Southern Bulgaria Research Articles

In situ assessment of health status and heavy metal bioaccumulation of adult Pelophylax ridibundus (Anura: Ranidae) individuals inhabiting polluted area in southern Bulgaria

• We study the health effects of heavy metal pollutants and their accumulation in frogs. • The frogs from the polluted area were anemic, with a suppressed hematopoiesis. • The frogs from the polluted area had a weakened immunity. • The tissues in frogs from the polluted area have significantly higher levels of heavy metals. In this study an assessment is made of how the marsh frog P. ridibundus individuals, being long-term inhabitants of an anthropogenically polluted habitat, are affected and what changes toxicants induce in the organism of anurans. In situ measurements of several morphophysiological and hematological parameters were performed to assess the health status of frogs, and after that the bioaccumulation of Pb, Cd, Zn and Cu in their bodies (muscles and liver) was determined. Moreover, P. ridibundus individuals were separated by sex to evaluate this mark as an inherent source of variability. The results revealed that the P. ridibundus individuals inhabiting an area polluted with industrial waste were anemic, with suppressed hematopoiesis and weakened immunity. In the tissues of frogs of both sexes inhabiting the polluted site, high levels of heavy metals and metalloids (Pb, Cd, Cu, Zn, As and Se) were found as compared to samples from a reference site. Furthermore, the levels of all metals and metalloids in these frogs were higher in the liver than in the muscles. Quantity differences were ascertained in the bioaccumulation of frogs inhabiting the polluted site: higher values of heavy metals in the tissues of females, and metalloids in the tissues of males.

Cenozoic thermal evolution of the Central Rhodope Metamorphic Complex (Southern Bulgaria)

We have combined new titanite, zircon, and apatite fission-track and apatite [U–Th–(Sm)]/He analyses with previously published U–Pb, Rb–Sr, and 40Ar/39Ar thermochronological data to reconstruct the Cenozoic thermal evolution of the Central Rhodope Metamorphic Complex (CRMC), exposed mainly in southern Bulgaria and to a lesser extent in northern Greece. Results reveal two phases of cooling. During the first phase, between ~ 37 and ~ 33 Ma, the CRMC experienced rapid cooling from partial melting at > 650 °C to ca 60 °C. Multiple generations of low-angle ductile-to-brittle fault zones accommodated the exhumation of the migmatitic core together with parts of its high-grade periphery. Oligocene volcanism and associated local elevation of the geothermal gradient is responsible for the resetting of some fission-track ages in the CRMC. The second cooling phase to temperatures of about 40 °C, between 24 and 13 Ma, is related to exhumation along high-angle normal faults in the southern part of the CRMC.

Structure of the Earth’s crust of the Eastern Rhodopes (Southern Bulgaria) from the regional deep reflection seismic profile Ivaylovgrad–Ardino

This paper presents a geological interpretation of the deep seismic profile Ivaylovgrad–Ardino, which was published in 1996. Four plates are distinguished according to their seismic features that build up the Eastern Rhodope Terrane. They have a total thickness of 22–24 km and layered structures with sub-oceanic character. The lower two plates (1, 2) are westward obducted on the Rila-Western Rhodope Terrane, forming one obduction complex. Plate 3 is probably also a part of the obduction complex. Plate 4 is thrust southward on all plates. A Kobilino Crypto-dome, comprising Plates 1 and 2 and covered discordantly by the third one, is found at the eastern part of the profile at 7–7.5 km depth. The two lower plates do not appear on the surface, but some ultrabasic to basic bodies are supposed to be parts of them, rising as tectonic slices. The Plate 3 is revealed on the surface at the eastern part of the seismic profile (east of Avren Fault), and is built up mainly by the Pre-Rhodopean Supergroup metamorphic rocks, respectively from the seismically indistinguishable Upper and Lower Allochthon. The Plate 4 appears mainly at the western end of the profile (between Mishevsko Village and Ardino Town), and is built up by the metamorphic rocks of the Rhodopean Supergroup from the Startsevo Lithotectonic Unit (or Middle Allochthon). Five fault and shear zone systems of different ages are distinguishable in all plates. Transparent areas in the plates are interpreted as magma chambers of the Paleogene volcanoes, others as Upper Cretaceous and Paleogene (?) plutons. Because these magmatic chambers are located in the sub-oceanic crust, both intermediate and acid Paleogene volcanics have isotopic characteristics similar to those of the metasomatized mantle.

Ancient burial mounds – biodiversity hotspots and refugees for natural flora and vegetation

Bulgaria is enormously rich in historical monuments. Burial mounds are one of the most numerous among them. They are spread all over the country but are localized in lowlands where active agriculture takes place. Patches of semi-natural vegetation are often preserved on the ancient burial mounds most of which are remnants from thousands years ago. The burial mounds which are generally surrounded by vast agricultural fields of monocultures often host the remnants of autochthonous flora. Besides being hotspots for biodiversity preservation, the ancient burial mounds are ideal objects for testing the theory of island biogeography. In our study we selected 577 mounds distributed near equally in northern and southern Bulgaria. Around each one mound a buffer of 200 m was outlined and the land use types were mapped aiming to identify the influence of land use on the floristic diversity. Our methodology includes sampling all vascular plants and their abundance within two sample plots of 25 m 2 positioned in the middle of north and south facing slopes. The scientific goal of our research is to reveal the significance of the burial mounds not only as cultural value, but also as natural treasure for the country. This would additionally emphasise their attraction as touristic objects.

Bessarabian Bulgarians – Commanders in the Serbian-Bulgarian War of 1885

After performing the September 18, 1885 Unification of Northern and Southern Bulgaria, Bulgarian unified army settled on the Bulgarian-Turkish border, as Turkey threatens war. But on November 14, 1885, something unexpected happens - the troops of Serbia attack Bulgaria without cause. Patriotic starts for the Bulgarian people Serbo-Bulgarian War of 1885 in this war to protect Bulgaria as commanders take an active part 16 Bessarabian Bulgarians. In this study we will look at their great merits. Lieutenant Colonel Daniel Nikolayev is the commander of the Bulgarian army, who organized the confrontation on Serbian territory. Major Avram Gudzhev is the commander of the West Corps, distinguished in the fighting near the town of Slivnitsa. Captain Olympi Panov is commander of the Bulgarian artillery and Captain Georgi Todorov is the commander of the Bulgarian cavalry. Captain Georgi Agura is the commander of the Breznitsa detachment, captured the town of Tsaribrod. The commanders of combat regiments are: Lieutenant Colonel Stefan Lubomski (Yambol Infantry Regiment), Major Peter Gruev (Second Artillery Regiment), Captain Stefan Kisov (Second Strumski Infantry Regiment) and Alexander Kessyakov (Sixth Tarnovo Infantry Regiment). In the battle of the Serbian-Bulgarian War of 1885, the officers of Bessarabian Bulgarians were also involved: Captain Georgi Yankov, Captain Dimitar Mitetelov, Captain Georgi Dermantchev, Lieutenant Ivan Zlatanov, Lieutenant Atanas Naszlovov, Lieutenant Stefan Kraev, Lieutenant Georgi Angelov died in the battle of Tran. The study looks at the merits of 16 Bessarabian Bulgarian officers and sums up their enormous contribution to the brilliant military victory over the enemy. In addition to the officers examined, Bessarabian Bulgarians, hundreds of sergeants, privates and volunteers were born in the Bulgarian army, born in the Bessarabia geographic area.

Description of Acanthocephalus anguillae balkanicus subsp. n. (Acanthocephala: Echinorhynchidae) from Proteus anguinus Laurenti (Amphibia: Proteidae) and the cave ecomorph of Asellus aquaticus (Crustacea: Asellidae) in Slovenia.

Acanthocephalus balkanicus Batchvarov et Combes, 1974 was incompletely described from the northern crested newt, Triturus cristatus (Laurenti) (Amphibia: Salamandridae), a possible synonym of the Balkan crested newt, Triturus ivanbureschi Arntzen et Wielstra, from a pond in village of Pesnopoy, southern Bulgaria. We provide a full description of adult males and females of the same taxon from the olm, Proteus anguinus Laurenti (Amphibia: Proteidae), the only exclusively aquatic cave-dwelling vertebrate in Europe, captured in Postojna-Planina Cave System in Slovenia. Cystacanths were also collected from the cave ecomorph of Asellus aquaticus (Linnaeus) (Crustacea: Asellidae) in the same location. Molecular analysis of specimens from Slovenia revealed that they are genetically almost identical to those of Acanthocephalus anguillae (Müller, 1780), a common parasite of European freshwater fishes. We propose to recognise the morphological and host differences by describing A. balkanicus as a new subspecies of A. anguillae. Acanthocephalus anguillae balkanicus is rather small and cylindrical with cylindrical proboscis having 10 rows of 6 hooks with simple roots each, long neck, large balloon-shaped lemnisci, small spherical anterior testis, and 6 club-shaped cement glands in 3 pairs. SEM images reveal more morphological details and the X-ray scans of gallium cut hooks shows considerably higher levels of phosphorus and calcium in adult hooks than in cystacanth hooks, especially in basal areas. Sulfur levels were higher in the arch and basal area of cystacanth hooks than adult hooks. Considering that both definitive and intermediate hosts of the Slovenian population of this acanthocephalan are bound to cave life, it is possible that its entire life cycle is uniquely completed underground.

CHEMICAL COMPOSITION OF CARDOON (CYNARA CARDUNCULUS L.) GROWN IN SOUTH BULGARIA

Comparative research has been conducted to allow us to determine the content of macro- and microelements in the vegetative and reproductive organs of Cynara cardunculus L. and quality of Cynara cardunculus L. oil. The experiment was performed on an agricultural field near Plovdiv (South Bulgaria). The contents of macro- and microelements in plant materials (roots, stems, leaves, seeds) and oils were determined. The oils were extracted using a Soxhlet apparatus from seeds of Cynara cardunculus L. The quantitative measurements were carried out with inductively-coupled plasma (ICP). Oil fatty acids characterization for unsaturated and saturated acids was performed by gas chromatography. The cardoon shows adaptability to local conditions and can be grown in southern Bulgaria and used for oil production. All plant parts of the cardoon are a rich source of macro and microelements and exhibit high nutritional value. The distribution of macro and microelements in the cardoon organs is selective, specific for the individual elements. Cd, Cu and Fe are accumulated in the roots, K - in the stems, Pb and Ca - in the leaves, and Zn, Mn, Mg and P - in the seeds. Cardoon seeds were a rich source of macro- and microelements (K, P, Mg, Ca, Fe, and Zn). Cardoon oil was abundant in unsaturated fatty acids (linoleic (61.67%%) and oleic acids (22.82%)), followed by palmitic acid (10.50%) and stearic acid (3.29%). Cardoon oil has a P/S index higher than 1 (4.2), which indicates that oil can have a good effect on human health and are oils suitable for consumption. Cardoon oil is a rich source of polyunsaturated linoleic fatty acid with potentially beneficial therapeutic activity.

EFFECT OF NITROGEN ON THE ACCUMULATION AND REUTILIZATION OF DRY MASS IN GRAIN SORGHUM

Accumulation and reutilization of dry mass until anthesis and during a grain fillingperiod of sorghum in response to nitrogen fertilization in rates 0, 60, 120, 180, 240and 300 kg N.ha-1 was studied in a field experiment. Grain sorghum hybrid ECAlize was grown under not- irrigated conditions in the experimental field ofAgricultural University of Plovdiv, Bulgaria. The experimental design was arandomized, complete block design with four replications with a size ofexperimental plots of 20 m2 after wheat as predecessor. Standard farming practicesfor the region of Southern Bulgaria were applied. It was established that nitrogenfertilization significantly increased the amount of accumulated dry mass at anthesisand total above ground dry mass at maturity compared to N0. Not significant effectof higher rates (180, 240 and 300 kg N.ha-1) on the dry mass accumulation ofsorghum was found. Average post anthesis net dry mass accumulation was 3291kg.ha-1 and its amount increased in parallel with the nitrogen rate up to N180. Thehighest dry mass translocation, translocation efficiency, and contribution of preanthesisassimilations of the grain was established at nitrogen rate N120 with values2073 kg.ha-1, 25.0 % and 41,8 %, respectively. Growth of sorghum at highernitrogen rates N180, N240, N300 significantly decreased efficiency of dry masstranslocation and contribution of pre-anthesis assimilations of the grain. Nitrogenfertilization had very strong negative correlation with dry mass translocationefficiency (-0.860*) and contribution of pre-anthesis assimilations of the grain (-0.863*). Very strong positive correlation (0.988**) was found between dry masstranslocation efficiency and contribution of pre-anthesis assimilations of the grain.

Agrobiological evaluation of the local walnut cultivars ‘Izvor 10’ and ‘Sheynovo’ in the climatic conditions of Southern Bulgaria

Agrobiological evaluation of the local walnut cultivars ‘Izvor 10’ and ‘Sheynovo’ in the climatic conditions of Southern Bulgaria

New data on Ceratitis capitata (Wiedemann) (Diptera: Tephritidae) from Bulgaria

The Mediterranean fruit fly Ceratitis capitata (Wiedemann, 1824) (Diptera: Tephritidae) is considered to be one of the world’s most destructive fruit pests because of its global distribution, wide host range and rapid dispersal. In the period 1956–2006, transient populations of the pest have been reported regularly in Bulgaria. The Bulgarian Food Safety Agency (BFSA) initiated monitoring of C. capitata in 15 regions of the country. The surveys were conducted during the period 2013–2018, using Jackson traps with attractant trimedlure and Tephri traps with Biolure. The presence of adults of C. capitata was confirmed in peach, apple and mixed orchards, as well as in private yards at five locations in southern and south-eastern Bulgaria: Blagoevgrad, Kyustendil, Pazardzhik, Plovdiv and Sliven. The results from the five-year monitoring showed a variable abundance of C. capitata adults captured in different years and localities. The highest mean captures were recorded in 2014 (195) and 2018 (422), no specimen of the C. capitata was found in 2017. In 2018 the most abundant captures were from fruit gardens in Plovdiv (297♀;65♂) and Sliven (18♀; 22♂). Over the entire study period, the lowest rate of adult captures was in July and August (only a few individuals in traps in each region). The population abundance began to increase at the beginning of mid-September and a peak was observed at the beginning of mid-October. The results on the seasonal population fluctuations obtained are similar to data from neighbouring countries: northern Greece, Montenegro, Croatia, Romania, and Turkey.

Biodiversity of soil fungal communities in agro-ecosystems using DNA metabarcoding

Soil fungi are key component of soil biota having an important role in many ecological processes. As pathogens, decomposers and plant mutualists they can affect plant and soil health in agro-ecosystems significantly. The impact of crop management practices on soil fungal communities is diverse and still poorly studied. The lack of knowledge is mainly related to their hidden life mode, high phenotypic diversity, the great heterogeneity of soil microhabitats, difficulty for culturing and species identification. Collecting data with high accuracy to detect effects relevant to ecosystem management is an ongoing challenge for soil ecological studies and biomonitoring. However, the combination of DNA-based identification methods and Next Generation Sequencing technology was recognized as a powerful tool to evaluate biodiversity in environmental samples, especially soil biodiversity. In the frame of the National Research Program "Healthy Foods for a Strong Bio-Economy and Quality of Life", soil microbiome diversity (fungi, prokaryotes and archaea) will be used as indicator for assessing soil and plant health, and ecosystem services in several agricultural ecosystems. Four crop types (apple, lavender, rose and pea) located in southern Bulgaria, and managed by conventional and organic farming have been selected. Two general objectives related to soil biodiversity study were envisaged: to examine the impact of cropping systems on microbiome structural and functional diversity, and to propose management measures and agronomic practices improving soil and plant health. to examine the impact of cropping systems on microbiome structural and functional diversity, and to propose management measures and agronomic practices improving soil and plant health. Here we present some preliminary results on soil fungal communities evaluated by using amplicon DNA sequencing of the internal transcribed spacer 2 (ITS2) rDNA region. Multiple core soil samples were collected from 18 sampling plots in June 2019. Fungal diversity and community structure were evaluated at different taxonomic levels. The most common and abundant taxa at all sites were Fusarium Link 1809, Solicoccozyma X.Z.Liu, F.Y.Bai, M.Groenew. & Boekhout 2015, Cladosporium Link 1816, Alternaria Nees ex Wallroth 1816, and Mortierella E.Coemans 1863. The multivariate statistics (PCA) comparing the overall microbial composition revealed loose clusters linked to crops and localities. The study provides a new comprehensive overview of soil fungal communities (composition and diversity) from Bulgarian agro-ecosystems using high-throughput DNA sequencing.

Nematode diversity in four crop types (pea, apple, lavender and rose) in southern Bulgaria

Nematodes represent one of the largest phyla in the animal kingdom and are a key component of the soil microfauna (organisms with body width <0.2 mm). Being a widespread and diverse group, they display a wide range of adaptations and lifestyle traits. Their functional role in soil food-webs is mostly related to their feeding type. The majority of terrestrial nematodes feed on plant roots, bacteria and fungi, while a small group of plant associated species spend part or their whole life cycle in roots. Some plant-feeding species are known as important pests that can parasitize various crops causing adverse effects on yield and production quality. Their effective management requires accurate detection and identification. In the frame of the National Research Program "Healthy Foods for a Strong Bio-Economy and Quality of Life", selected groups of soil nematodes are used as bioindicators for assessing soil and plant health, and ecosystem services in several agricultural ecosystems. Nematode communities from four crop types (pea, apple, lavender and rose) in southern Bulgaria managed by conventional and organic farming were sampled and investigated. Here we present some preliminary results on pea, lavender and rose associated nematode diversity. Multiple core samples from 18 sampling plots were collected in June 2019. Nematodes were isolated from 200 g of soil by decanting and sieving method, fixed, dehydrated and mounted on permanent slides. Overall, over 60 genera belonging to five trophic groups were identified. Approximately half of the nematode genera found are obligatory plant- and plant/fungus feeders. Parasitic nematodes were represented by 12 genera, some of which include important pests known to cause severe damages on crops e.g. Meloidogyne Goeldi, 1889, Pratylenchus Filipjev, 1934, Pratylenchoides Winslow, 1958 and Tylenchorhynchus Cobb, 1913.

Conservation significance and habitats variety in the Western Rhodope Mts. as a factor for the diversity of the ground beetles (Coleoptera: Carabidae)

This study concerns the Western Rhodope Mts. (Southern Bulgaria), the conservationally significant habitats and the carabid beetles occurring in them. All sixty-seven habitats are systematized according to their EUNIS level and type and conservation status, and the threats to the important carabid species are assessed. The association of the carabids with specific habitats and the attachment to particular environmental conditions are discussed. Carabids with conservational value are discussed and a list of the protected (four) and endemic (thirty-nine) species is given. The anthropogenic impacts in the area were also assessed. The main threats and problems related to the degradation and destruction of natural habitats and, hence, decreases to the conservation significance of the area, were established and systematised in eight categories, and measures for minimizing these negative impacts are proposed.

Ground beetles (Coleoptera: Carabidae) diversity from harvested oilseed rape fields (Brassica napus L.) in Southern Bulgaria

This study aimed at clarifying the species composition and ecological structure of carabid communities, in oilseed rape fields after rape harvest. Field work was carried out in 2018. Pitfall traps (5 in each site) were set in 10 sampling sites in Thracean Lowland and Sarnena Sredna Gora Mts. Captured beetles belonged to 66 species and 24 genera, representing 9% of the species and 19% of the ground beetle genera occurring in Bulgaria. The most diverse was genus Harpalus Latreille, 1802 (15 species), followed by the genera Amara Zimmermann, 1832 (7 species), Microlestes Schmidt-Goebel, 1846 (6 species) and Parophonus Ganglbauer, 1891 (5 species). Five species were new for the region of the Thracean Lowland: Amara (Bradytus) consularis (Duftschmid, 1812), Harpalus (Harpalus) caspius (Steven, 1806), H. (Pseudoophonus) calceatus (Duftschmid, 1812), Microlestes negrita negrita (Wollaston, 1854), Tachyura (Tachyura) parvula (Dejean, 1831). Three species: Amara (Zezea) fulvipes (Audinet-Serville, 1821), A. (Zezea) chaudoiri incognita Fassati, 1946 and Diachromus germanus (Linnaeus, 1758) were new records for the region of the Sarnena Gora. Seven species were new for the whole Sredna Gora Mts.: Acinopus (Acinopus) picipes (Olivier, 1795), A. (Oedematicus) megacephalus (P. Rossi, 1794), Carterus (Carterus) dama (P. Rossi, 1792), Harpalus (Harpalus) flavicornis flavicornis Dejean, 1829, H. (Pseudoophonus) griseus (Panzer, 1796), Licinus (Licinus) depressus (Paykull, 1790) and Microlestes maurus maurus (Sturm, 1827). Genera Acinopus Dejean, 1821, Carterus Dejean, 1830 and Licinus Latreille, 1802 were new geographic records for the Sredna Gora Mts. Twelve life form categories were established (7 zoophagous and 6 mixophytophagous). The analysis of the life forms showed a slight predominance of the mixophytophages (38 species; 58%) over the zoophages (28 species; 42%). There were no constant species occurring in all sampling sites (with 100% occurrence). Thirteen species appeared after the harvest (they were absent during the flowering and ripening of the rape), forty-four species disappeared (they were present during flowering and ripening), and twenty-nine species were present in all stages.

Ground beetles (Coleoptera: Carabidae) diversity from pastures in Southern Bulgaria

This study aimed at clarifying the species composition and ecological structure of carabids, associated with active pastures. Field work was carried out in 2017 and 2018. Pitfall traps (5 in each site) were set in 10 sampling sites in Thracean Lowland and Sarnena Sredna Gora Mts. Captured beetles belonged to 90 species and 33 genera, representing 12% of the species and 26% of the ground beetle genera occurring in Bulgaria. The most diverse was genus Harpalus (22 species), followed by the genera Amara (7 species), Microlestes (6 species), Ophonus (6 species) and Parophonus (5 species). Twenty species were new for the region of the Thracean Lowland: Amara fulvipes (Audinet-Serville, 1821), Anisodactylus binotatus (Fabricius, 1787), A. intermedius Dejean, 1829, Apotomus clypeonitens Müller, 1943, Calathus cinctus Motschulsky, 1850, Carterus gilvipes (Piochard de la Brûlerie, 1873), Gynandromorphus etruscus (Quensel en Schönherr, 1806), Harpalus fuscicornis Ménétriés, 1832, H. subcylindricus Dejean, 1829, Microlestes apterus Holdhaus, 1904, M. corticalis (L. Dufour, 1820), M. fulvibasis (Reitter, 1901), M. maurus (Sturm, 1827), M. minutulus (Goeze, 1777), Notiophilus laticollis Chaudoir, 1850, Pangus scaritides (Sturm, 1818), Parophonus laeviceps (Ménétriés, 1832), P. planicollis (Dejean, 1829), Polystichus connexus (Geoffroy in Fourcroy, 1785) and Pterostichus strenuus (Panzer, 1796). Twenty species were new for the whole Sredna Gora Mts.: Acinopus picipes (Olivier, 1795), A. megacephalus (P. Rossi, 1794), Amara anthobia A. Villa et G. B. Villa, 1833, Ditomus calydonius (P. Rossi, 1790), Harpalus albanicus Reitter, 1900, H. angulatus Putzeys, 1878, H. attenuatus Stephens, 1828, H. dimidiatus (P. Rossi, 1790), H. flavicornis Dejean, 1829, H. pumilus Sturm, 1818, H. pygmaeus Dejean, 1829, H. subcylindricus Dejean, 1829, H. tardus (Panzer, 1796), H. signaticornis (Duftschmid, 1812), Lebia scapularis (Geoffroy, 1785), Microlestes fissuralis (Reitter, 1901), M. fulvibasis (Reitter, 1901), M. maurus (Sturm, 1827), M. minutulus (Goeze, 1777) and Ophonus sabulicola (Panzer, 1796). Fourty-one species were new for the region of the Sarnena Sredna Gora. Genus Apotomus, Gynandromorphus, Pangus and Polystichus were new geographic records for Thracean Lowland. Genera Acinopus and Ditomus were new for the Sredna Gora Mts. Fourteen life form categories were established (9 zoophagous and 5 mixophytophagous). The analysis of the life forms showed a slight predominance of the mixophytophages (53 species; 59%) over the zoophages (37 species; 41%). Microlestes minutulus was a constant species occurring in all sampling sites.

Fluctuating asymmetry in Pelophylax ridibundus meristic morphological traits and their importance in assessing environmental health

Abstract The aim of this study was to investigate the levels of fluctuating asymmetry in Pelophylax ridibundus populations inhabiting the River of Sazliyka (southern Bulgaria), polluted with domestic sewage and industrial pollution. The study was conducted 5 years after the construction of a modern, wastewater treatment facility near the town of Stara Zagora, whose wastewater is one of the main pollutants of the river. The main objective was to compare the values of the integral indicator for developmental stability (FA) in P. ridibundus with those obtained in a previouis study, conducted before the construction of wastewater treatment facility; and on the basis of that comparison to make an additional independent assessment parallel to the physicochemical analyses. The tested frogs in the present study (25 males and 25 females individuals from each site) were adult and sexually mature. Fluctuating asymmetry was defined according to 10 morphological traits, using the index frequency of asymmetric manifestation of an individual (FAMI). On the basis of the observed average FAMI values the status of the populations (respectively the corresponding biotops) was rated according to a scale from 1 to 5, describing the degree of environmental contamination. Lower values of FAMI were found in the populations of P. ridibundus that inhabit relatively clean sites, whereas higher values of FAMI were found in the sites with anthropogenic pollution. The results of our work give us the opportunity to assume that FA in meristic morphological traits in this species of anurans can be used as a reliable biomarker, an alternative to physicochemical analyses that require expensive laboratory equipment and consumables.

INVESTIGATION OF MURINE RODENTS FOR THE PRESENCE OF LEPTOSPIRA DNA BY NESTED PCR

Leptospirosis is a zooanthroponosis with natural foci. People become infected with leptospires either directly from host animals or by means of certain elements of the external environment. Circulation of leptospires in nature is maintained by reservoirs and supporting hosts. For the first time in Bulgaria we applied nested PCR in examining organs of murine rodents for the presence of Leptospira spp. DNA. A total of 109 rodents were investigated after being collected from 4 districts in Southern Bulgaria: Plovdiv, Pazardzhik, Smolyan and Blagoevgrad. The genome of Leptospira spp. was found in 5 species of rodents. Results show that Microtus spp. is a potential carrier of leptospires, especially in urban areas. The high rate of leptospiral DNA-positive rodents captured in the region of Pazardzhik confirms the activity of the epizootic process in this natural focus, where epidemics of benign leptospirosis have been recorded in the past. The introduced method would help to clarify the epidemiological links more quickly in case of a leptospirosis outbreak in some regions. Stronger measures are needed to combat rats, murine rodents and their entry in warehouses, slaughterhouses and mass caterers, in order to maintain the cleanliness of open-air ponds, water sources and prevent contamination of food products. Future studies in this area would enrich the knowledge on the circulation of leptospires in their reservoirs in more areas of our country.

Seroprevalence of Hepatitis E Virus Infection in Pigs from Southern Bulgaria.

Hepatitis E virus (HEV) has been isolated from humans and several animals' species. During the last years, the knowledge of HEV infection dramatically changed and enriched. The aim of this study was to estimate the seroprevalence of HEV in industrial pigs in different districts of Southern Bulgaria. Three hundred sixty swine serum samples were tested for anti-HEV IgG antibodies. The samples were collected from four industrial farms from three districts of Southern Bulgaria. HEV-specific antibodies in porcine serum were detected by enzyme-linked immunosorbent assay (PrioCHECK HEV Ab porcine). The overall HEV seroprevalence was 60.3%. The seropositivity varied widely depending on age groups and investigated farms. The overall prevalence in weaners was 25%, in fattening pigs 75.8%, and in group of sows was found the highest HEV positivity of 80%. The occurrence of HEV positivity in sows and fattening pigs presented odds ratio (OR) = 17.200 (95% confidence interval [CI]: 8.8-33.7) and OR = 11.342 (95% CI: 6.1-21.0), respectively, compared to weaners. The study indicated that HEV is widespread in industrial farms in Bulgaria and presented high seroprevalence in pigs. The results found that HEV seropositivity showed age dependency. The National Health Authorities should raise awareness of HEV and its zoonotic potential.

Sedimentological and mineralogical characteristics of red soil in South Pirin Mountains (Southwest Bulgaria)

The northernmost derivation of the Mediterranean climatic influence and the wide distribution of carbonate rocks are factors that could explain red soils distribution in the lands of Southern Bulgaria. However, due to the mainly mountainous landscape, red soils can be found only on certain spots in Bulgaria. One of the most typical examples of red soil can be found in the lands of Nova Lovcha Village in Bulgaria, but this area was not studied in detail due to its border position. In this study, the catena principle was used to estimate the parental material and slope drainage relationships as factors in soil formation. Samples from different parts of the slope were analyzed for grain size, parent rock and soil mineralogy, pH, and humus content. The red soils of Nova Lovcha showed both local rocks origin in the deeper parts of the soil profiles and allochthone silicate elements in the upper horizons. The most relevant explanation for this mineralogical difference could be a transfer from another nearby area; Neogene alluvial deposits or from weathered older rocks, cropping out in the vicinity of the area. Our results show a relation between this particular landscape and the Greek Thracian allochthonous red soils. This confirms the variety of factors for red soil formation and explains the penetration of Mediterranean influence in the mountains of the Balkan Peninsula.

Utilization of low enthalpy geothermal energy in Bulgaria

Bulgaria is relatively rich in geothermal water of temperature in the range of 25°C-100°C and the total flow-rate exceeds 3,000 L/s. Generally, there are more than 170 geothermal fields: 102 of them are state-owned and the rest of them – belong to some municipalities. Up to 72% of the total known flow-rate from the reservoirs has a comparatively low temperature - up to 50°C. Flow-rates for individual sources vary within 1-20 L/s for most of the reservoirs. The highest temperature (approximately 100°C) is measured at the surface in Sapareva Banya near Rila Mountain. TDS (total dissolved solids) vary between 0.1 g/L and 1.0 g/L for most of the reservoirs in Southern Bulgaria, while in Northern Bulgaria it is significantly higher – the maximum is up to 150 g/L. The installed capacity amounts to about 97.5 MWt (for 2017), excluding the low grade energy use by ground source heat pumps (GSHP). Geothermal energy has only direct utilization - in balneology, heating of buildings, air-conditioning, greenhouses, geothermal ground source heat pumps, direct thermal water supply for industrial processes. Geothermal water is also used for bottling of potable water and soft drinks. Most of the hydrothermal sites are developed as mountainous or sea resorts. Electricity generation from geothermal water is not currently available in the country.