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  • 1
    Publication Date: 2022-04-04
    Description: Sewage disposal onto agricultural land may result in the high accumulation of organic wastes, which questions the applicability of typical elemental analysis used for the soil components. To monitor the contamination status of agricultural soils at a former sedimentation basin, after the long‐term cessation of wastewater irrigation, 110 locations (15–20 cm depth) and 4 boreholes (up to 100 cm depth) were sampled to determine pH, loss on ignition, and concentration of Ni, Cu, Pb, Zn, and Cr. Additionally, the applicability of portable X‐ray fluorescence (pXRF) for the soil samples highly influenced by the organic wastes was evaluated. The study revealed the presence of a relatively homogenous sewage waste layer (depth of 20 cm), characterized by slightly acidic to neutral pH (6.3–7.5), high organic matter (OM) accumulation (up to 49%), and elevated concentration (mg kg −1) ranges between: Pb (5–321), Cu (31–2828), Ni (10–193), Cr (14–966), and Zn (76–6639). The pXRF analysis revealed metal concentration increase in mineral samples (up to 50%). The regression models and correction factors demonstrated high correlation and significance of pXRF measurement with response to increasing OM content, with the lowest r 2 = 0.86 obtained for Ni. Correlation of pXRF and AES measurement illustrated element‐dependent response for soils high in organics. Zn, Cu, and Cr pXRF analysis led to a slight underestimation in lower values, but overall good correlations (0.87; 0.89; and 0.88 respectively). Pb and Ni pXRF measurement revealed higher deviation from the reference in both lower and higher concentrations (0.74 and 0.70, respectively).
    Description: German Federation of Industrial Research Associations http://dx.doi.org/10.13039/501100002723
    Description: Federal Ministry for Economic Affairs and Energy http://dx.doi.org/10.13039/501100006360
    Keywords: ddc:577.14
    Language: English
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  • 2
    Publication Date: 2022-12-05
    Description: Classification of atmospheric circulation patterns (CP) is a common tool for downscaling rainfall, but it is rarely used for West Africa. In this study, a two‐step classification procedure is proposed for this region, which is applied from 1989 to 2010 for the Sudan‐Sahel zone (Central Burkina Faso) with a focus on heavy rainfall. The approach is based on a classification of large‐scale atmospheric CPs (e.g., Saharan Heat Low) of the West African Monsoon using a fuzzy rule‐based method to describe the seasonal rainfall variability. The wettest CPs are further classified using meso‐scale monsoon patterns to better describe the daily rainfall variability during the monsoon period. A comprehensive predictor screening for the seasonal classification indicates that the best performing predictor variables (e.g., surface pressure, meridional moisture fluxes) are closely related to the main processes of the West African Monsoon. In the second classification step, the stream function at 700 hPa for identifying troughs and ridges of tropical waves shows the highest performance, providing an added value to the overall performance of the classification. Thus, the new approach can better distinguish between dry and wet CPs during the rainy season. Moreover, CPs are identified that are of high relevance for daily heavy rainfall in the study area. The two wettest CPs caused roughly half of the extremes on about 6.5% of days. Both wettest patterns are characterized by an intensified Saharan Heat Low and a cyclonic rotation near the study area, indicating a tropical wave trough. Since the classification can be used to condition other statistical approaches used in climate sciences and other disciplines, the presented classification approach opens many different applications for the West African Monsoon region.
    Description: A two‐step classification of daily atmospheric circulation patterns is used to describe seasonal and daily rainfall variability in West Africa. The approach clearly distinguishes between dry and wet patterns if sea level pressure and stream function at 700 hPa are used. The two wettest patterns trigger about half of heavy rainfall events in Central Burkina Faso. They are characterized by an intensified Saharan Heat Low and a cyclonic rotation indicating a tropical wave trough near the study area.
    Description: Bundesministerium für Bildung und Forschung http://dx.doi.org/10.13039/501100002347
    Keywords: ddc:551.5 ; circulation pattern ; classification ; downscaling ; heavy rainfall ; West Africa
    Language: English
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  • 3
    Publication Date: 2022-06-28
    Description: Braided reaches were common along near‐natural Alpine rivers, and the associated habitat dynamics supported plant and animal species specialized on early‐successional stages. The extensive riparian zones could mitigate climate change by absorbing floods and by retaining water during droughts. Human impacts largely reduced active river corridors through altered discharge and construction of dykes, while recent restoration projects aim at increasing river dynamics. The causes and consequences of Alpine river degradation are well understood, but there are only few quantitative studies on floodplain degradation and restoration. Thus, we have reconstructed historical changes of gravel bars along five Alpine rivers (Iller, Inn, Isar, Lech, and Wertach) in Southern Germany in the period 1808–2009, based on historical maps and aerial images. We found losses of 〉90% in gravel bar area along these rivers since the mid‐19th century. The decline was caused by a reduction of the active river corridor and by ongoing succession of the remaining open habitats. Within the past 30 years, at the Isar River, restoration measures were realized with the aim to widen the active river corridor and to recreate gravel bars. In four restored reaches, we found that 5% of the historical gravel bar area recovered, and that the proportion of restored gravel bar area was highest after intermediate flooding. We conclude that the active river corridors of German Alpine rivers are almost completely lost, and that more extensive restoration needs to be done to preserve the habitat dynamics and biodiversity of these systems, and to adapt Alpine rivers to climate change.
    Description: Deutsche Bundesstiftung Umwelt http://dx.doi.org/10.13039/100007636
    Keywords: ddc:551.35
    Language: English
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  • 4
    Publication Date: 2022-10-13
    Description: Accurate and reliable precipitation data with high spatial and temporal resolution are essential in studying climate variability, water resources management, and hydrological forecasting. A range of global precipitation data are available to this end, but how well these capture actual precipitation remains unknown, particularly for mountain regions where ground stations are sparse. We examined the performance of three global high‐resolution precipitation products for capturing precipitation over Central Asia, a hotspot of climate change, where reliable precipitation data are particularly scarce. Specifically, we evaluated MSWEP, CHIRPS, and GSMAP against independent gauging stations for the period 1985–2015. Our results show that MSWEP and CHIRPS outperformed GSMAP for wetter periods (i.e., winter and spring) and wetter locations (150–600 mm·year−1), lowlands, and mid‐altitudes (0–3,000 m), and regions dominated by winter and spring precipitation. MSWEP performed best in representing temporal precipitation dynamics and CHIRPS excelled in capturing the volume and distribution of precipitation. All precipitation products poorly estimated precipitation at higher elevations (〉3,000 m), in drier areas (〈150 mm), and in regions characterized by summer precipitation. All products accurately detected dry spells, but their performance decreased for wet spells with increasing precipitation intensity. In sum, we find that CHIRPS and MSWEP provide the most reliable high‐resolution precipitation estimates for Central Asia. However, the high spatial and temporal heterogeneity of the performance call for a careful selection of a suitable product for local applications considering the prevailing precipitation dynamics, climatic, and topographic conditions.
    Description: We present the first quantitative evaluation of global high‐resolution (below 12 km) precipitation products against independent ground observations over Central Asia. Our results show that MSWEP was best at representing temporal precipitation dynamics, and CHIRPS was most prominent in representing the volume and distribution of precipitation. This is especially the case of wet seasons, altitudes below 3,000 m, and regions dominated by spring and winter precipitation. Our analysis provides key insights on the precipitation products' suitability for local hydrological applications.
    Description: Leibniz‐Institut für Agrarentwicklung in Transformationsökonomien
    Description: Volkswagen Foundation http://dx.doi.org/10.13039/501100001663
    Keywords: ddc:551.6
    Language: English
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  • 5
    Publication Date: 2022-08-04
    Description: The 2011/2012 summer drought in Southeastern South America (SESA) was a short but devastating event. What would this event have looked like under pre‐industrial conditions, or in a +2 degC world? We find that climate change causes the region to be at a higher risk of drought. However, we found no large‐scale changes in the half‐month water budgets. We show that the climate change induced positive precipitation trend in the region outweighs the increased temperatures and potential evapotranspiration during the 2011/2012 drought. image
    Keywords: ddc:551.5
    Language: English
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  • 6
    Publication Date: 2022-10-04
    Description: We review the widely used concepts of “buoyancy” and “convective available potential energy” (CAPE) in relation to deep convection in tropical cyclones and discuss their limitations. A fact easily forgotten in applying these concepts is that the buoyancy force of an air parcel, as often defined, is non‐unique because it depends on the arbitrary definition of a reference density field. However, when calculating CAPE, the buoyancy of a lifted air parcel is related to the specific reference density field along a vertical column passing through that parcel. Both concepts can be generalized for a vortical flow and to slantwise ascent of a lifted air parcel in such a flow. In all cases, the air parcel is assumed to have infinitely small dimensions. In this article, we explore the consequences of generalizing buoyancy and CAPE for buoyant regions of finite size that perturb the pressure field in their immediate environment. Quantitative calculations of effective buoyancy, defined as the sum of the conventional buoyancy and the static vertical perturbation pressure gradient force induced by it, are shown for buoyant regions of finite width. For a judicious choice of reference density, the effective buoyancy per unit mass is essentially a unique force, independent of the reference density, but its distribution depends on the horizontal scale of the buoyant region. A corresponding concept of “effective CAPE” is introduced and its relevance to deep convection in tropical cyclones is discussed. The study is conceived as a first step to understanding the decreasing ability of inner‐core deep convection in tropical cyclones to ventilate the mass of air converging in the frictional boundary layer as the vortex matures and decays.
    Description: The buoyancy force of an infinitesimally small air parcel is non‐unique, depending on the arbitrary definition of a reference density field. When calculating the “convective available potential energy” (CAPE), the buoyancy of a lifted air parcel is related to the reference density field along a vertical column passing through that parcel. We generalize buoyancy and CAPE for buoyant regions of finite size that perturb the pressure field in their immediate environment and discuss the relevance to deep convection in tropical cyclones.
    Keywords: ddc:551.5
    Language: English
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  • 7
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    John Wiley & Sons, Ltd | Chichester, UK
    Publication Date: 2022-10-04
    Description: New cross‐validation diagnostics have been derived by further partitioning well‐established impact diagnostics. They are related to consistency relations, the most prominent of which indicates whether the first‐guess departures of a given observation type pull the model state into the direction of the verifying data (when processed with the ensemble estimated model error covariances). Alternatively, this can be regarded as cross‐validation between model error covariance estimates from the ensemble (which are used in the data assimilation system) and estimates diagnosed directly from the observations. A statistical cross‐validation tool has been developed that includes an indicator of statistical significance as well as a normalization that makes the statistical comparison largely independent from the total number of data and the closeness of their collocation. We also present a version of these diagnostics related to single‐observation experiments that exploits the same consistency relations but is easier to compute. Diagnostics computed within the Deutscher Wetterdienst's localized ensemble transform Kalman filter (LETKF) are presented for various kinds of bins. Results from well‐established in‐situ measurements are taken as a benchmark for more complex observations. Good agreement is found for radio‐occultation bending angle measurements, whereas atmospheric motion vectors are generally also beneficial but substantially less optimal than the corresponding in‐situ measurements. This is consistent with reported atmospheric motion vector height assignment problems. To illustrate its potential, a recent example is given where the method allowed identifying bias problems of a subgroup of aircraft measurements. Another diagnostic relationship compares the information content of the analysis increments with a theoretical optimum. From this, the information content of the LETKF increments is found to be considerably lower than those of the deterministic hybrid ensemble–variational system, which is consistent with the LETKF's limitation to the comparably low‐dimensional ensemble space for finding the optimal analysis.
    Description: New cross‐validation diagnostics are presented, allowing to test the consistent use of different observation types in the data assimilation system. The figure gives an example in which these new diagnostics allowed identification of the detrimental impact of a group of aircraft measurements (which as a consequence has now been blacklisted in the Deutscher Wetterdienst's operational system). More precisely, brown colors in this plot indicate regions where these aircraft measurements pulled the analysis state away from radiosonde observations.
    Keywords: ddc:551.5
    Language: English
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  • 8
    Publication Date: 2022-10-06
    Description: Trade wind convection organises into a rich spectrum of spatial patterns, often in conjunction with precipitation development. Which role spatial organisation plays for precipitation and vice versa is not well understood. We analyse scenes of trade‐wind convection scanned by the C‐band radar Poldirad during the EUREC4A field campaign to investigate how trade‐wind precipitation fields are spatially organised, quantified by the cells' number, mean size, and spatial arrangement, and how this matters for precipitation characteristics. We find that the mean rain rate (i.e., the amount of precipitation in a scene) and the intensity of precipitation (mean conditional rain rate) relate differently to the spatial pattern of precipitation. Whereas the amount of precipitation increases with mean cell size or number, as it scales well with the precipitation fraction, the intensity increases predominantly with mean cell size. In dry scenes, the increase of precipitation intensity with mean cell size is stronger than in moist scenes. Dry scenes usually contain fewer cells with a higher degree of clustering than moist scenes do. High precipitation intensities hence typically occur in dry scenes with rather large, few, and strongly clustered cells, whereas high precipitation amounts typically occur in moist scenes with rather large, numerous, and weakly clustered cells. As cell size influences both the intensity and amount of precipitation, its importance is highlighted. Our analyses suggest that the cells' spatial arrangement, correlating mainly weakly with precipitation characteristics, is of second‐order importance for precipitation across all regimes, but it could be important for high precipitation intensities and to maintain precipitation amounts in dry environments.
    Description: We analyse scenes of trade‐wind convection scanned by the C‐band radar Poldirad during the EUREC4A field campaign to investigate how trade‐wind precipitation fields are spatially organised, quantified by the cells' number, mean size, and spatial arrangement, and how this matters for precipitation characteristics. We conclude that the cells' size is important for both the amount and intensity of precipitation, whereas the cells' spatial arrangement is of second‐order importance for precipitation across all regimes, but possibly important for precipitation in dry environments.
    Description: Deutsche Forschungsgemeinschaft (DFG, German Research Foundation) under Germany's Excellence Strategy—EXC 2037 'CLICCS—Climate, Climatic Change, and Society'
    Description: https://doi.org/10.25326/217
    Description: https://doi.org/10.25326/79
    Keywords: ddc:551.5
    Language: English
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  • 9
    Publication Date: 2022-10-06
    Description: The Madden–Julian oscillation (MJO) is the dominant component of tropical intraseasonal variability, with wide‐reaching impacts even on extratropical weather and climate patterns. However, predicting the MJO is challenging. One reason is the suboptimal state estimates obtained with standard data assimilation (DA) approaches. These are typically based on filtering methods with Gaussian approximations and do not take into account physical properties that are important specifically for the MJO. In this article, a constrained ensemble DA method is applied to study the impact of different physical constraints on the state estimation and prediction of the MJO. The quadratic programming ensemble (QPEns) algorithm utilized extends the standard stochastic ensemble Kalman filter (EnKF) with specifiable constraints on the updates of all ensemble members. This allows us to recover physically more consistent states and to respect possible associated non‐Gaussian statistics. The study is based on identical twin experiments with an adopted nonlinear model for tropical intraseasonal variability. This so‐called skeleton model succeeds in reproducing the main large‐scale features of the MJO and closely related tropical waves, while keeping adequate simplicity for fast experiments on intraseasonal time‐scales. Conservation laws and other crucial physical properties from the model are examined as constraints in the QPEns. Our results demonstrate an overall improvement in the filtering and forecast skill when the model's total energy is conserved in the initial conditions. The degree of benefit is found to be dependent on the observational setup and the strength of the model's nonlinear dynamics. It is also shown that, even in cases where the statistical error in some waves remains comparable with the stochastic EnKF during the DA stage, their prediction is improved remarkably when using the initial state resulting from the QPEns.
    Description: Unsatisfactory predictions of the MJO are partly due to DA methods that do not respect non‐Gaussian PDFs and the physical properties of the tropical atmosphere. Therefore the QPEns, an algorithm extending a stochastic EnKF with state constraints, is tested here on a simplified model for the MJO and associated tropical waves. Our series of identical twin experiments shows, in particular, that a constraint on the truth's nonlinear total energy improves forecasts statistically and can, in certain situations, even prevent filter divergence. image
    Description: Deutsche Forschungsgemeinschaft : Heisenberg Award (DFG JA1077/4‐1); Transregional Collaborative Research Center SFB / TRR 165 “Waves to Weather” http://dx.doi.org/10.13039/501100001659
    Description: Office of Naval Research (ONR) http://dx.doi.org/10.13039/100000006
    Keywords: ddc:551.6
    Language: English
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  • 10
    Publication Date: 2022-10-06
    Description: The stochastically perturbed parametrisation tendency (SPPT) scheme is a well‐established technique in ensemble forecasting to address model uncertainty by introducing perturbations into the tendencies provided by the physics parametrisations. The magnitude of the perturbations scales with the local net parametrisation tendency, resulting in large perturbations where diabatic processes are active. Rapidly ascending air streams, such as warm conveyor belts (WCBs) and organized tropical convection, are often driven by cloud diabatic processes and are therefore prone to such perturbations. This study investigates the effects of SPPT and initial condition perturbations on rapidly ascending air streams by computing trajectories in sensitivity experiments with the European Centre for Medium‐Range Weather Forecasts (ECMWF) ensemble prediction system, which are set up to disentangle the effects of initial conditions and physics perturbations. The results demonstrate that SPPT systematically increases the frequency of rapidly ascending air streams. The effect is observed globally, but is enhanced in regions where the latent heating along the trajectories is larger. Despite the frequency changes, there are only minor modifications to the physical properties of the trajectories due to SPPT. In contrast to SPPT, initial condition perturbations do not affect WCBs and tropical convection systematically. An Eulerian perspective on vertical velocities reveals that SPPT increases the frequency of strong upward motions compared with experiments with unperturbed model physics. Consistent with the altered vertical motions, precipitation rates are also affected by the model physics perturbations. The unperturbed control member shows the same characteristics as the experiments without SPPT regarding rapidly ascending air streams. We make use of this to corroborate the findings from the sensitivity experiments by analyzing the differences between perturbed and unperturbed members in operational ensemble forecasts of ECMWF. Finally, we give an explanation of how symmetric, zero‐mean perturbations can lead to a unidirectional response when applied in a nonlinear system.
    Description: The stochastically perturbed parametrisation tendencies (SPPT) scheme is used at ECMWF to perturb the model physics and introduces state‐dependent perturbations into the parametrisation tendencies. The frequency of rapidly ascending air streams is systematically enhanced when SPPT is active. This effect is stronger when the latent heating is large (panel a), and is therefore more pronounced in the Tropics than in the Extratropics. In contrast, the impact of SPPT on the physical properties of the air streams, such as the latent heat release, is very small (panel b).
    Description: Helmholtz Young Investigator Group ‘Sub‐ Seasonal Predictability: Understanding the Role of Diabatic Outflow’
    Keywords: ddc:551.5
    Language: English
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  • 11
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    John Wiley & Sons, Ltd. | Chichester, UK
    Publication Date: 2022-09-22
    Description: This note is framed as an open question to the community regarding parameterisation schemes using the blocking layer depth to reduce the orographic gravity wave drag. It is the purpose of this note to argue that the current orographic gravity wave drag parameterisation in the vicinity of blocking is inadequate. Reducing the gravity wave amplitude (and thereby reducing the gravity wave drag) by assuming an effective mountain height dependent on the blocking depth is not realistic. The arguments given here will hopefully spark a debate and new considerations, ultimately leading to improvements in current orographic gravity wave drag parameterisations. This note illustrates that low‐level blocking can induce more gravity waves or gravity waves with a higher momentum flux (compared to the current parameterisation schemes). More realistic parameterisation schemes are likely to improve the models' performance. However, the fact is complex theories are needed to describe gravity wave excitation by orography so that it is difficult to represent gravity wave nature by a ‘too simple’ parameterisation scheme.
    Description: The purpose of this letter is to provide arguments that the current gravity wave drag parameterisation in the vicinity of blocking is inadequate. Reducing the gravity wave drag depending on the blocking depth is not a realistic representation. The letter lists five ways in which the blocking layer can result in a greater amount of gravity wave drag.
    Keywords: ddc:551.5
    Language: English
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  • 12
    Publication Date: 2022-08-09
    Keywords: ddc:551.6
    Language: English
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  • 13
    Publication Date: 2022-08-09
    Description: High wind speed (U) is one of the most dangerous natural hazards in North America and Europe. As a result, spatially explicit, statistical estimation of extreme U is of particular relevance for many sectors. However, the most common sources of wind speed data such as reanalysis data and in situ measurements are limited for this purpose due to their coarse spatial resolution and low representativeness. Thus, the main goal was to develop a high spatial resolution (250 m × 250 m) model (GloWiSMo‐X) for monthly mapping of the maximum hourly U for a 10‐year return period (U10yr) in North America and Europe. The multistep development of GloWiSMo‐X is based on 2544 hourly U time series available from the integrated surface global hourly meteorological data set (UNCEI), U time series from ERA5 (UERA5), and mean wind speed from the Global Wind Speed Model (U¯GloWiSMo). Firstly, the block maxima method was applied to estimate monthly wind speed for a 10‐year return period for both UNCEI (U10yr,NCEI) and UERA5 (U10yr,ERA5). Secondly, the least squares boosting approach was used to predict the target variable U10yr,NCEI yielding the predictions Û10yr. The predictor variables U10yr,ERA5, U¯GloWiSMo, continent, and month were used as input. It was found that the highest monthly continental means of Û10yr (U¯10yr) in January are 16.4 m/s in North America and 16.3 m/s in Europe. U¯10yr dropped to 13.4 m/s and 12.5 m/s in August. The annual cycle of U¯10yr is more pronounced in Europe than in North America. The central parts of the USA and Western Europe were identified as intracontinental regions with the highest U¯10yr. GloWiSMo‐X proves to be very broadly applicable as it covers two different continents and all months. The model validation by the mean squared error (MSE) demonstrates its improved predictive power compared to ERA5.
    Description: A high spatial resolution (250 m × 250 m) model (GloWiSMo‐X) for monthly mapping of the maximum hourly wind speed for a 10‐year return period in North America and Europe was developed. The highest monthly continental means are 16.4 m/s in North America and 16.3 m/s in Europe. Due to the pronounced annual cycle, it drops to 13.4 m/s and 12.5 m/s in August. image
    Description: Bundesministerium für Umwelt, Naturschutz und nukleare Sicherheit
    Keywords: ddc:551.5
    Language: English
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  • 14
    Publication Date: 2022-08-09
    Description: Organic matter management can improve soil structural properties. This is crucial for agricultural soils in tropical regions threatened by high rainfall intensities. Compared to conventional farming, organic farming is usually deemed to increase organic carbon and improve soil structural properties such as stability and permeability. However, how much, if any, buildup of organic carbon is possible or indeed occurring also depends on soil type and environmental factors. We compared the impact of seven years of organic farming (annually 13.6 t ha−1 of composted manure) with that of conventional practices (2 t ha−1 of farmyard manure with 150–170 kg N ha−1 of mineral fertilizers) on soil structural properties. The study was conducted on a Vertisol in India with a two‐year crop rotation of cotton soybean wheat. Despite large differences in organic amendment application, organic carbon was not significantly different at 9.6 mg C g−1 on average in the topsoil. However, the size distribution of water‐stable aggregates shifted toward more aggregates 〈137 μm in the organic systems. Cumulative water intake was lower compared to the conventional systems, leading to higher runoff and erosion. These changes might be related to the lower pH and higher exchangeable sodium in the organic systems. Our results indicate that higher application of organic amendments did not lead to higher soil organic carbon and associated improvement in soil structures properties compared to integrated fertilization in this study. Chemical properties may dominate soil aggregation retarding the uptake and integration of organic amendments for sustainable agricultural intensification in tropical, semiarid climates.
    Description: Biovision Foundation for Ecological Development http://dx.doi.org/10.13039/501100015593
    Description: Coop Sustainability Fund
    Description: Swiss Agency for Development and Cooperation (SDC)
    Description: Foundation fiat panis http://dx.doi.org/10.13039/501100011087
    Description: Liechtenstein Development Service http://dx.doi.org/10.13039/501100015698
    Description: https://doi.org/10.6084/m9.figshare.18665612
    Keywords: ddc:631.4
    Language: English
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  • 15
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    Springer
    In:  In: World Atlas of Submarine Gas Hydrates in Continental Margins. , ed. by Mienert, J., Berndt, C. 〈https://orcid.org/0000-0001-5055-0180〉, Tréhu, A. M., Camerlenghi, A. and Liu, C. S. Springer, Cham, pp. 451-461.
    Publication Date: 2022-01-06
    Description: The Black Sea has undergone several limnic and marine stages due to fluctuations in the global sea level. The exchange of saline water from the Mediterranean Sea to the Black Sea through the Bosporus Strait was interrupted when the sea level dropped below the Bosporus sill. This induced limnic conditions, while marine conditions were established after the reconnection to saline Mediterranean seawater. Extended river fan systems developed during sea level low-stands, providing large amounts of organic material being buried by rapid sedimentation on the slopes of the Black Sea margins. The biogenic degradation of this material produces most of the methane gas expelled into the anoxic water column today. This largely happens by ubiquitous cold vents at ~700 m water depth (i.e. at the stability boundary of methane hydrates) and by mud volcanoes in ~2000 m water depth. A significant amount of gas is expected to accumulate in the sediment within the methane hydrate stability zone. However, bottom-simulating reflectors, the seismic indicator for gas hydrates, are not found everywhere along the margin. Recent analyses of the Danube and Dniepr fans have revealed a discontinuous gas hydrate formation in an area with no active seeps, while areas of active seepage located in the vicinity of BSR reflections held no gas hydrates. In addition, the ongoing diffusion of salt into the uppermost Black Sea sediment pore space since the last glacial maximum further reduces the volume of the gas hydrate stability zone. Estimates of the total amount of gas stored in gas hydrates therefore require a detailed structural analysis prior to regional- or basin-scale modelling attempts.
    Type: Book chapter , NonPeerReviewed
    Format: text
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  • 16
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    Springer
    In:  In: World Atlas of Submarine Gas Hydrates in Continental Margins. , ed. by Mienert, J., Berndt, C. 〈https://orcid.org/0000-0001-5055-0180〉, Tréhu, A. M., Camerlenghi, A. and Liu, C. S. Springer, Cham, pp. 73-85.
    Publication Date: 2022-01-20
    Description: Marine electromagnetic methods provide useful and independent measures for the identification and quantification of submarine gas hydrates. The resistivity of seafloor sediments, drawn from area-wide electromagnetic data, mainly depends on the sediment porosity and the nature of the pore fluid. Gas hydrates and free gas are both electrically resistive. The replacement of saline water, thus conductive pore water with resistive gas hydrate or free gas, increases the sediment resistivity and can be used to provide accurate saturation estimates if the background lithology is known. While seismic methods are predominantly used to study the distribution of submarine gas hydrates, a growing number of global field studies have demonstrated that the joint interpretation of marine seismic and electromagnetic methods improves the evaluation of submarine gas hydrate targets. This article discusses the relationship between resistivity and free gas/gas hydrate saturation levels, how the resistivity of the sediment may be measured and summarizes the status and results of current and past field studies.
    Type: Book chapter , NonPeerReviewed
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  • 17
    Publication Date: 2022-04-29
    Description: Every year, vast quantities of plastic debris arrive at the ocean surface. Nevertheless, our understanding of plastic movements is largely incomplete and many of the processes involved with the horizontal and vertical displacement of plastics in the ocean are still basically unknown. In this chapter we review the dynamics associated with the transport of plastics and other pollutants at oceanic fronts. Fronts had been historically defined as simple barriers to exchange, but here we show that the role of these structures in influencing the transport of plastics is more complex. The tools used to investigate the occurrence of frontal structures at various spatial scales are reviewed in detail, with a particular focus on their potential applications to the study of plastic pollution. Three selected case studies are presented to better describe the role of fronts in favoring or preventing plastic exchanges: the large-scale Antarctic Circumpolar Current, a Mediterranean mesoscale front, and the submesoscale fronts in the Gulf of Mexico. Lastly, some aspects related to the vertical subduction of plastic particles at oceanic fronts are discussed as one of the most promising frontiers for future research. The accumulation of floating debris at the sea surface is mainly affected by the horizontal components of frontal dynamics. At the same time, vertical components can be relevant for the export of neutrally buoyant particles from the surface into the deep sea. Based on these evidences, we propose that submesoscale processes can provide a fast and efficient route of plastic transport within the mixed layer, while mesoscale instabilities and associated vertical velocities might be the dominant mechanism to penetrate the deeper ocean on slower but broader scales. We conclude that given the ubiquitous presence of fronts in the world’s ocean, their contribution to the global plastic cycle is probably not negligible and the role of these processes in vertically displacing neutrally buoyant microplastics should be investigated in more detail.
    Type: Book chapter , NonPeerReviewed
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  • 18
    Publication Date: 2022-05-20
    Description: The Barents Sea, located close to the Arctic Ocean, is a petroleum province featuring an extensive occurrence of gas hydrates and shallow gas in compacted sediments. Glacial erosion and uplift have contributed to the migration of gas originating from deeper rocks to the shallow sediments of this region, resulting in hydrates with higher-order hydrocarbons in addition to methane. This article documents reported gas hydrate indications and major controls on hydrate stability in the Barents Sea.
    Type: Book chapter , PeerReviewed
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  • 19
    Publication Date: 2022-05-25
    Description: Since global navigation satellite systems (GNSS) for determining the absolute geolocation do not reach into the ocean, underwater robots typically obtain a GNSS position at the water surface and then use a combination of different sensors for estimating their pose while diving, including inertial navigation, acoustic doppler velocity logs, ultra short baseline localization systems and pressure sensors. When re-navigating to the same seafloor location after several days, months or years, e.g. for coastal monitoring, the absolute uncertainty of such systems can be in the range of meters for shallow water, and tens of meters for deeper waters in practice. To enable absolute relocalization in marine data science applications that require absolute seafloor positions in the range of centimeter precision, in this contribution we suggest to equip the monitoring area with visual markers that can be detected reliably even in case they are partially overgrown or partially buried by sediment, which can happen quickly in coastal waters. Inspired by patterns successful in camera calibration, we create robust markers that exhibit features at different scales, in order to allow detection, identification and pose estimation from different cameras and various altitudes as visibility (and therefore the maximum possible survey altitude) in coastal waters can vary significantly across seasons, tides and weather. The low frequency content of the marker resembles a human-readable digit, in order to allow easy identification by scientists. We present early results including promising initial tests in coastal waters.
    Type: Book chapter , NonPeerReviewed
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  • 20
    Publication Date: 2022-06-02
    Description: While offshore groundwater has been utilized by coastal communities as far back as 1000 BC, only in the past 10 years has the global volume of fresh-to-brackish water hosted in offshore aquifers been truly appreciated. There are vast quantities (~300–500 × 103 km3) of offshore freshened groundwater sequestered in continental shelf sediments under water depths of less than 60 m within 110 km of the coastline. New marine geophysical methods now make it possible to map and quantify low salinity offshore groundwater bodies. To date, these offshore resources have not been developed. Offshore freshened groundwater could be produced if wells are located close to the shoreline and coastal desalination plants.
    Type: Book chapter , NonPeerReviewed
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  • 21
    Publication Date: 2022-07-11
    Description: Underwater images are challenging for correspondence search algorithms, which are traditionally designed based on images captured in air and under uniform illumination. In water however, medium interactions have a much higher impact on the light propagation. Absorption and scattering cause wavelength- and distance-dependent color distortion, blurring and contrast reductions. For deeper or turbid waters, artificial illumination is required that usually moves rigidly with the camera and thus increases the appearance differences of the same seafloor spot in different images. Correspondence search, e.g. using image features, is however a core task in underwater visual navigation employed in seafloor surveys and is also required for 3D reconstruction, image retrieval and object detection. For underwater images, it has to be robust against the challenging imaging conditions to avoid decreased accuracy or even failure of computer vision algorithms. However, explicitly taking underwater nuisances into account during the feature extraction and matching process is challenging. On the other hand, learned feature extraction models achieved high performance in many in-air problems in recent years. Hence we investigate, how such a learned robust feature model, D2Net, can be applied to the underwater environment and particularly look into the issue of cross domain transfer learning as a strategy to deal with the lack of annotated underwater training data.
    Type: Book chapter , NonPeerReviewed
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  • 22
    Publication Date: 2022-08-08
    Description: Fish food is an inevitable item in human consumption with healthy sourceof good quality proteins and fat. Aqua industry can help to improve food security,livelihoods for the poorest and to meet the world’s food demands. But producingmore seafood that is at affordable cost with rich nutrition is challenging for aquaindustry. Many factors affect the productivity of aqua industry; one such an impor-tant constraint is bacterial diseases. Hence, Aqua industry, a booming businesssector, immensely requires continued research with scientific and technical devel-opments, and innovations. Study of bacterialfish disease is one such thrust areawhich requires intense research to understand the causes and control bacterialdiseases infish. The appearance and development of afish disease is the result ofthe interaction among pathogen, host and environment. An insight into bacterialfishdiseases, clinical symptoms and treatment may help to manage the bacterial diseasesand so can make aqua industry a more profitablefield. This chapter deals withdifferent aspects of the most threatening bacterial diseases, occurring in farmedfishes and also in wildfishes, which are results infish loss and economic lossworldwide. A wide range of gram positive and gram-negative bacteria causingbacterial diseases, clinical symptoms, diagnosis, treatment, vaccines and the natureof water habitat are also discussed in this chapter.
    Type: Book chapter , NonPeerReviewed
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  • 23
    Publication Date: 2022-08-12
    Description: The Digital Earth project aimed for the integration of data science and Earth science. Here, we reflect on the main lessons learned that include the need for interdisciplinary collaboration, thinking out of the box, the concept of ‘thinking in workflows’ and models for the sustainable implementation of scientific software, data infrastructure and policies.
    Type: Book chapter , NonPeerReviewed
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  • 24
    Publication Date: 2022-08-12
    Description: Digital Earth is a project funded by the German Helmholtz Association with all centers of the research field Earth and Environment involved. The main goal of the Digital Earth project is to develop and bundle data science methods in extendable and maintainable scientific workflows that enable natural scientists in collaboration with data scientists to achieve a deeper understanding of the Earth system. This has been achieved by developing solutions for data analysis and exploration with visual and computational approaches with data obtained in a SMART monitoring approach and modeling studies, accompanied by a continuous evaluation of the collaboration processes. In this chapter, the history, setup, and focus of the Digital Earth project are described.
    Type: Book chapter , NonPeerReviewed
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  • 25
    Publication Date: 2022-08-17
    Description: The Digital Earth project aims at a strong interrelation between Data and Earth Science and a step-change in implementing data science methods within Earth science research. During the project, the progress of interdisciplinary collaboration and adoption of data science methods has been measured and assessed with the goal to trace the success of the project. This chapter provides the set-up of this evaluation and the results from two online questionnaires that were held after the start and before the end of the project.
    Type: Book chapter , NonPeerReviewed
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  • 26
    Publication Date: 2022-08-17
    Description: Diversity within marine microbiomes spans the three domains of life: microbial eukaryotes (i.e., protists), bacteria, and archaea. Although protists were the first microbes observed by microscopy, it took the advent of molecular techniques to begin to resolve their complex and reticulate evolutionary history. Symbioses between microbial entities have been key in this journey, and such interactions continue to shape the ecology of marine microbiomes. Nowadays, photosynthetic marine protists are appreciated for their activities as primary producers, rivalling land plant contributions in the global carbon cycle. Predatory protists are known for consuming prokaryotes and other protists, with some combining metabolisms into a mixotrophic lifestyle. Still, much must be learned about specific interactions and lifestyles, especially for uncultured groups recognized just by environmental sequences. With respect to the fate of protists in food webs, there are many paths to consider. Despite being in early stages of identifying interactions, whether mutualistic or death-inducing infections by parasites and viruses, knowledge is advancing rapidly via methods for interrogation in nature without culturing. Here, we review marine protists, their evolutionary histories, diversity, ecological roles, and lifestyles in all layers of the ocean, with reference to how views have shifted over time through extensive investigation.
    Type: Book chapter , PeerReviewed
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  • 27
    Publication Date: 2022-11-01
    Type: Article , NonPeerReviewed
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  • 28
    Publication Date: 2022-12-09
    Description: Data-driven science has turned into a fourth fundamental paradigm of performing research. Earth System Science, following a holistic approach in unraveling the complex network of processes and interactions shaping system Earth, particularly profits from embracing data-driven approaches next to observation and modeling. At the end, increasing digitalization of Earth sciences will lead to cultural transformation towards a Digital Earth Culture.
    Type: Book chapter , NonPeerReviewed
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  • 29
    Publication Date: 2022-12-19
    Description: A comprehensive study of the Earth system and its related processes requires a holistic examination and understanding of multidimensional data acquired with a large number of different sensors or produced by various models. To this end, the Digital Earth project developed a set of software solutions to study environmental data sets using visual approaches. In the following chapter, we present three data visualization products developed to deal with the challenges of the analysis and exploration of environmental data.
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  • 30
    Publication Date: 2022-12-19
    Description: Reliable data are the base of all scientific analyses, interpretations and conclusions. Evaluating data in a smart way speeds up the process of interpretation and conclusion and highlights where, when and how additionally acquired data in the field will support knowledge gain. An extended SMART monitoring concept is introduced which includes SMART sensors, DataFlows, MetaData and Sampling approaches and tools. In the course of the Digital Earth project, the meaning of SMART monitoring has significantly evolved. It stands for a combination of hard- and software tools enhancing the traditional monitoring approach where a SMART monitoring DataFlow is processed and analyzed sequentially on the way from the sensor to a repository into an integrated analysis approach. The measured values itself, its metadata, and the status of the sensor, and additional auxiliary data can be made available in real time and analyzed to enhance the sensor output concerning accuracy and precision. Although several parts of the four tools are known, technically feasible and sometimes applied in Earth science studies, there is a large discrepancy between knowledge and our derived ambitions and what is feasible and commonly done in the reality and in the field.
    Type: Book chapter , NonPeerReviewed
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  • 31
    Publication Date: 2022-04-07
    Description: Many large rivers used for navigation have lost their hydromorphological heterogeneity, which has led to the widespread loss of native biodiversity and the concurrent establishment of non‐native communities. While the effects on biodiversity are well‐described, we know little about how the loss of natural habitats and the restructuring of communities cumulate into effects on riverine food webs. We constructed binary and ingestion webs for benthic macroinvertebrates and their resources in the Elbe River (Germany) and compared if food chain length, food web complexity, robustness, ingestion rates, and consumer‐resource interaction strength differ among three shoreline engineering practices. Food webs at profoundly altered shorelines were significantly less complex and had significantly shorter food chains than the food web at the semi‐natural shoreline. However, food web robustness to a simulated loss of species was comparable at all shorelines. Total ingestion rates were up to eight times lower at highly altered shorelines due to significantly lower ingestion rates by native species. Predator–prey interaction strength was comparable among shorelines due to higher shares of non‐native predators, indicating that non‐native predators can be functionally equivalent to native predators. We attributed the observed food web differences to the absence of complex habitats at profoundly altered shorelines and the accompanied absence of specialized consumers. Our study provides empirical evidence that hydromorphological modifications reduce the efficiency of food webs to control organic matter dynamics and may ultimately affect the provisioning of riverine ecosystem services.
    Keywords: ddc:339.95 ; ddc:551.483
    Language: English
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  • 32
    Publication Date: 2022-04-01
    Description: Using a household and plot‐level survey conducted in Ethiopia, this study analyses the difference in farmers' adoption of sustainable land management (SLM) practices between their rainfed and irrigated plots. The paper also investigates the varying influence of different types of irrigation water management systems and associated irrigation technologies on the adoption of SLM practices in irrigated plots. After controlling for heterogeneity among different irrigation water management systems and technologies, we found that access to irrigation play major role in enhancing farmers' motivation to adopt more SLM practices. Furthermore, the combined effect of irrigation water management system and irrigation technology on type and number of SLM practices adopted is quite varied and very significant. The evidence highlights that farmers adopt more SLM practices in their plots with pump irrigation compared with those plots where gravity irrigation is applied because pump irrigation systems enhance complementarities with SLM practices. Finally, the findings underscore that the type of irrigation water management and the irrigation technology applied play an important role in restoring degraded lands and maintaining soil fertility, even when farmers' adoption of irrigation was not explicitly triggered by concerns for soil health.
    Description: Center for Development Research (ZEF), University of Bonn
    Description: CGIAR Research Program on Water, Land, and Ecosystems
    Description: Deutscher Akademischer Austauschdienst (DAAD) http://dx.doi.org/10.13039/501100001655
    Description: Dr. Hermann Eiselen Doctoral Program of the Foundation Fiat
    Description: Federal Ministry for Economic Cooperation and Development (BMZ) of Germany, The Water‐Energy‐Food Nexus: Global, Basin and Local Case Studies of Resource Use Efficiency Under Growing Natural Resource Scarcity
    Keywords: ddc:631
    Language: English
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  • 33
    Publication Date: 2022-04-01
    Description: Increased deposition of fine sediments in rivers and streams affects a range of key ecosystem processes across the sediment–water interface, and it is a critical aspect of river habitat degradation and restoration. Understanding the mechanisms leading to fine sediment accumulation along and across streambeds and their effect on ecological processes is essential for comprehending human impacts on river ecosystems and informing river restoration. Here, we introduce the HydroEcoSedimentary tool (HEST) as an integrated approach to assess hydro‐sedimentary and ecologically relevant processes together. The HEST integrates the estimation of sedimentary processes in the interstitial zone, as well as hydraulic, geochemical and ecological assessments, with a focus on brown trout early life stages. Compared to other methods, the HEST expands the possibilities to monitor and quantify fine sediment deposition in streambeds by differentiating between vertical, lateral and longitudinal infiltration pathways, and distinguishing between the depth (upper vs. lower layers) at which interstitial processes occur within the sediment column. By testing the method in two rivers with different degrees of morphological degradation, we detail the possible measurements and uses of the HEST, demonstrate its feasibility and discuss its reliability.
    Description: Alexander von Humboldt‐Stiftung http://dx.doi.org/10.13039/100005156
    Description: Bavarian State Ministry of Science and Arts (Bayerisches Staatsministerium für Wissenschaft und Kunst)
    Keywords: ddc:551.48 ; ddc:550.724
    Language: English
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  • 34
    Publication Date: 2022-04-01
    Description: In thermally stratified reservoirs, inflows form density currents according to the interplay between inflow temperature and reservoir stratification. The temperature of inflowing water is affected by catchment properties, including shading by riparian vegetation. We hypothesize that the degree of shading in the catchment can affect the inflow dynamics in downstream reservoirs by changing inflow temperature and consequently the nature of the density current. We test it for a subtropical drinking water reservoir by combining catchment‐scale hydrological and stream temperature modeling with observations of reservoir stratification. We analyze the formation of density currents, defined as under, inter and overflow, for scenarios with contrasting shading conditions in the catchment. Inflow temperatures were simulated with the distributed water‐balance model LARSIM‐WT, which integrates heat‐balance and water temperature. River temperature measurements and simulations are in good agreement with a RMSE of 0.58°C. In simulations using the present state of shading, underflows are the most frequent flow path, 63% of the annual period. During the remaining time, river intrusion form interflows. In a scenario without stream shading, average inflow temperature increased by 2.2°C. Thus, interflows were the most frequent flow path (51%), followed by underflows (34%) and overflows (15%). With this change, we would expect a degradation of reservoir water quality, as overflows promote longer periods of anoxia and nutrient loads would be delivered to the photic zone, a potential trigger for algae blooms. This study revealed a potentially important, yet unexplored aspect of catchment management for controlling reservoir water quality.
    Description: Bundesministerium für Bildung und Forschung http://dx.doi.org/10.13039/501100002347
    Description: https://doi.org/10.5281/zenodo.4746288
    Keywords: ddc:628.1 ; ddc:551.48
    Language: English
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  • 35
    Publication Date: 2022-04-01
    Description: Large artificial lakes and reservoirs affect the meteorological regime of the shore area and the local climate takes on a number of new features that were previously absent. This work focuses on the weather impact of the Alqueva reservoir, the largest artificial lake in Western Europe. An extensive set of numerical simulations using Meso‐NH mesoscale atmospheric model coupled with FLake (Freshwater Lake) scheme was carried out. The simulations covered a 12‐month period that was chosen to compose a so‐called Typical Meteorological Year. This artificial time period is meant to represent the typical meteorological conditions in the region and the model results are used to assess the changes in the local climate. To evaluate the raw impact of the reservoir, two different scenarios of simulations were compared: (A) with the reservoir as it exists nowadays and (B) without the reservoir using the older surface dataset. The results show decrease of air temperature during daytime (10–9°C) and nighttime increase (up to 10°C). In nearest towns, daily maximum temperature decreased and daily minimum temperature increased, which refers to milder weather conditions. Alqueva mainly showed suppression in fog formation in the nearby area. Local breeze regime was studied and monthly lake/land breezes were described.
    Description: Large lakes and artificial reservoirs can affect the meteorological regime of their coastal areas and impact the local climate. This work focuses on the weather impact of the Alqueva reservoir, the largest artificial lake in Western Europe, studied on the basis of mesoscale atmospheric modelling data over the 12‐month period composed in a typical meteorological year for the region of interest.
    Description: ALOP project
    Description: COMPETE 2020 ICT project
    Description: Fundação para a Ciência e a Tecnologia http://dx.doi.org/10.13039/501100001871
    Description: TOMAQAPA
    Description: http://mesonh.aero.obs-mip.fr/mesonh54/Download
    Keywords: ddc:551.6
    Language: English
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  • 36
    Publication Date: 2022-03-30
    Description: With increasing resolution of numerical weather prediction (NWP) models, classical subgrid‐scale processes become increasingly resolved on the model grid. In particular, turbulence in the planetary boundary layer (PBL) is vertically already partially resolved in contemporary models. For classical local PBL schemes, resulting up‐gradient heat transports cannot be treated correctly. Thus, nonlocal turbulence schemes have been developed in the past. As the horizontal grid sizes of NWP models become smaller than a few kilometers, the large turbulence eddies in the PBL will also start to become partially resolved in the horizontal direction. A very flexible way to formulate nonlocal turbulent exchange is the transilient matrix method, which is used here to develop a new turbulence parameterization. The resulting NLT3D scheme applies transilient mixing matrices to subgrid‐scale transports in all three dimensions. We compare results of WRF real‐case simulations including our scheme, a classical local turbulence scheme (MYNN), and an existing nonlocal one‐dimensional scheme (ACM2) with observations from field campaigns over homogeneous terrain (CASES‐99) and complex terrain (CAPTEX). Over homogeneous terrain, all three schemes similarly well capture the observed surface fluxes and radiosonde profiles, whereas over complex terrain more differences become obvious. During a tracer release experiment (CAPTEX) over the Appalachian mountain region, the mixing and vertical extent of the PBL turn out to be decisive to reproduce the observed advection speed of the tracer‐marked air mass. Deeper mixing not only accelerates surface winds but also enables tracer to travel faster at higher altitudes and then mix back to the ground. As results from a version of NLT3D with only standard horizontal Smagorinsky diffusion (NLT1D) demonstrate, simulating three‐dimensional turbulence can be beneficial already at horizontal grid sizes of a few kilometers.
    Description: Decreasing grid sizes in numerical weather prediction models demand the inclusion of nonlocal effects and horizontal turbulence in turbulence parameterizations. This is the motivation for the development of the nonlocal three‐dimensional turbulence (NLT3D) scheme. Vertical nonlocal mixing accelerates the horizontal transport of near‐surface tracers by fast advection at higher altitudes (see figure), and horizontal turbulence enhances tracer dispersion. As validated by observations, both effects are beneficial to the forecast quality already at grid sizes of a few kilometers.
    Description: Deutsche Forschungsgemeinschaft http://dx.doi.org/10.13039/501100001659
    Keywords: ddc:551.6
    Language: English
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  • 37
    Publication Date: 2022-03-31
    Description: Aerosol can affect clouds in various ways. Beside the microphysical impact of aerosol particles on cloud formation, the interference of aerosol with atmospheric radiation leads to changes in local heating, surface fluxes and thus mesoscale circulations, all of which may also modify clouds. Rather little is known about these so‐called semi‐direct effects in realistic settings – a reason why this study investigates the impact of absorbing aerosol particles on cloud and radiation fields over Germany. Using advanced high‐resolution simulations with grid spacings of 312 and 625 m, numerical experiments with different aerosol optical properties are contrasted using purely scattering aerosol as a control case and realistic absorbing aerosol as a perturbation. The combined effect of surface dimming and atmospheric heating induces positive temperature and negative moisture anomalies between 800 and 900 hPa, impacting low‐level cloud formation. Decreased relative humidity as well as increased atmospheric stability below clouds lead to a reduction of low‐level cloud cover, liquid water path and precipitation. It is further found that direct and semi‐direct effects of absorbing aerosol forcing have similar magnitudes and contribute equally to a reduction of net radiation at the top of the atmosphere.
    Description: Atmospheric aerosol particles can absorb solar radiation, altering the thermal structure of the atmosphere and surface fluxes. Using advanced high‐resolution simulations over Germany with grid spacings of 312 and 625 m, we find that boundary‐layer absorbing aerosol reduces low‐level cloud cover, liquid water path and precipitation. Direct and semi‐direct effects have similar magnitudes and contribute equally to a positive absorbing aerosol forcing.
    Description: German Ministry for Education and Research EU Horizon 2020 project CONSTRAIN
    Description: https://cera-www.dkrz.de/WDCC/ui/cerasearch/entry?acronym=DKRZ_LTA_1174_ds00001
    Keywords: ddc:551.5
    Language: English
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  • 38
    Publication Date: 2022-03-31
    Description: The local ensemble transform Kalman filter (LETKF) suggested by Hunt et al., 2007 is a very popular method for ensemble data assimilation. It is the operational method for convective‐scale data assimilation at Deutscher Wetterdienst (DWD). At DWD, based on the LETKF, three‐dimensional volume radar observations are assimilated operationally for the operational ICON‐D2. However, one major challenge for the LETKF is the situation where observations show precipitation (reflectivity) whereas all ensemble members do not show such reflectivity at a given point in space. In this case, there is no sensitivity of the LETKF with respect to the observations, and the analysis increment based on the observed reflectivity is zero. The goal of this work is to develop a targeted covariance inflation (TCI) for the assimilation of 3D‐volume radar data based on the LETKF, adding artificial sensitivity and making the LETKF react properly to the radar observations. The basic idea of the TCI is to employ an additive covariance inflation as entrance point for the LETKF. Here, we construct perturbations to the simulated observation which are used by the core LETKF assimilation step. The perturbations are constructed such that they exhibit a correlation between humidity and reflectivity. This leads to a change in humidity in such a way that precipitation is more likely to occur. We describe and demonstrate the theoretical basis of the method. We then present a case study where targeted covariance inflation leads to a clear improvement of the LETKF and precipitation forecast. All examples are based on the German radar network and the ICON‐D2 model over Central Europe.
    Description: The goal of this work is to develop a targeted covariance inflation (TCI) for the assimilation of 3D‐volume radar data based on the local ensemble transform Kalman filter (LETKF), adding artificial sensitivity and making the LETKF react properly to the radar observations. Perturbations to the simulated observations are constructed such that they exhibit an empirically derived correlation between humidity and reflectivity. This leads to a change in humidity in such a way that precipitation is more likely to occur.
    Description: Deutsche Forschungsgemeinschaft http://dx.doi.org/10.13039/501100001659
    Keywords: ddc:551.5
    Language: English
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  • 39
    Publication Date: 2022-03-28
    Description: We use symbolic regression to estimate daily precipitation amounts at six stations in the Alpine region from a global reanalysis. Symbolic regression only prescribes the set of mathematical expressions allowed in the regression model, but not its structure. The regression models are generated by genetic programming (GP) in analogy to biological evolution. The two conflicting objectives of a low root‐mean‐square error (RMSE) and consistency in the distribution between model and observations are treated as a multi‐objective optimization problem. This allows us to derive a set of downscaling models that represents different achievable trade‐offs between the two conflicting objectives, a so‐called Pareto set. Our GP setup limits the size of the regression models and uses an analytical quotient instead of a standard or protected division operator. With this setup we obtain models that have a generalization performance comparable with generalized linear regression models (GLMs), which are used as a benchmark. We generate deterministic and stochastic downscaling models with GP. The deterministic downscaling models with low RMSE outperform the respective stochastic models. The stochastic models with low IQD, however, perform slightly better than the respective deterministic models for the majority of cases. No approach is uniquely superior. The stochastic models with optimal IQD provide useful distribution estimates that capture the stochastic uncertainty similar to or slightly better than the GLM‐based downscaling.
    Description: We have fitted deterministic and stochastic empirical‐statistical downscaling models that represent different possible compromises between two conflicting objectives: (a) a low RMSE and (b) consistency in the distribution between downscaled series and reference observations. The graphic shows the skill of our downscaling models w.r.t. the two objectives (larger is better) for the station Sonnblick.
    Description: CRC/TR32: Patterns in Soil‐Vegetation‐Atmosphere Systems: Monitoring, Modelling and Data Assimilation; funded by the German Research Foundation (Deutsche Forschungsgemeinschaft DFG) http://dx.doi.org/10.13039/501100001659
    Keywords: ddc:551.577 ; ddc:550.2
    Language: English
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  • 40
    Publication Date: 2022-03-23
    Description: The modeling of the atmospheric boundary layer over sea ice is still challenging because of the complex interaction between clouds, radiation and turbulence over the often inhomogeneous sea ice cover. There is still much uncertainty concerning sea ice roughness, near‐surface thermal stability and related processes, and their accurate parameterization. Here, a regional Arctic climate model forced by ERA‐Interim data was used to test the sensitivity of climate simulations to a modified surface flux parameterization for wintertime conditions over the Arctic. The reference parameterization as well as the modified one is based on Monin–Obukhov similarity theory, but different roughness lengths were prescribed and the stability dependence of the transfer coefficients for momentum, heat and moisture differed from each other. The modified parameterization accounts for the most comprehensive observations that are presently available over sea ice in the inner Arctic. Independent of the parameterization used, the model was able to reproduce the two observed dominant winter states with respect to cloud cover and longwave radiation. A stepwise use of the different parameterization assumptions showed that modifications of both surface roughness and stability dependence had a considerable impact on quantities such as air pressure, wind and near‐surface turbulent fluxes. However, the reduction of surface roughness to values agreeing with those observed during the Surface Heat Budget of the Arctic Ocean campaign led to an improvement in the western Arctic, while the modified stability parameterization had only a minor impact. The latter could be traced back to the model's underestimation of the strength of stability over sea ice. Future work should concentrate on possible reasons for this underestimation and on the question of generality of the results for other climate models.
    Description: The modeling of the atmospheric boundary layer over sea ice is challenging. This is, among others, due to the distinct sea ice surface roughness and pressure ridges as shown in the image, and the often stably stratified atmosphere. We quantified the impact of used parameterizations and show that both surface roughness and stability dependence have a considerable impact on near‐surface turbulent fluxes and atmospheric circulation in Arctic climate simulations.
    Description: German Research Foundation (DFG)
    Description: Helmholtz Association (HGF), POLEX http://dx.doi.org/10.13039/100003872
    Description: Russian Science Foundation (RSF) http://dx.doi.org/10.13039/501100006769
    Keywords: ddc:551.5
    Language: English
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  • 41
    Publication Date: 2022-03-29
    Description: An idealized, three‐dimensional, numerical simulation of tropical cyclone evolution in a quiescent environment on an f‐plane is used to explore aspects of the cyclone's life cycle in the context of the rotating‐convection paradigm. In the 20‐day simulation, the vortex undergoes a life cycle including a gestation period culminating in genesis, a rapid intensification phase, a mature phase, a transient decay and re‐intensification phase, a second mature phase and a rapid decay phase. During much of the life cycle, the flow evolution is highly asymmetric, although important aspects of it can be understood within an azimuthally averaged framework, central to which are a boundary‐layer control mechanism and a new ventilation diagnostic. The boundary‐layer control mechanism provides an explanation for the gradual expansion of the inner core of the vortex. The ventilation diagnostic characterizes the ability of deep convection within a given radius to evacuate the mass of air ascending out of the boundary layer within that radius. The transient decay and re‐intensification phase is not associated with an eyewall replacement cycle, but rather with a hitherto undescribed process in which the eyewall becomes fragmented as a rainband complex forms beyond it. This process is interpreted as an interplay between the boundary layer and ventilation. The final rapid decay of the vortex results from the ever increasing difficulty of deep convection to ventilate the air exiting the boundary layer. Any unventilated air flows radially outwards in the lower troposphere and leads to spin‐down because of the approximate conservation of mean absolute angular momentum. If found in real cyclones, such transience or final decay might be erroneously attributed to ambient vertical wind shear. The results support the hypothesis that, even in a quiescent environment, isolated tropical cyclone vortices are intrinsically transient and never reach a globally steady state.
    Description: A three‐dimensional, idealized numerical simulation of tropical cyclone evolution on an f‐plane is used to explore aspects of the cyclone's life cycle in the framework of the rotating‐convection paradigm. In the simulation, which lasts for 20 days, the vortex undergoes a life cycle that includes a gestation period cultimating in genesis, a rapid intensification period, a mature stage followed by a transient decay and re‐intensification stage, a second mature stage and a final rapid decay stage. The results support the hypothesis that, even in a quiescent environment on an f‐plane, isolated tropical cyclone vortices are intrinsically transient and never reach a globally steady state.
    Description: U.S. Office of Naval Research http://dx.doi.org/10.13039/100000006
    Description: German Research Council
    Keywords: ddc:551.5
    Language: English
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  • 42
    Publication Date: 2022-03-29
    Description: Weather regime forecasts are a prominent use case of sub‐seasonal prediction in the midlatitudes. A systematic evaluation and understanding of year‐round sub‐seasonal regime forecast performance is still missing, however. Here we evaluate the representation of and forecast skill for seven year‐round Atlantic–European weather regimes in sub‐seasonal reforecasts from the European Centre for Medium‐Range Weather Forecasts. Forecast calibration improves regime frequency biases and forecast skill most strongly in summer, but scarcely in winter, due to considerable large‐scale flow biases in summer. The average regime skill horizon in winter is about 5 days longer than in summer and spring, and 3 days longer than in autumn. The Zonal Regime and Greenland Blocking tend to have the longest year‐round skill horizon, which is driven by their high persistence in winter. The year‐round skill is lowest for the European Blocking, which is common for all seasons but most pronounced in winter and spring. For the related, more northern Scandinavian Blocking, the skill is similarly low in winter and spring but higher in summer and autumn. We further show that the winter average regime skill horizon tends to be enhanced following a strong stratospheric polar vortex (SPV), but reduced following a weak SPV. Likewise, the year‐round average regime skill horizon tends to be enhanced following phases 4 and 7 of the Madden–Julian Oscillation (MJO) but reduced following phase 2, driven by winter but also autumn and spring. Our study thus reveals promising potential for year‐round sub‐seasonal regime predictions. Further model improvements can be achieved by reduction of the considerable large‐scale flow biases in summer, better understanding and modeling of blocking in the European region, and better exploitation of the potential predictability provided by weak SPV states and specific MJO phases in winter and the transition seasons.
    Description: The overall sub‐seasonal forecast performance (biases and skill) for predicting seven year‐round Atlantic–European weather regimes is highest in winter and lowest in summer. The year‐round skill horizon is shortest for the European Blocking and longest for the Zonal Regime and Greenland Blocking (see figure). Furthermore, the winter skill horizon tends to be enhanced following a strong stratospheric polar vortex but reduced following a weak one. Madden–Julian Oscillation phases 4 and 7 tend to increase and phase 2 to decrease the year‐round skill horizon.
    Description: Helmholtz‐Gemeinschaft http://dx.doi.org/10.13039/501100001656
    Keywords: ddc:551.6
    Language: English
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  • 43
    Publication Date: 2022-03-29
    Description: The Tianshan Mountains, with their status as ‘water tower’, receive quantities of precipitation that are among the highest in Central Asia. There are considerable knowledge gaps regarding the understanding of spatial and temporal patterns of precipitation over this water‐scarce region. Based on the Global Precipitation Climatology Centre (GPCC) data set, this study evaluated the precipitation variations over Tianshan Mountains on different time scales by using Mann‐Kendall (M‐K) test approaches and the ensemble empirical mode decomposition (EEMD) method. The results show that (a) most parts of Tianshan experienced increasing annual precipitation during 1950–2016 while Western Tianshan, which is the wettest region, faced a downtrend of precipitation during the same 67 years; (b) the annual precipitation in the Tianshan Mountains has exhibited high‐frequency variations with 3‐ and 6‐year quasi‐periods and low‐frequency variations with 12‐, 27‐year quasi‐periods. On the decadal scale, Tianshan had two dry periods (1950–1962 and 1973–1984) and two wet periods (1962–1972 and 1985–2016) and has experienced a tendency of continuous humidification since 2004; (c) the precipitation over the Tianshan Mountains shows a strong seasonality. In total, 63.6% of all precipitation falls in spring and summer. Distinctive differences are found in seasonal precipitation variations among the sub‐Tianshan regions. Obvious upward trends of precipitation over Eastern Tianshan were found in all seasons, with Eastern Tianshan entering a humid period as early as 1986. Northern and Central Tianshan experienced a decreasing trend in summer and spring. However, in the other seasons, those two sub‐Tianshan regions have been in humid periods since the 1990s. The precipitation over Western Tianshan showed an upward trend in summer and autumn. The obvious downward trends in spring and winter have led to dry periods in these two seasons from 1997–2014 to 2008–2016, respectively.
    Description: Most parts of Tianshan experienced increasing annual precipitation during 1950–2016 while Western Tianshan, which is the wettest region, faced a downtrend of precipitation during the same 67 years. Distinctive differences are found in seasonal precipitation variations among the sub‐Tianshan regions.
    Description: Humboldt‐Universität zu Berlin National Natural Science Foundation of China
    Description: China Scholarship Council (CSC)
    Keywords: ddc:551.6
    Language: English
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  • 44
    Publication Date: 2022-09-27
    Description: While the evidence for anthropogenic climate change continues to strengthen, and concerns about severe weather events are increasing, global projections of regional climate change are still uncertain due to model‐dependent changes in large‐scale atmospheric circulation, including over North Atlantic and Europe. Here, the Jenkinson–Collison classification of daily circulation patterns is used to evaluate past and future changes in their seasonal frequencies over Central Europe for the 1900–2100 period. Three reanalyses and eight global climate models from the Coupled Model Intercomparison Project phase 6, were used based on daily mean sea‐level pressure data. Best agreement in deriving relative frequencies of the synoptic types was found between the reanalyses. Global models can generally capture the interannual variability of circulation patterns and their climatological state, especially for the less frequent synoptic types. Based on historical data and the shared socioeconomic pathway 5 scenario, the evaluated trends show more robust signals during summer, given their lesser internal variability. Increasing frequencies were found for circulation types characterized by weak pressure gradients, mainly at the expense of decreasing frequencies of westerlies. Our findings indicate that given a high‐emission scenario, these signals will likely emerge from past climate variability towards the mid‐21st century for most altered circulation patterns.
    Description: Daily synoptic circulation patterns are derived using the Jenkinson–Collinson automated classification over Central Europe to evaluate past and future changes in their temporal frequencies. Reanalyses and eight global climate models from the CMIP6 were used based on the historical experiment and a high‐emission scenario. More robust signals were found during the summer season leading to emerging changes towards the mid‐21st century.
    Description: H2020 Marie Skłodowska‐Curie Actions http://dx.doi.org/10.13039/100010665
    Description: EU International Training Network (ITN) Climate Advanced Forecasting of sub‐seasonal Extremes (CAFE)
    Keywords: ddc:551.6
    Language: English
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  • 45
    Publication Date: 2022-07-26
    Description: Smallholder livelihoods throughout Central America are built on rain‐fed agriculture and depend on seasonal variations in temperature and precipitation. Recent climatic shifts in this highly diverse region are not well understood due to sparse observations, and as the skill of global climate products have not been thoroughly evaluated. We examine the performance for several reanalysis and satellite‐based global climate data products (CHIRPS/CHIRTS, ERA5, MERRA‐2, PERSIANN‐CDR) as compared to the observation‐based GPCC precipitation dataset. These datasets are then used to evaluate the magnitude and spatial extent of hydroclimatic shifts and changes in aridity and drought over the last four decades. We focus on water‐limited regions that are important for rain‐fed agriculture and particularly vulnerable to further drying, and newly delineate those regions for Central America and Mexico by adapting prior definitions of the Central American Dry Corridor. Our results indicate that the CHIRPS dataset exhibits the greatest skill for the study area. A general warming of 0.2–0.8°C·decade−1 was found across the region, particularly for spring and winter, while widespread drying was indicated by several measures for the summer growing season. Changes in annual precipitation have been inconsistent, but show declines of 20–25% in eastern Honduras/Nicaragua and in several parts of Mexico. Some regions most vulnerable to drying have been subject to statistically significant trends towards summer drying, increases in drought and aridity driven by precipitation declines, and/or a lengthening of the winter dry season, highlighting areas where climate adaptation measures may be most urgent.
    Description: Over the past four decades, precipitation trends are the main driver of drought trends, with temperature trends playing a small role. The most widespread drying and increases in aridity have occurred during the summer growing season. Based on delimitations of water‐limited and climate‐sensitive regions (brown shading) that are important for rain‐fed agriculture, some of these highly vulnerable regions overlap with areas of significant drying (red), highlighting potential prioritization areas for climate adaptation measures. image
    Description: Deutsche Forschungsgemeinschaft http://dx.doi.org/10.13039/501100001659
    Description: Frias Institute of Advanced Studies (FRIAS) http://dx.doi.org/10.13039/501100003190
    Description: National Science Foundation http://dx.doi.org/10.13039/100000001
    Keywords: ddc:551.6
    Language: English
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  • 46
    Publication Date: 2022-01-19
    Description: Global population projections foresee the biggest increase to occur in Africa with most of the available uncultivated land to ensure food security remaining on the continent. Simultaneously, greenhouse gas emissions are expected to rise due to ongoing land use change, industrialisation, and transport amongst other reasons with Africa becoming a major emitter of greenhouse gases globally. However, distinct knowledge on greenhouse gas emissions sources and sinks as well as their variability remains largely unknown caused by its vast size and diversity and an according lack of observations across the continent. Thus, an environmental research infrastructure—as being setup in other regions—is more needed than ever. Here, we present the results of a design study that developed a blueprint for establishing such an environmental research infrastructure in Africa. The blueprint comprises an inventory of already existing observations, the spatial disaggregation of locations that will enable to reduce the uncertainty in climate forcing’s in Africa and globally as well as an overall estimated cost for such an endeavour of about 550 M€ over the next 30 years. We further highlight the importance of the development of an e-infrastructure, the necessity for capacity development and the inclusion of all stakeholders to ensure African ownership.
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  • 47
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    In:  Human-Environment Interactions
    Publication Date: 2022-03-21
    Type: info:eu-repo/semantics/book
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  • 48
    Publication Date: 2022-09-26
    Type: Article , NonPeerReviewed
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  • 49
    Publication Date: 2022-01-07
    Description: It is a good method to utilize the grain size distribution curves and cumulative frequency curves of marine or river sediments to estimate the hydrodynamic conditions, transportation processes and sedimentary environment. However, researchers can only rely on Excel or Grapher to plot the curves one by one at the present day. The manual plotting procedures are complicated, and calculating the truncation points is time-consuming. To solve the aforementioned problems, we have developed a software tool to plot cumulative frequency curves and calculate the values of truncation points automatically. The software has the ability to plot curves of hundreds of samples accurately and rapidly, promoting researchers to analyze transport mechanisms and hydrodynamic environments. And it is convenient to apply the software to compare the processes of transportation and deposition between different samples.
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  • 50
    Publication Date: 2022-04-07
    Description: In times of accelerating climate change, species are challenged to respond to rapidly shifting environmental settings. Yet, faunal distribution and composition are still scarcely known for remote and little explored seas, where observations are limited in number and mostly refer to local scales. Here, we present the first comprehensive study on Eurasian-Arctic macrobenthos that aims to unravel the relative influence of distinct spatial scales and environmental factors in determining their large-scale distribution and composition patterns. To consider the spatial structure of benthic distribution patterns in response to environmental forcing, we applied Moran’s eigenvector mapping (MEM) on a large dataset of 341 samples from the Barents, Kara and Laptev Seas taken between 1991 and 2014, with a total of 403 macrobenthic taxa (species or genera) that were present in ≥ 10 samples. MEM analysis revealed three spatial scales describing patterns within or beyond single seas (broad: ≥ 400 km, meso: 100–400 km, and small: ≤ 100 km). Each scale is associated with a characteristic benthic fauna and environmental drivers (broad: apparent oxygen utilization and phosphate, meso: distance-to-shoreline and temperature, small: organic carbon flux and distance-to-shoreline). Our results suggest that different environmental factors determine the variation of Eurasian-Arctic benthic community composition within the spatial scales considered and highlight the importance of considering the diverse spatial structure of species communities in marine ecosystems. This multiple-scale approach facilitates an enhanced understanding of the impact of climate-driven environmental changes that is necessary for developing appropriate management strategies for the conservation and sustainable utilization of Arctic marine systems.
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  • 51
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    Kluwer
    In:  Orlando, Florida, Kluwer, vol. 27, pp. 559-932, (1-4020-2401-0, 792 pp.)
    Publication Date: 2004
    Keywords: Proceedings of a conference ; Tomography ; Acoustics ; Seismology ; Seismics (controlled source seismology) ; Textbook of physics ; Textbook of geophysics ; Textbook of mathematics
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  • 52
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    Kluwer
    In:  Dordrecht, 344 pp., Kluwer, vol. 20, no. Publ. No. 12, pp. 81-89, (ISBN 1-4020-1267-5 (hb), ISBN 1-4020-1268-3 (pb))
    Publication Date: 2004
    Keywords: Textbook of geophysics ; NOModelling ; GeodesyY ; Crustal deformation (cf. Earthquake precursor: deformation or strain) ; post-glacial ; Rheology ; Earth rotation ; Inelastic ; Seismology ; earth mantle ; post-seismic ; Dislocation
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  • 53
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    Kluwer
    In:  Dordrecht, 368 pp., Kluwer, vol. V/1, subvol. b, pp. 559-932, (ISBN: 1-4020-1827-4)
    Publication Date: 2004
    Keywords: Earthquake engineering, engineering seismology ; Textbook of geophysics ; Textbook of engineering ; Earthquake risk ; Site amplification ; vulnerability ; microzonation ; Earthquake hazard ; CD-Rom
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  • 54
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    Springer
    In:  Berlin, Springer, vol. 6, no. 22, pp. 71-80, (ISBN 0-87590-422-X)
    Publication Date: 2004
    Keywords: Textbook of mathematics ; Statistical investigations ; software
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  • 55
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    In:  International Journal of Earth Sciences, 93 . pp. 596-611.
    Publication Date: 2019-09-23
    Description: Carbonate precipitates on mounds and along tectonic scarps off the Costa Rica margin are manifestations of subduction-induced dewatering. The long-term dewatering history is recorded in mineralogical, petrological and isotope signals of carbonates recovered from these sites. The carbonates are strongly depleted in δ13C (−11 to −53‰ PDB) and enriched in δ18O (+4 to +8‰ PDB). Thermogenic methane and biogenic methane were identified as sources of the carbon. Chemoherm carbonates and seepage-associated carbonates formed in a focused flow regime have lighter δ13C values, while others formed in a more diffusive flow regime have slightly enriched C isotope values. Three fluid components were inferred based on the calculation of equilibrium δ18O: clay dehydration water, gas hydrate water and seawater. Calculated equilibrium δ18O values of carbonates from different down-core depths as well as from different precipitation stages show that the δ18O of the precipitating fluid is progressively depleted with time. Dolostones showing a methane-C source and a well constrained O-isotope signature are thought to have formed at depth in the sediment and subsequently became exhumed. Glauconitic sandstones cemented by methane-derived carbonate provide evidence that fluid and solid material have been expelled by the mud volcano.
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  • 56
    Publication Date: 2018-04-03
    Description: We examined the thermoregulatory behaviour (TRB) of roosting Humboldt penguins (Spheniscus humboldti) in north central Chile during summer and winter, when ambient temperatures (Ta) are most extreme. Each body posture was considered to represent a particular TRB, which was ranked in a sequence that reflected different degrees of thermal load and was assigned an arbitrary thermoregulatory score. During summer, birds exhibited eight different TRBs, mainly oriented to heat dissipation, and experienced a wide range of Ta (from 14 to 31°C), occasionally above their thermoneutral zone (TNZ, from 2 to 30°C), this being evident by observations of extreme thermoregulatory responses such as panting. In winter, birds exhibited only three TRBs, mainly oriented to heat retention, and experienced a smaller range of Ta (from 11 to 18°C), always within the TNZ, even at night. The components of behavioural responses increased directly with the heat load which explains the broader behavioural repertoire observed in summer. Since penguins are primarily adapted in morphology and physiology to cope with low water temperatures, our results suggest that behavioural thermoregulation may be important in the maintenance of the thermal balance in Humboldt penguins while on land.
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  • 57
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    In:  Marine Biology, 145 . pp. 1097-1106.
    Publication Date: 2018-06-07
    Description: We quantified the nitrogen and enzyme hydrolyzable amino acid (EHAA) concentrations of sediments prior to and after corals sloughed, ingested, and egested sediments layered onto their surfaces, for the three coral species Siderastrea siderea, Agaricia agaricites, and Porites astreoides in Jamaica. The percent nitrogen of the sediments egested by all three species was lower than in the sediments available to the corals. Additionally, the sediments sloughed (not ingested) by A. agaricites and P. astreoides were lower in percent nitrogen, while the sediments sloughed by S. siderea had the same percent nitrogen as that of the available sediments. The percent nitrogen of the sediments sloughed and egested by P. astreoides showed significant negative and positive relationships, respectively, to increasing sediment loads, while the percent nitrogen of the sediments sloughed and egested by both S. siderea and A. agaricites showed no relationship to sediment load. EHAA concentrations were not significantly different between the sloughed and available sediments but were significantly lower in the sediments egested by S. siderea and A. agaricites (EHAA concentrations were not measured for P. astreodies sediment fractions). Comparisons of the nitrogen and EHAA concentrations in the sloughed and egested sediments to what was available prior to coral processing show that maximum ingestion was between 0.1 and 0.2 µg N µg−1 coral N cm−2 and between 0.5 and 0.6 µg EHAA·cm−2. Maximum assimilation efficiencies were estimated to be 30–60% of the available nitrogen. The data show that corals ingest and alter the nitrogen concentration of particles that land on their surfaces. The corals’ abilities to process these sediments, and the sediments’ possible contributions to coral nutrition, are discussed based on these results.
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  • 58
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    In:  In: Oceanic hotspots: intraplate submarine magmatism and tectonism / R. , ed. by Hekinian, R., Stoffers, P. and Cheminee, J. L. Springer, ---, pp. 375-405.
    Publication Date: 2019-09-23
    Type: Book chapter , PeerReviewed
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  • 59
    Publication Date: 2017-02-06
    Description: A numerical model of the Atlantic Ocean was used to study the low-frequency variability of meridional transports in the North Atlantic. The model shows a behaviour similar to those used in previous studies, and the temporal variability of certain variables compares favourably to observed time series. By changing the depth and width of the sills between the subpolar North Atlantic and the Nordic Seas, the mean horizontal and overturning circulation as well as some water mass properties are modified significantly. The reaction of meridional oceanic transports to atmospheric forcing fluctuations remains, however, unchanged. The critical role of the surface heat flux retroaction term for the meridional heat transport in stand-alone ocean models is discussed. The experiments underline the role of atmospheric variability for fluctuations of the large-scale ocean circulation on time scales from years to decades, and they support the hypothesis that the mean overturning strength is controlled by the model representation of the density of the overflow water masses.
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  • 60
    Publication Date: 2017-05-24
    Description: Seismic reflection data document for the first time the existence of a BSR in a limited area west of the Dnieper Canyon in the northwestern Black Sea. Seismic wide-angle data suggest that gas hydrates occupy in average 15±2% of the pore space in a zone of 100 m in thickness. A conservative quantification of the amount of methane associated with this gas hydrate occurrence is about 12±3×1011 m3 (0.6±0.2 Gt of methane carbon). Conductive heat flow deduced from the BSR depth is in the range of 21±6 to 55±15 mW m−2.
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  • 61
    Publication Date: 2015-08-26
    Description: Sponges (phylum Porifera) are sessile marine filter feeders that have developed efficient defense mechanisms against foreign attackers such as viruses, bacteria, or eukaryotic organisms. Protected by a highly complex immune system, as well as by the capacity to produce efficient antiviral compounds (e.g., nucleoside analogues), antimicrobial compounds (e.g., polyketides), and cytostatic compounds (e.g., avarol), they have not become extinct during the last 600 million years. It can be assumed that during this long period of time, bacteria and microorganisms coevolved with sponges, and thus acquired a complex common metabolism. It is suggested that (at least) some of the bioactive secondary metabolites isolated from sponges are produced by functional enzyme clusters, which originated from the sponges and their associated microorganisms. As a consequence, both the host cells and the microorganisms lost the ability to grow independently from each other. Therefore, it was—until recently—impossible to culture sponge cells in vitro. Also the predominant number of “symbiotic bacteria” proved to be nonculturable. In order to exploit the bioactive potential of both the sponge and the “symbionts,” a 3D-aggregate primmorph culture system was established; also it was proved that one bioactive compound, avarol/avarone, is produced by the sponge Dysidea avara. Another promising way to utilize the bioactive potential of the microorganisms is the cloning and heterologous expression of enzymes involved in secondary metabolism, such as the polyketide synthases.
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  • 62
    Publication Date: 2015-01-28
    Description: Polyclonal antibodies that recognize the two subunits AmoA and AmoB of the ammonia monooxygenase (AMO) were applied to identify ammonia-oxidizing bacteria by immunofluorescence (IF) labeling in pure, mixed, and enriched cultures. The antibodies against the AmoA were produced using a synthetic peptide of the AmoA of Nitrosomonas eutropha, whereas the antibodies against the AmoB had been developed previously is against the whole B-subunit of the AMO [Pinck et al. (2001) Appl Environ Microbiol 67:118–124]. Using IF labeling, the AmoA antibodies were specific for the detection of all species of the genus Nitrosomonas. In contrast, the antiserum against AmoB labeled all genera of ammonia oxidizers of the β-subclass of Proteobacteria (Nitrosomonas, Nitrosospira, Nitrosolobus, and Nitrosovibrio). The fluorescence signals of the AmoA antibodies were spread all over the cells, whereas the signals of the AmoB antibodies were associated with the cytoplasmic membranes. The specificity of the reactions of the antisera with ammonia oxidizers were proven in pure and mixed cultures, and the characteristic IF labeling and the morphology of the cells enabled their identification at the genus level. The genus-specific IF labeling could be used to identify ammonia oxidizers enriched from various habitats. In enrichment cultures of natural sandstone, cells of the genera Nitrosomonas, Nitrosovibrio, and Nitrosospira were detected. Members of the genus Nitrosovibrio and Nitrosolobus were most prominent in enriched garden soil samples, whereas members of the genus Nitrosomonas dominated in enriched activated sludge. The antibodies caused only slight background fluorescence on sandstone and soil particles compared to oligonucleotide probes, which could not be used to detect ammonia oxidizers on these materials because of strong nonspecific fluorescence.
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  • 63
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    In:  In: The Organic Carbon Cycle in the Arctic: Present and Past. , ed. by Stein, R. and Macdonald, R. W. Springer, Berlin (u.a.), pp. 41-45. ISBN 3-540-01153-6
    Publication Date: 2015-02-19
    Type: Book chapter , NonPeerReviewed
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  • 64
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    In:  International Journal of Earth Sciences, 93 (4). pp. 645-651.
    Publication Date: 2015-03-23
    Description: Durch Vermittlung von Jörn Thiede gelangte das Geologenarchiv in den Besitz eines Videobands von einem Fernsehinterview mit Rosenqvist (auch gelegentlich Rosenquist), das Elen Roaldset (E.R.) im Geologischen Institut der Universität Oslo am 8.September 1988 führen konnte. Es umfasst den gesamten Lebenslauf und die wichtigsten wissenschaflichen Leistungen dieses aussergewöhnlichen Geologen und Mineralogen. Er wurde in Wien am 17. Mai 1916 geboren, kam aber mit seinen Eltern schon 1917 nach Oslo, wo er am 8. Oktober 1994 starb (K. Bjørlykke 1995). Im Folgenden sollen aus dem Interview nur seine wegweisenden Untersuchungen der Quicktone, seine fachliche Vielseitigkeit, sein gesellschaftliches Engagement und seine schwierigen Erfahrungen mit Deutschland herausgegriffen werden. Das in der Landessprache geführte Gespräch wurde von Geir Ebelfoff und Lars Erik Kastilan ins Deutsche transkribiert.
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  • 65
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    In:  In: Electronic Noses & Sensors for the Detection of Explosives. NATO Science Series, 159 . Springer, Berlin, Germany, pp. 279-288. ISBN 978-1-4020-2318-7
    Publication Date: 2015-10-20
    Description: Portable and automated field screening equipment would be very effective in assessing contamination due to explosives at many defense sites. A droplet based microfluidic lab-on-a-chip utilizing electrowetting has been presented for fully automated detection of TNT. Microliter droplets of TNT in DMSO and KOH in water are reacted on a chip in a programmed way. The same platform has integrated colorimetric detection. The detection of TNT is linear in the range of 12.5–50 µg/mL.
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  • 66
    Publication Date: 2015-02-13
    Description: The effect of microrelief and vegetation on methane (CH4) emission was investigated in a wet polygonal tundra of the Lena Delta, Northern Siberia (72.37N, 126.47E). Total and plant-mediated CH4 fluxes were measured by closed-chamber techniques at two typical sites within a low-centred polygon. During the study period, total CH4 flux averaged 28.0 ± 5.4 mg m−2 d−1 in the depressed polygon centre and only 4.3 ± 0.8 mg m−2 d−1 at the elevated polygon rim. This substantial small-scale spatial variability of CH4 emission was caused by strong differences of hydrologic conditions within the microrelief of the polygon, which affected aeration status and organic matter content of the soils as well as the vegetation cover. Beside water table position, the vegetation cover was a major factor controlling CH4 emission from polygonal tundra. It was shown that the dominant vascular plant of the study area, Carex aquatilis, possesses large aerenchyma, which serve as pathways for substantial plant-mediated CH4 transport. The importance of plant-mediated CH4 flux was strongly influenced by the position of the water table relative to the main root horizon. Plant-mediated CH4 transport accounted for about two-thirds of the total flux in the wet polygon centre and for less than one-third of the total flux at the moist polygon rim. A clipping experiment and microscopic-anatomical studies suggested that plant-mediated CH4 transport via C. aquatilis plants is driven only by diffusion and is limited by the high diffusion resistance of the dense root exodermes.
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  • 67
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    In:  In: The Organic Carbon Cycle in the Arctic: Present and Past. , ed. by Stein, R. and Macdonald, R. W. Springer, Berlin (u.a.), pp. 33-41. ISBN 3-540-01153-6
    Publication Date: 2015-03-03
    Type: Book chapter , NonPeerReviewed
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  • 68
    Publication Date: 2015-08-26
    Description: From cell cultures of Suberites domuncula was isolated a bacterial strain, SDC-1, which was identified by 16S ribosomal RNA sequence analysis as an α-Proteobacterium of the genus Ruegeria. The occurrence of the strain in sponge cell culture could be explained by its resistance to the antibiotics used in the isolation of sponge cell cultures or by the preservation of SDC-1 by host sponge cells. The fatty acid composition of SDC-1 is characterized by branched C-12 methyl fatty acids. Two new and 8 known cyclic dipeptides were isolated and characterized from the fermentation broth of SDC-1. Cyclodipeptides are one of the families of cell-cell signaling compounds and may have some role to play in sponge-bacteria interactions.
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  • 69
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    In:  Applied Biochemistry and Biotechnology, 119 (3). pp. 241-277.
    Publication Date: 2020-06-11
    Description: Culture pelleting and morphology has a strong influence on process productivity and success for fungal and filamentous bacterial cultures. This impact is particularly evident with early phase secondary metabolite processes with limited process definition. A compilation of factors affecting filamentous or pelleting morphology described in the literature indicates potential leads for developing process-specific control methodologies. An evaluation of the factors mediating citric acid production is one example of an industrially important application of these techniques. For five model fungal and filamentous bacterial processes in an industrial fermentation pilot plant, process development strategies were developed and effectively implemented with the goal of achieving reasonable fermentation titers early in the process development cycle. Examples of approaches included the use of additives to minimize pelleting in inoculum shake flasks, the use of large-volume frozen bagged inoculum obtained from agitated seed fermentors, and variations in production medium composition and fermentor operating conditions. Results were evaluated with respect to productivity of desired secondary metabolites as well as process scalability. On-line measurements were utilized to indirectly evaluate the cultivation impact of changes in medium and process development. Key laboratory to pilot plant scale-up issues also were identified and often addressed in subsequent cultivations.
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  • 70
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    In:  Geo-Marine Letters, 24 (2). pp. 75-85.
    Publication Date: 2017-05-24
    Description: Hydroacoustic methods are particularly suitable for investigations of the occurrence, cyclicity and amount of bubbles released at cold seeps without disturbing them. Experiments with a horizontally looking single beam transducer (40 and 300 kHz) directed towards artificially produced bubbles show that the backscattering strength of the bubbles increases with the gas flux rate independently of the bubble radii distribution. It is demonstrated that an acoustic system can be calibrated in such a way that gas flux rates of bubble-size spectra, as observed at natural seeps, can be directly related to the echo level of a known, acoustically insonified volume. No system-specific parameters have to be known except the beam width.
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  • 71
    Publication Date: 2016-05-18
    Description: The distribution of platinum group elements (PGE) in Cu- and Zn-rich samples from the Roman Ruins and Satanic Mills vent sites in the PACMANUS hydrothermal field (Papua New Guinea) was studied and compared to that from selected ancient volcanogenic massive sulfide (VMS) deposits. Samples from the Satanic Mills site are enriched in Pd and Rh when compared to samples from Roman Ruins and reach highest values in active and inactive Cu-rich black smoker chimneys and chalcopyrite-cemented dacite breccias (up to 356 ppb Pd and up to 145 ppb Rh). A significant positive correlation was established between Cu and Pd and Rh in samples from both vent sites. Comparisons of chondrite normalized patterns and values of Pd/Pt and Pd/Ir ratios in Cu-rich sulfides and probable source rocks (felsic volcanic rocks/MORB) along with the evidence for a magmatic component in the PACMANUS hydrothermal system indicate that leaching of back-arc volcanic rocks together with addition of magmatic volatiles to the convecting hydrothermal system was the most important factor for PGE enrichment at PACMANUS and likely at some PGE-enriched ancient VMS deposits.
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  • 72
    Publication Date: 2018-01-19
    Description: The Greens Creek polymetallic massive sulphide deposit is hosted in a typical polyphase deformed lower greenschist facies orogenic setting. The structure of the host rocks is well constrained, exhibiting a series of three superimposed ductile deformations followed by two brittle episodes. The ore is found both in fold hinges where early-formed depositional features are preserved and in fold limbs where primary features are typically strongly modified or obliterated. Samples from both settings have been investigated using electron backscatter diffraction (EBSD) coupled with forescatter orientation contrast (OC) imaging in order to observe the effects of deformation and lower greenschist facies metamorphism on pyrite. Results suggest that colloform pyrite may preserve information relevant to palaeoenvironment, that apparently simple textures are generally more complex, and that pyrite can deform plastically by dislocation glide and creep processes at lower temperatures and/or strain rates than generally accepted. This analysis indicates that EBSD and OC imaging provide powerful tools for observing textural relationships in pyrite that are not shown by more traditional methods. They should become routine tools for pyrite texture analysis.
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  • 73
    Publication Date: 2018-09-03
    Description: Pelado, Guespalapa, and Chichinautzin monogenetic scoria cones located within the Sierra del Chichinautzin Volcanic Field (SCVF) at the southern margin of Mexico City were dated by the radiocarbon method at 10,000, 2,800–4,700, and 1,835 years b.p., respectively. Most previous research in this area was concentrated on Xitle scoria cone, whose lavas destroyed and buried the pre-Hispanic town of Cuicuilco around 1,665±35 years b.p. The new dates indicate that the recurrence interval for monogenetic eruptions in the central part of the SCVF and close to the vicinity of Mexico City is 〈2,500 years. If the entire SCVF is considered, the recurrence interval is 〈1,700 years. Based on fieldwork and Landsat imagery interpretation a geologic map was produced, morphometric parameters characterizing the cones and lava flows determined, and the areal extent and volumes of erupted products estimated. The longest lava flow was produced by Guespalapa and reached 24 km from its source; total areas covered by lava flows from each eruption range between 54 (Chichinautzin) and 80 km2 (Pelado); and total erupted volumes range between 1 and 2 km3/cone. An average eruption rate for the entire SCVF was estimated at 0.6 km3/1,000 years. These findings are of importance for archaeological as well as volcanic hazards studies in this heavily populated region.
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  • 74
    Publication Date: 2018-05-28
    Description: Several epibiotic species reduce starfish (Asterias rubens) preference for the blue mussel Mytilus edulis in the Baltic. The aim of this study was to reveal whether this associational resistance was caused by structural or chemical aspects of the different epibionts. To assess structural epibiont effects, an in situ experiment was conducted with unfouled mussels and mussels equipped with artificial epibionts ('dummies') exposed to natural predation by A. rubens. The chemically inert dummies closely matched the structural properties of the locally common epibionts Balanus improvisus (barnacle), Ceramium strictum (red alga), Halichondria panicea (sponge), and Laomedea flexuosa (hydrozoan). Starfish fed indiscriminately in all treatments. Chemical effects of epibionts on the attractiveness of mussels for A. rubens were investigated by incorporating freeze-dried epibionts or mussel tissue into Phytagel pellets at natural concentrations. Starfish were allowed to choose among these structurally similar but chemically different prey items in an in vitro experiment. The predators exhibited significant preferences among the food pellets, which closely matched their preferences for corresponding natural mussel-epibiont associations. Thus, chemical aspects of epibionts appear to play a larger role in this associational resistance than do structural aspects. Implications of these indirect interactions for benthic communities are discussed.
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  • 75
    Publication Date: 2018-05-30
    Description: Late Holocene volcanic activity at Ruapehu has been characterizedby the generation of small (〈105 m3) to very large (〉107 m3) lahars and repeated,small to medium (VEI 1-3) tephra-producing eruptions. The Onetapu Formation groupsall lahar deposits that accumulated during the last 2,000 years on the southeastern Ruapehu ring plain. The andesitic tephras are grouped within the Tufa Trig Formation and are intercalated within the laharic sequence. By correlating these two formations with new radiocarbon ages obtained on interbedded paleosols, we reconstruct a detailed volcanic history of Ruapehu for this period. Clast assemblages identified in the laharic sequences record thelithologies of synchronous tephras and rocks within the source region. These assemblages suggest a strong genetic link between the development of Crater Lake, the variation in eruptivestyles, and the production of lahars. Lahar-triggering mechanisms include: (1) flank collapse ofhydrothermally altered and unstable portions of the cone; (2) phreatic and phreatomagmatic eruptions favoring the generation of snow-rich slurries and hyperconcentrated stream flows; (3) suddenCrater Lake rim collapse, releasing large amounts of water inducing debris flows; and (4) eruptions that generate large volumes of tephra on snow-covered slopes, later remobilized by heavy rain. Two major lahars in the Onetapu sequence had a volume≥ 4 × 107 m3, roughly 1 to 2 orders of magnitude larger than the 1953event leading to the Tangiwai disaster (151 casualties). One of these lahars crossed over a lowinterfluve currently separating the Whangaehu River from a stream feeding the Tongariro River,sometime since peat accumulated between AD 1400 and AD 1660. A repetition of such a large-scaleevent would have devastating consequences on the infrastructure, economy and environment withinthe distal areas of the two catchments. The 1995–1996 eruptions were a timely reminder ofthe hazards posed by the volcano.
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  • 76
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    In:  Theoretical and Computational Fluid Dynamics, 18 (2/4). pp. 97-103.
    Publication Date: 2018-01-19
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  • 77
    Publication Date: 2017-03-20
    Description: Polymetallic sulfide-sulfate mineralization enriched in Pb-Ag-As-Sb-Hg occurs in the Bransfield Strait, a late Tertiary-Quaternary marginal basin close to the Antarctic Peninsula. The mineralization is associated with bimodal volcanism and pelagic and volcaniclastic sediment in rifted continental crust. Hydrothermal precipitates have been recovered from two shallow (1,050–1,000 m water depth) submarine volcanoes (Hook Ridge and Three Sisters) in the Central Bransfield Strait. Mineralization at Hook Ridge consists of polymetallic sulfides, massive barite, and pyrite and marcasite crusts in semilithified pelagic and volcaniclastic sediment. Native sulfur commonly infills void space and cements the volcaniclastic sediment. The polymetallic sulfides are dominated by sphalerite with minor galena, enargite, tetrahedrite-tennantite, pyrite, chalcopyrite, and traces of orpiment cemented by barite and opal-A. The presence of enargite at Hook Ridge, the abundance of native sulfur, and the low Fe content of sphalerite indicate a high sulfur activity of the hydrothermal fluids responsible for mineralization. The sulfur isotopic composition of Hook Ridge precipitates documents the complexity of the sulfur sources in this hydrothermal system with variable influence of biological activity and possibly magmatic contributions. Homogenization temperatures and salinities of fluid inclusions in barite and opal-A suggest that boiling may have affected the hydrothermal fluids during their ascent. The discovery of massive barite-silica precipitates at another shallow marine volcano (Three Sisters volcano) attests to the potential for hydrothermal mineralization at other volcanic edifices in the area. The characteristics of the mineralization in the Bransfield Strait with rifting of continental crust, the presence of bimodal volcanism, including highly evolved felsic volcanic rocks, the association with sediments, and the Pb-Ag-As-Sb-Hg enrichment are similar to the setting of massive sulfide deposits in the Okinawa Trough, and distinct from those of sediment-dominated hydrothermal systems such as Escanaba Trough, Middle Valley, and Guaymas Basin. The geological setting of the Bransfield Strait is also broadly similar to that of some of the largest volcanogenic massive sulfide deposits in the ancient record, such as the Iberian Pyrite Belt.
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  • 78
    Publication Date: 2017-03-20
    Description: We present evidence for the origin of the Lyngen Gabbro of the Ordovician Lyngen Magmatic Complex in Troms, Northern Norway. The two magmatic suites of the Lyngen Gabbro strike parallel NNE-SSW, and have distinct magmatic signatures. We define these signatures by using major and trace-element analyses together with selected major- and trace-element mineral analyses and 143Nd/144Nd-isotope whole-rock analyses of gabbroic to tonalitic plutonic rocks from seven detailed cross-sections from this large gabbro-complex. The Western suite of the Lyngen Gabbro precipitated from magma that may have been derived from the same system as the associated volcanic rocks. The gabbros have high An-content (An〉90) of their plagioclases relative to co-existing mafic minerals. Together with somewhat high ɛNd(t) values (+6), this implies that the parental magmas were hydrous tholeiites similar to those found in back arc basins today. The Eastern suite, on the other hand, consist of cumulates that were precipitated from melts resembling those of ultra-depleted high-Ca boninitic magmas found in fore-arcs. Extremely high-An plagioclases (An〉95) co-exist with evolved mafic minerals and oxides, and the ɛNd(t) values are lower (+4) than in the Western suite. The Eastern suite has no volcanic counterpart, but dikes intersecting the suites have compositions that possibly represent its parental magma. The oceanic Rypdalen Shear Zone generally separates the two suites in the north, but several non-tectonic transitions from boninitic to tholeiitic signatures southwards advocate that the magmatism happened concurrently. The magmatic proximity between the suites, the hydrous magmatism and the absence of a silicic or calc-alkaline mature arc section, suggests that the Lyngen Gabbro formed in the Iapetus Ocean under conditions presently found in incipient arcs later emplaced as outer arc highs.
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  • 79
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    In:  Journal of Oceanography, 60 . pp. 719-729.
    Publication Date: 2017-10-11
    Description: Rising atmospheric CO2 and deliberate CO2 sequestration in the ocean change seawater carbonate chemistry in a similar way, lowering seawater pH, carbonate ion concentration and carbonate saturation state and increasing dissolved CO2 concentration. These changes affect marine plankton in various ways. On the organismal level, a moderate increase in CO2 facilitates photosynthetic carbon fixation of some phytoplankton groups. It also enhances the release of dissolved carbohydrates, most notably during the decline of nutrient-limited phytoplankton blooms. A decrease in the carbonate saturation state represses biogenic calcification of the predominant marine calcifying organisms, foraminifera and coccolithophorids. On the ecosystem level these responses influence phytoplankton species composition and succession, favouring algal species which predominantly rely on CO2 utilization. Increased phytoplankton exudation promotes particle aggregation and marine snow formation, enhancing the vertical flux of biogenic material. A decrease in calcification may affect the competitive advantage of calcifying organisms, with possible impacts on their distribution and abundance. On the biogeochemical level, biological responses to CO2 enrichment and the related changes in carbonate chemistry can strongly alter the cycling of carbon and other bio-active elements in the ocean. Both decreasing calcification and enhanced carbon overproduction due to release of extracellular carbohydrates have the potential to increase the CO2 storage capacity of the ocean. Although the significance of such biological responses to CO2 enrichment becomes increasingly evident, our ability to make reliable predictions of their future developments and to quantify their potential ecological and biogeochemical impacts is still in its infancy.
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  • 80
    Publication Date: 2019-09-23
    Description: The most important archive of Earth’s climate change through geologic history is the sedimentary rock record. Rhythmic sedimentary alternations are usually interpreted as a consequence of periodic variations in the orbital parameters of the Earth. This interpretation enables the application of cyclostratigraphy as a very precise chronometer, when based on the assumption that orbital frequencies are faithfully recorded in the sedimentary archive. However, there are numerous uncertainties with the application of this concept. Particularly in carbonates, sediment properties such as mineralogical composition and fossil associations are severely altered during post-depositional alteration (diagenesis). We here point out that the assumption of a 1:1 recording of orbital signals in many cases is questionable for carbonate rhythmites. We use computer simulations to show the effect of diagenetic overprint on records of orbital signals in the carbonate record. Such orbital signals may be distorted in terms of frequency, amplitude, and phase by diagenetic processes, and cycles not present in the insolation record may emerge. This questions the routine use of carbonate rhythmites for chronostratigraphic dating
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  • 81
    Publication Date: 2017-01-04
    Description: Copepoda (Calanus finmarchicus n=1,722, Paraeuchaeta norvegica n=1,955), Hyperiidae (n=3,019), Euphausiacea (Meganyctiphanes norvegica n=4,780), and the fishes Maurolicus muelleri (n=500) and Pollachius virens (n=33) were collected in the Norwegian Deep (northern North Sea) during summer 2001 to examine the importance of pelagic invertebrates and vertebrates as hosts of Anisakis simplex and their roles in the transfer of this nematode to its final hosts (Cetaceans). Third stage larvae (L3) of A. simplex were found in P. norvegica, M. muelleri and P. virens. The prevalence of A. simplex in dissected P. norvegica was 0.26%, with an intensity of 1. Prevalences in M. muelleri and P. virens were 49.6% and 100.0%, with mean intensities of 1.1–2.6 (total fish length ≥6.0–7.2) and 193.6, respectively. All specimens of C. finmarchicus and M. norvegica examined were free of anisakid nematode species and no other parasites were detected. P. norvegica, which harboured the third stage larvae, is the obligatory first intermediate host of A. simplex in the investigated area. Though there was no apparent development of larvae in M. muelleri, this fish can be considered as the obligatory second intermediate host of A. simplex in the Norwegian Deep. However, it is unlikely that the larva from P. norvegica can be successfully transmitted into the cetacean or pinniped final hosts, where they reach the adult stage. An additional growth phase and a second intermediate host is the next phase in the life cycle. Larger predators such as P. virens serve as paratenic hosts, accumulating the already infective stage from M. muelleri. The oceanic life cycle of A. simplex in the Norwegian Deep is very different in terms of hosts and proposed life cycle patterns of A. simplex from other regions, involving only a few intermediate hosts. In contrast to earlier suggestions, euphausiids have no importance at all for the successful transmission of A. simplex in the Norwegian Deep. This demonstrates that this nematode is able to select definite host species depending on the locality, apparently having a very low level of host specificity. This could explain the wide range of different hosts that have been recorded for this species, and can be seen as the reason for the success of this parasite in reaching its marine mammal final hosts in an oceanic environment.
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  • 82
    Publication Date: 2018-05-30
    Description: Participatory rural appraisal (PRA) methods and philosophies were trialed in a volcanic risk management planning and awareness activity for Savo Island, a historically highly destructive volcano in the Solomon Islands. Through a combination of methods we tried to combine the roles of facilitators and educators, and to involve the input of all stakeholders (from community to national government) in the process of volcanic risk management. The PRA approach was an ideal way to address the fundamental differences in outlook, education, needs, and roles of individuals and groups involved or affected. It was also an important catalyst to Savo island- or community-based planning initiatives, which are arguably the most important step toward the preparedness of the 2500 inhabitants of the island for any future destructive volcanic activity. We adapted almost every tenet of the PRA philosophy through inexperience, self-perceived importance and desire to combine both scientific and traditional views for Savo volcanic risk management planning. Nevertheless, what emerged from our experiences was an idea of how fundamentally well suited many PRA approaches are to initiating dialogue within diverse stakeholder groups, and deriving combined scientific/geologic and local/community risk assessments and mitigation action plans. The main challenge remaining includes increasing the involvement or voice of less powerful community members (women, youth, non-landowners) in risk management decision-making in such male-dominated hierarchical societies.
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  • 83
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    In:  Izvestiya, Atmospheric and Oceanic Physics, 40 (4). pp. 394-401.
    Publication Date: 2020-08-05
    Description: A planar problem of nonlinear transverse oscillations of the surface (warm) front of a finite width is considered within the framework of a reduced-gravity model of the ocean. The source of oscillations is the departure of the front from its geostrophic equilibrium. When the current velocity is linear in the horizontal coordinate and the front's depth is quadratic in this coordinate, the problem is reduced to a system of four ordinary differential equations in time. As a result, the solution is obtained in a weakly nonlinear approximation and strongly nonlinear oscillations of the front are studied by numerically solving this system of equations by the Runge-Kutta method. The front's oscillations are always superinertial. Nonlinearity can lead to a decrease or increase in the oscillation frequency in comparison with the linear case. The oscillations are most intense when the current velocity is disturbed in the direction of the front's axis. A weakly nonlinear solution of the second order describes the oscillations very accurately even for initial velocity disturbances reaching 50% of its geostrophic value. An increase in the background-current shear leads to the damping of oscillations of the front's boundary. The amplitude of oscillations of the current velocity increases as the intensity of disturbances increases, and it is relatively small if background-current shears are small or large.
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  • 84
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    In:  In: Coccolithophores. , ed. by Thierstein, H. R. and Young, J. R. Springer, Berlin, pp. 509-528. ISBN 978-3-642-06016-8
    Publication Date: 2018-02-06
    Description: Coccolithophores first became significant participants in the carbonate cycle in the Jurassic, but throughout the Jurassic they were largely restricted to shelf and epeiric sea environments. They spread into the open ocean in the Cretaceous, and with this became a major factor in governing the carbonate cycle in the sea. With the development of dissolution-resistant forms, such as Watznaueria barnesae, the coccolithophores perturbed the carbonate system and switched the major site of carbonate deposition from shallow seas to the deep ocean. Several major evolutionary steps in the development of the coccolithophores have forced further changes in the carbon cycle, favoring the deep sea as a site of carbonate deposition. Samples of recent coccolith assemblages from bottom sediments differ from those of living coccolithophores in surface waters. Many of the coccoliths of more delicate species, particularly holococcoliths, are dissolved in the water column or at the sediment surface and are only rarely preserved as fossils. They, along with the pteropods, form an important part of the shallow carbonate cycle. There appears to be a continuous gradation in the level of susceptibility of coccoliths to dissolution, from forms that dissolve in the near-saturated waters of the surface ocean to those that are among the most dissolution-resistant forms of calcite. This continuous dissolution spectrum is in contrast to the planktic foraminifera, in which dissolution of the tests also occurs in a sequence, but through a much more restricted depth range, the lysocline. Whereas the order of dissolution of planktic foraminifera follows their habitat, with warm-water species being most susceptible and cold-water forms most resistant to dissolution, the order of dissolution of coccoliths appears to be related to phylogeny. The steepness of the coccolith carbonate dissolution gradient appears to have changed over time. In the Oligocene almost pure nannofossil carbonate oozes devoid of terrigenous material were widespread, perhaps reflecting unusual climatic conditions on land. The overall effect of coccolithophore evolution has been to move carbonate deposition to the deep sea, where coccolith oozes accumulate on ocean crust and will ultimately be subducted. Only a fraction of the carbon in the subducted carbonate is returned to the surface through volcanic activity. If their activity were to continue for several hundreds of millions of years the coccolithophores would remove much of the carbon from the surface of the Earth to be emplaced in the mantle.
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  • 85
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    In:  Geo-Marine Letters, 24 (3). pp. 140-149.
    Publication Date: 2017-05-24
    Description: Gas emissions from mud volcanoes on Sakhalin Island and water-column gas flares arising from cold seeps in the Okhotsk Sea appear to be related. They are likely activated by tectonic movements along the transform plate boundary separating the Okhotsk Sea Plate from the Eurasian and Amur plates. Gas vents (flares) and methane anomalies occur in the waters offshore Sakhalin Island, along with NE-SW-trending mounds and fluid escape structures on the seafloor. The intersection of the NE-striking transverse faults on land with the Central Sakhalin and Hokkaido-Sakhalin shear zones apparently determines the sites of mud volcanoes, a pattern that continues offshore where the intersection with the East Sakhalin and West Derugin shear zones determines the sites of the submarine gas vents.
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  • 86
    Publication Date: 2019-09-23
    Description: Methane investigations carried out in the Okhotsk Sea show that the methane flux from the earth’s interior into the water column increased during periods of seismo-tectonic activity between 1988 and 2002. In this case, methane gas hydrates found on the northeast Sakhalin slope may have decomposed due to a reactivation of fault zones. Methane emissions in the Okhotsk Sea generally can be divided into two forms. Firstly, methane vents from decomposing gas hydrates and/or free gas exist below gas hydrate saturated sediments via fault zones, venting into the water column with high bubble concentrations that were recorded by echosounding. These hydro-acoustic anomalies were named “flares”. Methane concentration inside these flares reached 10,000–20,000 nl/l (background methane concentrations in the Okhotsk Sea are less than 90–100 nl/l). Secondly, methane migrates as seepage into the water column from oil- and gas-bearing sedimentary source rocks on the eastern Sakhalin shelf, without showing acoustic anomalies in the water column, probably by filtration and diffusion processes. In these areas methane concentration reached 500–3,000 nl/l. In seismo-tectonically active regions, like the northwestern part of the Okhotsk Sea, many new flares were observed. Their distribution and orientation are usually controlled by fault zones (East Sakhalin Shear Zone in the Okhotsk Sea).
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  • 87
    Publication Date: 2016-09-21
    Description: The ingestion of two size classes of natural particulate matter (PM) and the uptake of the associated nitrogen by four species of scleractinian corals was measured using the stable isotopic tracer 15N. PM collected in sediment traps was split into 〈63 and 〉105 µm size fractions and labeled with (15N-NH4)2SO4. Siderastrea radians, Montastrea franksi, Diploria strigosa, and Madracis mirabilis were incubated in flow chambers with the labeled PM in suspension (〈63 µm), or deposited onto coral surfaces (〉105 µm). Ingestion was detected for all four species (98–600 µg Dry wt. cm–2 h–1), but only for D. strigosa was any difference detected between suspended and deposited PM. Only the three mounding species, S. radians, M. franksi, and D. strigosa showed uptake of suspended and deposited particulate nitrogen (PN); whereas, the branched coral M. mirabilis had no measurable PN uptake. Only coral host tissues were enriched with 15N, with no tracer detected in the symbiotic zooxanthellae. Uptake rates ranged from as low as 0.80 µg PN cm–2 h–1 in S. radians to as high as 13 µg PN cm–2 h–1 in M. franksi. M. franksi had significantly higher uptake rates than S. radians (ANOVA, p〈0.05), while D. strigosa had a statistically similar uptake rate compared to both species. These results are the first to compare scleractinian ingestion of nitrogen associated with suspended and deposited particulate matter, and demonstrate that the use of PM as a nitrogen source varies with species and colony morphology.
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  • 88
    Publication Date: 2020-06-11
    Description: As part of an ongoing research program aiming at monitoring molecular changes in the tissues and metabolite trafficking in the hydrosphere of algae subjected to chemical stresses, we are discussing the various analytical techniques that have been employed to characterize, and sometimes to quantity these metabolites. High-field multinuclear and solid-state nuclear magnetic resonance (NMR) spectroscopies are powerful tools for metabolite characterization from extracts and in vivo, but quantification and kinetic aspects show some limitations. Modern MS (mass spectrometry) is extremely useful for fingerprinting samples against databases and when dealing with very low concentrations of metabolites, the limitations being set by the type of chromatographic separation and mode of detection coupled with the mass spectrometer. Regarding chemical communication, optimization in terms of resolution and efficiency of hydrosphere chemical analysis can theoretically be achieved in a system which integrates (i) a multiparametric incubation chamber, (ii) a gasphase or a liquid-phase separation system and (iii) mass spectrometer(s) equipped with one or two detectors responding to the analytical and quantitative needs. This text reviews some of the techniques that have been employed in various types of plant metabolic studies, which may serve as a basis towards an integrative analytical strategy directly applicable to the metabolomics of selected marine macrophytes.
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  • 89
    facet.materialart.
    Unknown
    Springer
    In:  In: The Climate in Historical Times. , ed. by Fischer, H. Springer, Berlin, pp. 91-108. ISBN 978-3-662-10313-5
    Publication Date: 2019-04-29
    Description: Instrumental climate records are too short to resolve the full range of decadal- to multidecadal-scale natural climate variability. Massive annually banded corals from the tropical and subtropical oceans provide a paleoclimatic archive with a clear seasonal resolution, documenting past variations in water temperature, hydrologic balance, and ocean circulation. Recent coral-based paleoclimatic research has focused mainly on the tropics, providing important implications on the past variability of the El Niño—Southern Oscillation phenomenon and decadal tropical climate variability. New records from some of the rare subtropical/mid-latitude locations of coral growth were shown to reflect aspects of dominant modes of Northern Hemisphere climate variability, e.g., the North Atlantic Oscillation/Arctic Oscillation. These natural climatic modes have important socio-economic impacts owing to their large-scale modulation of droughts, floods, storms, snowfall, and fish stocks. Coral records from key locations provide the opportunity to assess recent shifts of these modes with respect to the natural climate variability of the pre-instrumental period. Providing a better understanding of their dynamics, coral records, together with records derived from other paleoclimatic archives, are essential for a better predictability of future climate.
    Type: Book chapter , NonPeerReviewed
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  • 90
    facet.materialart.
    Unknown
    Springer
    In:  In: The Ocean Carbon Cycle and Climate. , ed. by Follows, M. and Oguz, T. NATO Science Series, Series IV: Earth and Environmental Sciences, 40 . Springer, Dordrecht, pp. 97-148. ISBN 978-1-4020-2087-2
    Publication Date: 2020-08-03
    Description: The bioavailability of nutrients represents one of the most important factors controlling the strength of the biological carbon pump and ultimately the impact of ocean biology on atmospheric CO2. Among those nutrients, the macro-nutrients nitrate (NO 2 - ) and phosphate (PO 4 -3 ) play a particularly important role in limiting biological productivity as evidenced by their often near complete exhaustion in surface waters. As near surface NO 2 - concentrations are generally somewhat lower than those of PO 4 -3 relative to the demand by phytoplankton, biological oceanographers have argued historically that NO 2 - rather than PO 4 -3 is the primary macro-nutrient controlling phytoplankton productivity[Smith, 1984; Codispoti, 1989; Tyrrell, 1999] . Geologists, in contrast, regarded PO 4 -3 as the primary controlling macronutrient[Codispoti, 1989]. They argued that while NO 2 - may indeed be the limiting factor at any given location and time, PO 4 -3 is truly the limiting factor on geological time-scales, because the biologically mediated fixation of the much more abundant dinitrogen gas (N2) into organic nitrogen is alleviating the scarcity of bioavailable nitrogen (Figure 1). Phosphate on the other hand, does not have such a biologically mediated source (Figure 1). It is therefore the geologically controlled balance between the riverine (and atmospheric) input of PO 4 -3 and its burial on the sea-floor that ultimately controls marine biological productivity. Tyrrell [ 1999] provided a synthesis of these two views by identifying NO 2 - as the proximate nutrient, while giving PO 4 -3 the role of being the ultimate nutrient.
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  • 91
    Publication Date: 2021-08-24
    Description: Changes in the protein, lipid, glycogen, cholesterol and energy contents, total amino acid and fatty acid profiles of Octopus vulgaris and O. defilippi tissues (gonad, digestive gland and muscle) during sexual maturation (spermatogenesis and oogenesis) were investigated. Both species showed an increase of amino acids and protein content in the gonad throughout sexual maturation (namely in oogenesis), but allocation of these nitrogen compounds from the digestive gland and muscle was not evident. The major essential amino acids in the three tissues were leucine, lysine and arginine. The major non-essential amino acids were glutamic acid, aspartic acid and alanine. With respect to carbon compounds, a significant increasing trend (P〈0.05) in the lipid and fatty acid contents in the three tissues was observed, and, consequently, there was also little evidence of accumulated lipid storage reserves being used for egg production. It seems that for egg production both Octopus species use energy directly from food, rather than from stored products. This direct acquisition model contrasts with the previous model for Octopus vulgaris proposed by O’Dor and Wells (1978: J Exp Biol 77:15–31). Most of saturated fatty acid content of the three tissues was presented as 16:0 and 18:0, monounsaturated fatty acid content as 18:1 and 20:1 and polyunsaturated fatty acid content as arachidonic acid (20:4n-6), eicosapentaenoic acid (20:5n-3) and docosahexaenoic acid (22:6n-3). Though cholesterol is an important precursor of steroid hormones, this sterol content exhibited variations that do not seem to be related with the maturation process. Moreover, significant differences (P〈0.05) were obtained between genders, suggesting that perhaps there is a greater physiological demand for cholesterol during spermatogenesis than oogenesis. If the component sterols of octopus are of a dietary origin, considerable variation in the cholesterol content between species might be expected on the basis of the sterol composition of their prey. The glycogen reserves increased significantly in the gonad and decreased significantly (P〈0.05) in the digestive gland and muscle of O. vulgaris (these trends were not evident in O. defilippi). Glycogen may play an important role in the maturation process and embryogenesis of these organisms, because carbohydrates are precursors of metabolic intermediates in the production of energy. It was evident that sexual maturation had a significant effect upon the gonad energy content, but the non-significant energy variation (P〉0.05) in the digestive gland and muscle revealed no evidence that storage reserves are transferred from tissue to tissue. The biochemical composition of digestive gland and muscle may not be influenced by sexual maturation, but rather by other biotic factors, such as feeding activity, food availability, spawning and brooding.
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  • 92
    Publication Date: 2021-09-06
    Description: Benthic divers are dependent on local resources and may therefore adopt different foraging strategies to cope with their energetic requirements in varying situations. We investigated the diet of gentoo penguins (Pygoscelis papua) at Kerguelen Islands, comparing its spatial and temporal variations with the general prey distribution. The study was conducted at four sites over 2 years. In total, 212 stomach contents were collected over the entire breeding season. The diet was composed mainly of neritic fish and crustaceans, with important spatial and seasonal variations. Fish dominated the diet at localities facing the open sea (from 38.0% to 94.6% by mass), whereas crustaceans dominated at the more protected site (84.3% by mass). Fish were more abundant in the winter diet and Euphausia vallentini, the major crustacean species, was more abundant in the summer diet. No inter-year variations were detected. These results are consistent with local prey availability, and highlight the large plasticity of the gentoo penguin diet and foraging behaviour.
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  • 93
    Publication Date: 2021-09-07
    Description: Within the Southern Ocean, Patagonian toothfish (Dissostichus eleginoides Smitt) and southern elephant seals (Mirounga leonina Linnaeus) forage mainly on fish and cephalopods. From what is known of their diets, the proportion of fish is greatest in toothfish diet. When foraging at-sea for squid, elephant seals and toothfish most often co-occur over continental shelves and submarine plateaux surrounding sub-Antarctic land masses within the Southern Ocean. I used traditional (non-molecular) techniques to compare the squid diet of these two predators. Of the 21 squid species identified, 10 were common to the diets of both predators. One species, Gonatus antarcticus, dominated (61%) the biomass of squid consumed by toothfish, but was of little importance to the elephant seals (2.3%). By contrast, Martialia hyadesi was the most important single species to the elephant seals’ diet (29%), but it contributed 1% to the toothfish diet. Onychoteuthids (Kondakovia longimana, Moroteuthis ingens and Morotenthis knipovitchi) were important to both predators’ diets. The median sizes of five cephalopod species (Slosarczykovia circumantarctica, Galiteuthis glacialis, Gonatus antarcticus, Moroteuthis ingens and Moroteuthis knipovitchi) which were common to both the seal and toothfish diets, were significantly larger in the toothfish stomachs than in the elephant-seal stomachs. Percent similarity indices for the squids that overlapped both diets were in some cases as high as 100%. However, after between-species differences in prey size consumption were accounted for, the similarities fell to between 20 and 50%. These results indicate that the strength of the trophic interaction between the seals and the fish might be weaker than previously thought. The consumption of significantly different-sized squid can also be used to suggest spatial (vertical) foraging separation of these two predators because there is evidence for ontogenetic change in the size of squid species with depth; older, and thus larger, squids live deeper than smaller individuals of the same species.
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  • 94
    Publication Date: 2021-08-13
    Description: Recent evidence suggests that, contrary to what was believed previously, most Loligo spp. females spawn multiple times and do not die immediately following a single spawning event. The present study used sustained focal observations of male/female pairs of the opalescent inshore squid Loligo opalescens Berry to examine the structure and behavior of near-bottom spawning groups. The study was carried out in a small area (10 km2) of Monterey Bay, California (36°36.1′N; 121°53.4′W), at depths of 25–45 m, using video cameras mounted on remotely operated vehicles. Behavioral observations were made primarily during daylight hours over known spawning beds in April and November 2000, and August 2001. Squid formed large aggregations in the water column where pairing occurred. Most commonly, only small numbers of active spawners were found at the substrate depositing egg capsules, and the mean operational sex ratio in the spawning groups was 1.87 males:1 female (range=1.0–8.5), although the ratio fluctuated rapidly as roving lone males joined and departed from the small spawning groups. On average, females (n=40) deposited 2.67 capsules (range 2–7) per focal observation at an average interval of 8.47 min between depositions (n=67). Following deposition of the capsules, females broke away from their consort males and jetted upwards to rejoin large schools located many meters above the substrate. Egg-capsule deposition was often interrupted by lone males seeking a mate, or by the approach of predators including fish and marine mammals. The results suggest that most of the communal egg beds in southern Monterey Bay are built up slowly through daily intermittent spawning, not in large “big bang” reproductive events as often depicted for L. opalescens.
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  • 95
    Publication Date: 2021-08-31
    Description: This study examined the diet of Antarctic fur seals, Arctocephalus gazella, from an active breeding colony at Cape Shirreff (62°28′S, 60°48′W), Livingston Island, South Shetland Archipelago, Antarctica. It analysed faecal samples from five consecutive years (1997–2001) and length distribution of krill taken by trawl nets in the vicinity of Livingston Island. Antarctic krill, Euphausia superba, was the most frequent prey item, followed by several myctophid species (Gymnoscopelus nicholsi, Electrona antarctica and Electrona carlsbergi), squid and penguin remains. From 1998 to 2001, a modal progression in krill size was evident, suggesting that A. gazella was depending on a strong krill cohort, at least over the study period. Analysis of size distribution and size selectivity of krill preyed upon by fur seals suggests a preference for larger krill (〉34 mm), despite the broader size range of preys items available.
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  • 96
    Publication Date: 2021-09-03
    Description: The age and habitat of the giant squid, Architeuthis sanctipauli Velain, 1877, were determined based on isotopic analyses of the statoliths of three female specimens captured off Tasmania, Australia, between January and March 1996. Assuming that the aragonite of the statoliths formed in equilibrium with seawater, δ18O analyses indicated that the squid lived at temperatures of 10.5–12.9°C, corresponding to average depths of 125–250 m and maximum depths of 500 m. The capture records indicated that these squid may have occasionally ranged still deeper, to as much as 1000 m. All the statoliths were labeled with bomb 14C (Δ14C=+22.9‰ to +44.6‰), consistent with the depths inferred from δ18O. A thin section through one of the statoliths revealed 351 growth increments grouped into check-ring structures every 10–16 increments. A model for statolith growth and the pattern of temporal change in Δ14C in the water column was used to estimate the ages of the three specimens. These estimates were very sensitive to the choice of depth range over which Δ14C values were integrated. Assuming that the capture depths represented the maximum habitat depths of these individuals, the calculations suggested an age of 14 years or less. More refined age estimates require a better understanding of the variation of Δ14C and temperature with depth in the areas in which the squids live.
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  • 97
    Publication Date: 2021-07-23
    Description: The size selectivity of a trammel net for herded oval squid Sepioteuthis lessoniana in Tateyama Bay, Chiba Prefecture, was estimated by comparison between the mantle length frequency distributions of oval squid caught by a trammel net and by a set net. The measured mesh sizes of the inner net of the trammel net and of the final section of the set net were 85.3 and 11.3 mm, respectively. In the trammel net fishery where oval squid are herded into the net, most of the oval squid are caught in the bag-shaped inner net. Hence, the logistic function was employed for the size selectivity curve of the trammel net. The ‘share each length's catch total’ (SELECT) model was implemented for the estimation of the selectivity curve. The size selectivity r(l) of the trammel net for the oval squid was expressed as a logistic function of the mantle length l: r(l)=exp (-18.57+0.88 l)/[1+exp (-18.57+0.88 l)]. From these logistic parameter estimates, the 50% selection mantle length and selection range (L75-L25) were calculated as 21.07 and 2.49 cm, respectively. The selection probability of oval squid whose mantle girth was equivalent to the mesh perimeter of the inner net was 0.09. Accordingly, oval squid of a girth smaller than the mesh perimeter were likely to pass through the mesh to escape from the net.
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  • 98
    facet.materialart.
    Unknown
    Springer
    In:  Theoretical and Computational Fluid Dynamics, 18 (2-4). pp. 129-136.
    Publication Date: 2018-01-19
    Type: Article , NonPeerReviewed
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  • 99
    Publication Date: 2018-07-02
    Description: In an enclosure study in Schöhsee, a small mesotrophic lake in Northern Germany, the impact of copepods and daphniids on the seston community was studied. In general, these two guilds differ in their feeding behaviour. Copepods actively select their food, with a preference for larger particles, whereas most cladocerans are unselective filter-feeders. In this study we investigate how the impact of the two different grazers affects zooplankton growth. We combine results obtained in the laboratory with results measured in situ in the enclosures. Copepods and cladocerans were cultured on seston from enclosures that were inhabited by density gradients of copepods or daphniids. We observed that Daphnia grew faster on seston that was pre-handled by copepods than on seston that was pre-handled by daphniids, and that somatic growth decreased with increasing densities of daphniids in the enclosures. In contrast, we observed no differences in development rates for copepods grown on the different media. The population growth rates of Daphnia in the Daphnia treatments were determined in the enclosures. Growth differences in both somatic- and population growth of Daphnia were correlated to food quality aspects of the seston. In the laboratory we found that Daphnia growth was correlated with several fatty acids. The strongest regression was with the concentration of 20:4ω3 (r2= 0.37). This particular fatty acid also showed the highest correlation with growth after normalisation of the fatty acids to the carbon content of the enclosures (r2= 0.33). On the other hand, in the enclosure the population growth correlated most to the particulate nitrogen content (r2= 0.78) and only to the N:C ratio, when normalised to carbon (r2= 0.51).
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  • 100
    Publication Date: 2018-05-30
    Description: Ambae Island is the largest of Vanuatu’s active volcanoes. It is also one of the nation’s potentially most dangerous, with 60 million m3 of lake-water perched at over 1340 m in the summit caldera and over the active vent. In 1995, small phreatic explosions, earthquake swarms and heightened gas release led to calls for evacuation preparation and community volcanic hazard awareness programs for the ~9500 inhabitants. Differences in perspective or world-view between the island dwellers adhering to traditional beliefs (Kastom) and external scientists and emergency managers led to a climate of distrust following this crisis. In an attempt to address these issues, rebuild dialogue and respect between communities, outside scientists and administrators, and move forward in volcanic hazard education and planning for Ambae, we adapted and applied Participatory Rural Appraisal (PRA) approaches. Initial gender-segregated PRA exercises from two representative communities provided a mechanism for cataloguing local traditional viewpoints and hazard perceptions. Ultimately, by combining elements of these viewpoints and perceptions with science-based management structures, we derived volcanic hazard management guidelines, supported by an alert system and map that were more readily accepted by the test communities than the earlier “top-down” plans imposed by outside governmental and scientific agencies. The strength of PRA approaches is that they permit scientists to understand important local perspective issues, including visualisations of volcanic hazards, weaknesses in internal and external communication systems, and gender and hierarchy conflicts, all of which can hinder community emergency management. The approach we describe has much to offer both developing and industrialised communities that wish to improve their awareness programs and mitigative planning. This approach should also enhance communication and understanding between volcanologists and the communities they serve.
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