•Habitat suitability maps of 5 keynote species in the Bulgarian region of the Black Sea.•SDMs utilize species presence only (PO) localities data.•SDMs are fitted considering biotic interactions and ...abiotic environment.•The estimated probabilities of species occurrences are validated with species abundance.•Resultant SDMs can be further implemented for conservation and stock management.
Over the past few years, predicting species spatial distributions has been recognized as a powerful tool for studying biological invasions in conservation biology and planning, ecology, and evolutionary biology. Species spatial distribution models (SDMs) are used extensively for assessing the effects of changes in habitat suitability, the impacts of climate change, and the realignment of the existing conservation priorities. SDMs relate known patterns of species occurrences to a specific set of environmental conditions. Accordingly, we have used MaxEnt SDM tool in order to provide habitat suitability models of 5 keynote fish species: European sprat (Sprattus sprattus L.), red mullet (Mullus barbatus, L.), horse mackerel (Trachurus mediterraneus, L.), bluefish (Pomatomus saltatrix, L.) and whiting (Merlangius merlangus, L.), inhabiting the Bulgarian region of the Black Sea. Presence-only (PO) data collected by pelagic surveys performed between 2017 and 2019 was further utilized to link known species occurrence localities with selected abiotic factors, such as surface sea temperature and salinity, dissolved oxygen, and speed of currents. Biotic interactions were also considered for fitting the patterns of habitat suitability models. The SDMs, obtained from the present research study, prove to have satisfactory predictive accuracy to be further implemented for conservation measures and planning, stock management policy-making, or ecological forecasting.
Global warming is increasing the frequency and severity of the marine heat waves, which poses a serious threat to the marine ecosystem. This study analyzes seasonal and interannual dynamics in the ...abundance and structure of the mesozooplankton community in Sevastopol Bay based on bi-monthly routine observations over 2003–2014. The focus is on the impact of the summer 2010 marine heat wave (MHW2010) on crustaceans belonging to different ecological groups. As a response to the MHW2010, three warm-water species (O. davisae, A. tonsa and P. avirostris) exhibiting the maximum seasonal density in latter summer showed a sharp increase in the annual abundance and their share in the mesozooplankton community. The increase in the annual abundance in 2010 of the eurythermal species P. parvus and P. polyphemoides exhibiting seasonal peaks in spring and autumn is not related to the MHW2010 but can be explained by a rise of temperature in the first part of the year. O. davisae and A. tonsa showed the most pronounced response among the species to the MHW2010, confirming that non-native species exhibited great flexibility as an adaptive response to environmental changes, especially in the case of climate warming. Among crustaceans observed in this study, O. davisae can be considered as an indicator of the environmental conditions associated with the warming of the Black Sea and the Mediterranean basin as a whole.
The red mullet (
Mullus barbatus
Linnaeus, 1758) is a keynote species for the Bulgarian Black Sea ecosystem and fisheries; nevertheless, existing knowledge on population status is very scarce. The ...present study was intended to assess the health status and adaptive potential of
M. barbatus
populations inhabiting the Bulgarian waters of the Black Sea. Our findings revealed that populations of
M. barbatus
are exposed to a variety of anthropogenic and environmental stressors. The species’ status was assessed using representative genetic, morphological, biochemical and chemical biomarkers from specimens obtained in the research area’s northern and southern regions. Based on mtDNA markers, genetic analysis revealed low haplotype and nucleotide diversity, typically observed in overexploited or “threatened” populations. Examining the morphology of the specimens revealed no discernible pattern of differentiation. Except for aluminium and chrome, metal and PAH concentrations in fish were below the regulatory thresholds. The specimens from the southern region ingested more microplastics than those from the northern region. The majority of specimens collected from the southern region also exhibited elevated levels of oxidative stress and decreased antioxidant defence, which can be interpreted as an early indication that they had reached the limits of their adaptive potential. Further research on the composite effects of the stressogenic environment on the Black Sea biota are critically needed, as well as the introduction of new indicators and thresholds at molecular and cellular levels for adequate monitoring of both the ecological state of the marine environment and its biota.
The Elatsite–Chelopech ore field in the northern part of the Panagyurishte district in Central Bulgaria comprises numerous spatially associated porphyry copper and epithermal gold deposits and ...prospects. In addition to the mineralization and alteration features, trace elements, lead and sulfur isotope signatures of sulfide minerals from porphyry copper, base metal and gold-base metal deposits/prospects have been studied. LA-ICP-MS analyses of pyrite, arsenopyrite and sulfosalt minerals validate them as major carriers for Au, Ag, Sb, Se and Co. Pyrite from the three types of mineralization has specific geochemical characteristics. Pyrite from the porphyry copper deposits/prospects has generally lower total trace element content compared to pyrite from the epithermal prospects, except for Se, Co and Ni. Pyrite from the base metal and gold-base metal veins is enriched in As, Au, Ag, Sb and Pb. In pyrite from the base metal deposits, Co and Ni have contents comparable to the pyrite from the porphyry copper deposits, while pyrite from the gold-base metal veins shows lower Co and Ni. Arsenopyrite from these deposits shows similar features. Similarly, sphalerite from the gold-base metal veins also has lower Co content compared to sphalerite from the base metal veins but higher In and Cu contents. In addition to the close spatial relationships between the Elatsite and Gorna Kamenitsa porphyry Cu deposits and Negarstitsa-West and Dolna Kamenitsa base metal prospects, as well as similarities in the mineralization and alteration styles, the lead isotopic (206Pb/204Pb = 18.61–18.68, 207Pb/204Pb = 15.64–15.65 for porphyry and 206Pb/204Pb = 18.55–18.67, 207Pb/204Pb = 15.64–15.68 for base metal) and sulfur isotopic (δ34S values of −3 to +1‰ for porphyry and δ34S values of −1.7 to +3.5‰ for base metal) signatures of sulfides support the idea of a genetic link between these two types of deposits. The porphyry and base-metal mineralization result from a common major ore-forming event during the Late Cretaceous, corresponding to deep/higher-temperature and shallower/distal/lower-temperature environments, respectively. In particular, more radiogenic lead (206Pb/204Pb = 18.41–18.47, 207Pb/204Pb = 15.67–15.76) and slightly different sulfur isotopic compositions (δ34S values of +3.5 to +10.6‰) of sulfides from the distal gold-base metal veins of Kordunsko Dere, Svishti Plaz and Shipkite might be a consequence of the interaction of the ore-forming fluids with an external older crustal and isotopically positive S source. Alternatively, a different fluid source/event for the formation of these gold-base metal veins may be suggested.
The Vathi porphyry Cu-Au±Mo deposit is located in the Kilkis ore district, northern Greece. Hydrothermally altered and mineralized samples of latite and quartz monzonite are enriched with numerous ...rare and critical metals. The present study focuses on the bulk geochemistry and the mineral chemistry of pyrite, chalcopyrite, magnetite, and titanite. Pyrite and chalcopyrite are the most abundant ore minerals at Vathi and are related to potassic, propylitic, and sericitic hydrothermal alterations (A- and D-veins), as well as to the late-stage epithermal overprint (E-veins). Magnetite and titanite are found mainly in M-type veins and as disseminations in the potassic-calcic alteration of quartz monzonite. Disseminated magnetite is also present in the potassic alteration in latite, which is overprinted by sericitic alteration. Scanning electron microscopy and laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) analyses of pyrite and chalcopyrite reveal the presence of pyrrhotite, galena, and Bi-telluride inclusions in pyrite and enrichments of Ag, Co, Sb, Se, and Ti. Chalcopyrite hosts bornite, sphalerite, galena, and Bi-sulfosalt inclusions and is enriched with Ag, In, and Ti. Inclusions of wittichenite, tetradymite, and cuprobismutite reflect enrichments of Te and Bi in the mineralizing fluids. Native gold is related to A- and D-type veins and is found as nano-inclusions in pyrite. Titanite inclusions characterize magnetite, whereas titanite is a major host of Ce, Gd, La, Nd, Sm, Th, and W.
The Gerakario Cu-Au porphyry deposit in the Kilkis ore district, northern Greece, contains epithermal quartz-stibnite veins on the eastern side of the deposit, which crosscut a two-mica gneiss. ...Metallic mineralization in these veins consists of stibnite + berthierite + native antimony + pyrite + arsenopyrite, and minor marcasite, pyrrhotite, chalcopyrite, löllingite, and native gold. Bulk geochemical analyses of the ore reveal an enrichment in critical and rare metals, including Ag, Au, Bi, Ce, Co, Ga, La, and Sb. Analysis of stibnite with LA-ICP-MS showed an enrichment in base metals (As, Cu, Pb), as well as weak to moderate contents of critical and rare metals (Ag, Bi, Ce, La, Re, Sm, Th, Ti, Tl). A statistical analysis of the trace elements show a positive correlation for the elemental pairs Ce-La, Ce-Sb, and La-Sb, and a negative correlation for the pair Bi-Sb. Fluid inclusions in the A-type veins of the porphyry-style mineralization show the presence of fluid boiling, resulting in a highly saline aqueous fluid phase (35.7 to 45.6 wt.% NaCl equiv.) and a moderately saline gas phase (14 to 22 wt.% NaCl equiv.) in the system H2O-NaCl-KCl at temperatures varying between 380° and 460 °C and pressures from 100 to 580 bar. Mixing of the moderate saline fluid with meteoric water produced less saline fluids (8 to 10 wt.% NaCl equiv.), which are associated with the epithermal quartz-stibnite vein mineralization. This process took place under hydrostatic pressures ranging from 65 to 116 bar at a depth between 600 and 1000 m, and at temperatures mainly from 280° to 320 °C.
The paper presents newly obtained field and laboratory data for flint raw materials and artefacts from northwestern Bulgaria. The field survey and associated analytical work were carried out in 2020 ...with the following purposes: i) identifying flint raw material outcrops in the region; ii) collecting suitable raw material samples from discovered outcrops and flint artefacts from newly excavated archaeological sites; iii) integrated laboratory analyses of the samples (micropetrography and geochemistry); iv) recording and updating information about archaeological sites in the “Archaeological Map of Bulgaria” information system in the Montana and Vidin regions; and v) GIS-based reconstruction (least-cost path models) of possible raw material procurement systems, based on similarities between samples from different archaeological sites and flint outcrops.The micro-petrography and trace elements, determined by LA–ICP–MS suggest that only a few specimens among the analysed artefacts from NW Bulgaria show similarities to the local raw materials. The artefacts sampled as macroscopically similar to the Balkan flint (BF) from the recently discovered Neolithic sites in NW Bulgaria show affinity with previously studied samples of BF from the Pleven–Nikopol region, where two main clusters of BF sources were identified and recorded in 2011. Additionally, GIS-determined pathways of flint distribution are suggested in the context of raw material procurement strategy and acquisition.
In the present study two analytical methods are applied to characterize chert artefacts and raw materials from northeastern Bulgaria (Ludogorie region): petrographic observation and laser ablation ...inductively coupled plasma mass spectrometry). Archaeological samples from 12 Chalcolithic sites from Bulgaria are analyzed as well as raw material from 6 outcrops in northeastern Bulgaria are identified and documented during a survey in 2012 when many raw material samples were collected. The chert raw material mostly occurs in various Quaternary secondary deposits, originating from destruction and disintegration of the Lower Cretaceous (Aptian) limestones in the area. The paper is aimed at tracing the provenance of the artefacts based on their petrographic characteristics and geochemical composition. The archaeological evidence shows a wide distribution of the Ludogorie chert throughout the country. On the basis of micropetrographic observations, Gurova and Nachev (2008) described two main chert types (Ravno and Kriva Reka). Our petrographic study confirmed the previous results and an additional chert type was distinguished, originating from primary and secondary deposits (quarries in Koprivetz and Krasen villages) and is represented by silicified limestones (bioclastic-peloidal packstones or grainstones). It is noteworthy that the first two types of chert were largely used for prehistoric artefact manufacturing while the last one is not attested among studied assemblages at all.
The Bulgarian prehistoric sequence is characterized by the use of particular raw materials in distinct ‘cultural’ contexts. The Karanovo I and II stages of the Early Neolithic (part of a ...supra-regional technocomplex in the Balkans) are recognisable by formal toolkits made of Balkan flint. The Chalcolithic period is famous for its superblades made of high-quality Ludogorie flint, which also attain a wider Balkan distribution. Despite a solid corpus of reliable data for northern Bulgaria from our previous field surveys and laboratory analyses, there are still questions that can only be resolved by further research.
This paper presents the results of petrographic and chemical (LA-ICP-MS) analyses of a series of archaeological artefacts and raw material samples collected during a survey in Shumen District of northeast Bulgaria. These data allow us to i) distinguish two new types of flint (Shumen I and II) which are represented by both raw material outcrops and artefacts and previously referred to as ‘Moesian flint’; and ii) expand our analytical data for the Kriva Reka type of Ludogorie flint, confirming its substantial role in prehistoric flint production, distribution and use. These results suggest a more complex network of raw material sources and distribution routes in prehistory than previously assumed.
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