Krka National Park Research Articles

Decoupling Sources of Anthropogenic Influences on Sediments of the Visovac Lake (Krka National Park, Croatia) Using Multiparametric Approach.

Historical changes of sediment characteristics and levels of inorganic and organic contaminants were studied in dated sediment cores from the Visovac Lake, situated in the Krka National Park, Croatia, to identify the main sources of anthropogenic pressures on this highly protected system. Depth distributions of lithogenic elements showed a steady decrease of terrigenous inputs due to the reduction in agricultural activities in the area, which was particularly pronounced during the 1991-1995 war in Croatia. Vertical and longitudinal distributions of Cd and Zn indicated that they are predominately of anthropogenic origin. The historical profiles of these toxic metals coincide well with the recorded production of metal industry in the upper reach of the Krka River with a sharp decrease reflecting the interruption by the war and slow recovery afterwards. By contrast, the recovery of the tourist industry in Krka NP after the war was accompanied by increasing contamination by elements characteristic of boat and car traffic (Sn, Cu, Pb) as well as oil pollution. The contamination with polycyclic aromatic hydrocarbons and polychlorinated biphenyls was only moderate. Although levels of metallic and organic contamination can be considered relatively low, the observed shift from industrial to tourism-related sources indicated that touristic activities should also be regarded as a possible threat for this vulnerable karst aquatic ecosystem.

Spatial and temporal variability of dissolved metal(loid)s in water of the karst ecosystem: consequences of long-term exposure to wastewaters

The metal(loid) variability in the sensitive karst ecosystem was addressed as possible indicator of short- and long-term exposure to the wastewaters, recognized as the main metal contamination sources. Industrial and municipal wastewaters are released without proper purification only 2 km upstream from the Krka National Park (KNP) in Croatia. The variability of dissolved metal(loid)s was studied in four seasons and eight locations: Krka River source (reference site, KRS), municipal wastewaters from the Town of Knin (KRK), industrial wastewaters from the screw factory (IWW), Brljan Lake in the KNP (KBL), and the tributaries Krčić (TKR), Kosovčica (TKO), Orašnica (TOR) and Butišnica (TBU). Water taken directly from IWW had several times higher concentrations of all elements than other locations and indicated industrial wastewater as the primary Mn, Zn, Co, Cs, and Fe source. Tributary Orašnica, flowing by IWW, was the most affected site, although higher metal concentrations were also found at other locations compared to KRS. Overall, spatial metal contamination followed the order: TOR>KRK>TKO>TBU>KBL>KRS. Seasonality was not pronounced, although the highest levels for most metals were observed in summer, dry season when the self-purification processes are reduced. Almost all elements had low tendency to bind with particles, therefore showing high presence in dissolved fraction and confirming their bioavailability and potential toxicity. Although metal concentrations increased over time, they were still low compared to metal-contaminated rivers. However, observed metal exposure and inter-site differences present a warning and indicate the need for the targeted continuous monitoring of potential hotspots to protect this karst ecosystem.

Vascular flora of Krka National Park (Croatia)

The vascular flora of Krka National Park recorded after its proclamation in 1985 is presented and analysed. In total, 1509 plant taxa within 582 genera and 132 families were recorded. The most represented families are Compositae, Poaceae and Fabaceae, while the dominant chorotypes are south-European and Eurasian. Life-form analysis demonstrated that vascular flora of NP Krka lies between the typical Mediterraneanand the central European spectrum, confirming the sub-Mediterranean phytogeographical position of this area. The analyses of medians of ecological indicator values for light, air temperature and soil moisture showed the domination of species typical for open, warm and dry habitats.

Attitudes and preferences of visitors of Krka National Park, Croatia

The primary function of national parks (NPs) is nature conservation, but for the majority of them, tourism also plays an important role. Tourism generates significant incomes, but the benefits are often unequally distributed in space, as are the disadvantages. The karst regions are generally less developed terrains in terms of traditional livelihoods, but due to their special morphology, tourism offers great opportunities. Nonetheless, mass tourism can also pose increased environmental risks. In this article, we examine the above questions on the example of Krka NP, especially from the perspective of tourists, as we conducted a questionnaire survey with visitors. The results confirmed that there is a high degree of spatial inequality both in the awareness of attractions and the distribution of tourist accommodation. This fact has already been recognised by the management of the NP, and serious steps have already been taken to reduce inequality, but their impact is not yet significant enough. Based on the survey, tourism in Krka NP is determined by same-day visits. Tourists who come here primarily consider waterfalls, lakes and rivers to be the most important values of the landscape, while cultural values are considered less significant and even less known. Local products are virtually unknown in the NP palette, so this could be a direction for development. Another point that could be developed is the awareness of visitors in the field of karstification. As the survey was conducted during COVID period, its impact on tourism was also briefly examined. This impact was manifested in the fact that the proportion of retirees and tourist buses was very small, whereas the majority of visitors (90%) arrived in the NP as independent travellers. For one third of foreigners, COVID played a role in choosing Croatia as a destination. As for domestic tourists, two thirds chose to find a destination in Croatia because of COVID.

Taxonomic and Functional Metrics of Ciliates and Amoeboid Protists in Response to Stream Revitalization

Tufa-depositing streams provide great microhabitat complexity and are therefore inhabited by various periphytic phagotrophic organisms such as ciliates and amoeboid protists. Recent removal of invasive plant species Ailanthus altissima (Mill.) Swinge from the Skradinski buk tufa barrier (Krka National Park, Croatia) resulted in changes in the barrier hydromorphology including the reactivation (revitalization) of dry streams. The objective of this study was to investigate: (1) the taxonomic and functional response of periphytic ciliates and amoeboid protists to stream revitalization by comparing taxonomic (i.e., abundance, species richness and diversity) and functional (i.e., functional diversity) metrics between revitalized (N) and control sites (C) during 1 and 2-months immersion period; (2) which environmental and (3) periphyton-associated factors shape the taxonomic and functional metrics and to what extent; (4) how duration of immersion affects taxonomic and functional metrics at revitalized sites. Our results showed that taxonomic and functional metrics of ciliates and amoeboid protists responded to the prevailing conditions characteristic of revitalized tufa-depositing streams: changing hydrology (occasional high flow or drought), soil drainage, and extensive inorganic matter, i.e., tufa deposition, although their responses were somewhat different. The two assemblages also showed different responses of taxonomic and functional metrics with respect to immersion duration: while the taxonomic and functional diversity of ciliates at N sites increased with longer immersion, indicating niche diversification, those of amoeboid protists hardly changed with time. Our results suggest that a comprehensive analysis of taxonomic and functional metrics of ciliates and amoeboid protists could be a good proxy for assessing revitalization of tufa-depositing streams. However, the temporal component should always be considered when conducting such studies, as the colonization processes of ciliates and amoeboid protists are quite complex, especially in tufa-depositing streams.

Inland-coastal demographic transformations in a karst area: a case study of the surroundings of Krka National Park (Croatia)

According to geographic possibilism, environment does not determine socio-economic development. However, the environment sets certain constraints and limitations for development. How do natural settings influence population dynamics? In this study, we examine this question using the example of Šibenik-Knin County, which includes Krka National Park (NP) with a GIS-based statistical approach. The following parameters represent natural factors: elevation, slope, distance from water, and proportion of karst areas. In addition, distance from Krka NP was also added as an independent semi-natural factor (despite the fact that it is a social construction). The dependent social parameters are population density for selected historical dates, population change, year of maximum population, natural increase, migration, and age index. The analysis units are the 199 settlements found in the county, and the 20 local administrative units (LAU2). The study period can be divided into five phases: from the first census in 1857 to 1921, there was a slow increase in most settlements; then a relatively constant phase up to 1961 (some settlements began shrinking in this period); a slow decrease until 1991; a rapid decrease during the next decade; and relative stabilisation to present day. These processes were also accompanied by significant inner and outer migrations. As for the relationships between natural and demographic factors, we found that although the coastal-inland area dichotomy is dominant in the study area, elevation has the highest correlation with most population parameters. However, distance from water is also significantly correlated with population change and migration in certain periods. In the inland areas, there are statistically significant differences between the demographic processes of fully-karstic and partially-karstic areas, while in the coastal zone, the karst effect is overshadowed by other social processes. The impact of Krka NP on the demographic characteristics of the surrounding settlements was statistically not detectable. Our final conclusion is that correlations between natural and population parameters are low or moderately strong but statistically significant in many cases, thus the basic principles of geographic possibilism are valid for the area.

Defining Natural Landscape Qualities of the Southern Part of the Krka National Park in Croatia

The paper is based on a review of the established principles for evaluating the natural qualities of landscapes and developing procedures that can contribute to current methods, upgraded with indicators derived from the perception and attitudes of the public. They were implemented into an integrated model of natural landscape qualities. The method included modeling of the natural landscape qualities for the southern part of the Krka National Park in Croatia. The first evaluation model was based on a survey whose responses were processed and classified using the AHP method and GIS. The results showed that the respondents recognize the diversity of land cover and relief forms and the degree of their fragmentation as the highest natural landscape quality. The second step included overlapping the vulnerability model of natural landscape qualities and the model of perception of natural qualities. It was found that the implementation of perceived natural qualities in the evaluation process affects the model of vulnerability of landscape quality. It also indicates the possibility of implementing the perceived natural qualities of certain landscape types into the complete landscape evaluation process, which encompasses all values in the space, including human perception. Therefore, the whole procedure pointed out the importance of the implementation of perceived values into landscape evaluation, something which is also emphasized by the European Landscape Convention (ELC).

Cover Feature: Recent Developments in Enantioselective Organocatalytic Cascade Reactions for the Construction of Halogenated Ring Systems (Eur. J. Org. Chem. 29/2021)

The Cover Feature shows three examples of cascade reactions leading to chiral halogenated cyclic molecules. The multiple reactions that take place in succession (cascade-like) once the reagents are mixed, provide a sustainable, atom-, step- and labor-efficient way to create chirality and molecular complexity. Easy-to-handle halogenating agents or synthetic building blocks and organocatalysts make this possible. The cascades of Buk Skradinski waterfall in the Krka National Park, Croatia illustrate the reaction pathways. More information can be found in the Minireview by A. M. Faisca Phillips and A. J. L. Pombeiro

PARENT MATERIAL AS A KEY DETERMINANT OF SOIL PROPERTIES IN SOUTHERN PART OF NATIONAL PARK KRKA, CROATIA

Parent material is an important factor in soil formation, especially in soils formed in Mediterranean region dominated by calcareous sedimentary rocks. Their basic properties (mineralogical composition, coherence, and permeability for water) influence the resistance to weathering and type of weathering products, its amount, particle size distribution, as well as the intensity of physicochemical transformations within the original rock residue. Thus, the aim of this study was to investigate the impact of parent material on soil properties in southern part of Krka National Park, Croatia. Weathering of carbonate parent material (limestones, dolomites, conglomerates, marls) along with other soil forming factors was the base for soil development in this area. Thus, Calcocambisols and Terra rossa, typical and ilimerized are the most widespread soil types, while Calcomelanosols, Colluvium and Rendzinas are as well represented, but in much lesser extent. Soil depth, presence of coarse fragments and carbonate content in these soils vary considerably depending on parent material, although factors such as relief, vegetation and anthropogenic impact cannot be neglected. In general, shallow soils ( 35 cm) were formed on limestones and conglomerates, while medium deep soils (35-70 cm) were formed on marly substrates. The content of coarse fragments of variable size in soils (fine gravel 2-6 mm to boulders 60-200 cm) is related to different weathering processes of parent material. The presence of carbonate nodules on soil surface and within soil profile also indicates pedogenetic processes related to different types of carbonate parent material.

Environmental and periphyton response to stream revitalization – A pilot study from a tufa barrier

The formation of tufa barriers is driven by specific physicochemical and biological factors which make them very sensitive to environmental changes. The barriers provide great microhabitat complexity and are therefore inhabited by various periphytic organisms, whose metabolic activity alters the microenvironment, directly or indirectly affecting the physicochemical conditions of calcite precipitation. After the invasive plant species Ailanthus altissima (Mill.) Swinge was identified as one of the main factors causing current dryness of streams at the Skradinski buk barrier (Krka National Park, Croatia), the invasive species was removed, resulting in changes in the hydromorphology of the barrier and reactivating previously dry streams. The objective of this study was to determine potential differences between control and revitalized sites (reactivated streams) with regards to periphyton and the associated environmental changes over an annual cycle. Clear patterns were observed between sites reflecting the substantial changes in the landscape following invasive species removal. Revitalized sites had lower flow velocity, conductivity, pH, alkalinity and total water hardness values while exhibiting higher values of dissolved organic matter, nitrites and orthophosphates due to the presence of soil-derived organic material and intensive soil drainage. Organic matter content was generally higher at revitalized sites but did not inhibit tufa deposition. The influence of the surrounding forest soil was reflected not only in the mineralogical analysis of tufa sediment, but also in the abundance and diversity of periphyton. Revitalized site communities exhibited higher abundance and diversity and were dominated by bacterivorous and omnivorous ciliates and cercozoans due to the abundant food resources of the soil. The results presented show that ecosystem responses to hydromorphological changes generated by invasive species removal can be efficiently detected and monitored at microscale (i.e., periphyton scale) through a comprehensive interdisciplinary approach. As the first study to examine the relationship between aquatic ecosystems and sediments in the context of tufa stream revitalization, this pilot study provides data and guidelines for future management plans applicable to various tufa depositing systems facing invasive species propagation, allowing better understanding and protection of this unique and vulnerable karstic feature.

The Burnum Project: a combination of archaeological research and communication in Cultural Heritage

The archaeological site of Burnum is the subject of scientific research conducted since 2005 by the members of the Department of History, Culture and Civilization of Bologna University in collaboration with the Department of Archaeology of the University of Zadar. The project makes use of the fundamental support of the Krka National Park, committed to protecting the environmental heritage of the river valley and from 2003 also to enhancing the rich historical and archaeological context of the area. In this regard, while the research activities at Burnum continue to return new data and information on the history of the site during the Roman period, the project is also focusing on issues concerning virtual reconstruction and multimedia technologies applied to cultural heritage, with the aim of capturing attention, simplifying understanding and removing usage patterns.

New species from the family Hydroptilidae in Croatian fauna collected in the Krka National Park with particular notice to biodiversity and DNA barcoding

New species from the family Hydroptilidae in Croatian fauna collected in the Krka National Park with particular notice to biodiversity and DNA barcoding

New European Lepidocyrtus Bourlet, 1839 (Collembola, Entomobryidae) with the first description of feeding-related dancing behaviour in Collembola.

The study of a springtail population from Krka National Park (Croatia) has allowed us to describe the new species Lepidocyrtus chorus sp. nov. and its dance-like behaviour. This study represents the first record of peculiar dancing behaviour related to search for food and feeding among Collembola. The new species is molecularly and morphologically assigned to the European Lepidocyrtus lignorum-group. Sequences of COXII and EF-1α genes, chaetotaxy and behaviour clearly help to differentiate the new species from the other species in the group.

Influence of technological and municipal wastewaters on vulnerable karst riverine system, Krka River in Croatia.

Exceptional natural value of karst rivers, as well as their potential as a source of drinking water supply, contributes to the importance of developing strict environmental protection. Although most of its watercourse is proclaimed national park, Krka River is impacted by technological and municipal wastewaters, which are released without proper purification only 2km upstream of the park border. In order to assess water ecological status of the Krka River, vulnerability of karst ecosystem and potential threat to the Krka National Park, spatial and temporal variability of physico-chemical and microbiological water parameters, as well as concentrations of 25 total dissolved metals/metalloids were evaluated. All parameters indicated deteriorated water quality near the wastewater influences, which was for certain metals and bacterial counts even comparable to other world rivers of technological/rural catchment. Downstream location pointed to purification processes in karst river, although nutrients and conductivity were still in a range below good water quality and Al, Co, Fe, Li, Mn, Ni, Sr, Ti, and Zn levels remained comparable to their levels in the pollution impacted area, especially in autumn, indicating season-dependent processes. Presented data provided background status and identified pollution influences in the karst riverine system which indicated potential risk for protected area and a need for comprehensive water quality assessment.

Hydrological analysis of Skradinski Buk tufa waterfall (Krka River, Dinaric karst, Croatia)

The paper analyses complex hydrological behaviour of Skradinski Buk, the tufa waterfall, formed on the downstream part of the Krka River located in the coastal part of the Croatian Dinaric karst. This waterfall is the central point of the Krka National Park (KNP) proclaimed in 1985. Skradinski Buk is the seventh, final and the largest tufa barrier on the Krka River. Morphology of Skradinski Buk is composed of 17 unevenly distributed steps and dozens of small depressions. Natural waterfall morphology strongly influenced the complex waterfall hydrological regime. Additionally, hydrological regime is disturbed by the operation of the hydroelectric power plant (HEPP) Jaruga. This paper analyses characteristic (minimum, mean, maximum) annual water levels and discharges monitored at two hydrological stations (Skradinski Buk Gornji-SBG and Nacionalni Park-NP). SBG controls the inflow of water into the waterfall, while the NP is established in order to control the use of water from the HEPP Jaruga operation. It is concluded that the HEPP Jaruga does not comply with the agreement signed between the KNP and the HEPP Jaruga. The goal of the paper is to give detailed hydrological analysis of the Skradinski Buk, which should play the crucial role in the protection of this wonderful and very vulnerable phenomenon.

Survival chances of ground nests in three different habitats in Krka National Park (Croatia)

Background and Purpose: Diverse Mediterranean wetlands sustain a high diversity of breeding birds. Breeding success of birds nesting on protected wetlands along river Krka is also influenced by predators. The aim of our study was to explore effects of predator pressures on ground nests of strictly protected birds using artificial nest located along environmental gradient. Materials and Methods: In May 2004 in locality Čulišićke bare, by placing out three batches of 25 artificially constructed ground nests in three different habitats: reed bed, marsh and meadow. The nests contained three chicken (real) eggs for the evaluation of nest predation rates, and plasticine (artificial) eggs for predator identification from tooth and bill imprints. Results and Conclusions: The number of nests depredated during one week was highest in wetland habitats: 52% was depredated in the marsh and 32% in the reed bed. However, a much lower damage rate (16%) was experienced in the meadow. The daily survival rate of nests did not differ significantly between the reed bed (0.95) and the marsh (0.91). However, the daily survival rates of nests in the meadow (0.98) was significantly higher (z = 2.49 P = 0.01) than in the marsh, bat no difference was found with comparing with the reed bed. Predators were difficult to determine because plasticine eggs usually disappeared from the nests in the reed bed. In the marsh and the meadow, primary predators were smaller birds, whereas small mammals were also important in the marsh. Nests in which predators succeeded in breaking at least one egg were later destroyed most by Hooded Crows (Corvus cornix). To apply these results for bird protection, the breeding success of certain threatened bird species should be monitored for a longer period.

A contribution to knowledge of freshwater molluscs (Mollusca) of the Krka River in the Krka National Park (Croatia)

A contribution to knowledge of freshwater molluscs (Mollusca) of the Krka River in the Krka National Park (Croatia)

Long-time emergence patterns of Limnophora species (Diptera, Muscidae) in specific karst habitats: tufa barriers

The hunter-fly genus Limnophora (Muscidae: Coenosiinae) is an important component of running water assemblages. Both adults and larvae are predators, the adults mostly feeding on blackflies (Simuliidae) and other small aquatic insects. This study was conducted at two tufa barriers in Plitvice Lakes National Park (NP) (tufa barrier Labudovac and tufa barrier Kozjak-Milanovac) and at two tufa barriers in Krka National Park (NP) (tufa barrier Roški slap and tufa barrier Skradinski buk). Adults were collected monthly from February 2007 until December 2013 at Plitvice Lakes NP and from September 2013 to October 2014 at Krka NP, using pyramid-type emergence traps. Over the 7-year study period at the Plitvice Lakes tufa barriers, a total of 193 specimens belonging to 6 species were collected, while during the 1-year study period at the Krka tufa barriers a total of 848 specimens belonging to 4 species were collected. Abundance of Limnophora specimens at the Krka NP sites was up to 30 times higher than at the Plitvice Lakes NP sites, which could be attributed to higher levels of potential food and higher water temperatures. The dominant species at the Plitvice Lakes sites were Limnophora pulchriceps and Limnophora riparia. At the Krka tufa barriers, the dominant species at site Roški slap was Limnophora croatica and at site Skradinski buk Limnophora riparia. The highest numbers of emerging specimens at all sites were present in the summer months. At the Plitvice Lakes sites most species were univoltine or bivoltine, while at the Krka sites most species were multivoltine. Water temperature was the main factor influencing the timing of emergence and the duration of the flight period. The highest abundance of Limnophora species was recorded over moss substrate. A significant positive correlation emerged between the numbers of emerging prey and the numbers of emerging specimens of Limnophora. These results give a new insight into the microhabitat preferences and prey-predator relationships of Limnophora.

Tachinid (Diptera: Tachinidae) parasitoids of spotted ash looper (Abraxas pantaria) in Krka National Park in Croatia

Background and purpose: Spotted ash looper , Abraxas pantaria (Lepidoptera: Geometridae) causes defoliations of narrow-leaved ash ( Fraxinus angustifolia ) in Croatia, mainly in Krka National Park. Since controlling pests with insecticides is not possible in protected areas, biological pest control might be a valuable option. The first step in the study of its application is the research on hosts and their natural enemies. Not much is known about the parasitoid spectrum of A. pantaria in Croatia, so the aim of this research is to identify the parasitoid species which could influence the population density of this potential forest pest. Materials and methods: Pupae of A. pantaria were studied in 2010 at several locations along the River Krka in Krka National Park. This area was chosen because total defoliation of ash was observed in 2010. Results and conclusions: Five tachinid species were reared from Abraxas pantaria : Phryxe nemea , Bactromyia aurulenta , Senometopia sp., Pales pavida and Eurysthaea scutellaris . All species are generalist parasitoids. Phryxe nemea is the first record for this host.

Tachinid (Diptera: Tachinidae) parasitoids of spotted ash looper (Abraxas pantaria) in Krka National Park in Croatia

Background and purpose: Spotted ash looper, Abraxas pantaria (Lepidoptera: Geometridae) causes defoliations of narrow-leaved ash (Fraxinus angustifolia) in Croatia, mainly in Krka National Park. Since controlling pests with insecticides is not possible in protected areas, biological pest control might be a valuable option. The first step in the study of its application is the research on hosts and their natural enemies. Not much is known about the parasitoid spectrum of A. pantaria in Croatia, so the aim of this research is to identify the parasitoid species which could influence the population density of this potential forest pest. Materials and methods: Pupae of A. pantaria were studied in 2010 at several locations along the River Krka in Krka National Park. This area was chosen because total defoliation of ash was observed in 2010. Results and conclusions: Five tachinid species were reared from Abraxas pantaria: Phryxe nemea, Bactromyia aurulenta, Senometopia sp., Pales pavida and Eurysthaea scutellaris. All species are generalist parasitoids. Phryxe nemea is the first record for this host.