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Vrana Lake near Biograd na Moru is a karst field filled with water and is the largest natural lake in Croatia, connected to the sea by a channel. It was declared as a Nature park in 1999, mostly because of the ornithological reserve in its area. Zooplankton plays a significant role in lake ecosystems, especially in determining the ecological status of lakes. The goals of the research were: (i) to determine the abundance, biomass and diversity of zooplankton ; (ii) to study the impact of biotic and abiotic factors on zooplankton dynamics ; (iii) to study the impact of fish predation on zooplankton dynamics. In the two years period (2018 and 2019), zooplankton samples were taken at three longitudinal stations. In order to analyze the dynamics of zooplankton several abiotic and biotic factors were observed: temperature, oxygen, conductivity, salinity, ph, transparency, nutrients, chlorophyll a, and fish predation. The research revealed a significant influence of temperature, salinity, dissolved oxygen, transparency as well as significant influence of ichthyofauna on the structure and dynamics of zooplankton. This study of planktonic zooplankton will provide insight into the trophic state of the lake, which will enable the determination of guidelines for further management of Vrana Lake and protection of this valuable and important habitat.

The aim of this study was to determine microcrustacean secondary production (P/B) and a herbivory ratio (ZB:PB) in the River Danube and a floodplain lake to reveal models in plankton food web functioning. P/B was used to assess population variation under different environmental conditions, while ZB:PB provided information on the zooplankton grazing intensity on algae. Seasonal changes, displayed by the hydrological regime, i.e., related water level fluctuation, were expected to explain different plankton patterns between the study sites as a result of unlike community composition and food quality. The structural equation modelling we used identified specific pathways of measured indexes at the individual localities. Although the direct impact of water level fluctuation on the studied communities was low, the following difference in abiotic components might have caused shifts in zooplankton assemblages that changed P/B and ZB:PB ratios. In the floodplain lake, P/B was primarily influenced by biotic components, and herbivory alteration was expressed through top-down control. On the contrary, P/B in the riverine system was controlled by an environmental element and herbivory was driven by the bottom-up resources. The results show the usefulness of the studied indexes in determining variations of zooplankton functional processes in the hydrologically dynamic environments.

In the pelagic food web of lakes, zooplankton offers the linkage between phytoplankton and fish, greatly affecting but also mirroring the functionality and stability of the ecosystem. Despite the increased interest on the development of water quality indices, incorporating zooplankton data on metrics used for the assessment of natural lakes remains a challenge. Here, we used information of natural lakes hosted in Eastern Mediterranean on zooplankton abundance, biomass, body weight and cladocerans' ratio to develop a novel zooplanktonic index (Zoo-IQ). Α 5- grade classification scheme was generated (Bad ≤6, 6 < Poor ≤10, 10 < Moderate ≤14, 14 < Good ≤18, 18 < High) for water quality assessment. The Zoo-IQ was originally parametrized based on data collected from 13 natural lakes, located in Greece and successfully classified hypertrophic lakes with poor quality and deep lakes with good quality, while it identified lakes subjected to restoration actions. Using independent data from five lakes hosted in Greece, Turkey and Croatia, Zoo-IQ successfully assessed their water quality. Specifically, from the 25 sampling cases, used for the development and the evaluation of the index, Zoo-IQ identified 5 as good, 8 as moderate, 11 as poor and 1 as bad. Our results demonstrate the potential of using Zoo-IQ for the assessment of lakes water quality in the Mediterranean. The proposed index could serve as a first step towards the development of similar indices in other climatic zones.

Here we present a first record of Baetis vardarensis Ikonomov, 1962 in Croatian freshwater habitats. The species was collected in February and March 2020 at two sites in the Sava River. With this record, Croatian mayfly species richness increased to a total of 85 species. In addition, one of the species previously known only from literature, Kageronia fuscogrisea (Retzius, 1783), was confirmed in Croatia. The species was collected in the Rečica River, in March 2020. These results confirm that our knowledge about mayfly fauna in different regions of Balkan Peninsula is still incomplete and is increasing with systematic studies.

Temporary rivers are dynamic freshwater ecosystems, supporting unique and often highly diverse terrestrial communities in the riparian habitats during the flowing phase. However, studies investigating the differences in orthopteran and cockroach (Insecta: Orthoptera, Blattodea) assemblages between riparian and adjacent upland habitats are scarce, despite their abundance and functional importance in terrestrial ecosystems. Orthopterans and cockroaches were sampled in 2014 at 72 sites along the temporary Krcic River (SE Croatia) in two habitat types—riparian and karst, using pitfall traps. Abundance, taxa richness, true diversity and conservation value of ground-dwelling orthopterans and cockroaches were significantly higher in the karst than in the riparian habitat. This result can be ascribed to significant differences in environmental factors: soil temperature, air humidity and vegetation structure, namely tree, shrub and herb layer abundances. Most assemblage parameters and spatial distribution of ground-dwelling orthopteran and cockroach taxa were driven by higher soil temperature and less developed tree layer in the karst, both groups preferring open habitats. Karst sites with a well-developed shrub layer and herb layer had the highest conservation value for rare ground-dwelling orthopterans (e.g. Paramogoplistes novaki) and locally rare cockroaches (e.g. Ectobius balcani), respectively. Nevertheless, densely vegetated riparian sites also harboured some locally valuable species (e.g. Troglophilus cavicola). This study highlights the importance of open karst habitats in promoting the diversity of ground-dwelling orthopterans and cockroaches, and contributes to the understanding of key environmental factors driving their habitat choice, as a prerequisite for efficient conservation and monitoring.

Microcrustacean species (Cladocera, Copepoda) as a significant component of the plankton assembly play diverse roles in floodplain ecosystems and cope with the heterogenic environment differently. Since alterations in the hydro regime are considered disturbance events for zooplankton development, we assessed whether and to what extent are Cladocera and Copepoda exposed to disturbances caused by hydro regime alterations in a floodplain lake. To evaluate the disturbance levels for individual microcrustacean assemblage in different water layers and between different hydrological phases, we applied the abundance/biomass comparison (ABC) method. Recorded microcrustacean assemblages highly depended on the hydrological state of the waterbody and diverged accordingly. Cladocera demonstrated to be more sensitive to change in specific environmental parameters like conductivity, temperature and transparency, while Copepoda exhibited no limitation by ecological variables. Although both groups were influenced by the bottom–up and top–down control, different disturbance intensity was recorded for the individual microcrustacean class. An undisturbed condition during isolation of the Lake allowed Cladocera to reach equilibrium while both microcrustacean groups exhibited moderate to high levels of disturbance following inundation. Regarding disturbance intensity, Cladocera expressed a weak distinction following hydro regime and water layer replacement. On the other hand, Copepoda disturbance levels notably depended on the position in the water column within a specific hydrological phase. Results of the ABC analyses gave a good representation of a real community dispersal in the studied Lake. However, more research is needed to re-evaluate here given levels of disturbance properly.

Two calanoid species,Arctodiaptomus laticeps(Sars, 1863) andEurytemora velox(Lilljeborg, 1853), are reported from the Danube River basin in Croatia. Our findings present the first record ofA. laticepsandE. veloxat the territory of Croatia. Both species were found in the lowland floodplain area during the spring-summer inundation throughout the years. Their occurrence in the waterbodies studied has not overlapped, and different environmental parameters characterized the periods of occurrence of the individual species. The existence ofE. veloxin this region seems to be permanent, whereas the appearance ofA. laticepsis rather confounding.

Predation is a biotic interaction that links water mites to different taxonomic groups of benthic invertebrates. Diptera larvae (Chironomidae) and microcrustaceans (Cladocera, Copepoda, Ostracoda) are known to be the most commonly preferred prey by water mites. Although these predatory interactions are known from observations and ex situ investigations, the distribution patterns and co-occurrence of water mites and their prey in littoral lentic habitats have been poorly studied. Our goal was to determine whether predation might serve as a significant factor in water mite assemblage composition and distribution. Samples were taken from littoral zones of 21 artificial lakes (reservoirs) in the Dinaric Western Balkan ecoregion of Croatia. At every site, 10 samples were collected with regard to shore slope in depth zones of up to 1 m. In total 490 samples were collected from April 2016 to July 2017. Data analysis showed that the spatial distribution of water mites was partially correlated with the environmental parameters we measured (explaining 45.1% of total water mite variation). A positive correlation between water mite abundance and diversity and depth gradient (favouring more stable conditions in deeper parts of the littoral zone) was also observed. Finally, water mite abundance and species richness variation were found to be best predicted by the abundance of potential prey groups. Predation was statistically determined to be a strong dispersion variable, most probably influencing both spatial distribution and composition of water mite assemblages.

Dissimilar life features of Rotifera, Cladocera and Copepoda enable these organisms to respond differently to changes in the hydrological regime which influence alterations in environmental characteristics. We investigated the effect of habitat heterogeneity (e.g. eupotamal, parapotamal, palaeopotamal) on individual zooplankton group assemblages and biodiversity indices (α, β and γ diversity) during hydro regime change in floodplain waterbodies. Dissolved oxygen and organic nitrogen concentrations changed significantly among hydrological states while water depth was affected by both site and hydro regime replacement. Each studied site supported different zooplankton assemblage that highly depended on species-specific responses to hydro regime change. Also, individual zooplankton groups exhibited different correlations with specific environmental parameters regarding site change. Throughout the study, rotifers′ local (α) and among- community (β) diversities were susceptible to the site and inundation change while the microcrustacean biodiversity pattern diverged. Copepods highly discriminated different habitat types and hydrological phases at the regional scale (γ diversity), while we found a complete lack of biodiversity dependence on both site and hydrology for Cladocera. Our results show that heterogeneous environments support the development of different zooplankton assemblages that express the within-group dissimilarities. They also point to the importance of identifying processes in hydrologically variable ecosystems that influence biodiversity patterns at an individual zooplankton group level. Our results suggest the use of appropriate zooplankton groups as biological markers in natural habitats and stress the importance of proper management in preserving biodiversity in floodplain areas.

Water mites are predators on microcrustations (Copepoda, Cladocera, Ostracoda) and insect larvae (mostly Diptera). Their communities usually have great diversity with high species richness but relatively low abundance. This may have important implications for poorly investigated predator-prey interactions of water mites in natural habitats. A sublacustrine karst spring Torak and the mouth of its tributary river Cikola were examined seasonally from August 2016 to June 2017, with the aim of determining water mite distribution connected to prey availability. Triplicate samples were taken with an Ekman dredge on three distinct depth zones (littoral, sublittoral and profundal zone) at both study sites. Both, the karst spring and the tributary river, had typical lentic water mite communities with no rhithrobiont or crenobiont taxa present. Water mite species richness, abundance and alpha diversity were not governed by depth, but rather by prey availability. Greater copepod, ceratopogonid and chironomid abundances were found to positively correlate with higher abundances of water mites. The population of Limnesia connata, previously reported from lime-poor waters exclusively, was most probably supported by vast prey availability, thus unexpectedly surviving in this karst environment. L. connata, Neumania vernalis and Piona longipalpis were recorded for the first time in Croatia, while L. connata was recorded for the first time in the Dinaric karst.

Peat bogs are highly endangered ecosystems worldwide. In the Western Balkans, they represent fragmented habitat patches, where insect diversity and implications for the habitat loss are poorly known. Carabid beetles and ants, widely used environmental indicators, were sampled by pitfall trapping in the largest and oldest Croatian peat bog and at its edges. We found that tyrphobiontic—bog specialist—species were absent in both taxonomic groups, which is likely due to biogeographical limitation for dispersal of these species into this region. With this study, tyrphophilous—typical of bogs—species have been recognised as environmental indicators in the Western Balkans peat bogs. Assemblages of both taxa were strongly affected by specific conditions in the peat bog – high soil moisture and Sphagnum moss dominance, showing that edges are more favourable habitats for both taxa. Overall, carabid beetle activity density was significantly higher at the edge than at the peat bog, while species richness increased for both taxa at the edge, but not significantly. Spatial distribution of tyrphophilous species differed between studied taxa, with ants being more abundant in the peat bog, and carabid beetles at the edge. Additionally, some stenotopic and globally endangered species preferred edges. Occurrence of tyrphophilous and globally endangered species highlights the great conservation value of peat bog habitats in the Western Balkans. However, successional changes in vegetation are changing hydrological conditions of the peat bog. Here we suggest active conservation measures to preserve these unique soil invertebrate zoocoenoses.

Istraživanja zooplanktona na području Parka prirode Kopački rit provođena su rijetko tijekom druge polovice 20. stoljeća. Većina se istraživanja bavila proučavanjem samo jedne skupine, bez prikupljanja većeg broja podataka i istovremenog istraživanja glavnih skupina zooplanktona. Od 2007. godine do danas provodi se kontinuirano istaživanje zooplanktona (Rotifera, Cladocera, Copepoda) u različitim vodenim tijelima Kopačkog rita i glavnome toku Dunava mjesečnom dinamikom. Cilj dugoročnog monitoringa je utvrditi povezanost promjene godišnjih doba i sastava zajednice zooplanktona te utvrditi utjecaj različitih lokaliteta u definiranju strukture zajednice. Također, posebna je pozornost posvećena proučavanju utjecaja hidrologije na razvoj zajednice zooplanktona. Rezultati su pokazali da su vodena tijela unutar poplavnog područja pogodna mjesta za razvoj svih skupina zooplanktona. Suprotno tomu, glavni tok rijeke Dunav pogodan je za razvoj samo kolnjaka i juvenilnih stadija planktonskih rakova koji postižu znatno manju brojnost u usporedbi s vodenim tijelima unutar poplavnog područja. Dugoročno istraživanje područja potvrdilo je da su kolnjaci najbrojnija skupina zooplanktona na području Kopačkog rita tijekom svih godišnjih doba i hidroloških faza. Ipak, različiti lokaliteti unutar poplavnog područja (kao što su jezera i kanali) podržavaju različite zajednice zooplanktona, čak i pri istome vremenu uzorkovanja. Sastav zajednice kolnjaka mijenja su učestalo tijekom izmjene hidroloških faza te se može prilagoditi novim uvjetima okoliša na svim lokalitetima. Za razliku od kolnjaka, veslonošci su iznimno selektivni u odabiru poželjnog okoliša te se ne razvijaju na pojedinim lokalitetima. Tijekom desetogodišnjeg istraživanja utvrđene su dvije nove vrste veslonožaca za faunu Hrvatske: Arctodiaptomus laticeps (Sars, 1863) i Eurytemora velox (Lilljeborg, 1853). Također su pronađene i dvije nove vrste veslonožaca na području hrvatskog dijela Panonske regije: Paracyclops fimbriatus (Fischer, 1853) i Macrocyclops albidus (Jurine, 1820). Dugogodišnje istraživanje pokazalo je da sastav zajednice te odnos pojedinih skupina zooplanktona može ukazivati na trofičko stanje vodenog tijela te može služiti kao pokazatelj njegova ekološkoga stanja.

False indigo (Amorpha fruticosa L.) is an invasive exotic plant introduced to Europe in the early 18th century. Its spread has been rapid, particularly in disturbed wetland habitats, where it forms dense impermeable monospecific stands and modifies habitat conditions. The impact of Amorpha fruticosa on native plant communities has been well analyzed, however knowledge concerning the possible effects on soil invertebrates and particularly carabid beetles is completely lacking. This study analyzed the impact of an Amorpha fruticosa invasion on carabid beetles and other soil invertebrates. Soil fauna was sampled by pitfall traps at natural habitats, initially colonized by Amorpha fruticosa, and habitats largely invaded by Amorpha fruticosa. In total 2, 613 carabid beetles belonging to 50 species and 72, 166 soil invertebrates were collected. The invasion of Amorpha fruticosa strongly affected the carabid beetle species composition, which clearly differed between all studied sites. Widespread euritopic carabid beetle species showed positive responses to Amorpha fruticosa invasion, while the activity density of open habitat species strongly declined. Mean individual biomass was significantly higher at invaded sites due to increased incidence of large carabids (genus Carabus Linné, 1758). Carabid beetle activity density and abundance of soil invertebrates were considerably higher at invaded sites than in natural sites. Conversely, the impact of Amorpha fruticosa on carabid beetle species richness and diversity was less pronounced, most likely due to immigration from adjacent habitats. Changes in carabid beetle species composition and abundance of soil invertebrates were most likely due to changes in vegetation structure and microclimate. The results suggest that Amorpha fruticosa invasion considerably affected carabid beetles, an insect group that is only indirectly related to plant composition. Therefore, severe future changes can be expected in invertebrate groups that are closely related to plant composition, since Amorpha fruticosa cannot be completely removed from the habitat and covers relatively large areas.

Peat bogs are unique wetland ecosystems of high conservation value all over the world, yet data on the macroinvertebrates (including mayfly assemblages) in these habitats are still scarce. Over the course of one growing season, mayfly assemblages were sampled each month, along with other macroinvertebrates, in the largest and oldest Croatian peat bog and an adjacent stream. In total, ten mayfly species were recorded: two species in low abundance in the peat bog, and nine species in significantly higher abundance in the stream. Low species richness and abundance in the peat bog were most likely related to the harsh environmental conditions and mayfly habitat preferences. In comparison, due to the more favourable habitat conditions, higher species richness and abundance were observed in the nearby stream. Three of the recorded species, Caenis luctuosa from the peat bog, and Eurylophella karelica and Leptophlebia marginata from the stream are new records for the Croatian mayfly fauna. Typical Central European life cycle patterns were confirmed for several species (e.g. Baetis vernus, Nigrobaetis niger, Electrogena ujhelyii), while for several others (e.g. Habrophlebia fusca, Paraleptophlebia submarginata) some discrepancies were observed. Therefore, these results provide new and valuable information on the ecology of mayflies in peat bog habitats.

To estimate the impacts of an Al-contaminated aquatic environment on DNA integrity in the blood cells of eastern mosquitofish Gambusia holbrooki Girard 1859 inhabiting Lake Njivice (Island of Krk, Croatia), an evaluation using the alkaline comet assay was carried out. Genome integrity was studied in parallel with the same fish species inhabiting the nearby, unpolluted Lake Ponikve. The amount of DNA damage in cells was estimated from three different parameters: comet tail length as the extent of genetic material migration, tail intensity (% DNA in the comet tail) and tail moment. The results indicate the loss of genome integrity in blood cells of mosquitofish inhabiting Lake Njivice and the genotoxicity of this aquatic environment. Using the same assay, acute genotoxicity of contaminated water and sediment was evaluated and confirmed on fish, mouse and human blood cells treated ex vivo. Results of the present study indicate that the alkaline comet assay applied to fish blood cells is a valuable tool for determining the potential genotoxicity of water pollutants and confirm its usefulness in the evaluation of DNA damage in fish living in Al-polluted waters.

In this pilot study, we evaluated the usefulness of the alkaline comet assay as a biomonitoring tool at the level of plankton communities affected by varying water quality. Zooplankton was collected in autumn 2007 and spring 2008 in two shallow lakes, one being predominantly polluted with aluminium compounds as result of water treatment process (Lake Njivice ; 45°10′ N, 14°30′ E) and the other unpolluted (Lake Ponikve ; 45°05′ N, 14°30′ E) used as control. Water and sediment chemistry parameters were assessed at both lake sampling sites. The results indicated that the main pollutant in both matrices was aluminium, whose concentrations exceeded the value of 0.15 mg/L− 1 legally accepted for drinking water by Croatian water quality regulations. Plankton composition of the investigated lakes showed that only a few species are dominant and appear at both sites. Cladocerans are represented by Daphnia magna Straus 1820, and copepods by the calanoid Eudiaptomus padanus etruscus (Losito 1901), the cyclopoid Cyclops sp. and dipterans by larvae of Chaoborus flavicans (Meigen 1830). Other species were determined only occasionally and with low abundance. As observed, the comet assay had adequate sensitivity to detect the differences in levels of DNA damage among the dominant zooplankton taxa. Zooplanktons collected in Lake Njivice show a lower degree of DNA integrity compared with animals from the reference lake (Lake Ponikve). Inter-species variability in DNA damage was observed, indicating different genome susceptibility to the same genotoxic pollutants present in the aquatic environment. Furthermore, in the polluted Lake Njivice, seasonal differences in the levels of DNA damage within particular species of zooplankton were also noted. Calanoida, Daphnia and Chaoborus mainly had higher values of all three comet parameters in autumn 2007 than in spring 2008. Feeding modes strongly influenced the level of DNA damage in zooplankton species studied. We assume that the mechanisms of DNA damage and genotoxicity, as detected in the present comet assay study, were similar as those described in previous studies dealing with pollution by toxic metals. Although it was a preliminary study, obtained results confirmed the high sensitivity of the comet assay for the detection of DNA damage in cells of zooplankton organisms. The alkaline comet assay on simple aquatic organisms, as confirmed here, might represent an additional parameter useful in environmental risk assessment, especially in cases when other bioindicator species are very scarce or absent.

The freshwater, free-living copepod fauna of Croatia has been sporadically investigated during last two hundred years. The first investigations were carried out by Sostanc (1888, 1899), Car (1901, 1902, 1906, 1911) and Krmpotic (1913a & b, 1914, 1924). Since then, Petkovski (1954, 1955, 1956, 1961, 1978, 1983), from Macedonia, has made significant contributions to the knowledge of copepod systematics and taxonomy, including the description of new species from Croatia. Sket (1986, 1988, 1994) and Brancelj (1991, 2001) from Slovenia have undertaken research on subterranean copepod species, while several Croatian scientists have also contributed to the knowledge of the copepod fauna (e.g. Matonickin & Pavletic 1967 ; Matonickin 1971 ; Misetic 1975, 1990a & b, 1992, 1993, 1995a & b ; Vrebcevic 1988, 1989, 1990, 1991a & b, 1992 ; Primc-Habdija 1982, 1993, 1995). The present paper is based on detailed analysis of all publications on Copepoda known to the authors, as well as personal communications. The first author has also contributed additional records, related to the distribution of Croatian copepods, which resulted from research conducted in the last decade (Bukvic 1996, 1998a & b ; Bukvic et al. 1997, 1998, 1999 ; Bukvic-Ternjej 2001 ; Terajej 1999, 1999/2000, 2001, 2002a & b, 2004 ; Ternjej & Tomec 2005 ; Tomec & Ternjej et al. 2002).

This paper reports on new distribution records of groundwater crustaceans for anchihaline habitats of the Kornati islands and presents observations on the frequency of the crustacean community. Research was conducted during September 2001 and 2003 in nine caves and two wells. Based on literature data and own research, a total of 33 crustacean taxa were determined, distributed in seven orders, 11 families and 15 genera. Our collections include four copepod species recorded for the first time for the Kornati islands, of which one species was also new for Croatia. Stygobiotic species make up 45% of the total crustacean fauna recorded at the researched localities. Most of the anchihaline crustaceans studied here are members of the order Cyclopoida. The most widespread species was Niphargus hebereri and the richest genus was Diacyclops. Vertical salinity gradients determine spatial distribution patterns of stygobiont crustaceans. The species richness of crustaceans here is strongly dependent on habitat morphology as well as on abiotic factors (e.g. salinity) and food supply. Crustacean diversity was higher in caves with steep salinity gradient. Records of crustacean species are listed with notes on their patterns of coexistence.

New records are provided for Limoniidae and Pediciidae from Croatia, with new distribution records for species in 12 different genera. Four genera and 18 species are newly recorded for Croatia. Until now, including this data, 87 Limoniidae and eight Pediciidae have been recorded from Croatia. In this paper we confirm presence of Ormosia (Oreophila) bergrothi (Strobl, 1895) and we give the first records of Dicranota (Paradicranota) pavida (Haliday, 1833) and Molophilus (Molophilus) repentinus Starý, 1971 from Balkan Peninsula.

The paper presents different morphological changes between two forms of C. hirundinella in shallow karstic Mediterranean lakes, Ponikve and Njivice. Both lakes are situated on the island of Krk, Northern Adriatic See. Trophic state parameters (chlorophyll a, phytoplankton biomass, species composition) as physical and chemical features (temperature, Secchi depth, pH, conductivity, oxygen, nitrates, nitrites, ammonium, phosphates) were measured during 1997/98. and 2000/01. Net samples were taken at one vertical profile at each lake. C. hirundinella f. gracile was presented during the whole investigated period in Lake Njivice. The same species was dominant in Ponikve Lake during 1997/98., while in 2000/01. strong develop of C. hirundinella f. austriacum was occurred. C. hirundinella f. austriacum was restricted to spring-summer time. Spring populations of Ceratium hirundinella f. austriacum showed larger variations in number of horns. It occurred as a formtype with five horns as well as a formtype without an antapical horn. C. hirundinella f. gracile showed a slight reduction and variation of the fourth horn through the changing seasons. An analysis of morphometric measurements between the samples showed the significant differences in length, width and V3 angle.

Pterostichus rhaeticus is widely distributed in northern and central Europe and has now been recorded for the first time in Croatia, and this record represents its southeasternmost distribution point. This species was only recently separated from the very common and widespread Pterostichus nigrita Paykull, 1790. These two sibling species differ in a few morphological features and can be certainly distinguished by the form of male and female genitalia. Therefore, we measured a few morphometric features, e.g. body length, elytrae length and width, male right paramere and female eighth abdominal sternite. In general, P. rhaeticus is significantly smaller and narrower than P. nigrita. However, in mixed populations, the differences in body size, length and width of elytrae were not observed and the overlap in sizes is considerable. Additionally, we noticed that the range edge individuals of P. rhaeticus are larger compared to individuals in central Europe. Most of the individuals of both species can be clearly and immediately identified by the shape of their genitalia, but in mixed populations these differences are possibly not so obvious, and measurements are necessary. P. rhaeticus is a tyrphophilous species that was exclusively found at three peatlands in Croatia. It was found in the open peat bog centre and adjacent shaded habitats, in both acidic peaty and alkaline soils with high soil humidity. According to present knowledge, this species can be considered an indicator species of peatland habitats in Croatia. These distinctive habitats are highly endangered in the Western Balkans, and therefore the survival of this and other bog-specific species depends on active conservation and protection measures.

The aim of our study was to investigate how exposure to heavy metal-rich waters from gypsum mining affects the morphology and levels of primary DNA damage in Gammarus balcanicus. Chemical analysis revealed increased concentrations of metals in water and sediment collected at a site impacted by gypsum mine wastewaters. The specimens also showed elevated total tissue metal levels when compared with the organisms collected at the reference site. The most prominent increase was observed for strontium, followed by iron, nickel, vanadium, aluminium, and manganese. The major pathway of entry for these toxic substances was through the degraded exoskeleton as a consequence of excessive strontium input (unbalanced calcium/strontium ratio) and altered permeability. Disturbed exoskeleton integrity was observed only in individuals collected downstream of the gypsum mine, which was confirmed by electron microscopy. Levels of primary DNA damage were evaluated using the alkaline comet assay in the haemolymph of the specimens.

Man-made activities such as mining generate certain amounts of metal contaminated wastes which can reach aquatic environment and cause the serious effects on different organisms and ecosystem. Chemical analysis of the environmental samples is the most direct approach to reveal their pollution status but it cannot always provide information on biological effects to different organisms, including fish. This study was aimed to investigate the in vitro cytotoxicity and genotoxicity of water and sediment samples from gypsum mining area using the channel catfish ovary (CCO) cell line. Results obtained by the WST-1 assay and alkaline comet assay revealed that exposure of CCO cells to the same concentrations of contaminated water and sediment samples caused significant decrease in cell viability and increased DNA damages. Chemical analysis of water and sediment samples showed that increased concentrations of strontium, aluminum and iron were mainly responsible for the observed cytotoxic and genotoxic effects in CCO cells. The study suggested that fish CCO cells could be useful biological test-system for water and sediment cytotoxicity and genotoxicity assessments.

In the framework of our research, this study was focused on crustaceans in the anchihaline caves along the Eastern Adriatic coast. From August 2002 to June 2006 we collected 99 samples in 39 anchihaline caves. A total of 33 crustacean taxa were identified. Affinities were found in the rare, endemic or ecologically restricted crustaceans recorded in fewer than 10 caves, belonging to copepods, isopods and amphipods. A high species richness was recorded in the Central Adriatic threshold and the South Adriatic Basin. Stratified caves rich in organic matter or even heavy metals had the highest species richness. The cave Medvjeđa špilja on Lošinj Island was detected as a hot spot with 12 recorded taxa.

The aim of present study was to investigate how the exposure to sulfate-rich surface waters affects the levels of primary DNA damage in haemocytes of leech Hirudo medicinalis. Samples of surface water were collected at two sites near gypsum factory (Knin, Croatia) and two reference sites. In the laboratory they were subjected to detailed chemical analysis and used in the toxicity testing. For that purpose, previously acclimatized individuals of H. medicinalis were sub-chronically (for 28 days) exposed to tested water samples. The levels of primary DNA damage were evaluated using the alkaline Comet assay in haemocytes collected at 7th, 14th, 21st and 28th day of exposure and compared with their baseline values. Genotoxic potency of the water sample with the highest sulfate concentration was further evaluated using the alkaline, neutral and hOGG1 modified Comet assay on human peripheral blood leukocytes exposed ex vivo for 30 minutes. The purpose was to explore which mechanisms are responsible for the DNA damage. Chemical analysis revealed that sulfate concentrations in two water samples collected in Mali kukar Lake (1630 mg/L SO4) and in Kosovčica River (823.3 mg/L SO4) exceeded the WHO and US EPA defined limits for sulfate in drinking water. Increased levels of metals were found only in water sample collected in Mali kukar Lake. However, out of 65 elements analyzed, only nickel and titanium exceed the value legally accepted in Croatia for drinking water. The levels of DNA damage estimated by the alkaline Comet assay in the haemocytes of medicinal leech increased with the duration of exposure to two sulfate-rich water samples. Since haemocytes sensitively responded to treatment, they could be used for the biomonitoring purposes. As observed on treated human peripheral blood leukocytes, all versions of Comet assay were effective in the detection of DNA damage which was measured in samples with sulfate concentrations equal or higher to levels legally accepted for drinking water. Based on the obtained results, we assume that genotoxicity was a consequence both of direct (single- and double strand DNA breaks) and indirect effects (oxidative damage) caused by combined effects of all contaminants present in the water samples tested. Our results point out the need of an in situ monitoring and purification of gypsum mine water, prior to its release in the natural environment.

Two gypsum karst lakes and one non-gypsum karst lake were studied for copepod and cladoceran species composition in relation to specific habitat characteristics. The investigation was conducted from March to June 2007. Four copepod and six cladoceran species were recorded. Gypsum karst lakes are characterized as sulphate lakes and they show significant differences from non-gypsum karst lakes in conductivity, TDS, alkalinity, calcium and sulphates. Data on environmental variables and zooplankton were analyzed using redundancy analysis (RDA). The model explained 65.73% of the variance of the crustacean zooplankton and environmental data by the first two axes. The analysis confirmed that the major environmental variables influencing zooplankton in gypsum karst lakes are conductivity, TDS, calcium and sulphates. In the non-gypsum karst lake, on the contrary, the major variables were oxygen concentration and alkalinity. Specific habitat characteristics of gypsum karst lakes influence the zooplankton community by reducing the number of species and leading to the dominance of one of them.

The ecology of polyps of Craspedacusta sowerbii has been poorly investigated. It is known that they live attached to hard surfaces. They have never been linked with any animal, in particular not with Dreissena polymorpha (zebra mussel), which is known to have only endosymbionts. This study was conducted in March 2004 in Ccaroningi-Lingi Lake. The lake is an oligo-mesotrophic man-made gravel pit in northeast Croatia. During this study, polyps were found singly or in colonies of two to five on willow twigs and on the shells of D. polymorpha collected from 8 m depth and on metal barrels. Brown hydra (Pelmatohydra oligactis) individuals were also present next to polyps of Craspedacusta on zebra mussel shells, collected from metal barrels. The presence of polyps of Craspedacusta and brown hydras together on live bivalve shells is significant, as we suggest that it marks the first record of commensalism of this kind.

Čingi-Lingi Lake is a gravel pit produced 25 years ago. During investigation of zooplankton in the year 2004 we determined eight species. Three of them are copepods and five of them are cladocerans. Čingi-Lingi Lake is the only locality where zooplankton in the Drava Valley region has been investigated., Jezero Čingi-Lingi je šljunčara nastala prije 25 godina. Tijekom istraživanja u 2004. godini u jezeru je utvrđeno osam vrsta planktonskih račića. Tri vrste spadaju u skupinu veslonožaca, a preostalih pet u skupinu rašljoticalaca. Jezero Čingi-Lingi je prvi i za sada jedini lokalitet na kojem su vršena istraživanja zooplanktona u Podravini.

This report describes an investigation of genotoxic effects in medicinal leech {; ; ; Hirudo verbana) exposed to water and sediment of Lake Njivice (Krk Island, Croatia) contaminated by aluminium compounds. The levels of primary DNA damage in leech haemocytes and loss of DNA integrity caused by acute and chronic exposure to contaminated water and sediment were investigated using the alkaline comet assay. Genotoxic effects induced by acute exposure to contaminants were evaluated on leech haemocytes and blood cells of fish and mouse treated ex vivo. The effects of chronic exposure were assessed on haemocytes sampled from an animal kept under laboratory conditions on contaminated water and sediment for 180 days. The results indicate the DNA damaging potential of aluminium compounds present in an excess amount in tested samples.

The species of freshwater Cyclopoida Cyclops bohater Kozminski 1933 was recorded during collection of zooplankton in one of the three Cingi-Lingi Lakes in August and September 2004. This is the first record for the Croatian fauna and also for the Balkan Peninsula. The Cingi-Lingi Lake is a gravel pit in the Podravina area of NW Croatia.

Data are given on the water quality, vegetation and benthic macroinvertebrates in 1980/81 and 2001 in the shallow, Mediterranean lake Jezero, Krk Island, Croatia. The main refuge for macroinvertebrates changed from submerged vegetation to bare flock and flock associated with reed decay. The flock originated from a flocculation process in a water treatment plant using aluminium salts as coagulants. Species richness decreased from 15 to 10 taxa and the number of individuals decreased by 88.3%. The low density of macroinvertebrates during the recent period is probably attributable to the shift in sediment characteristics, disappearance of submerged macrophytes and toxic effect of aluminium compounds.

The karst areas in Croatia, part of the Dinarides, have been defined biospeleologically as an area of high biodiversity in world terms, covering 26 thousand km2 in all. In this monograph we give data about the biodiversity of subterranean habitats and their biota primarily from a taxonomic perspective with special attention being paid to regional diversity. The diversified geomorphology, hydrology and climate have resulted in a remarkable range of different underground habitats in Croatia, viz. inland and coastal caves, superficial and deep phreatic networks, interstitial – hyporheic substrates and other infiltration zones, etc. In Croatia more than 500 obligate subterranean species and subspecies are known from caves and interstitial habitats. The majority of subterranean species in Croatia are terrestrial biota. There are 299 troglobiont and 170 stygobiont taxa (species and subspecies) recorded. Most subterranean species have very restricted ranges, almost 70% of them endemic to Croatia. Cave fungi are poorly known. Among them there are several important parasitic troglobionts and troglophilic species on cave coleopterans and troglophilic moths in Croatian caves. Some saprotrophic species could be troglobiotic too but their taxonomic and/or ecological status must be clarified in future research. With a respect to the number of troglobionts, the five largest animal groups are Coleoptera, Pseudoscorpiones, Araneae, Gastropoda and Diplopoda. The beetles (Coleoptera) are predominant. More than 100 cavernicolous beetles (species and subspecies) are known in Croatia. Among stygobionts, the Crustacea predominate. At least half of species described are Crustacea. Among Crustacea, the orders Syncarida and Thermosbaenacea are exclusively stygobiotic. Numerically, among crustacean stygobiotic Amphipoda dominate in caves and Copepoda in interstitial habitats. The only known stygobiotic sponge Eunapius subterraneus Sket et Velikonja inhabits several caves in Croatia. Also, the only known stygobiotic clam Congeria kusceri Bole inhabits a series of caves in Croatia. Other important groups include hydrozoa, planarians (Temnocephalida and Tricladida), snails (Mollusca: Gastropoda) and the only European stygobiotic Chordata Proteus anguinus Laurenti. The high taxonomic diversity of the subterranean biota of Croatia can be attributed partly to the geographical heterogeneity and a rather unique combination of various geological and ecological phenomena., Krško područje Hrvatske ukupne površine 26 tisuća km2, s dijelom dinarskog krša, biospeleološki je određeno kao područje velike biološke raznolikosti u svijetu. U ovoj monografiji podastiru se podaci o biološkoj raznolikosti podzemnih staništa i organizama primarno s taksonomskog aspekta i s posebnim osvrtom na regionalnu raznolikost. Geomorfološka, hidrološka i klimatološka raznolikost Hrvatske rezultirala je osobitim rasponom različitih podzemnih staništa, kao što su kontinentalne i priobalne špilje, mreža plitke i duboke freatičke zone, intersticij – hiporeička zona i drugi tipovi infiltracijskih zona, itd. Iz špilja i intersticijskih staništa Hrvatske poznato je preko 500 obveznih podzemnih vrsta i podvrsta. Većina podzemnih vrsta u Hrvatskoj su kopneni organizmi. Utvrđeno je 299 troglobionata i 170 stigobionata. Većina podzemnih vrsta ima vrlo ograničeno područje rasprostranjenosti, gotovo 70% je endemno za Hrvatsku. Špiljske gljive su vrlo slabo poznate. Među njima je nekoliko troglobionata i troglofila koji su paraziti na špiljskim kornjašima i troglofilnim leptirima. Neke subtroglofilne vrste možda su također troglobiontske, no njihov taksonomski i/ili ekološki status morala bi razjasniti buduća istraživanja. U pogledu najveće brojnosti troglobionata, pet je velikih skupina životinja – Coleoptera, Pseudoscorpiones, Araneae, Gastropoda i Diplopoda. Kornjaši (Coleoptera) su najdominantniji. U Hrvatskoj je poznato više od 100 kavernikolnih kornjaša (vrsta i podvrsta). Među stigobiontima dominiraju raci. Gotovo polovica opisanih vrsta su iz skupine Crustacea. Među racima, skupina Syncarida i Thermosbaenacea su isključivi stigobionti. Brojčano gledano, među stigobiontskim racima skupina Amphipoda dominira u špiljama, a skupina Copepoda u intersticiju. Jedina do danas poznata stigobiontska spužva Eunapius subterraneus Sket et Velikonja nastanjuje nekoliko špilja u Hrvatskoj. Također jedini poznati stigobiontski školjkaš Congeria kusceri Bole nastanjuje niz špilja u Hrvatskoj. Ostale važne skupine su obrubnjaci, virnjaci (Temnocephalida i Tricladida), puževi (Gastropoda) i jedini poznati stigobiontski kralježnjak Proteus anguinus Laurenti. Velika taksonomska raznolikost podzemnih organizama Hrvatske pripisuje se djelomično geološkoj heterogenosti i posebno jedinstvenom spoju različitih geoloških i ekoloških pojava.

Lake Vrana represents one of the largest freshwater lakes on a relatively small and entirely karstified island. According to its physical and chemical factors, this lake is oligotrophic, has a monomictic temperate with winter circulation and thermal stratification in summer. Transparency is high (11-17 m, Secchi disk). The main nutrients were low and vertically homogeneous in both years of the study. The mean concentration of nitrate was 0.212 mg L-1, phosphate 0.019 mg L-1 and the mean concentration of total phosphorus was 0.137 mg L-1. Mean chlorophyll-a concentration was low (0.246 mg L-1 in 1996 and 0.363 mg L-1 in 1997). The availability of these nutrients correlated to abundance in phytoplankton biomass. The Lake Vrana phytoplankton showed a wide biomass range, from 0.55 to 172.61 mg L-1. The cell number showed late autumnal and early spring maxima (9, 834 cells L-1 in November 1997 and 9, 983 cells L-1 in May 1996). The species Ceratium hirundinella (Dinophyceae) was dominant in the phytoplankton community. The other important species were Chroococcus limneticus (Cyanobacteria), Dinobryon sociale (Chrysophyceae), Cyclotella comta (Bacillariophyceae), Cosmarium abbreviatum, Oocystis lacustris, Schizochlamis gelatinosa, and Sphaerocystis schroeteri (Chlorophyceae). Zooplankton of wet weight biomass varied: 1078.57 &micro ; ; ; ; g L-1 (1996) and 126.24 &micro ; ; ; ; g L-1 (1997). Four species of copepods and three species of cladocerans were observed in the plankton of the Lake Vrana: Cyclops abyssorum ” divulsus” , Macrocyclops albidus, Macrocyclops distinctus, Megacyclops viridis, Daphnia longispina, Diaphanosoma brachyurum and Bosmina longirostris. Temporal distribution is characterised with maxima in May and June (1996) and February and June (1997). The abundance of zooplankton coincided with those of the phytoplankton.

Background and Purpose: Lake Vrana is shallow, Mediterranean, karstic lake, where water salinity is as an important ecological factor, because the lake is directly connected with the Adriatic Sea. Studies concerning zooplankton communities in these ecosystems are very scarce. To understand this very specific and unique ecosystem, the physical and chemical parameters and the makrozooplankton community structure in Lake Vrana were studied. Material and Methods: The investigation was conducetd monthly from January till December 2004 at four stations with different ecological characteristics (primarily depth, salinity, hydrology, nutrients supply). Chlorophyll a concentration was analyzed fluorometrically according to Method 445.0. Physical and chemical parameters (temperature, transparency, chlorinity, salinity, biological oxygen demand - BOD, dissolved oxygen - DO, ortho-phosphate, total phosphorus, chlorophyll a) were measured according to APHA. Data on environmental variables and makrozooplankton community were examined using Redundancy Analysis (RDA). Results: Among the 13 different species which are found in macrozooplankton community of Lake Vrana, the dominant species were Calanipeda aquedulcis Kritchagin (Copepoda), and Bosmina longirostris O.F. Műller, (Cladocera) which were present in all four stations during study period. The same occurring had Megacyclops gigas Claus, Alona sp., Alonella excisa Fischer, and Chydorus sphaericus O.F. Műller while other species appeared sporadically. The physical-chemical parameters showed temporal and spatial variations in Lake Vrana during study period resulting in different micro-habitat conditions on the studied sites. That is confirmed by the results of the RDA analysis that clearly shows the separation of stations due to the impact of studied indicators. According to multivariate analysis temperature, chlorophyll a and salinity have great influence on dynamics and structure of makrozooplankton in Lake Vrana. Conclusions: Temperature, chlorophyll a and salinity are ecological factors which define the development as well as dynamics and structure of macrozooplankton community in the Vrana Lake.