Plitvice Lakes Research Articles

Mineralogical, organic and isotopic composition as palaeoenvironmental records in the lake sediments of two lakes, the Plitvice Lakes, Croatia

Six sediment cores, the top 30–40 cm, from two lakes of different sizes, Lake Prošće and Lake Kaluđerovac, situated in the karst region of the Plitvice Lakes system, Croatia, were studied by mineralogical and structural, C/N and total organic carbon (TOC) and isotopic analyses (a14C and δ13C of carbonate and organic fractions). The study of the two karst lakes where sediment composition is mainly calcite, showed that organic matter (OM) also plays an important role, and that both fractions analysed simultaneously give a good overview of the processes in the lakes. The morphological and structural properties of the calcite particles at micron and submicron levels indicate that the calcite mineral phase is formed by active authigenic precipitation in the studied lake systems. In the small Lake Kaluđerovac, the measured distributions of carbonate and OM fractions, C/N, TOC, and a14C and δ13C values of both fractions along the sediment depth showed similar values for all three cores, with small variations in each core indicating very homogenous precipitation of autochthonous calcite inside the lake, without allochthonous fraction. In the bigger Lake Prošće, the large difference in sediment composition of the three cores indicated different conditions of sediment precipitation inside the lake. Significant fractions of land-derived carbonate and OM were recognized by mineralogical, C/N, a14C and δ13C values in the shallow, coastal area indicating that the sediment was a mixture of allochthonous and autochthonous fractions. In contrast, the composition of the deep-water sediment in the same lake indicated in-situ calcite precipitation and aquatic OM produced in the lake. Sedimentation rates of 0.7 cm/yr and from 0.3 to 0.7 cm/yr for Lake Prošće and Lake Kaluđerovac, respectively, were determined based on the a14C of macrofossils. Extreme hydrological events in 1981 and 2010 were identified by disturbances in carbon isotopes distributions in sediment profiles. No evidence of anthropogenic influence in either lake on the local level was found, but the response to the global 14C contamination was observed by a14C peaks in both, carbonate and organic fractions. Increased bioproductivity in the recent decades was observed in Lake Prošće which can be correlated with a slight increase in lake water temperature in the last three decades. This process can be associated with enhanced eutrophication in Lake Prošće.

Clinical and virological characteristics of hantavirus infections in a 2014 Croatian outbreak.

Croatia is endemic for hemorrhagic fever with renal syndrome (HFRS), with both Puumala (PUUV) and Dobrava virus (DOBV) documented. Several large outbreaks were recorded in 1995, 2002, and 2012. We analyzed demographic, clinical, laboratory, and virological characteristics of HFRS cases detected in three geographically close natural foci (Ogulin, Slunj, and the Plitvice Lakes surroundings) during the 2014 outbreak. From January to December 2014, 122 patients with suspected HFRS were tested for hantavirus IgM/IgG antibodies using an indirect immunofluorescence assay (IFA). Cross-reactive samples were further tested using a western blot (WB). For hospitalized patients from Ogulin area, clinical and laboratory data were analyzed. Acute infection was documented in 57 (46.7%) patients, of whom 75.4% were hospitalized. Ten (8.2%) patients were found to be IgG seropositive. Patients were 15-69 years of age and predominantly male (74.5%). The outbreak started in winter months, with most cases recorded from May to July (80.7%). The most frequently reported symptoms were fever (96.3%), chills/shivering (62.9%), and lumbar pain (48.1%). Mild clinical form was found in 66.7% patients, moderate in 18.5%, and severe in 14.8% patients (all but one infected with PUUV). One patient died. Using IFA, 48.8% patients showed monotypic antibody response, while in 51.2%, cross-reactive antibodies were found. PUUV was confirmed in 94.7% and DOBV in 5.3% HFRS cases by WB. Central mountainous Croatian regions are still highly endemic areas for HFRS. A higher percentage of severe PUUV infections could be at least partly associated with a patient's immune status.

Environmental factors affecting mayfly assemblages in tufa-depositing habitats of the Dinaric Karst

Remarkably, unlike other parts of Europe, the ecology of mayflies in the southeastern regions is still poorly known. Here we present the first comprehensive study of Ephemeroptera in the tufa-depositing habitats of the Dinaric Karst. The study was conducted in Plitvice Lakes National Park monthly during a one-year period (2007–2008) in different types of habitats (springs, streams, mountainous rivers, tufa barriers). The aims of the study were to determine mayfly composition, abundance, spatial distribution and habitat preferences, and to examine the environmental factors important for the structuring of mayfly assemblages in Plitvice Lakes National Park. The mayfly fauna of tufa-depositing habitats was composed of 14 species (20 taxa). Water temperature, pH and ammonium concentration were the most important environmental variables explaining mayfly assemblages. Mayfly assemblages grouped according to habitat type. Generally, the most favourable habitat type was mountainous stream, tufa barriers were less favourable, and the least favourable were springs. Our results confirmed that mayflies are a powerful tool as descriptors of their environment, as the presence or absence of certain mayflies was strongly influenced by physico-chemical water properties.

Epidemiological and clinical characteristics of hantavirus infections detected in three geographically close natural foci during the 2014 Croatian outbreak

Purpose: The aim of this study was to analyze epidemiological and clinical characteristics of hantavirus infections detected in Croatia during the 2014 outbreak. Methods and Materials: From January to December 2014, a total of 122 patients from three geographically close natural foci in the central mountainous Croatian region (Ogulin, Slunj and Plitvice Lakes surroundings) with clinical symptoms suggestive of hantavirus infection were tested for the presence of IgM/IgG antibodies to hantaviruses. Serologic tests were performed using a commercial IFA for the simultaneous detection of Puumala (PUUV), Dobrava (DOBV), Hantaan (HTNV), Seoul (SEOV) and Saaremaa (SAAV) (Euroimmun, Lubeck Germany). Cross-reactive samples were additionally tested using a western blot (Euroimmun, Lubeck Germany). For hospitalized patients clinical symptoms and laboratory parameters were analyzed. Results: Acute hantavirus infection was confirmed by detection of IgM/IgG antibodies in 57/46.7% patients, while 10/8.2% patients were IgG seropositive (previous exposure to hantaviruses). PUUV infection was detected in 88.1% and DOBV infection in 11.9% patients. Among acute cases, 75.4% were hospitalized. Males were infected more commonly than females (75.4%). The mean patient’s age was 37.9 (range 15- 69) years. Contact with rodents was noted in 59.3% patients. The outbreak started in winter months with majority patients (80.7%) reported from May to July. According to disease severity, mild clinical form was noted in 66.7%, moderate in 18.5% and severe in 14.8% patients. The most common clinical symptoms on admission were high fever (96.3%), chills/shivering (62.9%) and lumbal pain (48.1%). In 11.1% patients, respiratory symptoms with interstitial inflammatory infiltrates on X-ray were reported. Acute renal failure was noted in 74.1% patients but only 3.7% required hemodialysis. Laboratory abnormalities included albuminuria (96.3%), thrombocytopenia (81.5%, elevated urea and/or creatinine levels (70.4%) and elevated transaminases (25.9%). The mean duration of hospitalization was 9.6 (range 4-19) days. Only one PUUV infected patient developed multiorgan failure and died. Conclusion: Our results indicate that central mountainous Croatian regions are still endemic areas for hantavirus infections with circulation of both PUUV and DOBV. Compared to previous Croatian outbreaks, respiratory symptoms that are frequently detected in PUUV infection were reported less frequent.

Changes in the geochemical parameters of karst lakes over the past three decades – The case of Plitvice Lakes, Croatia

One of the major reasons for the increase in global air temperature since the early 20th century is considered to be the increase in the atmospheric CO2 concentration. Karst relief is considered an important carbon sink, but it can also be a natural source of carbon and CO2 emission. Aquatic systems in karst areas facilitate carbon exchange between the karst and the atmosphere, often through groundwater geochemical carbonate rock dissolution (carbon sink) and in the form of secondary calcium carbonate precipitation (possible carbon source).The protected area of Plitvice Lakes National Park, located in the karst region of Croatia, was chosen as a case study on karst geochemical processes. The lakes are also specific for their authigenic calcite precipitation in the form of tufa barriers and lake sediment. Physical and chemical data (temperature, pH, Ca2+, HCO3−, Mg2+ and CO2 concentrations, calcite saturation index (SIcalc), calcite dissolution ionic ratio (IRcalc), and Mg/Ca ratio) from water samples collected at 8 locations (2 springs, 2 rivers, and 4 lakes) from 1981 to 2014 were studied.The data were not collected systematically, so long-term changes have been mostly assessed through comparison between parameters from two selected periods (1981–1986 and 2010–2014) and through temporal correlations for each observed parameter in each calendar month.For the 33 years studied, an increase in air and water temperature, Ca2+ and HCO3− concentrations, calcite saturation index (SIcalc), calcite dissolution ionic ratio (IRcalc), and a decrease in the Mg/Ca ratio were observed. No statistically significant change was observed for pH or CO2 and Mg2+ concentrations. Average discharge rates did not display any significant change over the past three decades, however there was a change in their seasonal distribution.The significant increase in Ca2+ and HCO3− concentrations at lake locations were primarily caused by an increase in Ca2+ and HCO3− values in the water of the springs. Simultaneously, Mg2+ concentrations remained constant, which indicates higher levels of limestone (calcite) dissolution than dolomite dissolution. One of the reasons for this could be higher air/soil temperatures, resulting in higher soil CO2 production, which appears to result in the higher dissolution of calcite exclusively. An increase in HCO3− concentrations at the springs implies that karst groundwater is a carbon sink. Furthermore, the fact that the spatial decrease in HCO3− concentration in downstream waters was the same during the 1981–1986 and 2010–2014 periods implies that the entire observed karst lake system itself is a carbon sink.Temporal and spatial changes in SIcalc and IRcalc values in surface waters were mainly attributed to an increase in the intensity of bioactivity, which is in turn connected with an increase in water temperature.

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.

Lički i sjevernodalmatinski prostor u kontekstu suvremene regionalizacije Hrvatske

Suvremeni županijski ustroj Republike Hrvatske kao i strateško autocestovno povezivanje hrvatskih regija, posebice srednjeg i južnog dijela jadranskog priobalja kroz lički prostor, određuju nove funkcionalne poveznice središnjeg dijela Jadranske Hrvatske. Nasuprot recidivima nekadašnjih podjela i razgraničenja hrvatskoga prostora od Osmanskog Carstva, Habsburške Monarhije i Mletačke Republike, kraj 20. i početak 21. stoljeća označili su obnovljene procese prometnog, gospodarskog i funkcionalnog povezivanja suvremenoga ličkog i sjevernodalmatinskog prostora, slične nekadašnjim procesima u antici i u razdobljima afirmacije prvotne hrvatske državne jezgre. Izgradnja autoceste unutar Jadransko jonskog koridora, usmjerenost na najbliže priobalno pročelje sa zračnom i pomorskim lukama, povezivanje turističkih kompleksa na potezu Novalja / Karlobag – Nin – Zadar – Biograd – Vodice – Šibenik – Primošten – Rogoznica s plitvičkim turističkim kompleksom, veći broj nacionalnih parkova i parkova prirode, potiču kroz neposredne i lako uočljive društvenogeografske procese novo, pojačano povezivanje. Tome pridonosi i razmjerno jednostavno i spontano prožimanje u sferi trgovine, prometa, bankarstva, uprave, školstva, sudstva, sigurnosti itd., što omogućuje, unatoč pojedinim, politički usmjeravanim ili naslijeđenim rješenjima te lokalnim prijeporima uvjetovanim razlikama i preklapanjima interesnih grupa, svrsishodno i učinkovito suvremeno životno povezivanje u gravitacijski jedinstveni i funkcionalan regionalni kompleks. Značenje postojećih i afirmiranih gravitacijskih središta, među kojima se Zadar kao staro razvojno žarište i čvorište na jadranskom hrvatskom pročelju ističe, od prvorazrednog je značenja, posebice u razdoblju demografske recesije ne samo manjih i ruralnih, nego i većih gradskih središta i ovoga regionalnog kompleksa, ali i čitave Hrvatske. Znanstveno i multidisciplinarno prepoznavanje suvremenih procesa razvitka i prostornih odrednica kod odabira suvremenoga regionalnog ustroja Republike Hrvatske povezano je i sa suvremenim upravnoteritorijalnim, dakle naslijeđenim i tradicionalnim županijskim ustrojem. Jednako je poželjno uskladiti ih i s NUTS regionalizacijom (posebice NUTS-3 razine) Europske unije, što je zahtjevan, ali i neodgodiv zadatak radi ravnomjerne raspodjele egzistencijalnih dobara i uravnoteženog, decentraliziranog i što kvalitetnijeg razvitka ličkog i sjevernodalmatinskog prostora, kao i Hrvatske u cjelini, u budućnosti.

Bifurcation of the Korana River in the Plitvice Lakes National Park, Croatia

Downstream of the Plitvice Lakes National Park, water that pass through the water system of the lakes begins its flow as the Korana River. A few hundred meters downstream of the source zone, during the summer dry periods, there are losses of water in the riverbed resulting in its total drying. The sinking zone in that area is built of high permeable carbonate rocks and with the appearance of less permeable dolomite rocks, about 17 km downstream, the Korana River becomes a permanent river. This paper focuses on the explanation of hydrogeological relations in the zone where losses of water occur in the riverbed, relationship to the neighbouring Una River catchment, as well as possibilities of relocating the source of water supply from the Kozjak Lake (Plitvice Lakes) to the new site in the sinking zone of the Korana River. For this purpose hydrogeological researches were performed, with drilling of several piezometric boreholes and two tracing tests to determine the direction of groundwater flow during the dry season. The results show that during the dry periods in the sinking zone of the Korana River the groundwater level with active aquifer is about 25 m below the riverbed. This opens up the possibility of additional research to solve the problem of water-supply and relocation of water-supply capture in this area. Two tracing tests showed a connection with the Klokot spring (Bosnia and Herzegovina) in the neighbouring Una River catchment, which points to the transboundary character of this aquifer. At the source of the Klokot minimum discharge is around 3 m3/s and the maximum more than 75 m3/s. The capturing of about 60 l/s for water-supply in the Korana River sinking zone will not have impact on the amount of discharge at the Klokot spring. Key words: Dinaric karst, Korana River sinking zone, Plitvice Lakes, tracing test, transboundary aquifer, groundwater capturing. Hidrogeologija ponornega obmocja reke Korane dolvodno od Plitviskih jezer, Hrvaska Dolvodno od Nacionalnega parka Plitviska jezera vode, ki tecejo skozi sistem jezer, oblikujejo reko Korano. Nekaj sto metrov pod to izvirno cono v casu poletnih susnih obdobij voda v strugi ponika in s casom povsem presahne. Ponorno cono gradijo zelo dobro prepustne karbonatne kamnine in sele po prehodu na manj prepustne dolomite približno 17 km nižje po strugi Korana postane stalna reka. V clanku so obravnavane hidrogeoloske razmere v coni ponikanja vode v strugi in odnosi s sosednjim porecjem reke Une, pa tudi možnosti prestavitve vira oskrbe s pitno vodo iz jezera Kozjak (Plitviska jezera) na novo lokacijo v ponorni coni reke Korane. V ta namen so bile izvedene hidrogeoloske raziskave, izvrtanih je bilo vec piezometrskih vrtin in izvedena sta bila dva sledilna poskusa za dolocitev smeri podzemnega toka v casu nizkih vod. Rezultati so pokazali, da je v susnih obdobjih v ponorni coni reke Korane nivo podzemne vode z aktivnim vodonosnikom približno 25 m pod strugo. To odpira možnost dodatnih raziskav za resitev problema oskrbe z vodo in prestavitve zajetja vode na tem obmocju. Oba sledilna poskusa sta dokazala povezavo z izvirom Klokot (Bosna in Hercegovina) v sosednjem porecju reke Une, kar kaže na cezmejni znacaj vodonosnika. Minimalni pretok izvira Klokot je približno 3 m3/s, maksimalni pa vec kot 75 m3/s. Zajetje za oskrbo z vodo v ponorni coni reke Korane z izdatnostjo približno 60 l/s ne bo imelo vpliva na pretok izvira Klokot. Kljucne besede: Dinarski kras, ponorna cona reke Korane, Plitviska jezera, sledilni poskus, cezmejni vodonosnik, zajetje podzemne vode.

Distributional patterns of fecal indicator bacteria in spring area of Plitvice Lakes National park

Background and purpose: Fecal indicator bacteria (FIB) have widespread use as indicators of water quality and health hazards. The purpose of this study was to determine distributional patterns of FIB and to assess their origin on several sites in spring area and in vertical profile of Proscansko Lake in Plitvice Lakes National Park. Materials and Methods: The study was conducted from March to January 2013 on 9 sampling sites. Standard microbiological methods were used to determine densities of total coliforms (TC), fecal coliforms (FC), fecal streptococcus (FS), Pseudomonas aeruginosa (PS) and Clostridium perfringens in water samples. Results and Conclusions: Source area sustained higher densities of FIB compared to Proscansko Lake, throughout the study period. Sampling site White River below the village had highest values of certain FIB, indicating Plitvicki Ljeskovac as main fecal pollution source. There were seasonal differences in TC and FC with July and October displaying increased densities, the latter probably due to heavy rainfall. The ratio FC/FS in July indicated contamination of mainly animal origin. At the sampling site of Matica River estuary in Proscansko Lake, an increased densities of TC and FC bacteria were observed compared to other sites and depths, possibly due to source streams influence and stratification conditions. This study showed that the indicator bacteria of fecal contamination in the spring area of the Plitvice Lakes National Park are present and their quantity and distribution patterns depend on season, weather conditions and different effects in water column of the lake. Keywords : total coliforms, fecal coliforms, FC/FS ratio, Pseudomonas aeruginosa , source streams, lake, protected area

Distributional patterns of fecal indicator bacteria in spring area of Plitvice lakes National park

Background and purpose: Fecal indicator bacteria (FIB) have widespread use as indicators of water quality and health hazards. The purpose of this study was to determine distributional patterns of FIB and to assess their origin on several sites in spring area and in vertical profile of Prošćansko Lake in Plitvice Lakes National Park. Materials and Methods: The study was conducted from March to January 2013 on 9 sampling sites. Standard microbiological methods were used to determine densities of total coliforms (TC), fecal coliforms (FC), fecal streptococcus (FS), Pseudomonas aeruginosa (PS) and Clostridium perfringens in water samples. Results and Conclusions: Source area sustained higher densities of FIB compared to Prošćansko Lake, throughout the study period. Sampling site White River below the village had highest values of certain FIB, indicating Plitvički Ljeskovac as main fecal pollution source. There were seasonal differences in TC and FC with July and October displaying increased densities, the latter probably due to heavy rainfall. The ratio FC/FS in July indicated contamination of mainly animal origin. At the sampling site of Matica River estuary in Prošćansko Lake, an increased densities of TC and FC bacteria were observed compared to other sites and depths, possibly due to source streams influence and stratification conditions. This study showed that the indicator bacteria of fecal contamination in the spring area of the Plitvice Lakes National Park are present and their quantity and distribution patterns depend on season, weather conditions and different effects in water column of the lake. Keywords: total coliforms, fecal coliforms, FC/FS ratio, Pseudomonas aeruginosa, source streams, lake, protected area

Distribution of rotifers and other meiofauna in the bryophytes and hyporheic zone of a karst hydrosystem – an example of a nested community

The meiofauna assemblages inhabiting the bryophyte-covered tufa barriers were investigated in the barrage system of Plitvice Lakes (Croatia). The main aims of the present study were: (1) to analyse the structure of the rotifer community and other meiofaunal communities in the bryophytes and the hyporheic tufa zone; and (2) to determine the influence of food sources on the meiofauna. Our results indicate that meiofauna were a constant and abundant component in bryophytes and tufa. Of the nine identified groups (Catenulida, Gastrotricha, Nematoda, Rotifera, Hydrachnidia, Oligochaeta, Copepoda, Tardigrada and Chironomidae (Diptera)), rotifers (50%) and nematodes (40%) were most abundant. Rotifers were the most diverse meiofaunal group and reached their highest numbers within the bryophytes. Also, the highest amount of ultrafine particulate organic matter, as a potential food source for rotifers, was recorded in this layer. Nematodes were the dominant meiofaunal group in deeper tufa layers. They are an omnivorous trophic group and different food sources (such as phytal remains or other meiofauna) were available in tufa layers. Meiofaunal assemblages were significantly nested and their composition was under the influence of community established in surface bryophyte mats. Information on these often overlooked faunal groups is essential for estimates of overall abundance, species richness and productivity in freshwater ecosystems.

Demographic characteristics of Lika region

The aim of this paper is to review and point out the demographic situation and processes happening in Lika Region (Republic of Croatia) today, as well as to describe the changes in the population structure with particular emphasis on changes in the ethnic structure of the population that have occurred over the past two decades. For centuries, Lika has been inhabited by the population of dual religious structure with different socio-cultural and linguistic characteristics. The area where the diverse population of Lika’s variety lives today is characterized by clear and steady depopulation, changed population structure (age, ethnicity) and changed adiministative and territorial organization. Jovan Cvijic in his Balkan Peninsula and the South Slavic Countries in this group (Lika’s variety) places the population living “between the Velebit mountain on the west and Kapela and Pljesevica on the east”. This is the area of today’s southwestern Croatia, consisting of two towns (Gospic, Otocac) and eight municipalities (Brinje, Donji Lapac, Gracac, Lovinac, Perusic, Plitvice Lakes, Udbina, Vrhovine), belonging to two counties (Lika-Senj, Zadar).

Seiches in the Plitvice Lakes

A campaign of high-frequency measurements of water level was carried in the two largest of the Plitvice Lakes, Prosce and Kozjak, to study seiches in the lakes. Measurements were performed at 1-min sampling rate during a 46-day interval, at two opposite ends in each lake, which also provided information on the phase relations. Power spectra were calculated to determine the periods of the normal modes. The observed peaks in the spectra were interpreted with the help of theoretical results obtained by the simple numerical method of Defant, where two different historical bathymetries were used. The lake Prosce oscillates at the periods of 8.5 min, 5.0 min, 3.3 min and 2.2 min, the oscillations being related respectively to uni-, bi-, three- and five-nodal seiche modes, whereas the four-nodal mode (2.5-2.7 min) was not significant during the experiment. The lake Kozjak oscillates at 9.0 min, 4.9 min and 2.6 min, which corresponds respectively to the uni-, bi- and four-nodal mode, the five-nodal mode is likely at the period of 1.9 min, while the three-nodal mode (~ 3.4 min) was not generated ; the deeper sub-basin displays its own principal mode at the period of 2.3 min. The discrepancy between the observed and the calculated periods is attributed to poor representation of the basin by the historical bathymetries, especially at Prosce, but also to changes in basin depth, due to continuous process of tufa growth.

The impact of multiple anthropogenic contaminants on the terrestrial environment of the Plitvice Lakes National Park, Croatia.

The anthropogenic impact on the terrestrial environment of the Plitvice Lakes National Park (PLNP) was investigated through the analysis of three groups of major contaminants (persistent organochlorine pollutants including 15 organochlorine pesticides (OCPs) and 17 polychlorinated biphenyls (PCBs), trace elements/heavy metals (6 major and 23 trace constituents), and anthropogenic radionuclides ((90)Sr, (134)Cs, and (137)Cs)) in three terrestrial compartments (soil, air, and bioindicators of air contamination) during 2011-2013. The correlation coefficients of element mass fractions with soil properties indicated that total Fe and Al minerals, soil organic matter (OM), and organic carbon (OC) content affected the mass fractions of most trace elements in the topsoils. The annual and spatial distributions of heavy metals in total deposited matter (TDM) indicated that the metals came from natural sources and long-range transfer of particulate matter. The PCB and OCP levels found in soil and conifer needles corresponded to global environmental pollution levels by persistent organic pollutants and represented the lower end of the mass fraction ranges reported in the relevant literature. Analyses of anthropogenic radionuclides in bioindicators (conifer needles, lichens, and mosses) showed low but measurable activity concentrations of (134)Cs (for the first time after the Chernobyl accident), which indicated origin from the March 2011 Fukushima Nuclear Power Plant accident. Our overall results indicated that human activity inside or near the PLNP had no significant impact either on contaminant spread by air or on their content in topsoils.

Isotope analyses of the lake sediments in the Plitvice Lakes, Croatia

Abstract The analyses of radioactive isotopes 14C, 137Cs and 210Pb, and stable isotope 13C were performed in the sediment cores, top 40 cm, taken in 2011 from karst lakes Prošće and Kozjak in the Plitvice Lakes National Park, central Croatia. Frozen sediment cores were cut into 1 cm thick layers and dried. 14C activity in both carbonate and organic fractions was measured using accelerator mass spectrometry technique with graphite synthesis. 137Cs, 210Pb, 214Pb and 214Bi were measured by low level gamma spectrometry method on ORTECHPGe detector with the efficiency of 32%. Distribution of 14C activity from both lakes showed increase of the 14C activity in the top 10–12 cm in both carbonate and organic fractions as a response to thermonuclear bomb-produced 14C in the atmosphere in the sixties of the 20th century. Anthropogenically produced 137Cs was also observed in sediment profiles. Sedimentation rates for both lake sediments were estimated based on the unsupported 210Pb activity. Different 14C activity of the carbonate fraction (63–80 pMC, percent of modern carbon) and organic fraction (82–93 pMC) is the result of geochemical and biological processes of the sediment precipitation in the lake waters. This is also confirmed by the δ 13 C values of both fractions. Carbon isotope composition, a 14 C and δ 13 C, was compared with the lake sediments from the same lakes collected in 1989 and 2003.

Morpho-functional classifications of phytoplankton assemblages of two deep karstic lakes

Morpho-functional classifications of phytoplankton are increasingly used in ecological studies of different aquatic ecosystems. The aim was to compare three different classifications: (a) functional groups (FG); (b) morpho-functional groups (MFG); and (c) morphologically based functional groups (MBFG), and to detect how well can the biomass of phytoplankton groups based on different classifications be explained by environmental conditions of two different karstic lakes in the National Park Plitvice Lakes. Phytoplankton biomass in Lake Kozjak was lower than in Lake Prosce (total avg. 1.13 and 2.59 mg l−1, respectively). Several diatoms (Cyclotella spp., Discostella stelligera, Synedra sp., Ulnaria ulna var. acus) with Dinobryon divergens were dominant in Kozjak, while Prosce was characterized by Dinobryon sociale, D. divergens, Cryptomonas sp., Stephanodiscus sp. and Fragilaria crotonensis. The best results in describing the phytoplankton succession were obtained using MBFG approach although it is less sensitive in describing variability of individual descriptive algal groups in this environment than FG and MFG. Nonetheless, because of distinct differences among dominant phytoplankton groups in these systems, MBFG classification was shown to be applicable, as supported by statistical analyses. FG and MFG classifications showed a high level of similarity, thus proving to be applicable to deep karstic lakes.

Natural Regeneration of Beech Forests in the Strict Protected Area of the Plitvice Lakes National Park

Natural Regeneration of Beech Forests in the Strict Protected Area of the Plitvice Lakes National Park

First record of Diamesa thomasi Serra-Tosio, 1970, from Croatia

Plitvice National Park is situated in the mountainous karst area of Croatia. When conducting studies of the chironomid fauna of the park, we found that Diamesa thomasi Serra-Tosio, 1970 were abundant in the stream Bjela rijeka. The streams Bijela rijeka and Crna rijeka form the Matica River, which is the main surface-water supplier of the lakes in the park. This is the first record of D. thomasi in Croatia. The river’s source, the Bijela rijeka spring, is located at an altitude of 719 m a.s.l. at 44°50’05” N and 15°33’43” E. The Bijela rijeka spring is a rheocrene that dries out only during extremely dry years (Marusic & Curuvija 1991). Spring water emerges from substrate composed mainly of cobbles and sand with a few interspersed moss-covered boulders. Because of these characteristics, it is considered a psammorheocrene type of spring (Gerecke et al. 1998). The tree canopy is open during spring, and there is much aquatic vegetation and accumulated allochthonous organic material during autumn and winter.

Heavy metal contents in water, sediment and fish in a karst aquatic ecosystem of the Plitvice Lakes National Park (Croatia)

An evaluation of the quality status of the pristine karst, tufa depositing aquatic environment of the Plitvice Lakes National Park based on the analysis of heavy (ecotoxic) metals was examined for the first time. Analyses of trace metals in water, sediment and fish (Salmo trutta, Oncorhynchus mykiss, Squalius cephalus) samples were conducted either by stripping voltammetry (Zn, Cd, Pb and Cu) or cold vapour atomic absorption spectrometry (Hg). The concentration of dissolved trace metals in water was very low revealing a pristine aquatic environment (averages were, in ng/L: 258 (Zn), 10.9 (Cd), 11.7 (Pb), 115 (Cu) and 1.22 (Hg)). Slightly enhanced concentrations of Cd (up to 50 ng/L) and Zn (up to 900 ng/L) were found in two main water springs and are considered as of natural origin. Observed downstream decrease in concentration of Cd, Zn and Cu in both water and sediments is a consequence of the self-purification process governed by the formation and settling of authigenic calcite. Anthropogenic pressure was spotted only in the Kozjak Lake: Hg concentrations in sediments were found to be up to four times higher than the baseline value, while at two locations, Pb concentrations exceeded even a probable effect concentration. The increase of Hg and Pb was not reflected on their levels in the fish tissues; however, significant correlations were found between Cd level in fish tissues (liver and muscle) and in the water/sediment compartments, while only partial correlations were estimated for Zn and Cu. A high discrepancy between values of potentially bioavailable metal fraction estimated by different modelling programs/models raised the question about the usefulness of these data as a parameter in understanding/relating the metal uptake and their levels in aquatic organism. The aquatic environment of the Plitvice Lakes National Park is characterized, in general, as a clean ecosystem.

Sources, Distribution and Behavior of Major and Trace Elements in a Complex Karst Lake System

Sources and distribution of major and trace elements were investigated in the Plitvice Lakes, a pristine cascade hydrological system of sixteen karst lakes situated in a sparsely populated area of the central Croatia. Water and surface sediment samples from 17 locations, including springs, tributaries and lakes, were analyzed for the content of 22 elements by high-resolution inductively coupled mass spectrometry. Principal component analysis of the collected data set showed that different springs and tributaries displayed distinct multielemental compositions, reflecting primarily the differences in their corresponding geological backgrounds. It was shown that the springs situated in the Upper and Middle Jurassic dolomite bedrock represented the main source of several trace elements, including some toxic metals (Cd, Zn, Ni and Tl), to the Plitvice Lakes system. The concentrations of most of the trace elements (Mn, Fe, Al, Cd, Zn, Cu, Ni, Pb, Co, Cr and Tl) showed decreasing spatial trends in the downstream direction, from sources to the lakes. Such a distribution was interpreted to be a consequence of an efficient removal of the dissolved elements in the lentic parts of the system, mainly by co-precipitation with authigenic calcite and Mn oxides. Nevertheless, most of the elements in the lake sediments were highly correlated with Al, which indicated their prevalent association with terrigenic material. It was shown that the multicascade system of the Plitvice Lakes had an enhanced autopurification efficiency regarding the elimination of most of the trace metals from the aqueous phase.