: Copernicus GmbH
    Publication Date: 2021
    detail.hit.zdb_id: 2069216-X
    detail.hit.zdb_id: 2064587-9
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  • 6
    In: JAMA Network Open, American Medical Association (AMA), Vol. 6, No. 1 ( 2023-01-19), p. e2251512-
    Abstract: One of the biggest challenges when using anti–vascular endothelial growth factor (VEGF) agents to treat retinopathy of prematurity (ROP) is the need to perform long-term follow-up examinations to identify eyes at risk of ROP reactivation requiring retreatment. Objective To evaluate whether an artificial intelligence (AI)–based vascular severity score (VSS) can be used to analyze ROP regression and reactivation after anti-VEGF treatment and potentially identify eyes at risk of ROP reactivation requiring retreatment. Design, Setting, and Participants This prognostic study was a secondary analysis of posterior pole fundus images collected during the multicenter, double-blind, investigator-initiated Comparing Alternative Ranibizumab Dosages for Safety and Efficacy in Retinopathy of Prematurity (CARE-ROP) randomized clinical trial, which compared 2 different doses of ranibizumab (0.12 mg vs 0.20 mg) for the treatment of ROP. The CARE-ROP trial screened and enrolled infants between September 5, 2014, and July 14, 2016. A total of 1046 wide-angle fundus images obtained from 19 infants at predefined study time points were analyzed. The analyses of VSS were performed between January 20, 2021, and November 18, 2022. Interventions An AI-based algorithm assigned a VSS between 1 (normal) and 9 (most severe) to fundus images. Main Outcomes and Measures Analysis of VSS in infants with ROP over time and VSS comparisons between the 2 treatment groups (0.12 mg vs 0.20 mg of ranibizumab) and between infants who did and did not receive retreatment for ROP reactivation. Results Among 19 infants with ROP in the CARE-ROP randomized clinical trial, the median (range) postmenstrual age at first treatment was 36.4 (34.7-39.7) weeks; 10 infants (52.6%) were male, and 18 (94.7%) were White. The mean (SD) VSS was 6.7 (1.9) at baseline and significantly decreased to 2.7 (1.9) at week 1 ( P   & amp;lt; .001) and 2.9 (1.3) at week 4 ( P   & amp;lt; .001). The mean (SD) VSS of infants with ROP reactivation requiring retreatment was 6.5 (1.9) at the time of retreatment, which was significantly higher than the VSS at week 4 ( P   & amp;lt; .001). No significant difference was found in VSS between the 2 treatment groups, but the change in VSS between baseline and week 1 was higher for infants who later required retreatment (mean [SD], 7.8 [1.3] at baseline vs 1.7 [0.7] at week 1) vs infants who did not (mean [SD] , 6.4 [1.9] at baseline vs 3.0 [2.0] at week 1). In eyes requiring retreatment, higher baseline VSS was correlated with earlier time of retreatment (Pearson r  = −0.9997; P   & amp;lt; .001). Conclusions and Relevance In this study, VSS decreased after ranibizumab treatment, consistent with clinical disease regression. In cases of ROP reactivation requiring retreatment, VSS increased again to values comparable with baseline values. In addition, a greater change in VSS during the first week after initial treatment was found to be associated with a higher risk of later ROP reactivation, and high baseline VSS was correlated with earlier retreatment. These findings may have implications for monitoring ROP regression and reactivation after anti-VEGF treatment.
    Type of Medium: Online Resource
    ISSN: 2574-3805
    Language: English
    Publisher: American Medical Association (AMA)
    Publication Date: 2023
    detail.hit.zdb_id: 2931249-8
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