ALBERT

Description: The macrofauna in soft sediments of the deep seafloor is generally diverse and represents a comparatively well-studied faunal group of deep-sea ecosystems. In the abyss of the Clarion Clipperton Fracture Zone (CCFZ) in the NE Pacific, macrofauna are major contributors to benthic biodiversity. Their distribution, composition, and diversity have been frequently investigated to assess the potential impacts of future mining activities on the resident fauna. In this study, patterns of densities and community structure of CCFZ macrobenthic infauna and their relationships with a range of environmental and climatic variables were examined, with a special focus on communities from the eastern German contract area (referred to as BGR CA). However, comparisons were also made with other contractor areas (e.g., IFREMER, IOM, GSR) and one Area of Particular Environmental Interest (APEI3). Material for this study was obtained by means of a box corer during six expeditions to the CCFZ between 2013 and 2018 resulting in 148 samples. Our study uncovered notable spatial and temporal variations in both faunal densities and community composition. While areas within the BGR CA exhibited a similar community composition, slight differences were observed between the various CAs and APEI3. Surprisingly, we found an unexpected negative correlation between food availability and both macrofaunal density and community structure that may be attributed to differences in sampling methodologies and pronounced temporal variation. Furthermore, we explored the impact of climatic fluctuations associated with the El Niño/Southern Oscillation (ENSO) on macrofaunal densities, observing an increase during warm (El Niño) events. Our findings underscore the challenges of accurately assessing spatial and temporal variations in the absence of standardised sampling protocols. Hence, we emphasize the importance of adopting standardised protocols to enhance data comparability, thereby fostering a deeper understanding of the underlying factors influencing spatial and temporal changes in macrofauna community structure within the CCFZ.

Description: Predatory non-indigenous species (NIS) have profound impacts on global ecosystems, potentially leading to native prey extinction and reshaping community dynamics. Among mechanisms potentially mediating predator impacts and prey invasion success are predator preferences between native vs. non-indigenous prey, a topic still underexplored. Using functional response and prey preference experiments, this study focused on the predation by the non-indigenous Japanese brush-clawed shore crab, Hemigrapsus takanoi, between the native gammarid Gammarus duebeni and the analogous non-indigenous Gammarus tigrinus. Although H. takanoi showed subtle differences in its functional response type between the two prey species, its preferences across their environmental frequencies were not strongly influenced by the prey invasion scenario. The findings highlight the need for a comprehensive understanding of interactions in ecosystems with multiple NIS, offering fresh insights into complex feeding interactions within marine environments.

Description: Seismic data analysis often faces the challenge of random noise contamination from various sources. To overcome this, innovative noise attenuation methods utilizing seismic signal properties are needed. This study focuses on efficiently suppressing random noise in the domain of time and frequency by accurately estimating instantaneous frequency using the single-valued group delay characteristic of seismic signals. The time-reassigned synchrosqueezing transform (TSST) and its second-order variant (TSST2) offer high-resolution time-frequency representations (TFRs) for noise suppression. Expanding on these advancements, we propose an efficient noise suppression method that integrates the adaptive thresholding model into the TSST2 framework and employs sparse representation of the TFR through low-rank estimation. This method effectively attenuates noise while preserving essential signal information. The proposed approach operates trace by trace on recorded data, initially transforming it into a sparse subspace using TSST2. The adaptive thresholding model then decomposes the resulting TFR into sparse and semi-low-rank components, achieving a high-resolution and sparse TFR for efficient separation of noise and signal. After noise suppression, the seismic data can be fully reconstructed by inversely transforming the semi-low-rank component data into the time domain. This method addresses previous limitations in noise attenuation techniques and provides a practical solution for enhancing seismic data quality.

Description: Gas chimneys and gas clouds in the subsurface media are known as one of the indications of possible petroleum reservoirs. Investigations of their properties are mostly initiated by seismic attribute interpretation on reflection seismic data. However, due to the complexity of their behavior and their difficult interpretation of seismic attributes, state-of-the-art methods are mostly required to be applied on the seismic data to prevent any misinterpretation. This is mostly done through attribute integration and multi-attribute analysis. This research presents a study on seismic attributes and integration on several 2D seismic reflection lines from the Gorgan Plain. It is located in Northeast Iran, on the western border of the region’s well-known Kopeh-Dagh fold and thrust belt, and southeastern border of the South Caspian Basin. Hydrocarbon systems of the Gorgan Plain are poorly known and have not been widely studied, but according to preliminary investigations, this region has the potential for hydrocarbon occurrences. The aim of this study is to investigate presence and then delaminate the affected area of possible gas chimneys that are related to possible hydrocarbon reservoirs. Gas chimneys are assumed to be created due to the routes, mostly made by faults, that provoke light hydrocarbons components to migrate toward the surface. Preliminary interpretations of seismic reflection data in this study revealed that at least two gas chimneys occurred within the Gorgan Plain. As it was mentioned, since they are mostly due to the faulting above the hydrocarbon reservoir, gas chimney and heavy faulting might exhibit the same effects on the seismic data and then on its attributes, which are amplitude reduction and high damping on energies, distortion of the waveshape and seismic velocity reduction. Thus, care should be taken in separation of these two different geologic phenomena on seismic attributes. This also was done in this study through utilized integration of the most relevant seismic attributes such as Instantaneous-phase, Chaos, Variance and Remove-bias attributes. Based on the result of interpretations and according to the evolution of the basin and its structural reconstruction on other studies, gas chimneys of the Gorgan Plain, are in relation to the operation of fault zones in Cenozoic erathem in the region. These fault zones which cut the entire Cenozoic erathem, create the pathway for vertical migration of hydrocarbons through Cheleken formation (reservoir rock) and its overburden sedimentary sequences. In other words, operation of fault zones within Cenozoic sedimentary sequence, is the main reason for gas seepage in the Gorgan Plain, which is also shown in seismic data.

Description: A stratigraphic complex composed of mass transport deposits (MTDs), where the gas occurrence allows for the formation of a gas chimney and pipe structure, is identified based on seismic interpretation in the QiongDongNan area of the northern South China Sea. During the Fifth Gas Hydrate Drilling Expedition of the Guangzhou Marine Geological Survey, this type of complex morphology that has close interaction with local gas hydrate (GH) distribution was eventually confirmed. A flow-reaction model is built to explore the spatial–temporal matching evolution process of massive GH reservoirs since 30 kyr before the present (BP). Five time snapshots, including 30, 20, 10, and 5 kyr BP, as well as the present, have been selected to exhibit key strata-evolving information. The results of in situ tensile estimation imply fracturing emergence occurs mostly at 5 kyr BP. Six other environmental scenarios and three cases of paleo-hydrate existence have been compared. The results almost coincide with field GH distribution below the bottom MTD from drilling reports, and state layer fracturing behaviors always feed and probably propagate in shallow sediments. It can be concluded that this complex system with 10% pre-existing hydrates results in the exact distribution and occurrence in local fine-grained silty clay layers adjacent to upper MTDs.

Description: Oceanic intraplate volcanoes sometimes experience late-stage eruptive activity known as rejuvenated volcanism, and contrasting interpretations for its petrogenesis depend on the compositional characteristics. In the Juan Fernández Ridge (JFR), a volcanic chain approximately 800 km in length emplaced on the Nazca Plate, some subaerial occurrences of rejuvenated volcanism have been recognized on the Robinson Crusoe and Santa Clara Islands, both part of the same deeply eroded shield volcano complex. This study aims to understand the origin and magmatic evolution of rejuvenated volcanism on Santa Clara Island, emplaced after ~2.15 Ma of quiescence above the shield sequence, mainly via the analysis of unpublished geochemical and isotopic data. Field reconnaissance identified two nearly coeval rejuvenated sequences on Santa Clara Island: Bahía W (BW) and Morro Spartan (MS), both formed by basanitic and picro-basaltic lava flows with brecciated levels and local intercalations of sedimentary and pyroclastic deposits. In comparison to the chemical signature of the preceding shield-building stage (comprised mainly of basalts and picrites), the two rejuvenated sequences exhibit a notable enrichment in incompatible elements, but the Sr, Nd, and Pb isotopes are very similar to the FOZO mantle endmember, with an apparent additional contribution of HIMU and EM1 components. The geochemistry of lavas revealed the involvement of various processes, including contamination by ultramafic xenoliths, high-pressure fractional crystallization of olivine and clinopyroxene, and potential partial assimilation of oceanic lithospheric components. While the oceanic lithosphere has been considered as a potential source, the isotopic data from Santa Clara lies outside of the mixing curve between depleted mantle (DM, here represented by the North Chile Rise and the East Pacific Rise) and the previous shield stage, suggesting that a lithospheric mantle is not the primary source for the rejuvenated stage volcanism. Therefore, we favor an origin of the rejuvenated volcanism from the mantle plume forming the JFR, supported by similarities in isotopic signatures with the shield stage and high values of 208Pb/204Pb (only comparable to San Félix—San Ambrosio in the vicinity of JFR), implying the presence of a regional source with radiogenic 208Pb/204Pb isotope ratios. In addition, isotopic variations are subparallel to the mixing line between HIMU and EM1 components, whose participation in different proportions might explain the observed trends. In conclusion, we propose that the source of the rejuvenated volcanism on Santa Clara Island is a heterogeneous mantle plume, the same one that fed the shield stage. The rejuvenated volcanism is derived from a secondary melting zone away from the main axis of the plume.

Description: Weather causes extremes in photovoltaic and wind power production. Here we present a comprehensive climatology of anomalies in photovoltaic and wind power production associated with weather patterns in Europe considering the 2019 and potential 2050 installations, and hourly to ten-day events. To that end, we performed kilometer-scale numerical simulations of hourly power production for 23 years and paired the output with a weather classification which allows a detailed assessment of weather-driven spatio-temporal production anomalies. Our results highlight the dependency of low-power production events on the installed capacities and the event duration. South-shifted Westerlies (Anticyclonic South-Easterlies) are associated with the lowest hourly (ten-day) extremes for the 2050 (both) installations. Regional power production anomalies can differ from the ones in the European mean. Our findings suggest that weather patterns can serve as indicators for expected photovoltaic and wind power production anomalies and may be useful for early warnings in the energy sector.

Description: Animals have a deep evolutionary relationship with microbial symbionts, such that individual microbes or an entire microbial community can diverge alongside the host. Here, we explore these host-microbe relationships in Echinometra, a sea urchin genus that speciated with the Isthmus of Panama and throughout the Indo-West Pacific. We find that the eggs from five Echinometra species generally associate with a species-specific bacterial community and that the relatedness of these communities is largely congruent with host phylogeny. Microbiome divergence per million years was higher in more recent speciation events than in older ones. We, however, did not find any bacterial groups that displayed co-phylogeny with Echinometra. Together, these findings suggest that the evolutionary relationship between Echinometra and their microbiota operates at the community level. We find no evidence suggesting that the associated microbiota is the evolutionary driver of Echinometra speciation. Instead, divergence between Echinometra and their microbiota is likely the byproduct of ecological, geographic, and reproductive isolations.

Description: Until now, proxy records have been the primary tool for quantitative reconstructions of the physical world of the ancient and late antique Mediterranean. This chapter demonstrates the combined use of proxy datasets and the hitherto underutilized potential of earth system models in the scientific and historical study of past environmental variations and impacts on human societies. Results from model simulations are able to explain hydroclimatic anomalies observed in the proxy records and provide links to relevant mechanisms. The Late Roman Dry Period and the Late Roman Wet Period of the mid-fourth to early eighth centuries AD are each associated with the increase in the frequency of subsistence crises and with the accelerated infrastructural adaptations of communities and agricultural expansion, respectively. The chapter concludes with an examination of the historical and climatic contexts behind one such anomaly, a subsistence crisis in Cappadocia in the late 300s AD.

Description: Arabian Sea upwelling in the past has been generally studied based on the sediment records. We apply two earth system models and analyze the simulated water vertical velocity to investigate coastal upwelling in the western Arabian Sea over the last millennium. In addition, two models with slightly different configurations are also employed to study the upwelling in the 21st century under the strongest and the weakest greenhouse gas emission scenarios. With a negative long-term trend caused by the orbital forcing of the models, the upwelling over the last millennium is found to be closely correlated with the sea surface temperature, the Indian summer Monsoon and the sediment records. The future upwelling under the Representative Concentration Pathway (RCP) 8.5 scenario reveals a negative trend, in contrast with the positive trend displayed by the upwelling favorable along-shore winds. Therefore, it is likely that other factors, like water stratification in the upper ocean layers caused by the stronger surface warming, overrides the effect from the upwelling favorable wind. No significant trend is found for the upwelling under the RCP2.6 scenario, which is likely due to a compensation between the opposing effects of the increase in upwelling favorable winds and the water stratification.