Hydrological Changes Research Articles

Interannual hydrological changes affect plant communities across different elevation zones in plateau lakeshores: insights from Lake Erhai

Interannual hydrological changes affect plant communities across different elevation zones in plateau lakeshores: insights from Lake Erhai

The Functional Response of Estuarine Fish Communities to Hydrologic Change in a Semi-Arid Ecosystem

Functional assessment approaches were used to identify the responses of fish to environmental change in the San Antonio Bay System (Texas, USA). Using a 26-year coastal fisheries dataset (1993–2018), multivariate analyses revealed relationships between functional group abundance and freshwater inflows in the upper segments (Hynes Bay and Guadalupe Bay), but the patterns were decoupled from inflows in the lower bay segments (San Antonio Bay, Ayres Bay and Espiritu Santo Bay). In Hynes and Guadalupe Bays, freshwater migrant carnivores accounted for a significant fraction of the community irrespective of the gear, year or flow. Freshwater stragglers (omnivores and carnivores) were often present in the upper reaches of the bay. In the lower reaches, marine migrant omnivores were present during high and low flows in Espiritu Santos Bay, but only during low flows in Ayres Bay. Marine migrant carnivores were more important in gill nets irrespective of the flow conditions. The five most abundant fish were estuarine resident carnivores and omnivores, accounting for 53.5% of the community. Declines in the abundance of functional groups occurred during the 2011–2014 drought, with rebounds in 2015–2018. Functional methodologies provide insights into estuarine ecosystems and can serve as management tools to assess changes in fish assemblages.

Hydrological changes and its impacts on prehistoric human welfare in the western Tibetan Plateau since the last deglaciation

In recent decades, the rapidly changing climate environment in the Tibetan Plateau (TP) poses significant challenges to human survival and future sustainable development. The suitability and stability of the climate in the TP undoubtedly affected the living conditions and welfare of prehistoric humans. However, few studies have attempted to link climate stability and the survival of ancient humans, especially considering their lesser adaptability in responding to rapid environmental changes. The Xiada Co is a Neolithic period archaeological site in the western TP. In this study, we reconstructed the hydrological changes in the basin over the past 15,000 years using X-ray fluorescence (XRF) elemental analysis on the Xiada Co cores. The XRF results revealed three main paleoenvironmental units during the entire study interval. The late Pleistocene prior to ~10,000 cal year BP was characterized by more rapidly fluctuating hydrologic conditions. The early and middle Holocene (~10,000–4000 cal year BP) by stable hydrologic conditions, and the late Holocene to present by a return to more variable conditions. Using the calculation method of Square Chord Distance (SCD), a quantitative dissimilarity comparison was made regarding the climate variations in the western TP for 15 time periods. The results showed that the climate and hydrology were relatively stable during the period of occupation of the region (8500–7500 years BP), which provided a stable and suitable living environment for the hunter-gatherers at the site. This study illustrates how the paleoenvironment influenced the survival of hunter-gatherers in the extremely harsh western TP.

River stabilization reshaped human-nature interactions in the Lower Yellow River Floodplain

Floodplains are crucial agricultural and populated areas worldwide. Rivers typically shape human activities within floodplains through water supply and flood risk, forming unique human-nature interaction patterns. Given that river systems have undergone significant transformations globally, understanding the response of these interactions to hydrological changes is elementary. Here, using the Lower Yellow River Floodplain (LYRF) as a case, where continuous levees distinctly outline the river-influenced floodplain from a homogenous cultivated plain and the river's hydrology has undergone dramatic alterations since the 1990s, we analyzed how the human-nature interactions respond to river hydrological changes. This study found that the flood-prone nature of the Lower Yellow River has weakened from 1986 to 2021 as shown by decreased surface water extent and inundated extent of cropland. The intensity of agriculture inside the LYRF has been lower but experienced faster development than outside, minimizing the disparity between them. Meanwhile, human activities in the floodplain have moved closer to the river. These changes in human-nature interactions in the LYRF can be explained by the river stabilization caused by upstream regulation, underscoring the significance of integrated river governance in managing human-nature system in floodplain areas.

Innovative management strategies for groundwater logging in Aswan city and maximization of its benefits using modeling techniques

Groundwater levels vary from region to another and sometimes in different zones in the same country due to different boundary conditions and extraction rates. Therefore, understanding intricate aquifer systems and predicting how they will react to hydrological changes require the use of groundwater models. In Egypt, the groundwater levels in the Nile Delta aquifer decrease causing problems to the delta ecosystem while it is rising in Aswan area due to the presence of Nasser Lake causing several damages to the city’s buildings and infrastructures. In order to maximize its benefits and lessen the harm brought on by inadequate groundwater management in the city of Aswan, the height of the groundwater level in that city was examined, appraised, and groundwater management scenarios were established in this study. To achieve the objectives of the study, a simulation of Aswan aquifer’s groundwater system is built based on a quasi-three-dimensional transient groundwater flow model using MODFLOW. The model was calibrated and verified. Four management scenarios are tested. The fifth scenario, in this scenario, the four scenarios combined together at the same time and with the same conditions and ratios were proposed to be implemented. The results of the proposal to implement the four scenarios together showed that the rates of decline in groundwater levels in the last stage will be 12.44%. The study results reveal that a better understanding of the simulated long-term average spatial distribution of water balance components is useful for managing and planning the available water resources in the Aswan aquifer.

Application of the Analytic Network Process for Sub-Watershed Prioritization in the Huehuetan River Basin, Chiapas, Mexico

Sub-watershed prioritization is essential for developing watershed management plans that maximize impact with minimal resources. This study used a multicriteria decision-making approach to rank sub-watersheds by degradation status in the Huehuetan River Basin, Chiapas, Mexico. The eight sub-watersheds in the basin were classified using the Analytic Network Process (ANP) model, evaluating morphometry, hydrology, hillslope stability, soil water saturation, land-use change, and socioeconomic factors. The results identified hydrology and land-use change as the most influential criteria, with weights of 20.62% and 19.82%, respectively, driven mainly by surface runoff and deforestation. Swtr 08 and Swtr 07 were identified as the highest-priority sub-watersheds, covering 24.31% of the basin area, with 55.31% of Swtr 08 classified as unstable and showing a combined high-vegetation loss of 16.46 km2. The entire watershed showed an annual vegetation loss rate of 146 ha year−1. Increasing the weighting by 50% resulted in greater variability in priority rankings, with runoff and low vegetation showing maximum global ranges of −44.33% and 30.25%, respectively, instability decreasing by 33.94%, and peak flow increasing by 18.20%. These findings emphasize the need for focused interventions in the vulnerable subwatersheds of the upper basin to manage runoff, curb deforestation, and reduce soil instability.

Hydrologically sensitive carbonates: Tectonic and groundwater controls on synrift sedimentation in the Late Jurassic–Early Cretaceous of the western Cameros Basin, Northern Spain

AbstractBasin hydrology and subcrop are key controls on carbonate sedimentation in continental basins. Hydrologically sensitive carbonates can record groundwater fluctuations within an aquifer in deep time. Late Jurassic extension, footwall uplift, erosion and karstification of marine Jurassic carbonates in the western Cameros Basin (Spain) saw deposition of ?Upper Kimmeridgian‐Tithonian syntectonic alluvial fan deposits (Señora de Brezales Formation). Biogenic laminar calcretes and phreatophytic rhizocretions record roots exploiting capillary fringe groundwater. Progressive infill of rift topography and footwall erosion lowered sedimentary gradients and clastic supply during deposition of the ?Tithonian–Berriasian Rupelo Formation. Distal alluvial marls (Las Viñas Member) contain charophytes, with 2 m thick carbonate lenses at the top reflecting intermittent rise of groundwater in ponds on the basin floor. Stacked palustrine limestones with rare charophytes and laminar calcretes (Ladera Member) record overstep of seasonal carbonate wetlands onto basin margins and footwall highs with intense pedogenetic modification during lengthy seasonal exposure. Overlying Berriasian charophyte‐ostracod wackestones, displaying microkarst cavities and interbedded intraclastic conglomerates, with vivianite sauropod bones, footprints and polygonal desiccation cracks at the top (Mambrillas de Lara Member) record open lacustrine conditions with limited subaerial exposure and high water tables. Desiccation‐cracked limestones and marls with correlatable evaporite horizons (Rio Cabrera Member) contain marginal marine foraminifera and dasycladaceae at the top. Lagoonal conditions reflected transgression to seaward and intermittent marine connection via the Basco‐Cantabrian Basin. The distribution and thicknesses of hydrologically sensitive carbonates reflected onlap onto a faulted and karstified marine Jurassic carbonate pediment and the subtle influence on hydroperiod of fault (and potentially localised Triassic salt) controlled differential subsidence and transgressive groundwater rise. Hydrological facies evolution reflects progressive basin infilling and eustasy beyond. Transitions in this continental succession from clastic to carbonate facies and from closed to open hydrology record hydrological change over time rather than contemporaneous deposition under Walther's Law.

Distinct responses of climate-growth and iWUE in Fagus sylvatica L. at two low elevation sites in southern Italy

In this study, using a dendrological and isotopic approaches, we investigated the responses to climate of two pure Fagus sylvatica L. stands (Campobraca and Falode) in the southernmost part of the distribution range in southern Italy. The δ13C data were used for calculating the intrinsic water use efficiency (iWUE) as a proxy of the balance between the water and carbon cycles. The results showed that the iWUE of both stands was sensitive to the amount of precipitation during the summer months (negative, significant effect) and to atmospheric CO2 concentration. Growth was sensitive to climate only in the Campo Braca site; the most influential variables were the VPD (vapour pressure deficit) and precipitation of the summer months that had a negative and a positive effect, respectively. The iWUE showed a negative correlation with growth in Campo Braca and a non-significant one in Falode. Water availability was the most influential variable on F. sylvatica growth and physiology. The iWUE increase was mainly driven by atmospheric CO2 concentration, and by decreased precipitation, as a response of the trees to drought. Our results highlight the importance of understanding the hydrological changes due to climate change for forecasting/modelling forest responses. CO2 increase does not compensate for the effect of adverse climate on F. sylvatica in the forests of southern Italy, while local conditions play an important role in determining tree growth.

Holocene Floodplain Transformation Through Catchment‐Scale Human‐Environment Interactions: An Interdisciplinary Case Study of the Gete Catchment (Belgium)

ABSTRACTFloodplains across the European loess region transformed from nature‐ to human‐dominated environments during the Holocene. A general framework of this evolution is well established, but it is less clear how differences in timing—observed within and between catchments—can be explained. Although human impact is an important driver, little attention has thus far been paid to the actual human activities involved, their intensities, and spatiotemporal patterns. By adopting an interdisciplinary approach, this study provides insight into the evolution of both environmental (e.g., local floodplain geoecohydrology and regional land cover) and human dynamics (e.g., demography and land use) in the Belgian Gete catchment. Results show that the observed changes in land cover and floodplain geoecology can indeed be attributed to spatiotemporal variations in human impact. Human‐induced vegetation change, driven by population growth and associated agrarian production, resulted in hydrological changes and localized colluviation. Catchment‐scale improvement of hillslope‐channel connectivity initiated alluviation in the valleys and completed the transformation from forested marsh to open floodplain with overbank sedimentation. In turn, this allowed people to settle in the floodplains in the Early Medieval period, laying the foundations for our present‐day landscape.

Using mercury and lead stable isotopes to assess mercury, lead, and trace metal source contributions to Great Salt Lake, Utah, USA

Great Salt Lake is a critical habitat for migratory birds that is threatened by elevated metal concentrations, including mercury (Hg) and lead (Pb), and is subject to severe hydrologic changes, such as declining lake level. When assessing metal profiles recorded in Great Salt Lake sediment, a large data gap exists regarding the sources of metals within the system, which is complicated by various source inputs to the lake and complex biogeochemistry. Here, we leverage Hg and Pb stable isotopes to track relative changes in metal source contributions to Great Salt Lake over time. Mercury and Pb concentrations increase in sediments deposited after 1920 and peak between 1965 and 1995, following closure of several local smelters and the onset of increased emission controls. The nominal associations above are confirmed via Hg stable isotopes in pre-1920 background sediments, which reflect atmospheric inputs from regional and global origin, whereas Hg and Pb stable isotopes together indicate that elevated metal concentrations in mid-late 20th century sediments reflect increased mining/smelting inputs. The observed minimal rebound towards pre-1920 Pb isotope signatures in 21st century sediments indicates that mining/smelting inputs, though reduced, remain a primary source of Pb to Great Salt Lake. In contrast, the more pronounced rebound of Hg stable isotope signatures to pre-1920 values indicate a greater contribution of atmospheric inputs of regional/global origin to current Hg inputs, though Hg concentrations are ~10 times greater than pre-1920 background values due to global increases in atmospheric Hg concentrations or possibly slow recovery from local contamination. The importance of regional/global Hg sources to the system suggests that reductions in Hg bioaccumulation in the open water food webs of Great Salt Lake are more dependent on national and global reductions in Hg emissions and management strategies to limit methylmercury production within system. This work highlights the utility of using coupled Hg and Pb stable isotope values to assess trace metal pollution sources and pathways in aquatic systems.

Long-Term Impacts of Runoff and Coastal Reclamation on Tidal Bore Variations in the Qiantang River Estuary, China

Tidal bore dynamics in estuarine environments are influenced by both natural hydrological changes and human activities, such as coastal reclamation. This study focuses on the Qiantang River estuary, assessing the impacts of runoff variations and reclamation on tidal bores over the past five decades. By employing statistical and time-frequency methods, including the Mann–Kendall test, ordered clustering, and wavelet analysis, the relationships between tidal bore height, river discharge, and reclamation activities are examined. The results indicate that increased freshwater discharge reduces bore intensity over short timescales of 0.3 to 1.2 years, while decreased runoff amplifies it. Over longer periods of 4.1 to 8.3 years, a positive correlation emerges, with changes in runoff preceding variations in tidal bore height. Coastal reclamation, particularly the narrowing of channels, has significantly reduced the bore height at Yanguan, especially in the years following the 2000s. Additionally, the long-term interactions of other factors influencing tidal bores are explored. These findings reveal a delayed estuarine response to human modifications, highlighting the necessity of long-term monitoring and adaptive management strategies to mitigate these impacts. The study provides valuable insights into the complex interplay of natural and human factors, offering guidance for future estuarine management and conservation efforts.

Evolution mechanism of physical morphology of oxbow lake in the middle Yangtze River

Oxbow lakes, formed through river meandering cutoffs, are recognized as key components of river ecosystems, characterized by both fluvial and lacustrine features. The focus of previous research has been placed primarily on post-disconnection changes, leaving gaps in the understanding of their long-term morphological evolution. This gap is addressed through a comparative analysis of gate-controlled and naturally connected oxbow lakes over a 30-year period. In this study, Tian’ezhou Lake (gate-controlled) and Shangchewan Lake (naturally connected), located in the middle Yangtze River, are investigated. Key morphological parameters such as curvature, shoreline development index, and shrinkage rate were measured using Google Earth Engine (GEE). The influence of hydrological and meteorological factors on lake morphology was analyzed through Redundancy Analysis (RDA). Significant morphological changes were observed from 1990 to 2000. During this period, Tian’ezhou’s curvature was found to increase by 0.003/year, while Shangchewan’s curvature decreased by 0.011/year. After the construction of the Three Gorges Dam (TGD), a reduction in the rate of morphological evolution was detected, particularly between 2000 and 2010, when Tian’ezhou’s curvature decreased by 0.071/year and Shangchewan’s increased by 0.04/year. Post-2010, no significant changes in planar morphology were recorded in either lake. It was revealed by RDA that annual precipitation from 1990 to 1999 played a dominant role in influencing the morphological evolution of both lakes. From 2000 to 2020, water level fluctuations and hydrological connectivity emerged as the primary drivers. Gate control at Tian’ezhou Lake mitigated extreme water level fluctuations, contributing to a more stable environment and a slower rate of morphological evolution compared to Shangchewan. The findings underscore the importance of balanced water management strategies, integrating both natural and engineered hydrological interventions. Practical guidance is provided for ecological restoration and river management, with an emphasis on maintaining stable habitats and ensuring ecosystem resilience in response to hydrological changes.

Awakening: Potential Release of Dormant Chemicals from Thawing Permafrost Soils under Climate Change.

Permafrost is a crucial part of the Earth's cryosphere. These millennia-old frozen soils not only are significant carbon reservoirs but also store a variety of chemicals. Accelerated permafrost thaw due to global warming leads to profound consequences such as infrastructure damage, hydrological changes, and, notably, environmental concerns from the release of various chemicals. In this perspective, we metaphorically term long-preserved substances as "dormant chemicals" that experience an "awakening" during permafrost thaw. We begin by providing a comprehensive overview and categorization of these chemicals and their potential transformations, utilizing a combination of field observations, laboratory studies, and modeling approaches to assess their environmental impacts. Following this, we put forward several perspectives on how to enhance the scientific understanding of their ensuing environmental impacts in the context of climate change. Ultimately, we advocate for broader research engagement in permafrost exploration and emphasize the need for extensive environmental chemical studies. This will significantly enhance our understanding of the consequences of permafrost thaw and its broader impact on other ecosystems under rapid climate warming.

Impact of extreme rainfall and flood events on harmful cyanobacterial communities and ecological safety in the Baiyangdian Lake Basin, China

Globally, climate change has intensified extreme rainfall events, leading to substantial hydrological changes in aquatic ecosystems. These changes, in turn, have increased the frequency of harmful algal blooms, particularly those of cyanobacteria. This study examines cyanobacterial community dynamics in the Baiyangdian Lake Basin, China, after heavy rainfall and flooding events. The aim was to clarify how such extreme hydrological events affect cyanobacterial populations in floodplain ecosystems and assess related ecological risks. The results demonstrated a significant increase in cyanobacterial diversity, exemplified by an increase of the Shannon diversity index from an average of 1.7 to 2.1 (p < 0.05). Following heavy rainfall and subsequent flooding, the average relative abundance of cyanobacteria in the microbial community increased from 7.59 % to 9.62 %, along a notable rise in the abundance of harmful cyanobacteria. The community structure exhibited notable differences after flooding, showing an increase in species richness, but a decrease in community tightness and clustering, as well as a reduction in niche overlap among harmful cyanobacteria. Environmental factors such as dissolved oxygen, water temperature, and pH were identified as crucial predictors of harmful cyanobacterial community differences and abundance variations resulting from flooding. These findings provide a critical framework for predicting ecological risks associated with the expansion of bloom-forming cyanobacteria in large shallow lake basins, particularly under intensified rainfall and flooding events. This insight is essential to anticipate potential ecological disruptions in sensitive aquatic ecosystems.

Runoff Change Characteristics and Response to Climate Variability and Human Activities Under a Typical Basin of Natural Tropical Rainforest Converted to Monoculture Rubber Plantations

Climate variability and human activities are major influences on the hydrological cycle. However, the driving characteristics of hydrological cycle changes and the potential impact on runoff in areas where natural forests have been converted to rubber plantations on a long-term scale remain unclear. Based on this, the Mann–Kendall (MK) and Pettitt breakpoint tests and the Double Mass Curve method were employed to identify the variation characteristics and breakpoints of precipitation (P), potential evapotranspiration (ET0), and runoff depth (R) in the Wanquan River Basin (WQRB) during the 1970–2016 period. The changes in runoff attributed to P, ET0, and the catchment characteristics parameter (n) were quantified using the elastic coefficient method based on the Budyko hypothesis. The results revealed that the P and R in the WQRB exhibited statistically insignificant decreasing trends, while ET0 displayed a significant increasing trend (p &lt; 0.05). The breakpoint of runoff changes in the Jiabao and the Jiaji stations occurred in 1991 and 1983, respectively. The runoff changes show a negative correlation with both the n and ET0, while exhibiting a positive correlation with P. Moreover, it is observed that P and ET0 display higher sensitivity towards runoff changes compared to n. The decomposition analysis reveals that in the Dingan River Basin (DARB), human activities account for 53.54% of the runoff changes, while climate variability contributes to 46.46%. In the Main Wanquan River Basin (MWQRB), human activities contribute to 46.11%, whereas climate variability accounts for 53.89%. The research findings suggest that runoff is directly reduced by climate variability (due to decreased P and increased ET0), while human activities indirectly contribute to changes in runoff through n, exacerbating its effects. Rubber forest stands as the prevailing artificial vegetation community within the WQRB. The transformation of natural forests into rubber plantations constitutes the primary catalyst for the alteration of n in the WQRB. The research findings provide important reference for quantifying the driving force of hydrological changes caused by deforestation, which is of great significance for sustainable management of forests and water resources.

Insights into the seasonal variation, distribution, composition and dynamics of microplastics in the Ganga River ecosystem of Varanasi City, Uttar Pradesh, India.

The current study explores the seasonal dynamics of microplastic (MP) pollution in the Ganga River of Varanasi City, Uttar Pradesh, India, focusing on water and sediment samples collected during pre-monsoon and post-monsoon periods. The analysis shows significant variations in MP occurrence, shape dynamics, color distribution, and size composition across diverse sampling sites. During the pre-monsoon season, MP concentrations ranged from 17 to 36 particles/L in water samples and 160 to 312 particles/kg in sediment, indicating a moderate to high level of contamination. Post-monsoon sampling showed higher MP concentrations at most sites, indicating the influence of seasonal hydrological changes on MP distribution. Shifts in MP shape dynamics were observed between seasons, with films, foams, fragments, and filaments showing variable distributions. Similarly, color variations in MPs exhibited site-specific patterns, with white, brown, blue, and other colors being predominant. These findings highlight the diverse sources and compositions of MPs in the river ecosystem, highlighting the complexity of MP pollution dynamics. Polymer-type distributions further elucidated the composition of MPs, with notable contributions from polyethylene terephthalate, rayon, polyester, and polyvinyl chloride. PCA analysis revealed significant shifts in particle size and shape distribution between pre-monsoon and post-monsoon periods in both water and sediment samples, with post-monsoon samples showing an increase in larger particles and filaments. These changes highlighted key factors driving the variance in microplastic contamination across different sites. The prevalence of these polymers features diverse sources of MP pollution, including textiles, packaging materials, and industrial waste. Ongoing monitoring and research are crucial to understanding its sources, distribution, and impact on river ecosystems, essential for protecting aquatic biodiversity and human health.

Recent Advances (2018–2023) and Research Opportunities in the Study of Groundwater in Cold Regions

ABSTRACTIncreasing greenhouse gas levels drive extensive changes in Arctic and cold‐dominated environments, leading to a warmer, more humid, and variable climate. Associated permafrost thaw creates new groundwater flow paths in cold regions that are causing unprecedented environmental changes. This review of recent advances in groundwater research in cold environments has revealed that a new paradigm is emerging where groundwater is at the center of these changes. Groundwater flow and associated heat and solute transport are now used as a basis to understand hydrological changes, permafrost dynamics, water quality, integrity of infrastructure along with ecological impacts. Although major advances have been achieved in cold regions' cryohydrogeological research, the remaining knowledge gaps are numerous. For example, groundwater as a drinking water source is poorly documented despite its social importance. Lateral transport processes for carbon and contaminants are still inadequately understood. Numerical models are improving, but the highly complex physical‐ecological changes occurring in the arctic involve coupled thermal, hydrological, hydrogeological, mechanical, and geochemical processes that are difficult to represent and hamper quantitative analysis and limit predictive capacity. Systematic long‐term observatories where measurements involving groundwater are considered central are needed to help resolve these research gaps. Innovative transdisciplinary research will be critical to comprehend and predict these complex transformations.

Soil Organic Carbon Stocks Depend Differently on Physicochemical Features in Subtropical Seasonally Flooded Wetland and Non‐flooded Shoreland Forest

ABSTRACTIn recent years, an increasing number of ecosystems are threatened by seasonal flooding, changing non‐flooded shoreland (NF) into seasonally flooded wetland (SF), but the consequences of this hydrological change for soil organic carbon (SOC) dynamics remain unknown. In this study, we investigated how the SOC content was determined by flooding duration and soil physicochemical variables in adjacent SF and NF at six depths (0–10 cm, 10–20 cm, 20–30 cm, 30–50 cm, 50–70 cm, and 70–100 cm) at Shengjin Lake in subtropical China. Soil physicochemistry and SOC composition were analyzed, and Fourier‐transformed infrared spectroscopy (FTIR) was used to resolve the SOC composition. Neither SOC content nor the vertical distribution of SOC was distinguishable between the sites. However, FTIR data revealed that plant‐originated aliphatics and amides were higher at NF than SF sites, with the opposite pattern for aromatics. At SF sites, SOC content was positively affected by soil moisture and flooding duration and was negatively impacted by soil particle size at most soil layers. At NF sites, SOC content was mainly affected by silt and total Fe at the top 20 cm soil, while a higher fraction of plant‐derived labile C was positively correlated to SOC contents at 30–100 cm depth. The results hence indicated a strong effect of seasonal flooding on SOC dynamics in terrestrial ecosystems. SOC stabilization induced by low mineralization and high adsorption played a central role at SF sites, while SOC formation through plant input was more important at NF sites. Our findings suggest that management strategies designed to conserve SOC will need to be site‐specific.

A revised marine fossil record of the Mediterranean before and after the Messinian salinity crisis

Abstract. The Messinian salinity crisis and its precursor events have been the greatest environmental perturbation of the Mediterranean Sea to date, offering an opportunity to study the response of marine ecosystems to extreme hydrological change and a large-scale biological invasion. The restriction of the marine connection between the Mediterranean and the Atlantic Ocean resulted in stratification of the water column and high-amplitude variations in seawater temperature and salinity already from the early Messinian. Here, we present a unified and revised marine fossil record of the Mediterranean (https://doi.org/10.5281/zenodo.13358435, Agiadi et al., 2024) that covers the Tortonian stage, the pre-evaporitic Messinian stage, and the Zanclean stage and encompasses 23 032 occurrences of calcareous nannoplankton, dinoflagellates, foraminifera, corals, ostracods, bryozoans, echinoids, mollusks, fishes, and marine mammals. This record adheres to the FAIR principles, is updated in terms of taxonomy, and follows the currently accepted stratigraphic framework. Based on this record, knowledge gaps are identified, which are due to spatiotemporal inconsistencies in sampling effort and the distribution of sedimentary facies, as well as the inherent differences in the preservation potential between the groups. Additionally, sampling bias in old records may have distorted the record in favor of larger, more impressive taxa within groups. This record is now ready to be used to answer both geological and biological questions about the Mediterranean Sea and beyond and is amendable when new fossil data are brought to light.

Strengthening of the hydrological cycle in the Lake Chad Basin under current climate change

Central Sahel is affected by a reinforcement of rainfall since the beginning of 1990s. This increase in rainfall is affected by high inter-annual variability and is characterized by extreme rain events causing floods of unprecedented magnitude. However, few studies have been carried out on these extreme events. Moreover, with current climate change expected to strengthen the hydrological cycle, we don’t know if these events could become more frequent. Here, we report the hydrological changes that currently occur in the Lake Chad basin. Based on ground observations and satellite data, we focused on the 2022 flood event, demonstrating that it was the most important event from the last 60 years, comparable to what occurred during the last wet period between the 1950s and the 1960s. We showed that under this precipitation regime and if warming is not regulated at a global scale, the return period of the 2022 major riverine flood is expected to be between 2 and 5 years. By using modelling experiments, our study also suggested that in the next decade, future flow rates of the main rivers draining the Lake Chad basin could reach the values observed in the 1950s. These results strongly suggest anticipating water management in a context of poor infrastructural development.