The upstream part of the karst estuary of the Krka River (Prokljan Lake) on the Eastern Adriatic Coast was studied by combining high-resolution seismic data, analyses on sediment cores, and ...radiocarbon dating to reconstruct the late Quaternary stratigraphy of the estuary. The sedimentary infill consists of up to 20 m of freshwater and estuarine deposits divided into four seismostratigraphic units corresponding to several stages of development since the last glacial period. The lowstand stage is assumed to correspond to fluvial incision and sediment bypass associated with glacial periods. The postglacial transgressive stage is marked by the growth of calcareous tufa barriers and fluvio-lacustrine deposition. The onset of marine influence in the estuary (Prokljan Lake) was recorded at the beginning of the Holocene (>10,500 cal y BP) with the deposition of brackish sediments with a strong freshwater influence. Calcareous tufa barriers prevented direct rapid flooding of Prokljan Lake in the period from >10,500 cal y to ∼7200 cal y BP. Finally, the transgressive brackish deposition changed to estuarine/marine highstand deposition in a salt-wedge estuary during the late Holocene (∼4000–3000 cal y BP). The late Quaternary deposition in this unique karst setting showed dramatic changes. It was primarily influenced by rapid sea-level rise, climate changes, estuarine geomorphology and relatively low sediment supply.
•Late Quaternary palaeoenvironmental evolution of a karst Krka River estuary was analysed.•Sea-level, climate changes and tufa barrier deposition controlled the sedimentation.•The flooding of Prokljan Lake started at the begginning of the Holocene.•Tufa barriers had an important role in stepwise flooding of the lake.•Present estuarine conditions developed in the late Holocene.
Cytosolic distributions of nonessential metals Cd and Tl and seven essential elements among compounds of different molecular masses were studied in the liver of brown trout (Salmo trutta) from the ...karstic Krka River in Croatia. Analyses were done by size exclusion high performance liquid chromatography and high resolution inductively coupled plasma mass spectrometry. Common feature of Cd and Tl, as highly toxic elements, was their distribution within only two narrow peaks. The increase of cytosolic Cd concentrations was reflected in marked increase of Cd elution within low molecular mass peak (maximum at ∼15 kDa), presumably containing metallothioneins (MTs), which indicated successful Cd detoxification in brown trout liver under studied exposure conditions. Contrary, the increase of cytosolic Tl concentrations was reflected in marked increase of Tl elution within high molecular mass peak (maximum at 140 kDa), which probably indicated incomplete Tl detoxification. Common feature of the majority of studied essential elements was their distribution within more peaks, often broad and not well resolved, which is consistent with their numerous physiological functions. Among observed associations of essential metals/nonmetal to proteins, the following could be singled out: Cu and Zn association to MTs, Fe association to storage protein ferritin, and Se association to compounds of very low molecular masses (<5 kDa). The obtained results present the first step towards identification of metal-binding compounds in hepatic cytosol of brown trout, and thus a significant contribution to better understanding of metal fate in the liver of that important bioindicator species.
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•Analysis of trace element distributions in the hepatic cytosol of brown trout.•Fractionation of cytosolic biomolecules by size exclusion HPLC.•Succesful detoxification of highly toxic metal Cd by binding to metallothioneins.•Incomplete Tl detoxification shown in Tl binding to compounds larger than 100 kDa.•Reports on distribution profiles of essential elements Co, Cu, Fe, Mn, Mo, Se, Zn.
Koristeći se pristupom regionalne i lokalne povijesti u studiji se na primjeru Lovinačkog kraja u Lici analiziraju dramatične političko-društvene i kulturno-demografske preobrazbe izazvane osmanskom ...ekspanzijom u XVI. stoljeću. Ovaj kraj u svemu je dijelio sudbinu ostalih područja Like i Krbave koji su se našli na razmeđu suprotstavljenih imperija, stekavši tako karakter udaljene osmanske periferije i iskustvo „režima krajina“ koje će potrajati do duboko u XIX. stoljeće. Rad se primarno temelji na osmanskim izvorima, naročito poreznim katastarskim popisima za područje koje se od 1574. našlo u sastavu nahije Cvituša. Propituju se brojne dimenzije diskontinuiteta prouzročenih disolucijom krbavskog kneštva („zemlje Ivana Karlovića“) krajem XV. i početkom XVI. stoljeća te formiranjem vojno-upravnih struktura osmanskog „serhata“ u XVI. stoljeću. Analizira se kako su se navedeni dinamični procesi odrazili na lokalnom lovinačkom primjeru, posebice u kontekstu promjena naseljenosti, stanovništva i prostorne organizacije. Sagledavaju se osmanski planovi izgradnje fortifikacijskog sustava, kolonizacijske i fiskalne politike. Također se daje uvid u novonastali konfesionalni raspored i stanje vjerskih objekata.
The concentration and isotopic composition of uranium (δ238U, 234U/238U activity ratio) in combination with traditional isotopes (δ18O, δ13C) were examined as potential tracers of authigenic ...carbonate formation in a karst aquifer. The U concentration and 234U/238U activity ratios in the tufa-precipitating sections of two connected karst rivers (Krka and Zrmanja, Croatia) decreased downstream in water and in precipitated carbonate due to active self-purification processes, i.e. adsorption of isotopically lighter U(VI) on mineral particles, sedimentation and co-precipitation with carbonate. The isotopic composition of carbonate in tufa mostly resembled the 234U/238U activity ratio and the δ238U values of dissolved U in water but was also affected by the presence of detrital carbonate flushed into the river from soil and weathered bedrock. This interpretation was supported by the δ18O and δ13C values of tufa, which were shifted out of equilibrium with river water and dissolved in organic carbon and in their isotopic signature, which showed the presence of lithic carbonate. Large fluctuations of the δ238U values of water, leachable U (eluted in acetic acid buffered with Na-acetate) and residual U fraction could not be fully explained by available data due to the overlapping U isotopic signatures of leachable (mainly carbonate) and residual fractions of soil, bedrock and tufa. Therefore, a long-term, systematic, seasonal and event-based observation of the isotopic composition of dissolved and suspended particulate U in water is necessary. Nevertheless, the U isotopes were found to have the potential to be used as identifiers of authigenic carbonate and the storage of CO2 in terrestrial river sediments, to improve knowledge on fluxes within local and global biogeochemical carbon cycle.
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•New insight of understanding possible environmental influences on tufa formation•Combination use of traditional and U isotopes was evaluated in the karst aquifer.•U isotopic composition was analysed with MC-ICP-MS.•δ13C, δ18O and U values confirmed carbonates authigenic origin.•U isotopes are relevant for the construction of the CO2 mass balance.
Understanding the potential bioavailability of trace metals (TM) in marine systems is of prime importance to implement adapted regulations and efficiently protect our coastal and estuarine waters. In ...this study Diffusive Gradients in Thin films (DGT) technique with two different pore size was used to evaluate the potentially bioavailable fractions (DGT-labile) of Cd, Co, Cu, Ni, Pb and Zn at various depths of a highly stratified estuary (the Krka River estuary, Croatia) both in winter and summer. DGT-labile concentrations were compared to (1) total dissolved concentrations, (2) concentrations of labile species measured by anodic stripping voltammetry (ASV-labile) for Cu and (3) concentrations derived by chemical speciation modelling. High correlation between dissolved and DGT-labile concentrations was found for all metals, except for Zn where contamination problems prevented reliable conclusions. Percentages of DGT-labile fractions over total dissolved concentrations were (AVG ± SD): 92 ± 3%, 64 ± 2%, 23 ± 5%, 61 ± 3% and 57 ± 6% for Cd, Pb, Cu, Ni and Co, respectively. No significant difference was found between trace metal concentrations measured with an open pore and restricted pore devices, implying the predominance of kinetically labile metal complexes smaller than 1 nm. For Cu, ASV-labile and DGT labile concentrations were highly correlated (0.97) with ASV-labile concentration being around 35% lower than that of the DGT-labile. Modelling of chemical speciation reliably predicted dynamic (free, inorganic and part of organic complexes) concentration of Cd, whereas dynamic concentrations of Cu and Pb were underestimated by 32% and 65%, respectively. In view of the relative simplicity of DGT devices, they are well suited for the monitoring effort of coastal waters, informing on potentially bioavailable concentrations of TM and thereby, helping to achieve good environmental status of coastal waters, as stipulated within the EU Water Framework Directive.
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•DGT-labile percentages of dissolved concentrations: Cd > Pb ≈ Ni ≈ Co > Cu•High correlation between dissolved and DGT-labile trace metals (TM)•No difference between open and restricted pore DGT-labile concentrations•ASV-labile Cu ~35% lower than DGT-labile concentrations•Modelling predicts correctly DGT-labile Cd, but underestimates Pb and Cu.
In order to assess the extent of existing anthropogenic influence on biota of the vulnerable karst ecosystem of the Krka River, multi-biomarker approach was applied in the intestinal tissue of brown ...trout Salmo trutta Linnaeus, 1758. Biomarkers of the general stress (total cytosolic proteins), oxidative stress (malondialdehyde), antioxidant capacity (catalase activity, total glutathione) and of an exposure and effect of contaminants, especially metals (metallothionein) and organophosphorous pesticides and metals (acetylcholine esterase activity) were compared in the intestine of fish from the reference site (river source) and downstream of the technological and municipal wastewater impacted site (town of Knin) in two seasons, October 2015 and May 2016. Biological response was additionally evaluated by metal/metalloid concentrations in intestinal cytosol. Site-specific differences were observed as significantly higher As, Ca, Co, Cu, Se and Sr concentrations in intestinal cytosol of fish from the contaminated compared to the reference site. Significant seasonal differences existed for Ni, Cd, Mo, Cs and Na, with higher levels in autumn, following the trend of most of the dissolved metal levels in the river water. Impact of improperly treated wastewaters was also confirmed by significantly increased levels of glutathione, total proteins and Foulton condition indices, with 1.5, 1.13 and 1.12 times higher average values in fish from that site compared to the river source, respectively. The other biomarkers showed similar trend and pointed to specific biological changes regarding oxidative stress or metal exposure in fish from the anthropogenically impacted site, especially in autumn, but without significant differences. Thus, the anthropogenic impact still seems to be only moderate, although cytosolic metals and most of the biomarkers in fish intestine were confirmed as initial indicators of pollution impact, which pointed to the need of continuous monitoring of the Krka River in order to protect this natural karst world phenomenon.
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•Multi-biomarker approach was assessed as an early sign of pollution in karst river.•Fish intestine was evaluated as an indicator organ responsible for dietborne uptake.•Wastewater impact was evident from biomarker and cytosolic metal responses.•Intestinal biomarkers pointed to rising need of strict monitoring of water quality.
This paper demonstrates the possibilities of GIS implementation in the preventive phase of firefighting activities for the Šibenik-Knin County. Multicriteria GIS analysis (GIS-MCDA) was applied in ...derivation of the wildfire risk ignition index. Four groups of criteria were used: vegetation, geomorphometry, anthropogenic impact, and climate elements. Wildfire risk ignition models were derived based on the decision-maker method through (1) the experience of the local fire commander and (2) following the examples of good practice. Furthermore, the coverage and the passability of the National park (NP) Krka roads were analyzed in relation to the standard intervention time from the competent fire brigades. The nearest fire brigades and the fastest routes to the most endangered zones within the NP Krka have been derived. The results indicate that the area of Šibenik-Knin County belongs to the moderate/moderately high risk of fire ignition and that the coverage of the NP Krka roads within the standard intervention time is not satisfactory.
The karstic Krka River is characterized by having lower dissolved organic carbon (DOC) concentrations (~30 μM) than coastal seawater (~60 μM). This peculiarity, together with the pristine nature of ...this area, makes the Krka River estuary a natural laboratory where it is possible to discriminate among the different dissolved organic matter (DOM) sources (riverine, marine and produced in-situ) and to study the main processes of DOM production and removal. The hypothesis behind this work is that in winter, due to the high discharge of the river, most of the DOM has a terrestrial signature, whereas in summer autochthonous DOM compose the main fraction of the DOM pool because of the reduced discharge, the high temperature and primary production. Our data shows that DOM in the river mainly consists of terrestrial molecules, as suggested by the high chromophoric content and low spectral slope (S275–295) values, as well by the predominance of humic-like substances. DOM in the seawater features the concentration and optical properties of the “typical” marine DOM from open sea waters. In summer, low riverine discharge and high temperature promote the intense biological activity, with an increase in DOC concentrations of up to 148 μM, resulting in a non-conservative behavior of DOM in the estuary. The high stratification combined with a decoupling between production and removal processes can explain the observed DOM accumulation. In the bottom layer DOM was released and quickly removed when oxygen was available, whereas in hypoxic waters the production of DOC, chromophoric DOM (CDOM) and fluorescent DOM (FDOM) was linearly related to oxygen consumption. Our work highlights the need of further studies combining chemical and biological information in order to gain new insights into the main processes responsible for DOM dynamics in this system.
•The Krka River is characterized by lower DOC concentration than the coastal area.•In the Krka River estuary, DOM shows a non-conservative mixing.•Production of highly chromophoric DOM in hypoxic area.•In the Krka River estuary was possible to discriminate different DOM sources.
Anchialine caves are common in Mediterranean karstic shorelines and elsewhere, delivering point-source fresh groundwater and nutrients to the coastal ocean. Here, we first quantified submarine ...groundwater discharge (SGD) in a typical karstic system (Zaton Bay, Croatia) receiving groundwater from anchialine caves using a radon (222Rn) mass balance model. We then combine our new observations with the literature to provide a Mediterranean-scale estimate of karstic fresh SGD nutrient fluxes. We found that SGD and related nutrient fluxes in the upper brackish layer were much higher than those in the underlying layer in Zaton Bay. In the upper brackish layer, both SGD (m d−1) and associated nutrient fluxes (mmol m−2 d−1) in the wet season (SGD: 0.29–0.40; DIN: 52; DIP: 0.27) were significantly higher than those in the dry season (SGD: 0.15; DIN: 22; DIP: 0.08). Red tides were observed in the wet season but not in the dry season. Nutrient budgets imply that SGD accounted for >98% of the total dissolved inorganic nitrogen (DIN) and phosphorous (DIP) sources into Zaton Bay. These large SGD nutrient fluxes with high N/P ratios (190–320) likely trigger and sustain red tide outbreaks. Combining our results with 30 previous studies in the region revealed that point-source DIN and DIP fluxes via karstic fresh SGD may account for 8–31% and 1–4%, respectively, of riverine inputs in the Mediterranean Sea. Overall, we demonstrate the importance of karstic SGD as a source of new nutrients with high N/P ratios to the Mediterranean Sea and emphasize how SGD lagging precipitation can drive red tide outbreaks.
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