Bulgarian Black Sea Research Articles

Historical Development of the Bulgarian Black Sea Resorts

Historical Development of the Bulgarian Black Sea Resorts

Sedimentological and engineering geological features of the Sarmatian limestones along the Black Sea Coast between the capes of Kaliakra and Shabla

This article aims to present the results of geotechnical studies of the main rock complexes that compose the periphery of the Dobrudzha Plateau in the area from Cape Kaliakra to Cape Shabla (Bulgarian Black Sea Coast), directly related to the development of hazardous geological processes. Sediments of the Sarmatian age were studied: carbonate tempestites, Mactra limestones (Karvuna Formation), nubecular (foraminiferal), reef and bioclastic limestones (Odartsi Formation). The corresponding microscopic and petrographic analyses of the studied sediments are also presented. Studies of collapses in caves near Cape Kaliakra show that they occur in friable peloidal limestones, with disturbances following stratification. This is confirmed by laboratory tests of samples showing lower strength indicators, namely in the direction to the layering. The results of laboratory tests of specimens from the sections between the village of Tyulenovo and Cape Shabla, including foraminiferal, reef and bioclastic limestones, show higher values of physical and mechanical parameters compared to limestones at Cape Kaliakra. In the case of the bioclastic limestones, higher strengths are found crosswise to the layering, and in the case of compressive strength, the ratio is double. The obtained data provide valuable information about the engineering geological parameters of the main varieties in which the rock deformations are developed, which can be used in the analysis of slope stability.

A study of the microbiology of the intestinal tract in different species of Teleost fish from the Black Sea

This paper presents a study on the microbial status of different fish species and their habitats in the Bulgarian Black Sea area. The samples were collected in the period of January 2021 until March 2021. The fish species we used in this study were Black Sea turbot (Scophthalmus maximus), round goby (Neogobius melanostomus), shore rockling (Gaidropsarus mediterraneus) and European anchovy (Engraulis encrasicolus). The BIOLOG system was used for microbiological determination. From the different fish species, different species of microorganisms were isolated (using selective nutrient media). From the torbut, we isolated species Enterococcus villorum with 24 × 103 cells in 1 ml, Moraxella nonliquefaciens with 70 × 103 cells in 1 ml and Pseudomonas synxantha with 123 × 103 cells. Pseudomonas putida was isolated from the round goby with 20 × 103 cells in 1 ml. The species Streptococcus entericus with 123 × 103 cells in 1 ml was isolated from the shore rockling. Pseudomonas fulva with 60 × 103 cells in 1 ml was isolated from the European anchovy. A total of 223 × 103 cells in 1 ml of Pseudomonas agarici were isolated from Trachinus draco. Pseudomonas tolaasii with 145 × 103 cells in 1 ml were isolated from Merlangius merlangus. A different species of bacteria of the genus Pseudomonas was found for each of the investigated species of Black Sea fish. Apparently, the species Pseudomonas is characteristic of marine Teleostei and is important for the life and metabolism of these vertebrates. These microorganisms probably are resident species and developed not as result of pollution or environmental change.

Battered by Geopolitical Winds, Bulgaria Struggles to Restart Much Needed Reforms

Battered by Geopolitical Winds, Bulgaria Struggles to Restart Much Needed Reforms

Natural resource governance in the Bulgarian Black Sea: Identifying context-sensitive institutional arrangements

ABSTRACT The main objective of this article is to study the local governance dynamics around natural resources in the delimitated Marine reserve Kaliakra, on the Bulgarian Black Sea coast. Our research focuses mainly on formal/informal institutional arrangements for that zone. This article aims to achieve several objectives. First, it seeks to contribute to the common pool resources (CPR) theories, applying Ostrom’s socio-ecological framework and broaden its scope to the larger institutional context. Second, it will focus specifically on one marine protected area and the harvesting of the invasive species Rapana Venosa in the Bulgarian Black Sea. Although formal institutions are important in setting the rules for natural resource governance, this study finds that informal institutions, specific to the country’s context, tend to shape the results and objectives of this governance and reflects the socio-economic characteristics of the macro context in which it is embedded.

Flood Resilience, Viability, and Growth Response to Seawater Immersion of Bermudagrass (Cynodon dactylon (L.) Pers.)

A holistic approach to sustainable coastal zone management assigns the development of nature-based and low-cost strategies for coastal protection during extreme meteorological events. This determines the growing interest in plant species with high salt tolerance, and the study of their flood resilience in order to determine their capacity for flooding and erosion control. Bermudagrass (Cynodon dactylon (L.) Pers.), with its vast rhizome system, has the major characteristic features of useful plant stabilisers of coastal sand dunes. This study aims to define the effects of flooding stress caused by storms on viability, survival ability, and growth response of bermudagrass in flooding simulations in order to define its flooding resilience. C. dactylon showed high resilience and tolerance to salt from seawater during flooding simulations. The Critical Decomposition Time of C. dactylon is estimated at 144 h, which is more than the maximum-duration flood recorded for the Bulgarian Black Sea Coast. Untreated rhizomes showed less viability than those treated with seawater in flooding simulations. Changes in resistance, viability, biomass, and vegetative allocation were more significant, with the water as an influencing factor. The temperature of seawater and duration of submergence had no significant effect. As a median value species between psammophytes from the Poaceae family and the Cyperaceae family, bermudagrass can be used as a model plant in flooding simulations.

Habitat suitability models of five keynote Bulgarian Black Sea fish species relative to specific abiotic and biotic factors

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.

‘The Black Sea Is Our Mallorca’: The Making of the Tourist Experience in the German Democratic Republic

Abstract This article analyses the construction of the East German holiday experience in the 1960s and 1970s, when tourism became a mass phenomenon on both sides of the Iron Curtain. First, it discusses the role played by the West in shaping the expectations of GDR tourists. Mallorca was the ultimate, but not sole, destination, that influenced how East Germans imagined tourism abroad. Secondly, the article tackles how expectations compared with actual experiences. State surveillance, scarcity and lack of means were common challenges that East Germans had to face and clashed with the glittering image of tourism with which they were inundated from West Germany. The Bulgarian Black Sea emerged as a substitute for that Western tourism as other possibilities, such as socialist Cuba or Yugoslavia, were limited. Touring in Bulgaria became a long-lasting experience. The article approaches the multiple meanings of this type of vacation abroad. Political, experiential and personal implications shaped East Germans’ holidays and entangled experiences and expectations, and the article provides a broad understanding of the meanings of vacation and tourism for citizens of East Germany.

Contribution to the Knowledge of Bromus Diandrus–Rigidus (Poaceae) Polyploid Complex in the Bulgarian and Romanian Floras

Comparative morphological and ploidy level survey of the polyploid complex B. diandrus-rigidus in the Bulgarian and Romanian floras was performed. Critical examination of the morphology of the collected specimens revealed B. diandrus is represented in both floras. The species has already been reported for Romania under the name B. rigidus. For Bulgaria, the species has been very recently reported on a conference poster with a single gathering from 2020. Here, we provide more records of the species along the whole Bulgarian Black Sea coast floristic region, with the oldest gathering dating back to 2003. Ploidy level estimation of the Bulgarian accessions by flow cytometry revealed all studied populations are octoploid which is congruent with data from elsewhere, and confirms B. diandrus is present in the Bulgarian flora. For both the Bulgarian and Romanian floras alien status of the species has been inferred.

The unexpected diversity in Amphora sensu lato (Bacillariophyta) at Sozopol Bay, the western Black Sea

During a survey of benthic diatoms from the Bulgarian Black Sea coast near the historic town of Sozopol, we found a high diversity of Amphora sensu lato taxa at a single site and on a single type of artificial substratum. A total of 40 taxa from the current genera Amphora, Halamphora, Seminavis and Tetramphora were recognized during light microscopy (LM) and scanning electron microscopy (SEM) observations. We were able to identify with a high degree of certainty only 6 taxa based on the literature, whereas for 19 taxa (or almost 50% of all taxa) we could not find even sufficiently similar species, and they remained unidentified to species level. Many of the species had small valve dimensions. The paper presents all taxa with short morphometric data and microphotographs under LM and SEM, where possible. All taxa are discussed and compared with similar known taxa. The illustrative materials in earlier works from the Black Sea and species descriptions, where such were available, were also consulted. Diversity of Amphora sensu lato in the Black Sea coastal waters seems to be underestimated, whereas some of the past records are uncertain. A discussion on the current state of knowledge of Amphora sensu lato species from the Black Sea is given.

Trace metal accumulation in tissues of wedge clams from sandy habitats of the Bulgarian Black Sea coast

The aim of the present study was to carry out an initial screening of trace metals bioaccumulation in soft tissues of the wedge clam (Donax trunculus Linnaeus, 1758) from different localities of the Bulgarian Black Sea coastal area and to evaluate the bioindicator potential of this species. Wedge clams were collected in June and September 2020 from sublittoral sandy habitats at different localities of the Bulgarian Black Sea coast. Soft tissues of individual clams were digested with nitric acid followed by ICP-OES analytical determination. The content of trace metals in the wedge clams differed significantly amongst localities. Higher metal content was present in wedge clams from Sveti Vlas, Shkorpilovtsi, Slanchev Bryag, Ahtopol and Kranevo. The highest values of lead (Pb) (2.51 mg/kg) and cadmium (Cd) (0.32 mg/kg) were found in samples from Sveti Vlas and the highest concentration of copper (Cu) (34.12 mg/kg), iron (Fe) (269.52 mg/kg) and nickel (Ni) (0.32 mg/kg) were detected in wedge clams from Shkorpilovtzi. Maximum content of chromium (Cr) (0.58 mg/kg) was present in samples from Slanchev Bryag, together with high values of Fe. The highest concentration of zinc (Zn) (18.04 mg/kg) together with high values of Cr and Fe were measured in wedge clams from Irakli. In conclusion, the wedge clams from the localities known to have higher coastal inflows and touristic pressures, i.e. Varna, Shkorpilovtzi, Sveti Vlas, Slanchev Bryag and Ahtopol accumulated significantly higher metal elements in their tissues. Only few significant seasonal differences in the concentration of metal elements in wedge clams were present and the observed seasonal variations were probably connected to the hydrological parameters of the ecosystems. The wedge clam D. trunculus is a suitable bioindicator for assessment and monitoring of metal pollution in the Bulgarian Black Sea environment.

State of the antioxidant defense system in wedge clams from Bulgarian Black Sea as a measure of resistance to environmental impacts

Pollution and climate change can induce oxidative stress (OS) in aquatic organisms. Reduced activity or incoordination between antioxidant enzymes in marine bivalves may cause cellular impairment with effects on higher levels of ecological organization. The present study aims to assess the condition factor and the activity of antioxidant enzymes catalase (CAT), superoxide dismutase (SOD), glutathione peroxidase (GPx), glutathione-S-transferase (GST), and glutathione concentration (GSH) in soft tissues of Donax trunculus (Linnaeus, 1758) as indicators of the state of marine ecosystems along the Bulgarian Black Sea coast. The wedge clams were sampled manually from different localities in June and in September. The activity of antioxidant enzymes and GSH concentrations varied both seasonally and among localities. Higher values of GSH, SOD and GPx were registered in wedge clams collected in autumn compared to those collected in summer. In wedge clams higher activity of the major phase II detoxification enzyme GST was observed in summer at localities with intensive tourism, suggesting an activation of the cell detoxification processes, presumably in response to increased environmental pressure. In conclusion, the observed presence of elevated enzyme activities suggested activation of the antioxidant protection system of the wedge clams in response to environmental pressure, indicating their ability to cope with induced OS and adapt to local conditions, and thus maintain ecosystem health.

Comparative study on the oxidative stress of commercially important fish species from localities with different ecological conditions along the Bulgarian Black Sea coast

The aim of the present study was to perform a pilot assessment and analysis of the oxidative stress (OS) level in four commercially important fish species (round goby, red mullet, sprat and horse mackerel) from different localities of the Bulgarian Black Sea coast. The fish were sampled during trawl selectivity experiments. The OS level in the fish was assessed by measuring lipid peroxidation (LPO), glutathione concentration (GSH), activities of superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx) and glutathione-S-transferase (GST), as well as acetylcholine esterase (AChE) in gills and liver. Round goby and red mullet caught in the Nessebar Bay showed clear signs of OS with the highest levels of LPO and GST activities, accompanied by the lowest AChE activities in both liver and gills. On the contrary, round goby caught near Maslen Nos (a region with good ecological conditions) were least affected by OS with low LPO and high GSH concentrations and SOD activity. There were no significant differences in the OS bioindicators of horse mackerel from the different localities. Sprat caught in Nessebar Bay, compared to those caught from the other localities, showed presence of OS indicated by lower GSH levels and relatively higher CAT, GPx and GST activities, accompanied by low AChE activity in gills. It can be concluded that round goby and red mullet were more vulnerable to OS induced by marine environmental factors than the horse mackerel and sprat. However, their antioxidant defense system allows them to tolerate and adapt to the environment of their habitats. Further studies are needed for the assessment of OS in important fish species in the Bulgarian part of the Black Sea.

Seasonal variations of the microflora of wedge clam Donax trunculus (Linnaeus, 1758) from the region of Arkutino (Bulgarian Black Sea aquatory)

The main goal of the present study was to investigate the impact of the state of the environment on the microbiota of the wedge clam Donax trunculus (Linnaeus, 1758) from the region of Arkutino (Bulgarian Black Sea aquatory). The species Enterococcus hirae was isolated during the summer (from May to August). The species P. mendocina prefers the warmer months and the species P. alcaligenes the colder ones. The temperature followed a course of decrease during the period September 2020 to January 2021, followed by a slow increase from February 2021. Comparing May 2020 with May 2021, it became evident that in 2021 the temperature was 1.5 °C lower. We can say that the number of the species P. alcaligenes was twice as high in May 2021. It is likely that this species preferred lower optimum temperatures and constant other parameters. For the species Enterococcus hirae such dependence was not observed - the number remained constant in May, but with increasing temperature the number of microorganisms decreased during the summer months. The species seemed to preferably develop at pH 7.78. The species A. gyllenbergii preferably grows at temperatures between 20.3–25.7 °C and the optimal temperature was 25.7 °C. For C. farmeri the optimum conditions were temperature 26.2 °C and pH 7.3. The species E. vulneris was probably related not only to the increase in water temperature, but also to the anthropogenic factor, as it was found only in July.

Seasonal changes in the pro/antioxidant status of mussels Mytilus galloprovincialis (Lamarck, 1819) from Bulgarian Black Sea coastal habitats

The pro/antioxidant status of marine macrozoobentic organisms is being increasingly applied in environmental monitoring and conservation programs. The oxidative stress level in marine bivalves can provide valuable information not only on the health of the organisms and their populations, but also on the current state of habitats and ecosystems. The aim of the present study was to make the first comprehensive investigation of the seasonal changes in the antioxidant activity in different organs (gills, digestive gland and foot) of M. galloprovincialis from representative Bulgarian Black Sea coastal habitats. The lipid peroxidation and glutathione levels, as well as activities of the antioxidant enzymes catalase, superoxide dismutase, glutathion peroxidase, glutathion reductase, glucose-6-phosphate dehydrogenase and glutathione-S-transferase of the organs were measured spectrophotometrically. Our hypothesis was that enhanced environmental pressure during the summer season, induced by multiple factors (biogenic, abiogenic and anthropogenic) led to weakening of the antioxidant protection in mussels at the beginning of autumn. The reaction of the mussel organism to the multiple stress factors was specific for the target organ and the type of the biomarker. Significant differences were present in the activity of the antioxidant system in mussels from the northern and southern coastal locations. The seasonal changes in the pro/antioxidant status of mussels were primarily due to specific seasonal changes in factors concerning the marine environment at the concrete locality. Further research is obviously needed to confirm the present results and provide a more complete data of seasonal and spatial changes in the antioxidant defense system of mussels from the Bulgarian Black Sea coastal area and their implementation in biomonitoring programs.

Assessment of PAHs accumulation in Donax trunculus (Linnaeus, 1758) (Bivalvia, Donacidae) from the Bulgarian Black Sea Coast

Anthropogenic pollution of marine ecosystems is one of the main sources of polycyclic aromatic hydrocarbons (PAHs). Marine bivalves are often used as bioindicators of environmental pollution due to their wide distribution and capability of xenobiotic bioaccumulation. The aim of the present study was to assess the presence of PAHs in soft tissues of wedge clams Donax trunculus (Linnaeus, 1758), collected from sublittoral sandy habitats at different locations off the Bulgarian Black Sea coast. Wedge clams from the different locations showed variations in the content of accumulated PAHs’ compounds. The concentrations of PAHs were measured by gas chromatography system with mass spectrometry detection. The total PAHs content (sum of 13 PAHs’ compounds) measured was in the range from 5.59 to 50.50 ng/g wet weight and was comparable with other European studies. The compounds phenanthrene and fluorene were most abundant in all analyzed samples. The results showed that low molecular weight (LMW) PAHs (2 and 3 aromatic rings) were predominant, accounting for 91% of the total PAHs levels, while high molecular weight (HMW) PAHs (4–5- and 6- rings) presence was 8.9% on average. The ratio LMW/HMWPAHs was higher than one, suggesting predominant pollution of petrogenic origin. The concentrations of benzo (a)pyrene did not exceed the limit set in EC Regulation although it was detected in 20% of the analyzed samples. In conclusion, maximum overall PAHs content was found in clams from Arkutino, while minimum PAHs content was present in samples from Elenite. The Sum PAH4 (sum of four polycyclic aromatic hydrocarbons: benzo[a]pyrene, chrisene, benzo[a]anthracene, and benzo[b]fluoranthene) in the wedge clams for all localities studied was below legislation limits. Data from the present research can be used for assessing pollution levels in the marine environment and also risk of human exposure to PAHs using D. trunculus as bioindicator species.

Seafaring along the Bulgarian Black Sea Coast in the Ottoman Period, Based on the Finds from the Late Eighteenth- Early Nineteenth-Century Kitten Shipwreck

Seafaring along the Bulgarian Black Sea Coast in the Ottoman Period, Based on the Finds from the Late Eighteenth- Early Nineteenth-Century Kitten Shipwreck

Current distribution of Zostera seagrass meadows along the Bulgarian Black Sea coast (SW Black Sea, Bulgaria) (2010-2020).

BackgroundThe current distribution of Zostera spp. seagrass meadows along the Bulgarian Black Sea coast was studied. We used a combination of historical and recent observations of the habitat along the studied coastline. Remote sensing data (satellite images, sonar side-scans) was groundtruthed with georeferenced drop camera observations, scuba diving sampling and georeferenced scuba diving photo and video transects.New informationТhe total area of the habitat type ‘MB548 - Black Sea seagrass meadows on lower infralittoral sands’ (EUNIS habitat type list 2019) in the study area is 916.9 ha, of which only 17.9 ha are in man-made sheltered environments (harbours). All seagrass meadows identified in 1978-79 were also located during the current survey, despite the increased eutrophication pressure and overall degradation of benthic habitats in the western Black Sea during the 1980s and early 1990s.

LIFEWAY INTERPRETATIONS FROM ANCIENT DIET IN THE VARNA CEMETERY

SummaryRescue excavations in the urbanized area of the Varna Bay in 2017 have brought to light 15 prehistoric burials whose grave goods and AMS dating have unequivocally related them to the famous Copper Age cemetery in Varna on the Bulgarian Black Sea coast. The newly excavated area was called Varna 3 and the ten AMS‐dated individuals from there and 19 individuals from the Varna 1 cemetery were subjected to FRUITS modelling for the purposes of dietary reconstruction. There is no link between diet and grave deposition but differentiation in diet does exist in terms of sex. The results showed overall isotopic consistency with a small group of five outliers, among whom is a five‐year‐old girl with steppe aDNA ancestry, who is considered to be a migrant to the Varna area. We discuss the social implications of the dietary and aDNA results that reveal a more complex pattern than had previously been considered.

Served on a Plate: A Late Medieval Ceramic Vessel with Sgraffito Decoration of a Sailing Ship from the Ropotamo Underwater Excavations, Black Sea, Bulgaria

We report on the interpretation of a late medieval Eastern Mediterranean glazed ceramic vessel with sgraffito decoration depicting a sailing ship. The artefact represents a chance find that was recovered outside the excavation area of the Ropotamo underwater archaeological excavations on the Southern Bulgarian Black Sea Coast in 2017. Fragments of late medieval sgraffito-decorated ceramics with depictions of sailing ships are rare. Complete examples can be considered exceptional. The Ropotamo artefact is of particular interest due to the freehand execution of its decoration, which suggests some understanding of contemporary ship proportions and seafaring practices on behalf of the artisan. The specimen is analyzed against similar artefacts and discussed in the context of maritime graffiti from the Black Sea and Eastern Mediterranean regions. The aim is to establish its potential for studying archaeological ceramics and evaluate the extent to which the decoration reflects aspects of Eastern Mediterranean maritime culture of the late Byzantine and early post-Byzantine periods. More research is required to appreciate the full potential of the Ropotamo artefact. A hypothesis for origin, dating and significance has been proposed. However, due to a shortage of published parallels, it may be subject to further refinements in the future in case more stratified similis are identified.