Plitvice Lakes Research Articles

Impact of the Jenkyns Event on shallow-marine carbonates and coeval emerged paleoenvironments: the Plitvice Lakes region, Croatia

Early Jurassic (late Pliensbachian–early Toarcian) Large Igneous Province (LIP) magmatism affected the entire ocean-atmosphere system culminating in a cascade of paleoenvironmental perturbations known as the Jenkyns Event which globally impacted marine, transitional and terrestrial paleoenvironments. Carbonate platforms at low latitudes in the Western Tethys realm drowned or shifted to non-skeletal production during the early Toarcian due to sea level rise, global warming, and ocean acidification. Unlike deep-marine deposits, shallow-marine carbonates present a challenge in defining global geochemical signals due to common diagenetic modifications. An integrated dataset including δ13Ccarb and δ18Ocarb, TOC, biomicrofacies, SEM, XRD, and palynological study of two stratigraphic successions in the Plitvice Lakes region, Bjelopolje (BJ) and Plitvice Spring (PS), in Croatia, provides an overview of the paleoenvironmental evolution and lateral facies changes in a peritidal setting during the Early Jurassic on the Adriatic Carbonate Platform (AdCP). The investigated stratigraphic succession starts with upper Pliensbachian, peloid-ooid-bioclastic grainstones alternating with fenestral and massive mudstones overlain by lower Toarcian, lagoonal, bioturbated, “spotted” limestones with horizons indicative of short-lived subaerial emergence during the early Toarcian. A negative excursion in δ13Ccarb, foraminifer assemblages, and the predominance of Classopollis pollen within the “spotted” limestones marks the stratigraphic position of the Jenkyns Event. Global-scale events (sea level variation, climate change, C-cycle perturbation, anoxia) operated simultaneously with local to regional synsedimentary tectonics and eustatic movements that preserved the AdCP carbonate factory from collapse or drowning but resulted in pronounced facies differentiation on the shallow-marine carbonate platforms.

Benthic macroinvertebrate communities change along a karstic barrage-lake system

Barrage-lake systems are a rare natural phenomenon with specific ecological characteristics that are greatly affected by tufa formation. Our main goal was to investigate benthic macroinvertebrate communities and their longitudinal variations within the lakes arranged in cascades in the Dinaric karst hydrosystem. Each lake within the Plitvice Lakes system studied presented with a distinct community, showing the effects of the barrage-lake system on the macroinvertebrates in these lakes. We observed a downstream decrease in taxa richness, abundance and Shannon diversity index along the longitudinal profile of the studied barrage-lake system. This pattern is most probably a result of decreased organic matter and increased tufa deposition. Overall, our results suggest that the hydrosystem studied represents a sequence of sediment sinks in which lakes retain and accumulate organic matter and fauna. Therefore, each lake acts as a filtering screen and consequently appears to be a small ecosystem. Each lake has its own community characteristics, regardless of the fact that water flows from one lake to the next, connecting them and creating very similar abiotic conditions in each lake along the system.

The Emergence of the Family Scirtidae (Insecta: Coleoptera) in Lotic Karst Habitats: A Case Study over 15 Years.

Due to ongoing changes and a decline in biodiversity, science today should rely on long-term species-based ecological studies. We have conducted a long-term ecological dynamics study on the water beetle family Scirtidae, which, although it is very abundant in benthic communities, is still poorly studied. The main objective of this study was to investigate the population aspects (composition, diversity, sex ratio) and ecological aspects (emergence patterns, seasonal dynamics and preferences for environmental factors) of the family Scirtidae over 15 years in Plitvice Lakes NP, Croatia. The study was conducted at three sites and in five different substrate types. A total of three taxa with different distributions were recorded in the study area: Hydrocyphon novaki and H. deflexicollis on the tufa barriers and the Elodes sp. in the spring area. The sex ratio was in favour of males in spring and early summer, while it shifted in favour of females towards the end of autumn. The abundance and emergence of the family were primarily determined by the environmental parameters which showed the greatest fluctuations over a period of 15 years: water temperature, water discharge and oxygen saturation. Our results clearly show that Scirtidae can be used as indicators of stream zonation and habitat quality. Based on the methodology and the results of this study, we conclude that Scirtidae should be used in future monitoring and protection measures in karst freshwater habitats in southeastern Europe.

Vegetational and Structural Features of Forest Clearings in Plitvice Lakes National Park

The impact of various ecological factors, biogeographical position and both former and current anthropogenic activity in Plitvice Lakes National Park greatly influenced the development of different habitat types, including forest clearings. Due to the insufficient knowledge of this habitat type, based primarily on general descriptions within the National Habitat Classification of the Republic of Croatia (NN 27/2021, NN 101/2022), this paper deals with presenting their vegetational and structural characteristics in the national park area. The following taxonomic keys were used to determine plant species: Tutin et al. (1964-1980), Pignatti (1982), Javorka and Csapody (1991) and Martinčič et al. (1999). Furthermore, scientific nomenclature of plant species was conducted using Flora Croatica Database (Nikolić 2012), while threat status was aligned by the Red Book of Vascular Flora of Croatia (Nikolić and Topić 2005). Also, protection level was adjusted according to the Regulation on strictly protected species (NN 144/2013, NN 73/2016). Spectrum of life forms and chorological types were aligned according to Pignatti (2005). Vegetation was studied in accordance with the principles of the Braun-Blanquet approach (Braun-Blanquet 1964). Together with the basic parameters of the selected plots, the research also included the collection of structural parameters of forest clearings according to Medak et al. (2023). Based on conducted research, a total of 98 plots of forest clearing habitats were established with a total of five different forest clearing communities. The largest number of forest clearing communities belonged to Salicetum capreae, followed by Eupatorietum cannabini, Atropetum bella-donae, Telekium speciosae and Rubetum idaei. A total of 257 species of vascular plants were identified in the area and classified into 60 families. The most represented family was Asteraceae, while the highest relative representation of life-forms belonged to hemicryptophytes (H). Furthermore, the most represented chorologycal type in the area was Eurasian (20.6%). The habitat type contained a total of 11 strictly protected (SZ), 6 nearly threatened (NT), 3 vulnerable (VU), 2 data-deficient (DD) and 4 endemic species. In addition, the largest number of plots had an anthropogenic origin, irregular type (shape), occupied a small area (less than 1000 m2) and were located along the edges of both forests and forest roads. The results of this paper represent the first vegetational and structural data of forest clearings in the national park area which contribute to an expansion of our knowledge and understanding of this habitat type, and form a starting point for the necessary future research.

Diversity of horseflies (Diptera: Tabanidae) of highly protected nature areas in Croatia: an overview

In Croatia, 55 taxa of Tabanidae (species and subspecies) were recorded in 17 of 22 highly protected nature categories, including Strict Reserves, National Parks and Nature Parks. These taxa amounted to 70.51% of the Tabanidae fauna of Croatia. New records were discovered for the following 22 species in all three protected nature categories: Silvius alpinus (Scopoli, 1763); Chrysops caecutiens (Linnaeus, 1758); Hybomitra distinguenda (Verrall, 1909); Hybomitra muehlfeldi (Brauer in Brauer & Bergenstamm, 1880); Hybomitra pilosa (Loew, 1858); Hybomitra solstitialis (Meigen, 1820) nec Lyneborg (1959); Tabanus autumnalis Linnaeus, 1761; Tabanus bovinus Linnaeus, 1758; Tabanus bromius Linnaeus, 1758; Tabanus cordiger Meigen, 1820; Tabanus exclusus Pandellé, 1883; Tabanus glaucopis Meigen, 1820; Tabanus maculicornis Zetterstedt, 1842; Tabanus shannonellus Kröber, 1936; Tabanus sudeticus Zeller, 1842; Tabanus tergestinus Egger, 1859; Tabanus unifasciatus Loew, 1858; Haematopota grandis Meigen, 1820; Haematopota italica Meigen, 1804; Haematopota pandazisi (Kröber, 1936); Haematopota pluvialis (Linnaeus, 1758) and Dasyrhamphis ater (Rossi, 1790). Similarities among Tabanidae fauna in four Nature Parks (Kopački rit, Lonjsko polje, Medvednica and Papuk) located in continental Croatia ranged from 55.81% to 74.41%. Nature Parks (Biokovo, Dinara, Učka and Vransko Lake) in Mediterranean part of Croatia had similarities ranging from 0% to 57.14%. In National Parks, the highest similarity (47.61%) was recorded between the Plitvice Lakes and Krka.

The Dynamics of Stand Structure Development and Natural Regeneration of Common Beech (Fagus sylvatica L.) in Plitvice Lakes National Park

The authors investigate the structural characteristics, regeneration processes, growth, development, and survival of a young generation of common beech (Fagus sylvatica L.) based on three periodic measurements (1998, 2009, and 2018). The studied forest community (Lamio orvale-Fagetum sylvaticae (Ht. 1938) Bohridi 1963) is situated within a forest reserve in Plitvice Lakes National Park, Croatia. Monitoring was carried out according to UN/ECE (2000) for systematic and repeated research. The basic structural indicators, structural canopy elements, and appearance of the young generation were measured as the basic conditions of natural restoration in repeated phytocenological surveys (1980, 1988, 2004). The distribution of the number of trees of the first two measurements (1998–2009) indicates a distribution with pronounced right asymmetry. The structural dynamics observed during the surveys and alongside vegetation surveys indicate the dynamics of the growth and development of beech. The results show that the main drivers of development dynamics in protected forest ecosystems are structural breaks (gaps) that occur in stands due to the action of abiotic and biotic factors. The passive management model in effect in the national park should be replaced with a more active approach to facilitate natural processes with the aim of preserving and renewing the forest ecosystem.

Long-Term Chironomid Emergence at a Karst Tufa Barrier in Plitvice Lakes National Park, Croatia.

Chironomids are found in all types of freshwater habitats; they are a ubiquitous and highly diverse group of aquatic insects. Plitvice Lakes National Park is the oldest and largest national park in Croatia and consists of numerous and diverse freshwater habitats, making the area an ideal location for long-term research into the chironomid emergence patterns and phenology. The main objectives of this study were to identify the composition of the chironomid community, determine the phenology of the identified species, and assess the main factors influencing their emergence in Plitvice Lakes. During 14 years of research, more than 13,000 chironomids belonging to more than 80 species were recorded. The most abundant species was found to be Parametriocnemus stylatus. The highest abundance of chironomids was recorded in lotic habitats with faster water current over substrates of moss and algae and pebbles. Water temperature and the availability of organic matter were found to be the main factors that drive chironomid emergence at the tufa barrier studied. In the last years of this study, a prolonged flight period was observed. Although this is not statistically significant (at this stage of the study), it could be due to a higher water temperature in winter.

Central European Group for Separation Sciences (CEGSS)—Brief History and Memoirs on the Creation and Activity

The origin of the International Symposia on Separation Sciences (ISSS) can be found in the national gas chromatography scientific meetings held in Zagreb, Croatia, from 1967 and later at Plitvice Lakes until 1988 [...]

And There Were the Plitvice Lakes. The Landscapes of the Croatian Lake District in the Romantic Journey Put na Plitvice

Put na Plitvice (The Road to Plitvice, 1860) is the first of the travelogue in Croatian language describing an expedition to the Croatian Lake District. The work of art is of significant “world-creating” and “culture-creating” value, introducing the Plitvice Lakes into the Croatian national text and into the national landscape, hence the biblical allusion in the title. It will therefore be a world-creating narrative, of bringing into existence and therefore giving a symbolic dimension of the work of art.I focus on the landscape-painting aspects of the text, understanding landscape as the manner of constructing and formulating the world, as a way of perceiving and incorporating it into cultural traditions. It is therefore rough, monumental, wild like a traversed space, which should be included in the category of picturesque and sublimity. Veber’s representation of nature illustrates how it was seen at the time within the framework of the national-revival programmes

Effect of Climate Change on Water Temperature and Stratification of a Small, Temperate, Karstic Lake (Lake Kozjak, Croatia)

As closed systems, lakes are extremely vulnerable to climate change. Understanding the response to climate change is crucial for effective management and conservation of the lakes and their associated ecosystems. This study focuses on Lake Kozjak, Croatia, a small lake belonging to the Plitvice Lakes system. This system represents a unique hydrogeological karstic phenomenon, closely dependent on a delicate biochemical balance necessary for tufa formation. We apply a simple one-dimensional model, SIMO v.1.0, to predict future water temperature in Lake Kozjak under three scenarios (RCP2.6, RCP4.5 and RCP8.5) from 2006 to 2100. The model was calibrated using measured water temperature profiles and meteorological data from a nearby station. In addition to analyzing the average temperatures of the epilimnion, hypolimnion and the whole lake, we also studied the surface and bottom layer temperatures and their relation to specific forcing parameters. The Schmidt stability index was used as a quantitative indicator to assess lake stability. The simulation results indicate average lake water temperature increase of 0.51, 1.41 and 4.51 °C (100 y)−1 for RCP2.6, RCP4.5 and RCP8.5, respectively. This increase in the water temperature is not accompanied by a substantial strengthening of stratification under RCP2.6 and RCP4.5 scenarios due to the temperature raise being present both in the epilimnion and hypolimnion. However, significant lengthening of the stratification period is observed even for the most stringent scenario, 16, 28 and 47 d (100 y)−1 for RCP2.6, RCP4.5 and RCP8.5, respectively. The predicted water temperature increase and prolonged stratification period may carry serious ecological and environmental implications.Highlights• Mean lake water temperature is projected to increase by 0.51 to 4.51 °C (100 y)−1.• Baseline scenario surface temperature increase of 5.2 °C (100 y)−1 is predicted.• Stratification period is predicted to lengthen by 16 (RCP2.6) to 47 days (RCP8.5).• Substantial stratification strengthening is expected only under RCP8.5.

New records of the rare liverwort Mannia triandra (Scop.) Grolle in Croatia

Mannia triandra (Scop.) Grolle is a rare thalloid liverwort species, known from a few, mostly sporadic, historical records in Croatia. In the recent years, two findings have been recorded on Mt Žumberačka Gora and one from Plitvice Lakes, and subsequently published. During 2022, two adjacent populations close to these previously known localities were found, but also a first locality in Gorski Kotar region (in the canyon of the River Kamačnik) was recorded. In addition, an old literature record from the area of Dubrovnik city from the beginning of the 20th century was found while browsing literature for this paper. Thanks to these new findings, we are now closer to a better understanding of the species ecology and habitat preferences in Croatia.

Hydrochemical and Seasonally Conditioned Changes of Microbial Communities in the Tufa-Forming Freshwater Network Ecosystem.

Freshwater network ecosystems consist of interconnected lotic and lentic environments within the same catchment area. Using Plitvice Lakes as an example, we studied the changes in environmental conditions and microbial communities (bacteria and fungi) that occur with downstream flow. Water samples from tributaries, interlake streams, connections of the cascading lakes, and the Korana River, the main outflow of the system, were characterized using amplicon sequencing of bacterial 16S rRNA and fungal ITS2 genes. Our results show that different environmental conditions and bacterial and fungal communities prevail among the three stream types within the freshwater network ecosystem during multiple sampling seasons. Microbial community differences were also confirmed along the longitudinal gradient between the most distant sampling sites. The higher impact of "mass effect" was evident during spring and winter, while "species sorting" and "environmental selection" was more pronounced during summer. Prokaryotic community assembly was majorly influenced by deterministic processes, while fungal community assembly was highly dominated by stochastic processes, more precisely by the undominated fraction, which is not dominated by any process. Despite the differences between stream types, the microbial community of Plitvice Lakes is shown to be very stable by the core microbiome that makes up the majority of stream communities. Our results suggest microbial community succession along the river-lake continuum of microbial communities in small freshwater network ecosystems with developed tufa barriers. IMPORTANCE Plitvice Lakes represent a rare freshwater ecosystem consisting of a complex network of lakes and waterfalls connecting them, as well as rivers and streams supplying water to the lake basin. The unique geomorphological, hydrological, biogeochemical, and biological phenomenon of Plitvice Lakes lies in the biodynamic process of forming tufa barriers. In addition to microbial communities, abiotic water factors also have a major influence on the formation of tufa. Therefore, it is important to understand how changes in environmental conditions and microbial community assembly affect the functioning of the ecosystem of a freshwater network with developed tufa barriers.

Extreme freshwater discharge events exacerbated by climate change influence the structure and functional response of the chironomid community in a biodiversity hotspot

Global climate change is expected to exacerbate extreme discharge events in freshwater ecosystems as a consequence of changes in precipitation volume and snow cover duration. Chironomid midges were used as a model organism in this study because of their small size and short life cycles, which enable fast colonization of new habitats and great resilience. This resilience is often expressed in easy recolonization after an extreme event. Chironomid samples together with physico-chemical water measurements were collected for 14 years, between 2007 and 2020, in a karst tufa barrier that is part of the Plitvice Lakes National Park in Croatia. More than 13,000 individuals belonging to >90 taxa were collected. Mean annual water temperature increased by 0.1 °C during this period. Multiple change-point analysis revealed three main periods by discharge patterns: the first one from January 2007 to June 2010, the second from July 2010 to March 2013, characterised by extreme low discharge, and the third from April 2013 to December 2020, characterised by an increase in extreme peak discharge values. Based on multilevel pattern analysis, indicator species of the first and the third discharge period were detected. The ecological preferences of these species indicate an environmental change related to the changes in discharge. Along with species composition, functional composition has changed with the abundance of passive filtrators, shredders and predators increasing over time. Species richness and abundance did not change over the period of observation, thus emphasizing the importance of species-level identification in detecting the earliest community response to change that would otherwise be overlooked.

Environmental Changes Recorded in Tufa from the Korana River, Croatia: Geochemical and Isotopic Approach

Between 1979 and 2003, a 35 cm thick layer of laminated tufa formed around a wooden pillar located at the beginning of the Korana River, which emerges from the Plitvice Lakes, Croatia. The laminated tufa structure allowed for the stratigraphic analysis of mineral, elemental and δ18O and δ13C isotope composition. Results are compared to other carbonate archives (lake sediments) from the Plitvice Lakes and to measured water physical–chemical data collected in the same time. An increase in water temperature and decrease in Mg/Ca ratio was observed during that period. Results showed that the tufa Mg/Ca ratio and δ18O could not be used as a temperature proxy, while an observed δ18O increase after 1990 was attributed to increase in evaporation rate. Furthermore, the constant increase in redox-sensitive elements (Mn) towards the external part of tufa may indicate periodic events of anoxia at the sediment/water interface. Local enrichment factors (LEFs) for potentially toxic elements were calculated using the background function and Al as the normalizing element. The LEFs showed an enrichment pattern of Cu and Pb in 1983 and 2001, which could indicate their anthropogenic origin and the sensitivity of the tufa to environmental changes.

Protected area management effectiveness and COVID-19: The case of Plitvice Lakes National Park, Croatia.

Post-pandemic recovery of PA requires prioritisation risk framework to identify specific objectives that should be addressed first and which require additional effort or funding. Facing a crisis PA will allocate financial resources in a way that sustains primary functions such as conservation until negative trends change, or at least until financial resources become available. PAs require a paradigm shift, which includes tailoring of financial mechanisms to practical and policy purposes, effective allocation of financial resources, and responsible tourism recovery plans that capture the value and efforts of conservation through tourism and investments in nature-based solutions for sustainable tourism within PA.

Podróż wokół pstrągów: Put na Plitvice Adolfa Vebera Tkalčevicia. Tekstotwórcza rola motywów kulinarnych

Adolfo Veber Tkalčević (1825–1889) a Croatian philologist, writer, passionate traveler and a Catholic clergyman is the author of the first Croatian account of the travel to the Croatian “Lake District” Put na Plitvice (Road to Plitvice, 1860). As a travel narrative, this book has a “worldbuilding” potential, introducing the Plitvice Lakes to Croatian culture, to the national landscape. In this article,Ifocus on the culinary theme of the trip. One of its side goals was savouring the trouts, but throughout the entire trip the tables of wanderers did not want to fill with them, offering the text-forming abundance instead. The journey “around theempty table” is a kind of self-portrait of “explorers” ready for a “heroic” attitude for the common good. Bearing in mind the specificity of Croatian Romanticism, which this work represents, I read the text in a cultural, anthropological and identity context, referring to the classics of discourse, and devoting less attention to travel studies.

GIS-Based Visitor Count Prediction and Environmental Susceptibility Zoning in Protected Areas: A Case Study in Plitvice Lakes National Park, Croatia

The most valuable protected natural areas, including national parks, are subjected to the increased visitors count and density, threatening the environmental sustainability and biodiversity conservation. To establish a basis for land management to mitigate these influences, the novel geographic information (GIS)-based environmental susceptibility zoning method was proposed. The study area covered the Plitvice Lakes National Park, as the oldest and largest national park in Croatia, using the historical 20-year visitor data with 19 tourist and hiking routes. Two geospatial analysis methods were evaluated as follows: (1) short-term prediction of visitors count data based on a 10-year historical intervals, and (2) the environmental susceptibility zones delineation method integrated two fundamental factors in the assessment of environmental impacts from route density and historical visitors count on a monthly basis. Four accuracy assessment metrics indicated a moderate accuracy of short-term visitors count prediction, with the coefficient of determination ranging from 0.700 to 0.951. The routes which continue from both entrances indicated the largest visitors load is in the central part of the park, mostly located in the moderately restricted zone. These observations indicated moderate present environmental susceptibility with stable outlook, providing an insight for the nature park management adjustment.

Exploring Tourist Preferences on the Visitor Management System: the Case Study of Plitvice Lakes National Park

This study aims to develop an online survey on the tourist perception of the visitor management system of the Plitvice Lakes National Park in Croatia. As tourists are particularly sensitive to organisational issues related to the Park management, a bottom-up approach based on visitors’ opinions has been applied. First of all, a brief chronology has been reconstructed that retraces the most significant stages of the Park. Subsequently, an online questionnaire was structured on the basis of the current Park Management Plan with a focus on the macro-topics concerning the visitor management system. The survey was distributed using the Google Form application. A total of 214 questionnaires were collected in the period between May and July 2022. The sample was statistically analysed to detect the main habits of the Park users. The Mann-Whitney-Wilcox U test and the Kruskal-Wallis test were applied to identify the differences in the priorities attributed by visitors to the various management actions. Among the main findings of the research, the authors identified that national visitors (i.e. Croatian) place a higher priority on the implementation of services and infrastructure than tourists from other countries. In addition, those who have visited the Park on multiple occasions have higher safety expectations than those who have only visited the Park once. This category of visitors also considers it more important to take into account the opinions of visitors. Furthermore, with regard to retail and souvenir shops, tourists are generally inclined to set a lower priority for intervention than that attributed to other management aspects. The results of this study can be of great value to Park managers, who should consider visitors as key stakeholders in the decision-making process that is the foundation for managing this important natural resource.

Stability of travertine barrier on Milino Lake

In March 2018, part of the travertine barrier at Milino Lake, in Plitvice Lakes National Park in Croatia, broke off, significantly altering the flow of water over the barrier. Encouraged by this event, the Faculty of Civil Engineering in Rijeka conducted a monitoring and analysis of the erosion dynamics of the travertine barriers on Plitvice Lakes. Within the project, the analyses of the stability of the travertine barriers were carried out. To the author's knowledge, physical and mechanical properties of travertine have been determined for the first time on samples excluded from travertine barriers between cascading lakes. In addition, no one has previously checked the stability of the travertine barrier located between the two lakes. The maximum compressive and tensile stresses calculated on a numerical model of the broken part of the barrier are compared with the compressive and tensile strength determined by laboratory tests on travertine samples taken from the broken barrier. By comparing the calculated stresses and determined travertine strength, it was found that the stability of the analysed part of the broken travertine barrier at Milino Lake was compromised even if only the self-weight of the collapsed part of the barrier is taken into account.

Lake-land breezes over a small elongated lake (Kozjak, Plitvice Lakes, Croatia)

The temperature of a small elongated lake (2.3 km by 0.1-0.6 km; maximum depth of 46 m) located in a mountaneous area was measured during July-September period over three years (2018-2020) at the depth close to the lake surface (0.2 m). Concurrent standard meteorological variables were measured in the vicinity of the lake. Criteria based on atmospheric and lake conditions were defined to detect the days with persistent lake-land breeze (LLB) events. The results showed that 17.7% of the investigated days were associated with LLB events. These days were accompanied by elevated energy in the normalized wavelet spectra for the wind speed at period of 24 hours. Daytime onshore lake breezes were mainly channeled in the along-lake direction due to the surrounding topography. Accordingly, during the daytime, diurnal wind veering was distorted. However, during the nighttime, a clear clockwise wind rotation was present. In addition, the results exhibited a clear relationship between the lake-land temperature difference and the strength of the LLBs.