Search Results (43)

This article presents the results of hydrological research on the Ruda River, which is the largest tributary of the Cetina River, located in the Dinaric karst of Croatia. The hydrology of this river has been altered after the construction of the Orlovac Hydropower Plant (HP) and the Buško Blato reservoir in 1973. The main aim of this study was to generate new knowledge about the hydrological functioning of the river, with a focus on the discharge and water temperature regimes that experienced the most severe alterations. The methodology is based on classical hydrological, statistical, and time-series analysis methods, adapted to the particularities of the study area and available data. Daily and hourly time series of air temperature, precipitation, water temperature, and discharge are analyzed to find trends, change points, inter-annual, seasonal, and sub-daily variations, durations, time shifts, and linear dependencies. The results obtained provide information on the effects of climate change, the duration of diffuse, conduit, and mixed flow, the importance of groundwater exchange, retention times, heat transfer times, and reference water temperatures. It determined the role of the operational mode of the Orlovac HP in discharge from the spring, in inter-annual and sub-annual water redistribution, and in hydropeaking and thermopeaking. The obtained information defines the present state of the Ruda River hydrology and illustrates alterations. Full article

Earthquakes are among the most catastrophic natural disasters, primarily due to their immediate potential to cause loss of human life. However, their impact extends beyond the initial seismic event, particularly in karst systems, where groundwater resources are highly sensitive to geodynamic disturbances. The abundance of karst springs within these terrains makes them critical water sources for many communities, yet earthquakes can significantly disrupt their discharge patterns and degrade water quality. This study examines the vulnerability of karst springs to seismic activity, focusing on two case studies that illustrate distinct earthquake-induced hydrogeological effects. The first case investigates the temporary failure of the Opačac Spring near Imotski, Croatia, following the Mw 3.7 earthquake on 7 September 2018. This spring experienced a complete cessation of discharge for four days, as recorded by continuous hydrograph monitoring, before recovering due to the release of accumulated groundwater behind a temporarily blocked conduit. The second case explores the impact of seismic activity on water quality, focusing on the sensitive freshwater lens of the karstic Island of Vis in response to the Mw 6.1 earthquake on 22 April 2022, near Stolac, Bosnia and Herzegovina. Despite the epicenter being over 150 km away, water quality monitoring revealed notable changes, emphasizing the influence of seismic disturbances on fragile groundwater systems in carbonate island environments. Using a multidisciplinary approach, integrating seismic data analysis with hydrological and hydrogeological observations, this study investigates the mechanisms through which earthquakes alter karst water systems. A proposed vulnerability assessment framework is introduced, aiming to correlate earthquake intensity, proximity, and hydrogeological response to better predict karst spring failure and water quality degradation. This model provides valuable insights for disaster preparedness, water resource management, and risk mitigation strategies in karst terrains, highlighting the necessity of incorporating karst hydrogeology into regional earthquake response planning. Full article

In the Plitvice Lakes National Park, several hydrogeological catchments can be distinguished, but their boundaries are not clearly defined. This study focused on the Matica River catchment area, which covers the main contributors to the lake system and its overall water balance. An initial assessment indicated that the Matica River catchment is among the most vulnerable areas due to the anticipated land-use expansion related to agriculture and tourism. This research provides critical hydrogeological data supporting sustainable management in response to the increasing extremes of floods and droughts induced by climate change. Two separate campaigns (March 2023 and April 2025) were carried out, each involving three simultaneous tracer injections using different fluorescent dyes. The results of earlier tracer tests were evaluated; furthermore, a hydrochemical analysis of the spring water offered valuable insights into subsurface processes and anthropogenic impacts. Tracing in the southwest clarified the boundary between the Plitvice Lakes and Una River catchments. In the Homoljac polje, the tracer responses highlighted a triple junction between the Plitvice Lakes, Gacka, and Una River catchments. In the southeastern Brezovac polje, the boundary between the Crna Rijeka and Bijela Rijeka catchments was delineated in detail. Full article

Vegetation phenology has lately gained attention in the context of studying human-induced climate change and its effects on terrestrial ecosystems. It is typically studied on various regional and temporal scales. This research focused on the microscale in dolines on the Northernmost part of the Dinaric Alps. The aim was to determine the timing of flowering onset and relate it to topographic and ecological conditions. We studied (1) the floristic gradient along N–W transects divided in 2 m × 2 m plots, from top slopes to the bottom of dolines, and identified discrete groups in relation to this gradient and (2) provided their diagnostic species and communities. The results indicate that the early spring onset of flowering of ground vegetation in the bottom and lower slopes of dolines is stimulated by high spring moisture and nutrient availability, as well as the open canopy of the mesophilous deciduous forests. The flowering onset on the upper slopes and karst plateau starts later, which is due to the precipitation peak in May/June and higher temperatures and light availability of the open canopy of thermophilous deciduous forests. The delayed onset of flowering in late summer in rocky crevices and rocky places is due to a particular physiology stimulated by the harsh site conditions. The phenology pattern along the doline topographic gradient is inverse to general patterns in vegetation phenology. Further study on the role of doline soils should be made to study their impact on phenology. Full article

This study examines speleothems, sediments, rock, and water to assess geochemical and mineralogical processes in deep karst systems. Focusing on Slovačka jama cave (−1320 m deep) and the Velebita cave system (−1026 m deep), we identify elemental and mineralogical anomalies that provide valuable records of element transport, mineral formation, and paleoenvironmental changes. Heavy metal anomalies (Al, B, Co, Mn, Na, Tl, Ba, Be, Cr, Cu, Fe, K, Pb, Rb, Ti, U, Zn) at 300–400 m of depth in Slovačka jama indicate a complex interplay of geological conditions, geomorphological processes, atmospheric deposition, and potential anthropogenic influences. Factor analysis reveals two elemental associations: (1) Fe, Pb, Cu, and Zn, linked to terrigenous aluminosilicates, and (2) Cd, Cr, Mo, and Ni, suggesting airborne or geological sources. Mineralogical analysis confirms the dominance of calcite, with quartz, clay minerals, feldspars, magnetite, and goethite also detected. High magnetic susceptibility values in sediment-rich samples suggest Fe-rich mineral inputs from weathering, biogenic activity, or industrial sources. Ba anomalies in feldspar-rich samples and Sr accumulation at depth indicate distinct geochemical processes. These findings enhance our understanding of deep karst geochemistry, crucial for paleoenvironmental reconstructions and groundwater protection. Full article

Karst bauxites are valuable terrestrial records of paleoclimate and tectonic evolution formed under tropical to subtropical conditions during the subaerial exposure of carbonate platforms. This study explores Croatian bauxite deposits within the Adriatic–Dinaric Carbonate Platform (ADCP), with a focus on the distribution and enrichment of rare earth elements (REE) across eight bauxite horizons from the Triassic to Neogene periods. The research applies statistical analyses of geochemical data, as well as developed models, to assess the factors influencing REE distribution and fractionation. The study found that variations in parent material, along with changes in paleogeographical and paleotectonic settings, significantly affected the REE content. The median REE concentrations in the analyzed bauxite horizons range from approximately 250 to 570 mg/kg. Notable REE enrichment was observed in the Late Paleogene, particularly in the Middle and Upper Eocene horizons. The analysis highlights the importance of physicochemical conditions, such as Eh and pH, during the weathering processes that lead to bauxite formation. The results suggest that the presence of REE-bearing minerals, rather than clay minerals, could possibly contribute to elevated concentrations of heavy REE (HREE). These findings indicate that Croatian bauxites, enriched in REE and associated trace elements, are significant not only as geological markers of past climatic and tectonic events but also as potential sources of critical raw materials. This study underscores the potential for the economic exploitation of these deposits in the context of modern technological demands. Full article

The black olm (Proteus anguinus parkelj Sket & Arntzen) is an endemic species found exclusively in the Dobličica River subterranean water systems of the Dinaric karst in southern Slovenia. These unique habitats are vulnerable to contamination due to rapid water flow, primarily from nitrates from agricultural fertilisers and untreated urban wastewater. The safe limit of nitrate concentration for olms is 9.2 mg NO₃⁻/L, yet measurements in karst springs have shown levels ranging from 3 mg to over 20 mg NO₃⁻/L. The SWAT modelling tool assessed agri-environmental and land use scenarios for their impact on nitrate leaching. Using the model, we identified hotspots with high nitrogen leaching potential that require immediate attention and implementation of better agricultural practices for fertiliser use. For these hotspots, the most effective approach combines scenarios of cover crops (R2), reduced fertilisation (R3), crop rotation (R4), and conversion of cropland to grassland (E2, E4, E5), potentially decreasing nitrate leaching by up to 60%. Implementing the best scenarios is expected to reduce nitrogen levels below the limit value of 9.2 mg NO₃⁻/L, essential for maintaining the black olm habitat. Full article

Cavernicolous scorpions are difficult to collect and study due to their often inaccessible habitats. Some have evolved unique morphological adaptations, known as troglomorphies, including reduced sclerotization and pigmentation, reduction and/or loss of eyes, attenuation and elongation of the appendages, which assist them to thrive in dark, humid and low-energy input environments. Cavernicolous scorpions are classified into accidentals, trogloxenes, troglophiles, and troglobites. The Balkans, and particularly the Dinaric Karst region, host a diverse cave-adapted fauna, including scorpions. Despite an 1895 report of a blind scorpion from Bosnia and Herzegovina, the first truly troglobitic European scorpion, Euscorpius studentium Karaman, 2020, was only described a few years ago, based on two immature specimens. In the present contribution, this unique species is redescribed based on the first adult specimens; the ecological classification of all currently known cavernicolous Euscorpiidae Laurie, 1896, is updated; a key to the identification of cavernicolous scorpions occurring in the Dinaric Karst is provided; and the historical and geographical factors affecting the distribution and conservation of cavernicolous scorpions in the Balkans is reviewed. Full article

The mountain forests in Europe, especially the ecosystems dominated by Norway spruce [Picea abies (L.) Karst], are facing major challenges due to climate change. Climatic stress factors such as increased temperatures and drought contribute to reduced growth and increased mortality, especially at lower altitudes. In this study, which was conducted in the northern Velebit region, the growth dynamics and climate sensitivity of Norway spruce were analyzed using standard dendrochronological methods. The focus was on samples collected at altitudes between 1135 and 1545 m. The results show two different growth trends: a positive trend from 1950 to 1977, followed by a negative trend from 1977 to 2013. Precipitation proved to be a key factor for the stability of spruce growth, while the high summer temperatures of the previous year correlated negatively with growth increment. In addition, trees at higher altitudes showed greater resistance to climatic stress. These results underline the crucial role of precipitation and site-specific conditions in maintaining the vitality of spruce forests in mountainous regions, and suggest that climate change could further destabilize spruce ecosystems in the Dinaric Alps. Full article

Functional diversity is a key component of biodiversity that reflects various dimensions of ecosystem functioning and the roles organisms play within communities and ecosystems. It is widely used to understand how ecological processes influence biotic assemblages. With an aim to increase our knowledge about dragonfly ecological requirements in tufa-depositing karst habitats, we assessed functional diversity of their assemblages, various life history traits (e.g., stream zonation preference, substrate preference, reproduction type), and relationship between functional diversity and physico-chemical water properties in three types of karst lotic habitats (springs, streams, and tufa barriers) in a biodiversity hotspot in the western Balkan Peninsula. Dragonfly functional diversity was mainly characterized by traits typical for lotic rheophile species with medium dispersal capacity. Among the investigated habitats, tufa barriers, characterized by higher (micro)habitat heterogeneity, higher water velocity, as well as lower conductivity and concentration of nitrates, can be considered as dragonfly functional diversity hotspots. Functional diversity and most of the life history traits were comparable among different substrate types in the studied habitats, indicating higher importance of habitat type in shaping dragonfly functional diversity patterns in karst lotic habitats. Our results should be considered in the management and conservation activities of vulnerable karst freshwater ecosystems and their dragonfly assemblages. Full article

Phytoplankton is a polyphyletic group of organisms that responds rapidly to environmental conditions and provides a reliable response to changes, making it a good ecological indicator for water quality monitoring. However, a gradient is almost essential for a reliable relationship between pressure and impact. In a low-gradient environment, ingenuity is required to outsmart the limitations of the commonly used linear relationship. Here, we examine changes in biomass and functional biodiversity by analysing larger data sets (2013–2022) in six ecologically diverse, natural, deep Croatian karst lakes with low nutrient gradients using nonlinear correlation coefficients and multivariate analyses in 209 samples. We found that phytoplankton biomass was most strongly influenced by nutrients, salinity and alkalinity, while light availability and total nitrogen strongly influenced phytoplankton functional biodiversity. An additional analysis of the TN:TP ratio revealed that the oligotrophic Lake Vransko is nitrogen-limited, and lakes Kozjak and Prošće are phosphorus-limited. This further clarified the relationship of phytoplankton to nutrients despite the low gradient. The complex analysis in this study provides a new perspective for predicting changes in the structure and succession of phytoplankton in deep karst lakes for successful management under apparent anthropogenic pressure and climate change. Full article

Magnetism in Croatian caves has been significantly underexplored, despite the well-documented preservation of cave sediments. This study investigates whether magnetic susceptibility can be effectively recorded in Croatian caves and, if so, whether there are differences between in situ and laboratory measurements, as well as the extent of these differences. The focus is on two prominent sites within the Velebit Mountain range of the Dinaric Karst: the deep Slovačka Cave and the extensive Crnopac Cave System (ex. Kita Gaćešina Cave). Magnetic susceptibility was measured in soft sediments using the Kappameter KM-7 for in situ assessments and the Bartington MS2B System for laboratory analyses. The comparison of the two devices aimed to evaluate the feasibility of detecting magnetic susceptibility variations within carbonate sediments. Sampling locations were selected based on preliminary assessments of magnetic susceptibility variations and accessibility for sampling. Characteristic samples from each profile underwent X-ray powder diffraction analysis. Results revealed significant variations in magnetic susceptibility across each profile under both in situ and laboratory conditions. In situ measurements ranged from −45 × 10⁻⁵ SI to 120 × 10⁻⁵ SI, while laboratory measurements ranged from 4.00 × 10⁻⁵ SI to 99.40 × 10⁻⁵ SI. The portable Kappameter KM-7 provided satisfactory results for preliminary investigations, while the Bartington MS2B System demonstrated high precision in analyzing these variations in detail. These findings support the potential for further investigations into magnetic susceptibility in karst cave environments, with an emphasis on understanding depositional history and the timeline of climate and tectonic changes. Full article

The Dinaric karst in the north differs from the rest of the karst in Croatia in terms of karstification depth. The infiltrating precipitation drains in cascades from deeply karstified mountainous areas to the shallow or fluviokarst, forming the tributaries of the Kupa River. Time series analyses were conducted on a 5-year dataset to elucidate the hydrogeological conceptual model of the area and clarify disparate findings from tracer tests under varying hydrological conditions. The flow duration curve, autocorrelation functions, and recession curves were used to evaluate the spring discharge variability, the karstification degree, and the karst aquifer’s size. The crosscorrelation function and temperature dynamics were employed to assess the spring’s response to recharge and the hydrogeological system behavior. Comparative analysis with previous studies was conducted to contextualize the obtained results. The research outcomes delineated several key findings: (i) the deep karst zone is less developed than the shallow karst zone; (ii) groundwater exchange is significantly faster in shallow karst; (iii) groundwater divides in the Kapela Mountain are zonal; (iv) the homogenization of groundwater occurs during periods of high water levels; (v) fast water exchange transpires without concurrent groundwater temperature homogenization; and (vi) a definition of the boundary between deep and fluviokarst in Croatia. Full article

The Biospeleological Station (BS) in Postojna Cave, with a volume of 36,000 m³, has served as an underground biological laboratory since 1931, receiving 100,000 visitors annually. Historical cave micro-climate monitoring was performed in 1933 and 1963, and continuous monitoring of cave air temperature and carbon dioxide concentration at hourly intervals started in 2015. Micro-climatic data collected between 2015 and 2024 has helped us to understand the relationship between natural underground environment and anthropogenic impact, thereby aiding expert recommendations to cave managers for the mitigation of anthropogenic micro-climatic effects. Results strongly support the policy that, during summer, when outdoor temperatures are higher than in the cave, solid metal doors connecting the BS with the rest of the cave (Stara Jama) should be kept open. Such a simple mitigation act helps to decrease anthropogenically increased air temperature and carbon dioxide concentrations, thereby maintaining suitable micro-climatic conditions for the exhibition of cave animals. Closure during the COVID-19 pandemic (2020–2021) resulted in the lowest temperatures recorded. BS visitation increases air temperature by 1 °C, highlighting the need for management strategies to maintain suitable conditions for cave fauna exhibition. Full article

The Western Balkan’s Vjetrenica Cave in southern Bosnia and Herzegovina is renowned for high richness of subterranean species. However, the data on its fauna have been published only in monographs printed in a small number of copies, making them hardly accessible to the wider scientific community. To overcome this issue, we compiled the data from published monographs with the data from our own recent field surveys. Further, as they are connected via water channels or small crevices in bedrock, we defined the Vjetrenica Cave System as a system comprising Vjetrenica and Bjelušica Caves and Lukavac Spring. Altogether, 93 troglobiotic, i.e., obligate subterranean aquatic (48) and terrestrial (45), taxa were reported for the system, verifying the Vjetrenica Cave System as the second richest locality in subterranean biodiversity in the world. The global uniqueness of the system is also reflected in the fact that as many as 40 troglobiotic species were described from the system. Finally, we reviewed the factors endangering this unique subterranean community and questioned whether it will withstand human-induced changes and pressures due to infrastructural development in southern Bosnia and Herzegovina. Full article