Bottom and Suspended Sediment Backscatter Measurements in a Flume—Towards Quantitative Bed and Water Column Properties

For health and impact studies of water systems, monitoring underwater environments is essential, for which multi-frequency single- and multibeam echosounders are commonly used state-of-the-art technologies. However, the current scarcity of sediment reference datasets of both bottom backscatter angular response and water column scattering hampers empirical data interpretation. Comprehensive reference data derived from measurements in a controlled environment should optimize the use of empirical backscatter data. To prepare for such innovative experiments, we conducted a feasibility experiment in the Delta Flume (Deltares, The Netherlands). Several configurations of sonar data were recorded of the flume floor and suspended sediment plumes. The results revealed that flume reverberation was sufficiently low and that the differential settling of fine-sand plumes in the water column was clearly detected. Following this successful feasibility test, future comprehensive experiments will feature multi-frequency multi-angle measurements on a variety of sediment types, additional scatterers and sediment plumes, resulting in reference datasets for an improved interpretation of underwater backscatter measurements for scientific observation and sustainable management

Diel and seasonal methane dynamics in the shallow and turbulent Wadden Sea

The Wadden Sea is a coastal system along the fringe of the land–sea borders of Denmark, Germany and the Netherlands. The Wadden Sea is extremely productive and influenced by strong variations in physical and biological forcing factors that act on timescales of hours to seasons. Productive coastal seas are known to dominate the ocean's methane emission to the atmosphere, but knowledge of controls and temporal variations in methane dynamics in these vastly dynamic systems is scarce. Here we address this knowledge gap by measuring methane inventories and methanotrophic activity at a temporal resolution of 1 h over a period of 2 d, repeatedly during four successive seasons in the central Dutch Wadden Sea. We found that methane dynamics varied between colder and warmer seasons, with generally higher water column methane concentrations and methanotrophic activity in the warmer seasons. The efflux of methane to the atmosphere was, on the other hand, lower in the warmer seasons because of lower wind speeds. On a diel scale, tides controlled methanotrophic activity, which increased ∼40 % at low tide compared to high tide. We estimate that methane oxidizing bacteria reduce the methane budget of the Dutch Wadden Sea by only 2 %, while ∼1/3 escapes to the atmosphere and ∼2/3 are flushed out into the open North Sea at ebb tide. Our findings indicate that tides play a key role in controlling methane dynamics and methanotrophic activity and highlight the importance of high-resolution and repeated sampling strategies to resolve methane dynamics in fast-changing coastal systems.</p

This work was supported by The Department of the Interior Alaska Climate Adaptation Science Center, which is managed by the USGS National Climate Adaptation Science Center.

53 pages : color illustrations, color maps ; 28 cmThis report is designed as a living document to inform the community, decision makers, and academics and to serve as a learning and teaching tool. The nine key messages summarized on pages 6 and 7 are intended for use as a quick reference. Unique for this type of report, these key messages highlight actions by Juneau's civil society, including local nonprofit organizations.We thank the City and Borough of Juneau (CBJ) for its support in bringing this vital information on climate change to the Juneau community and to others. Thanks especially to all the co-authors and other contributors. The inclusion of such a diverse array of material, including local knowledge, was made possible by the many elders, scientists, and local experts who contributed their time and expertise. The report is online at acrc.alaska.edu/ juneau-climate-report. It is an honor to be the lead editor and project manager for this critical effort. We have a chance to save our world from the most extreme effects of climate change. Let us take it. Gunalchéesh, sincerely, James E. Powell (Jim), PhD, Alaska Coastal Rainforest Center, UASWelcome / Thomas F. Thornton -- Juneau's climate report: History and background / Bruce Botelho -- Using this report -- Acknowledgements / James E. Powell -- A regional Indigenous perspective on adaptation: The Central Council of Tlingit & Haida Indian Tribes of Alaska's Climate Change Adaptation Plan / Raymond Paddock -- Nine key messages -- What we're experiencing: Atmospheric, marine, terrestrial, and ecological effects. Climate. Setting and seasons / Tom Ainsworth -- More precipitation / Rick Thoman -- Higher temperatures / Rich Thoman -- Less snowfall / Eran Hood -- Ocean. Surface uplift and sea level rise / Eran Hood -- Extensive effects of a warming ocean / Heidi Pearson -- Increasing ocean acidification / Robert Foy -- Land. More landslides / Sonia Nagorski & Aaron Jacobs -- Mendenhall Glacier continues to retreat / Jason Amundson -- Tongass Forest impacts and carbon / Dave D'Amore -- Animals. Terrestrial vertebrates in A¿¿ak'w & T'aak¿łu Aani¿¿ / Richard Carstensen -- Three animals as indicators of change / Richard Carstensen -- Insects / Bob Armstrong -- What we're doing: Community response. Upgrading ifrastructure and mitigation / Katie Koester -- Upgrading utilities and other energy consumers / Alec Mesdag -- Growing demand for hydropower / Duff Mitchell -- Leading a shift in transportation / Duff Mitchell -- Maintaining mental health through community and recreation / Linda Kruger & Kevin Maier -- Food security / Darren Snyder & Jim Powell -- Large cruise ship air emissions / Jim Powell -- Tourists' views on climate change mitigation / Jim Powell -- Lowering greenhouse gas emissions / Jim Powell & Peggy Wilcox -- Residents taking action / Andy Romanoff & Jim Powell -- Summary and Recommendations -- References -- Graphics and data sources -- Appendix: Juneau nonprofit climate change organization

A comprehensive overview of radioguided surgery using gamma detection probe technology

The concept of radioguided surgery, which was first developed some 60 years ago, involves the use of a radiation detection probe system for the intraoperative detection of radionuclides. The use of gamma detection probe technology in radioguided surgery has tremendously expanded and has evolved into what is now considered an established discipline within the practice of surgery, revolutionizing the surgical management of many malignancies, including breast cancer, melanoma, and colorectal cancer, as well as the surgical management of parathyroid disease. The impact of radioguided surgery on the surgical management of cancer patients includes providing vital and real-time information to the surgeon regarding the location and extent of disease, as well as regarding the assessment of surgical resection margins. Additionally, it has allowed the surgeon to minimize the surgical invasiveness of many diagnostic and therapeutic procedures, while still maintaining maximum benefit to the cancer patient. In the current review, we have attempted to comprehensively evaluate the history, technical aspects, and clinical applications of radioguided surgery using gamma detection probe technology

Hyperossification in the vertebral column of Devonian placoderm fishes (Arthrodira)

Skeletal bone enlargement (hyperossification) was thought to only occur in endochondral and dermal bones (e.g., endoskeletons of marine tetrapods and dermal bones of certain jawless vertebrates, placoderms, and teleost fishes). However, in some arthrodiran placoderms (basal jawed vertebrates), i.e., Millerosteus minor, Compagopiscis croucheri, Eastmanosteus calliaspis, several types of bone enlargement also occur within the endoskeleton, affecting the vertebral column. Significantly, placoderm endoskeletal bone is thought to be thin-walled, ossifying only in the fibrous layer surrounding a cartilage precursor (historically called perichondral bone), rather than endochondrally/dermally. Hyperossification differs among these three species, revealing a range of internal and external bone morphologies undescribed for the placoderm endoskeleton. Thus, neural arches of M. minor are swollen in external appearance, in cross-section showing considerable deposition of layered, compact bone. In contrast, the arches of E. calliaspis are unswollen externally, with the neural spine cortex composed of the thin perichondral bone expected for placoderms. Histologically, though, the arch comprises numerous layers of perichondral bone. In C. croucheri, as in E. calliaspis, the spine and arch are unswollen externally, but the perichondral bone is thickened and compact, more similar to the condition in M. minor. Vertebral hyperossification in these taxa differs considerably in the degree and mode of cortical tissue thickening, via addition of tissue to the bone’s external (periosteal) and/or internal (endosteal) surfaces. Hyperossifcation in these arthrodires demonstrates that increases in endoskeletal bone mass are not restricted to crown-group gnathostomes (Chondrichthyes + Actinopterygii), representing a first step in the evolution of this process, involving modifications to cortical bone layers

Monitoring underwater nourishments using multibeam bathymetric and backscatter time series

Natural and man-induced coastal erosion endanger life and environment in coastal areas worldwide. For sedimentary barrier coasts, beach and underwater nourishments are an efficient coastal protection strategy. To optimize nourishments and to understand their impact on the marine environment, monitoring strategies are required. In this study, we investigate the potential of multibeam echosounder (MBES) data, providing both bathymetry and backscatter (BS), for monitoring the evolution of the nourished sediment and morphodynamics over time. A time series of seven MBES measurements, as well as two sets of box cores, vibrocores and seismic data were acquired of a channel-side nourishment near the Wadden Sea island Ameland (The Netherlands), between April 2017 and May 2019. In general, a high confidence of the acoustic reliability of the BS time series measurements is demonstrated. The unsupervised Bayesian classification method, supported by ground-truthing, is employed to produce a time series of sediment maps, revealing sediments ranging from sandy mud to sand with varying amounts of shell fragments. Based on the sediment maps, the nourished sediment could be distinguished from the natural sediment. Within one year, the shell-rich pre-nourishment seabed is recreated by washing out finer sediments, which are deposited towards the main tidal channel. Using the seismic data and vibrocores, the shell-rich pre-nourishment seabed could be identified in the subsurface after being buried by the nourishments, supporting the general findings. Furthermore, a rapid development of steep bedforms with increasing sediment sorting is observed in parts of the nourished areas. This study shows that high-resolution sediment maps obtained from a time series of MBES BS together with bathymetry reveal morphodynamic and sedimentary processes of nourishment evolution and can advance underwater nourishment strategies.Aircraft Noise and Climate Effect

Geofysische opnamen ten behoeve van het geoarcheologisch vooronderzoek in de Winput Zuid (plangebied Marker Wadden)

Voor het natuurontwikkelingsproject Marker Wadden', dat thans wordt uitgevoerd in het Markermeer, vindt grootschalig grondverzet plaats waaronder de aanleg van zandwinputten voor het werk. Bij dit grondverzet kunnen eventueel voorkomende archeologische waarden in de ondergrond van het plangebied Marker Wadden worden aangetast. In dit rapport is ten behoeve van het prospectief archeologisch vooronderzoek van de Winput Zuid de onderwaterbodem van dit gebied onderzocht. De aandacht lag specifiek op de top van het begraven Pleistocene oppervlak. Met name de hoge delen van het oppervlak zijn er archeologisch gezien kansrijk voor bewaard gebleven erfgoed uit de steentijd. Het onderzoek is uitgevoerd als een combinatie van geofysische opnamemethoden, te weten: sonderingen (CPT's), het Boomer seismisch meetsysteem, en het Electrical Resistivity Tomography meetsysteem (ERT). Met CPT's en Boomer seismiek werden eerst 4 geologische raaien over het zandwingebied gezet. Met het verworven inzicht in de profielopbouw werd vervolgens een kaart van de top van het Pleistocene oppervlak vervaardigd, waarbij een erosiegebied van Holocene getijdengeulinsnijdingen (lage archeologische verwachting) en een niet-erosief gebied aan Pleistocene oppervlakte gekarteerd is. Het Pleistocene oppervlak heeft haar hoogste ligging in het oostelijk deel van de Winput Zuid, op een diepte rond de 12 m -NAP. De ERT meetresultaten bevestigen de ligging van de Holocene geulinsnijdingen maar in het niet-erosieve Pleistocene gebied fluctueren de ERT weerstand metingen (te) sterk. De ERT grote meetuitslagen worden daar niet bevestigd door de CPT en Boomer metingen en zijn om die reden niet gebruikt voor het Pleistocene hoogtelijnen patroon voor het Pleistocene niet-erosieve top zandgebied