Search Results (4)

Utilizing a multi-biomarker approach, we assessed the potential adverse effects of pollutants on subcellular responses in the digestive gland of the freshwater mussel Unio crassus from a historically contaminated lowland section (KIZ) of the river Mrežnica compared to its less impacted upstream karstic section (REF) and their seasonality (spring vs. autumn). This approach accounted for the diverse modes of action of pollutants by including biomarkers of metal exposure (metallothioneins, MT), general stress (total cytosolic proteins, TP), antioxidative capacity (catalase, CAT; glutathione, GSH; glutathione-S-transferase, GST), oxidative damage (malondialdehyde, MDA), and neurotoxicity (acetylcholinesterase, AChE). Only in spring, MT concentrations were 15% higher at the REF site (4.38 ± 1.06 µg mg proteins⁻¹) compared to the KIZ site (3.69 ± 0.63 µg mg proteins⁻¹), likely related to elevated Cd bioaccumulation due to the karstic substrate. Regardless of the season, mussels from KIZ showed consistently lower TP and GSH, with significantly higher CAT, GST, and MDA levels, indicating elevated stress, activation of antioxidant defenses, and oxidative damage from chronic exposure to pro-oxidant pollutants, including metal(loid)s and organic contaminants (e.g., ibuprofen, nicotine). Compared to the REF site, AChE activity at the KIZ site was higher in late spring and lower in early autumn, indicating seasonal variability in AChE activity at the contamination-impacted location driven by fluctuating exposure to neurotoxicants, such as drugs and insecticides. Overall, biomarker responses indicated that mild historical pollution, reinforced by current low-capacity sources, has an observable impact on mussel health, posing long-term risks to sediment-dwelling aquatic organisms. Full article

The impact of the long-term historical contamination of the Mrežnica River with textile industry wastewaters on metal/metalloid bioaccumulation in the muscles of the young northern pike (Esox lucius) (0+ to 3+) was evaluated, as well as the association of bioaccumulated metal/metalloid concentrations in the muscle with fish physiology. Increased levels of several elements (As, Bi, Cs, Co, Cu, Zn), bioaccumulated in fish muscle, were occasionally found in front of the former factory, but the obtained metal/metalloid concentrations in muscle were in general either comparable or even lower than in the fish from moderately contaminated freshwaters. Calculated target hazard quotients indicated that the current risk for humans, arising from consumption of the northern pike meat originating from a historically contaminated section of the Mrežnica River, was negligible. The influence of biological factors, especially seasonal physiological changes, on metal/metalloid bioaccumulation was confirmed, indicating the importance of the involvement of these parameters in the freshwater pollution assessment, but also in the estimation of the human health hazard. The increased bioaccumulation of several metals/metalloids in fish muscle at a historically contaminated site pointed to the need for continuous supervision of fish health and biodiversity in freshwaters impacted by currently suspended long-term contamination sources. 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 investigation area is located in the world-famous Dinaric karst. This study presents a conceptual model of groundwater dynamics and its interaction with surface waters, extending from the natural water retention of the Drežničko Polje to the spring zone on the far side of the Kapela Mountain range, including a description of the regional groundwater flow in the Zagorska Mrežnica spring zone. The aim of this research was to determine the possibility of an artificial enlargement of the natural retention of this karst field. Large amounts of water could be exploited in this way for the existing hydroelectric power plants of Gojak and Lešće on the Donja Dobra River. The prolonged retention of the water wave in the Drežničko Polje would extend its efficiency in regards to the production of electrical energy, and simultaneously achieve the mitigation of floods that frequently occur in the broader area of Ogulin. Photogeological analysis of the area was performed, together with geological and hydrogeological mapping, groundwater tracing, measurements of water flows in streams and springs, exploratory drilling and measurements of water levels in 26 piezometric boreholes in the Drežničko Polje. Available meteorological data from nearby weather stations (Jasenak, Drežnica and Modruš) were exploited, as well as hydrological data collected specifically for the modelling of runoff. Based on the results of the data processing, this study has determined: (1) the dynamics of the groundwater flow from the Drežničko Polje to the spring area of the Zagorska Mrežnica, (2) the dynamics of recharge and discharge of the natural retention of the Drežničko Polje; and (3) an improved interpretation of the Zagorska Mrežnica karst spring dynamics. The obtained results of groundwater flow dynamics indicate typical karst flow conditions in the Dinaric Karst, but also contain some specific features. Full article