Southeastern Bulgaria Research Articles

Visual and refractive outcome after 12 years of treatment of type 1 prethreshold retinopathy of prematurity.

In this study, the best corrected visual acuity (BCVA) and refraction in preterm-born infants in South-Eastern Bulgaria after 12 years of treatment for type 1 prethreshold retinopathy of prematurity were presented, and the outcomes of laser treatment and cryotherapy were compared.

Enhancing the Fermentation Process in Biogas Production from Animal and Plant Waste Substrates in the Southeastern Region of Bulgaria

Annually, a huge amount of waste from plant biomass and animal manure is produced from agriculture and animal farming. Many studies provide information on the biomethane potential of agricultural and livestock wastes, but only a few studies have investigated the application of the substrates in combination. The objective of the study is to enhance the fermentation process in the digester for biogas production, obtained from animal and plant waste substrates. In four batch processes for three months, the temperatures and the residence time of the substrates in the fermenter were analyzed. Simultaneously, electricity and thermal energy were produced via cogeneration units, which were exported to the public grid and city heating network. The plant substrate is a silage mixture of corn and wheat waste. The animal substrate is a mixture of beef and pig manure. Animal and vegetable waste raw materials are collected and transported to the site, located in the region of southeastern Bulgaria. The total annual consumption of animal and plant waste is 17,971 t/year. The enhancement of the process leads to the production of 1,506,000 Nm3 CH4/a of methane, the generation of which requires 299.63 MWh/a of electricity and 649.09 MWh/a thermal energy.

The Teacher Training Institute in Burgas: А Time-Honoured Productive Tradition

The opening of the Teacher Training Institute in Burgas in 1943 as the first post secondary educational institution was logical and decisive for the prospects and future trends in education on a regional scale. During its 57 years of existence, Hristo Botev Teacher Training Institute became a centre for training, qualification and retraining of teachers, a cultural and educational hub. Its history was traced using archival sources, published memories and personal documents that have been put in scientific circulation for the first time. For the purpose of analysis, the historical and pedagogical approach, cultural and historical retrospection, and historical comparative analysis have been applied. The collected facts and their scientific interpretation lead to the conclusion that, chronologically, the Teacher Training Institute was the first step towards making Burgas a university city. Its establishment marked the beginning of a tradition that today allows us to talk about Burgas as the training centre for pedagogical staff in Southeastern Bulgaria

At a crossroads: Genetic lineages and dispersal routes of Morimusasper (Sulzer, 1776) s.l. (Coleoptera, Cerambycidae) in Bulgaria.

The present study fills a knowledge gap in the distribution and genetic variation of Morimus populations in the Balkans, by studiyng the representatives of the genus in Bulgaria - M.asperfunereus Mulsant, 1862, M.verecundusbulgaricus Danilevsky, 2016 and M.orientalis Reitter, 1894. Additional information is provided for Albania and northern Greece. The mitochondrial cytochrome C oxidase subunit I (COI) marker and the nuclear internal transcribed spacer 2 (ITS2) were used for the genetic analyses. Three of the previously-defined mitochondrial lineages (Lb/HgA, L2 and L3) were detected in Bulgaria, as well as a new lineage (Str) from the Strandzha Mountains (south-eastern Bulgaria). A total of 24 distinct haplotypes, 20 of them in Bulgaria, were found. Bulgarian populations of Morimus demonstrated relatively high nucleotide diversity. The L3 COI lineage was confirmed as the most diverse and frequent in the Balkans. The L3 lineage is dominant in most of Bulgaria, but was not identified in the easternmost parts near the Black Sea coast, where the L2 and Str lineages were found. New data highlighted two dispersal routes of the L2 mitochondrial lineage on the Balkan Peninsula: 1) northwards along the Black Sea coast and 2) westwards, across the Balkans where only disjunct populations remain. North-western Bulgaria seems to be the eastern limit of the basal lineage Lb/HgA distribution. Our results show high levels of genetic exchange between most of the mitochondrially defined lineages, yet some of the easternmost populations probably remained isolated for comparatively longer periods.

A fox on the hunt: red fox (Vulpes vulpes) was able to subdue and kill an adult coypu (Myocastor coypus) in a protected site in south-eastern Bulgaria

In the present study, we report on a rare predatory behaviour in the red fox (Vulpes vulpes Linnaeus, 1758). In the early evening of 03.03.2023 we detected a red fox attacking and killing a coypu (Myocastor coypus Molina, 1782). We were able to document the event by the use of camera with tele-lens. The red fox was known to feed on smaller prey like insects, smaller rodents, lagomorphs, birds and others. Data on attacks on large and potentially dangerous prey are rather scarce and we discuss on the potential trigger for that predatory behaviour.

Geophysical Techniques for Monitoring of Integrated Mine Waste Storage Facility: Case Study of Southeastern Bulgaria

The extraction of mineral resources usually generates varying amounts of extractive waste, which require appropriate management. Extractive waste management is complicated and difficult process. It encompasses a lot of actions and many different competences. Here must be taken into account the mining excavation method, processing methods, beneficiation and overall mineral treatment. The results obtained from these study provide an important basis for the quantification and management of environmental impacts of the Integrated mine waste facility (IMWF) at the “Ada Tepa” gold mine. The aim of this research is to monitoring the process of internal water drainage into constructed cells of the facility. This task is performed using geophysical method based on electrical resistivity measurements made on the ground surface. Electrical resistivity tomography is commonly used to solve mining and engineering issues, because it is efficient and environmentally sound. This study demonstrates the efficiency of electrical resistivity tomography in detecting the saturated zones in the IMWF.

A new species within the genus Bithynia (Gastropoda: Bithyniidae) from northwestern Türkiye

In Türkiye, the family Bithyniidae is represented by two genera: Bithynia (Leach, 1818) and Pseudobithynia (Glöer & Pešić, 2006). Recent studies have shown that Bithyniidae species have a broad distribution across southeastern Europe, including Greece, Montenegro, and Bulgaria. In Türkiye, a total of 14 species have been documented so far, with nine belonging to the genus Bithynia and five to Pseudobithynia. We found a new Bithynia species in Kocaçay Stream, situated in the southern Marmara Region. This newly identified species has been compared with all known congeners from nearby ecosystems in Türkiye and neighbouring countries. http://www.zoobank.org/urn:lsid:zoobank.org:pub:C9665C20-F606-4763-8C82-E0DCFB23C7D8

Trichinella proficiency testing in Southeastern European countries

In some Southeastern European (SEE) countries, like Serbia, Romania, and Bulgaria, trichinellosis is one of the most important foodborne zoonotic diseases. In those countries, EU regulation and local authorities require the staff of laboratories performing official controls on meat to be properly trained and to check their competence by participating regularly in proficiency testing (PT). PTs are organized by National Reference Laboratories for Trichinella of each country and involve all official laboratories testing meat. In Romania and Bulgaria, the organization of PT for the detection of Trichinella larvae in meat by Magnetic Stirrer Method (MSM) started in 2012. In Croatia and Serbia PT was first organized in 2015 and 2017, respectively. This study presents data on the performance obtained by official laboratories of SEE countries that organize PT at national level and compares the performance obtained by laboratories belonging to different countries. Results suggest that the constant participation in PT leads to an increase in the performance of participating laboratories by positively affecting the staff accuracy in sample testing by MSM. Since the percentage of recovered larvae was in some cases suboptimal (<80%) and occasionally very poor (<40%), there is room for improvement. The regular participation in PT by laboratories involved in official controls on meat intended for human consumption is fundamental to guarantee consumer safety.

Chalcolithic Bone Spindle Whorls in Bulgaria: Finds from the “Tilkiyuk” Settlement Mound (Sadievo, Southeastern Bulgaria)

Chalcolithic Bone Spindle Whorls in Bulgaria: Finds from the “Tilkiyuk” Settlement Mound (Sadievo, Southeastern Bulgaria)

Phylogeography of the European ground squirrel, Spermophilus citellus (Rodentia: Sciuridae), in the Balkans

Abstract The Balkan Peninsula acted as a refugium for many steppic species during the Pleistocene, resulting in a high genetic variability, which, in some cases, presents a northward decreasing latitudinal gradient. In the present study, we investigate the genetic diversity of the European ground squirrel (Spermophilus citellus) in its Balkan distribution, sampled comprehensively across its entire distribution in Greece (133 samples from 21 localities). These samples are compared with others from Serbia (54 samples from eight localities) and the available published data from its range in Europe (124 sequences from GenBank). Our results show that the genetic diversity of the Greek and Serbian populations is not correlated with a latitudinal gradient. However, when the entire European range is considered, the model that best fits the genetic variation of the species is based on the ‘centre–periphery’ hypothesis. The founder (centre) populations of the species were most probably situated in south-eastern Bulgaria and European Turkey and underwent rapid expansion post-glacially, during the Holocene, both northwards (Central Europe) and southwards (Greece), as revealed by the decreased genetic diversity and phylogeographical inference analysis in these marginal regions. These results indicate a particular phylogeographical history of a European species and set a baseline for conservation management in its southern populations.

Crocus speciosus (Iridaceae)—A New Species for the Bulgarian Flora

This is the first report on the autumn-flowering species Crocus speciosus, belonging to C. ser. Speciosi from the Bulgarian flora. The species was found in Southeastern Bulgaria, in the area between Ahtopol and Rezovo. Re-examining the Bulgarian collections, the earliest specimen was collected in 1975, was probably overlooked, and most likely determined as C. pulchellus. The nearest known localities of the species are on the territory of Türkiye. In this study, we compared C. pulchellus and C. ibrahimii using DNA sequence data from the nuclear ITS1/2 region and morphological features. Our study showed a close relationship between the specimens from Bulgaria and the recently deposited data of C. speciosus and their separation from the closely related C. pulchellus. Together with the previously cited white anthers as a key feature for determination, the molecular data confirmed a clear distinction between the samples with white anthers in the two species. The morphological data of our taxon overlapped with the description of C. ibrahimii. The molecular data strongly supported the affiliation of C. speciosus s.l., but did not support the recognition of C. ibrahimii as a separate species and it should be referred to as a subspecies of C. speciosus subsp. ibrahimii Rukšāns.

Diet composition of the long-legged buzzard (Buteo rufinus) in southeastern Bulgaria

Abstract During 2018–2022, the local breeding population of the long-legged buzzard (Buteo rufinus) in southeastern Bulgaria was monitored in the territory of three districts of Sliven, Yambol and Burgas. Diet data were collected in 15 breeding pairs. Overall, we identified 290 prey items. We used three methods for diet analysis that produced different results: (1) collecting prey remains (68 individuals, 23.5%), (2) collecting pellets and skeletal materials (42 individuals, 14.5%), and (3) collecting data on a diet using trail cameras (180 individuals, 62.1%). The dominant part of the diet formed mammalian species (69.3%, ten species and some undetermined Rodentia and other Mammalia). Birds were less represented but with similar species richness (21.0%, 11 species and pigeons (Columba sp.), thrushes (Turdus sp.), undetermined Passeriformes and Galliformes). Compared to birds, the proportion of Reptilia was lower (9.3%, two species). Amphibia were represented only with one specimen of the common toad (Bufo bufo). The dominant diet of long-legged buzzards in southeastern Bulgaria was European souslik (Spermophilus citellus, 31.0%), followed by sibling vole (Microtus mystacinus, 25.5%). Less abundant taxa were undetermined Passeriformes (6.9%), lesser mole rat (Nannospalax leucodon, 5.9%), pigeons (4.5 %), blotched snake (Elaphe sauromates, 3.8%), Balkan green lizard (Lacerta trilineata, 3.5%), European hare (Lepus europaeus, 3.1%), common magpie (Pica pica, 2.8%), Colubridae (1.7%), common blackbird (Turdus merula, 1.4%), domestic chicken (Gallus gallus domesticus, 1.0%) and Eurasian skylark (Alauda arvensis, 1.0%). Spermophilus citellus was the most abundant species in the Yambol district samples and the most abundant species in the data obtained from trail cameras. In the Burgas district, the dominant species was Microtus mystacinus. When comparing the diet spectrum of Buteo rufinus from other authors, birds occurred more frequently than reptiles in our material.

Geochemical and petrographic investigation of the provenance of white marble decorative elements from the Roman Villa Armira in south-eastern Bulgaria

The paper presents evidence of Roman marble production in the Balkan region, specifically from the south-eastern Rhodope Mountain area (modern Bulgaria) and Armira. Although the Roman marble trade and production in antiquity are well known in Prokonnesos, Thasos, and several other production sites, marble deposits from inland Thrace have received far less attention. In 2018–2019, a systematic survey of south-eastern Bulgaria (Roman Thrace) was carried out by our team in collaboration with the National Archaeological Institute with Museum in Bulgaria. White marble quarries and outcrops were investigated in situ with the goal of characterizing the macroscopic qualities of the stone. Quarry samples were collected and analyzed through various techniques—petrography, isotopic, and chemical analyses—and compared with the architectural decorative marble and artifacts from the Roman villa at Armira. We demonstrate that the geochemical and petrographic features of these samples indicate a marble provenance restricted to a few selected sources. We conclude that the local marble from the Armira and Kamilski Dol quarries was widely used for the complete architectural program of the Roman villa of Armira.

Diet shifting of tortoise-eating Golden Eagles (Aquila chrysaetos) in southeastern Bulgaria

Top predators may adapt their diets to changes in prey availability where human-induced environmental changes are intense. This long-term study of the breeding-season diet of Golden Eagle (Aquila chrysaetos) in the Strandzha Mountains analyzed shifts in diet caused by the population decline in principal prey species, the tortoises (Testudo hermanni and T. graeca). Tortoises comprised 50.0% of the eagle diet by prey number in the 1990s, but that share collapsed to 5.8% in 2014–2021. During this later interval, Golden Eagles preyed more intensively on lighter-weight prey such as Northern White-breasted Hedgehog (Erinaceus roumanicus, an increrase of 28.2% by number) and Edible Dormouse (Glis glis, an increase of 14.9% by number). Hedgehogs predominated in the diet of an individual eagle nest site for the first time in 1998 and became the principal prey in 2014–2021. Differences in food niche breadth and proportions of mesopredators between tortoise- and hedgehog-dominated individual annual diets were not significant, corresponding to a low level of food stress. The only eagle with an annual diet dominated by Squamata (snakes and lizards) was an exception, having the widest food niche. Young domestic ungulates have almost completely disappeared from eagle diets at the same as the reduction of tortoises, corresponding to a concurrent decline of livestock farming. The results obtained here have relevance to conservation management of both predator and prey populations.

Rise and fall: Results of a multidisciplinary study and 5-year long monitoring of conservation translocation of the European ground squirrel.

The current publication gives a detailed assessment of the results from a population reinforcement of a European ground squirrel's (Spermophiluscitellus) colony in south-eastern Bulgaria. The reinforcement was planned and implemented along with multidisciplinary research of the adaptation process (including radiotelemetry, parasitological study and assessment of the stress in the animals) and regular monitoring (yearly burrow counting). Although the donor and recipient populations were genetically similar, morphometrical data indicated variations in the body size probably due to the difference in population densities in the two sites. The monitoring revealed that the burrows were aggregated and there was a positive correlation in the spatial distribution of the ground squirrels' burrow holes and the colonies of Harting's vole (Microtushartingi) - another social ground-digging rodent that co-inhabits the study area. The first results showed successful reinforcement according to the three classical evaluation criteria: the individuals survived the translocation process, they successfully reproduced and an initial population growth was observed, based on the burrow entrances' count - from 36 in 2017 to 280 in 2020. In 2021, however, a considerable decline in the abundance of the population was recorded - 58.5% decline in the burrow number and 36% decline in the colony area. A decrease was also observed in the abundance of the Harting's voles' colonies. A review of all the collected information suggests it is unlikely that the decrease is due to helminth parasites, translocation stress or other behaviour issues. The most probable explanation is the bad weather conditions - unusually high rainfalls combined with relatively high temperatures in January 2021. In conclusion, we strongly emphasise the need for detailed and long-term monitoring after conservation translocation and careful evaluation of all the influencing factors before, during and after such actions.

Influence of some environmental factors on the distribution of zooplankton complexes in Mandra Reservoir, in Southeastern Bulgaria

The aim of the present study was to trace the influence of some environmental factors (w.temperature, wind, transparency, depth) on the distribution of zooplankton communities in the system Reservoir Mandra and the ecotone zones formed at the confluence of rivers Fakiyska, Sredetska, Izvorska and Rusokastrenska. Four samplings were performed at seven sites between February 2020 and January 2021. After determining the species composition and abundance, the results were subjected to structural analysis and Canonical Correspondence Analysis (CCA). A total of 67 taxa were identified, constituting about 48% of the Rotifera group, 27% of Cladocera and 19% of the Copepoda and only 6% from Protozoa. The Shannon-Weaver index for individual species diversity was between 2.37 and 0.62. The positive and negative correlation of zooplankton distribution in CCA shows that the relative abundance of any species depends on specific environmental variables. Analysis showed that temperature and wind had the strongest impact on the distribution of zooplankton.

Application of Remote Sensing Data for Assessment of Bark Beetle Attacks in Pine Plantations in Kirkovo Region, the Eastern Rhodopes

Intensive forest afforestation with native pine species was developed in the 1960s on degraded and deforested lands in the region of the Eastern Rhodopes (south-eastern Bulgaria). Severe damage by wet snow was registered in the coniferous forests of the Rhodopes in March 2015. In the following years, bark beetle attacks were registered on the broken and felled fresh wood. As a result, bark beetle infestation spots appeared in the pine plantations. In the period 2019–2021, damage caused by bark beetles was assessed in the region of State Forestry Kirkovo (the Eastern Rhodopes, south-eastern Bulgaria). An integrated approach using the data of the information system of the Executive Forest Agency (ISEFA), remote sensing data obtained by an “eBee SQ” unmanned aerial vehicle (UAV) equipped with a “Parrot Sequoia” multispectral camera, and subsequent terrestrial observations, was applied. ISEFA data showed that there was no serious damage caused by abiotic and biotic factors in the pine forests of SF Kirkovo until 2014. Snow damage in 2015 affected 513 ha of pine plantations, and bark beetle infestations reached up to 1316 ha in 2016. In 2019, a total of 226.87 ha of pine plantations were captured in three localities—Fotinovo, Kirkovo, and Kremen. The relative share of damage caused by bark beetles was greater in P. sylvestris plantations (15.3–23.0%), compared to damage in P. nigra (2.3%). Four different categories of normalised difference vegetation index (NDVI) were separated in bark beetle infestation spots—living trees, dead trees, grass and shrub vegetation, stones and rocks. The NDVI values in locations with living trees varied between 0.500 (spaces between tree crowns) and 0.700 (central part of the crown projection) (an average of 0.617). In the locations with dead trees, the average values of NDVI of lying trees was 0.273, and in standing trees, NDVI varied between 0.275 (central part of crown projections) and 0.424 (spaces between tree crowns). In the locations with grass and shrub vegetation, stones and rocks, the average NDVI was 0.436 and 0.329, respectively. In the field study, average defoliation of 31.2–32.3% was registered in P. sylvestris plantations, and 47.4% in P. nigra plantations. Defoliations mainly were caused by pine processionary moth (Thaumetopoea pityocampa) and fungal pathogens (Dothistroma septosporum and Lecanosticta acicola). The damage was caused by Ips acuminatus (in P. sylvestris only), and I. sexdentatus, Tomicus piniperda and T. minor (in P. sylvestris and P. nigra). Infestations by other xylophages, such as Phaenops cyanea, Rhagium inquisitor, and Pissodes spp., were also found on pine stems.

Change in agronomic characteristics and essential oil composition of coriander after application of foliar fertilizers and biostimulators

Nowadays the biologically active substances are very attractive, because they are harmless and ecological friendly. Their application is not only economically profitable, but also improves the action of the fertilizers and increases the yields. The study aims to investigate the effect of some foliar fertilizers and biostimulators on the elements of productivity, seed yield and the essential oil content and composition of Lozen 1 coriander (Coriandrum sativum L.) cultivar. The field trial was carried out on leached Smolnitsa soil type in the region of the village of Zhrebino, South-Eastern Bulgaria in the period 2018–2020. The experiment was arranged according to the randomized complete block design in four replications with a plot size of 15 m2, after predecessor wheat. The treatment of coriander with the leaf fertilizer Masterblend in a dose of 2.5 kg ha-1 resulted in an average yield increase of 11.8% compared with the untreated control. After treatment with the foliar applied products an increase in the essential oil content from 2.9% to 9.6% was established, as the highest values were obtained when using the biostimulator Fertigrain – 1.26% and the foliar fertilizer Masterblend – 1.25%. The most frequent components of the essential oil were linalool, γ-terpinene, α-pinene and camphor. The highest values of linalool were observed after the application of the products Masterblend and Poly Plant. The used products stimulated the biological potential of the tested cultivar and could be recommended for further investigations by other essential oil crops.

Mineralogical Characterization of Early Bronze Age Pottery from the Svilengrad-Brantiite Site, Southeastern Bulgaria

Several pottery sherds from the Svilengrad-Brantiite site, Bulgaria, were mineralogically and petrographically analyzed. The aim was to add information to the very scarce material data available for Early Bronze Age pottery in the southeastern Thrace plain, Bulgaria, in order to examine a possible raw-material source of the pottery. The characterization techniques applied were optical microscopy (OM), petrographic microscopy (PM), scanning electron microscopy coupled with energy dispersive X-ray spectroscopy (SEM-EDS), X-ray fluorescence (XRF) spectroscopy, and X-ray diffraction (XRD). The pottery samples consisted of two typological groups: a local-made type and a cord-impressed decoration type influenced by foreign cultures. All of the samples were produced from fine clay pastes that had a quite similar composition, with abundant mineral grains of similar mineral composition and fragments of metamorphic and granitic rocks. The chemical compositions of each mineral in the grains and fragments were almost identical, and consistent with those from metamorphic and granitic rocks from the Sakar-Strandja Mountains near the study site. The clay paste compositions corresponded to those of illite/smectite mixed-layer clay minerals or mixtures of illite and smectite, and the clay-mineral species were consistent with those in Miocene–Pleistocene or Holocene sediments surrounding the site.

VARIABILITY OF SEEDLING TRAITS IN SEMI-DWARF AND NON-DWARF SPRING BARLEY CULTIVARS

The aim of the present study was to study some seed and seedling characteristics and their relationship with plant height in semi-dwarf and non-dwarf spring barley varieties. The study was conducted at the Institute of Agriculture - Karnobat, Southeastern Bulgaria during the 2019 and 2020 growing seasons. Ten semi-dwarf and ten non-dwarf cultivars of spring barley from the USA and Canada were studied. The semi-dwarf cultivars showed significantly lower mean values for the length of coleoptile and seedling and seminal root number compared to non-dwarf cultivars. However, there were semi-dwarf cultivars with a coleoptile length similar to that of non-dwarf cultivars. Correlation analysis showed a significant association of plant height with seedling length and seminal root number. The rest of the seedling characteristics were uncorrelated with plant height and, hence allowing breeding for that trait without compromising high seedling vigour.