Grzegorz Skrzypek

Parasitic copepods may provide minimally invasive biochemical tracers of isotope patterns in large sharks, but their utility requires empirical evaluation. We assessed whether parasitic...

Global warming and permafrost thaw have significantly altered landscapes and hydrological conditions in permafrost regions. While site‐specific process studies have described hydrological changes during thawing, basin‐scale impact assessments and streamflow modeling remain challenging due to landscape heterogeneity and complex interactions. This study introduces a space‐for‐time framework using thermokarst lake indicators to quantify elevation‐dependent hydrological shifts driven by permafrost degradation. On the Qinghai‐Tibet Plateau, findings suggest a gradual transition in precipitation‐runoff regimes, with warm‐season precipitation becoming increasingly delayed and increasingly contributing to cold‐season runoff. Currently, continuous permafrost dominates high elevation, transitioning to discontinuous permafrost at mid‐elevation and seasonally frozen ground at low elevation, a gradient expected to diminish under future climate scenarios. Water yield mirrors this zonation, originating primarily from continuous and discontinuous zones, and declining in seasonally frozen areas. As thawing progresses, the overall water yield is projected to decrease. Simulations indicate that thawed low‐elevation landscapes will buffer runoff pulses from higher elevations, delaying seasonal discharge and reducing basin‐scale outflow, ultimately diminishing downstream water availability. Our analysis demonstrates the primary influence of landscape connectivity in shaping runoff dynamics and biogeochemical pathways in mountain systems undergoing permafrost degradation.

Changing rainfall patterns driven by climate change are altering the seasonal delivery of organic matter from rivers to estuaries, with consequences for food-web dynamics in many regions worldwide. The importance of riverine subsidies to estuarine food webs is poorly understood, particularly at a high spatial resolution (1–2 km). This study provides a high-resolution assessment of seasonal (summer and winter) variation in riverine contributions to the diets of clams ( Katelysia spp. ) within a temperate estuary in southern Australia. We examined a simplified food web, using stable carbon and nitrogen isotopes to measure and evaluate clam gill tissue (ctenidia), particulate organic matter from riverine, estuarine, coastal and benthic sources (< 200 μm), and seasonal macroalgae. The summer food web was compartmentalized, with riverine resources estimated to comprise 8.4 to 18.0% of clam diets. Clam diets at sites with greater riverine influence included comparatively more rPOM. The stable isotope signatures of the food sources in winter were less distinct, preventing the use of mixing models to estimate clam diets. The winter decline in δ ¹³ C for clams at two sites, indicates greater reliance on riverine organic matter and reveals pronounced spatial heterogeneity in resource use at fine spatial scales. These results suggest that clam gill tissue may be a useful indicator for resolving high-resolution seasonal food web isoscapes. These findings highlight the importance of incorporating fine-scale ecosystem features, including creeks and small tributaries, into the design and interpretation of estuarine food-web studies, given that such localized inputs emerge more clearly at higher spatial resolutions.

Global climate change is profoundly affecting precipitation patterns worldwide, including the exacerbation of aridity in dryland regions. Here, we examined the variability in rainfall stable hydrogen and oxygen isotope compositions ( δ ¹⁸ O and δ ² H) at five locations in subtropical northwest Australia over 10 years (2015–2024) to better understand the mechanisms driving precipitation and to identify moisture sources. We found that precipitation with low δ ² H and δ ¹⁸ O was predominantly observed during months with high rainfall, confirming the significant impact of the “amount effect” at most sites. δ ² H and δ ¹⁸ O were positively correlated with the stratiform fraction of total precipitation, which indicates the importance of sub‐cloud evaporation losses during stratiform events. The mean sub‐cloud evaporated fraction was estimated at ∼30%; a back trajectory analysis revealed that up to 47% of rain moisture during the wet season was recycled from land evapotranspiration. Differences between arithmetic and volume‐weighted monthly mean stable isotope compositions highlight the seasonal significance of small‐volume rainfall events for monthly means. We propose a new “cut‐off” approach to eliminate the disproportionate influence of a high proportion of low‐volume rainfall on the stable isotope composition of monthly precipitation and Local Meteoric Water Lines.

Global climate change is reshaping precipitation regimes worldwide and intensifying aridity across many dryland regions. These changes also impact the dry subtropics of northwestern Australia. In this region, the strong spatial and temporal variability of rainfall complicates the characterisation of hydrologic processes, making it challenging to assess groundwater recharge, manage water resources effectively, and protect vulnerable ecosystems.The region is marked by a distinct dry winter season (April-October) and a wet summer season (November-March), and it receives a far greater proportion of cyclone-driven rainfall than most other parts of Australia. These cyclonic systems contribute to pronounced seasonal and interannual variability, producing intense but short-lived flash-flooding events separated by extended droughts. During the study period (2015–2024), more than 80 % of total rainfall occurred between December and March across the five monitored weather stations. Mean annual rainfall ranged from 288 to 366 mm, while mean relative humidity remained low (30-37 %). Consequently, potential evaporation rates were extremely high, often exceeding 3000 mm/y.To better understand the atmospheric processes governing precipitation formation and moisture sourcing in this environment, we analysed ten years of rainfall stable hydrogen and oxygen isotope compositions (δ¹⁸O and δ²H) from five sites. We also analysed 1,101 air parcel trajectories corresponding to rain events at five sites over the study period. Rainfall with low δ²H and δ¹⁸O values occurred predominantly during high-rainfall months, demonstrating a strong ‘amount effect’ at most locations. Both, stable hydrogen and oxygen isotope compositions were positively correlated with the stratiform fraction of total precipitation, indicating substantial sub‑cloud evaporation during stratiform events. On average, ~30 % of rainfall was lost to sub‑cloud evaporation, and back‑trajectory analysis showed that up to 47 % of wet-season moisture originated from recycled land evapotranspiration.Differences between arithmetic and volume-weighted monthly isotope means highlight the seasonal importance of small-volume rainfall events. To address this bias, we introduce a new “cut‑off” method designed to reduce the disproportionate influence of low‑volume rainfall on monthly isotope compositions and on the construction of Local Meteoric Water Lines.

Arid and semiarid zones cover roughly 70 % of Australia, including the Pilbara region of Western Australia. The Pilbara experiences low seasonal rainfall of ~350 mm/y, with nearly 80 % of precipitation estimated to be lost to evaporation. Subsurface water fluxes are vital to ecohydrological functioning in these environments, yet remain poorly understood. This study integrates stable water isotopes (δ2H and δ18O) with direct hydrometric observations to characterise soil moisture dynamics in semiarid floodplain soils. The aim is to constrain isotope-based inferences using physically measured soil water fluxes to clarify how episodic water inputs are partitioned, retained, and lost in semiarid floodplains under increasing water scarcity. Vertically resolved isotope profiles were combined with continuous measurements from smart lysimeters and soil-moisture probes across six sites. To our knowledge, this work represents the first combined application of smart lysimeters and stable isotope analyses in natural environments in Australia. Near-surface moisture is strongly affected by evaporation, with elevated δ2H and δ18O values extending to the depths of ~50 cm. Below this zone, isotope compositions remain comparatively uniform, indicating limited vertical exchange and minimal deep percolation. Only substantial rainfall events (> 60-90 mm) generated transient pulses characterised by low δ-values consistent with episodic deep infiltration. Spatial variability across sites revealed systematic gradients in moisture retention and isotope composition that correspond to soil texture and structure. Shallow infiltration exhibited highly variable instantaneous rates (3.33 – 300 mm/hr), controlled primarily by rainfall intensity and surface conditions. Together, these multi-method observations provide a detailed understanding of flow paths and hydrological transformations in strongly evaporative semiarid environments, demonstrating how stable isotopes, combined with lysimeters and soil moisture probes, can resolve catchment-scale responses and enhance water balance quantification and tracing.

Understanding the dynamics of water and salt migration in seasonally frozen agricultural soils is critical for effective arid land management. This study combined field monitoring with a three-method extraction strategy for stable isotope analyses (direct vapor equilibration, centrifugation, and cryogenic vacuum distillation). By integrating resulting isotope signatures into an Isotope Mass Balance (IMB) model, we quantitatively differentiated phase-state water pools. The results confirmed that freezing induces significant Rayleigh fractionation, enriching ice in heavy isotopes relative to mobile water. In contrast, the bound water fraction remains hydraulically isolated and isotopically distinct, requiring its exclusion from phase-change calculations. Coupling with geochemical modelling (FREZCHEM) revealed that salt migration is controlled by the interplay between thermally driven convective fluxes and concentration-driven diffusive fluxes, although individual ion exhibited distinct redistribution pathways.Cryogenic precipitation regulates soil salt transport regime: extensive surface crystallization reduces dissolved ion concentrations, thereby maintaining the steep upward gradient required for continuous salt accumulation. The model demonstrated that crystallization accounted for up to 40.5 % of the total salt load incorporated into solid phases during freezing. These solid salts create a "geochemical trap" in which re-dissolution lags behind the initial spring meltwater pulse, significantly reducing leaching efficiency. Consequently, sustainable salinity management cannot rely on hydraulic regulation alone. Effective irrigation strategies must integrate groundwater management with the specific composition of the salt load to overcome these persistent geochemical constraints.

Understanding how rainfall alleviates vegetation water stress is critical for predicting ecosystem functioning in semi-arid regions under future climate conditions. This study quantifies vegetation water stress relief using the Crop Water Stress Index (CWSI) over the past 24 years in the Wanna Munna Flats of the Pilbara Basin, Western Australia, a semi-arid region characterized by a mean annual precipitation of 381 mm, a mean air temperature of 24 °C, and a potential evapotranspiration of approximately 2850 mm.A modified Run Theory framework was employed to characterize individual stress relief events, defined as deviations of a reconstructed CWSI time series for a representative woody species (Mulga, Acacia aneura) from a reference stress condition (mean CWSI = 0.68). The results indicate that this woody species experiences persistent water stress, with a long-term mean CWSI of 0.52. In total, 191 stress relief events were identified over the 24-year study period.On average, a relief event persists for 19 days (interquartile range: 8–36 days) and exhibits a relief magnitude of 1.9 CWSI·stress·day (range: 0.7–6.1), generated by 13.4 mm of cumulative precipitation (range: 3.8–42.6 mm) distributed over several days. Event-scale cumulative precipitation is the dominant control on both relief magnitude and duration. However, for comparable annual precipitation totals, higher rainfall intensity reduces stress relief efficiency.Random Forest analyses further indicate that vegetation growth responses are primarily triggered by stress relief events associated with precipitation exceeding 17 mm, which account for 41.9 % of all recorded events. A pronounced step change in stress relief occurs when event-scale precipitation exceeds 56 mm, although only 42 such events were observed during the 24-year period.Overall, this study provides a quantitative framework for characterizing water stress relief dynamics and reveals the nonlinear vegetation responses to rainfall in natural semi-arid ecosystems.

Pluvial flooding driven by short-duration, high-intensity rainfall is a dominant hydrological process in semi-arid regions, where surface water is typically sparse and ephemeral. In such environments, flood inundation plays a critical role in regulating surface-groundwater interactions, episodic groundwater recharge, and associated ecological processes. However, these regions are often characterised by a severe lack of ground observation, making remote sensing an essential tool for flood detection and analysis. Flood mapping methods that rely on optical remote sensing are widely used and are well-suited for studying large permanent or semi-permanent water bodies. However, because they rely on threshold-based separation of water from dry land, they perform poorly in detecting shallow, transient inundation, particularly where vegetation obscures the surface water signal.This study introduces a 1×1 km pixel-based linear interpolation framework for mapping flood dynamics in vegetated semi-arid plains by integrating multi-temporal satellite thermal imagery with topographic constraints. Flood extent is quantified using daily flood-fraction estimates, defined as the proportion of inundated area within each pixel, derived from MODIS diurnal land surface temperature difference. To address data gaps, the framework employs a spatial-temporal reconstruction that combines machine-learning-based interpolation with terrain-informed predictors derived from high-resolution digital elevation models, including elevation metrics, local slope, and the topographic wetness index.The framework is applied to a terminal basin in the semi-arid region of northwestern Australia, characterised by extensive plains. Rainfall in the region is highly seasonal, occurring predominantly between December and March, with mean daily maximum air temperatures typically ranging from 30 to 40°C. Ten major rainfall-driven flood events since 2002 were analysed. Flood inundation metrics, including inundation duration, event-scale recession characteristics, and cumulative inundation duration, are computed at a resolution of 1 km² to characterise the persistence and spatial connectivity of surface-water bodies.The results indicate that individual pluvial flood events typically produce inundation lasting approximately 10-20 days, with the decline in total inundated area following an approximately linear recession behaviour. Over the study period (23 yrs), cumulative inundation duration varies spatially across the plain, with individual pixels experiencing between 148 and 166 days of flooding. The spatial and temporal variation of flooded area fraction reveals that inundation dynamics across the plain differ fundamentally from the gradual contraction of a continuous lake surface. Instead, the pluvial flood recession appears as a mosaic of short-lived, spatially fragmented water bodies confined to disconnected topographic depressions. Building on this inundation behaviour and integrating flood fraction dynamics with DEM-derived terrain attributes, we develop a predictive model for the spatial distribution of pluvial flooding across the plain.This study provides a transferable framework for enhancing flood representation and hydrological assessment in data-sparse, dryland environments. By delivering pluvial inundation extents and dynamics, this approach enables improved parameterisation and evaluation of surface hydrodynamic models and surface-groundwater interaction models.

Sustainable groundwater management in water-scarce semiarid environments is challenging because it relies on understanding the intricate coupling between episodic recharge and hydrochemical evolution. In this study, conducted in the Pilbara region of Western Australia, ~6000 water analyses from ~1,800 groundwater boreholes and ~300 surface-water sites collected over a decade of monitoring (2015–2024) were used to develop a conceptual model of groundwater hydrochemical evolution.Stable hydrogen and oxygen isotope compositions indicate that groundwater recharge is not seasonal but instead occurs during sporadic tropical cyclones, which deliver precipitation with distinctly lower δ2H and δ18O values than local groundwater. Self-Organizing Maps (SOM), applied to stable isotope and hydrochemical data, identified five distinct categories that capture hydrochemical transition from recharge sources to endorheic basins. The evolutionary pathway begins in freshwater headwaters, where sulfide oxidation generates acidity that enhances carbonate dissolution and silicate weathering. As groundwater moves to alluvial plains, geochemical control shifts towards cation exchange, ultimately cumulating in low-lying zones where evaporative concentration dominates, and brine formation occurs. Structural Equation Modelling (SEM) confirms a fundamental spatial regime shift between inland and coastal systems. Inland chemistry is primarily controlled by topography and, at times, by internal rock-water interactions. Conversely, coastal water hydrochemistry is related to distance to the coast.Hydrochemical categories serve as effective proxies for hydraulic behaviour. Hydrochemically "young" recharge freshwaters exhibit dynamic water level responses to cyclonic events, whereas evolved, saline waters in the alluvial plains maintain comparatively stable water tables. These patterns demonstrate that hydrochemical evolution and hydraulic dynamics are tightly coupled, reflecting systematic differences in water retention times across the landscape. Together, they reveal a clear transition from lithological controls in recharge zones to salinity-driven physical controls in terminal areas.These findings indicate that sustainable yield assessments should distinguish between the rapid-response behaviour of headwater systems and the storage-dominated dynamics of downstream alluvial basins.