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Recent Submissions
Abundance, biomass and seasonal dynamics of Cyclopoida (Crustacea, Copepoda) in Vaya Lake (Burgas Lake), Bulgaria
(Plovdiv University "Paisii Hilendarski", 2026-06-03) Nenova, Elena
A quantitative analysis of Copepoda abundance and biomass in Vaya Lake (Burgas Lake, Bulgaria) was conducted at 11 sampling stations during 2003–2007, with samples collected seasonally (autumn, winter, spring and summer). The cumulative abundance recorded during the study period was 26.48 × 106 ind./m3, corresponding to a mean abundance of 6.62 × 106 ind./m3. Copepodites dominated the community (14.89 × 106 ind./m3), followed by Nauplii (9.96 × 106 ind./m3). Among adult copepods, Cyclops vicinus Uljanin, 1875 ranked third in abundance (1.36 × 106 ind./m3), whereas Thermocyclops oithonoides (G.O. Sars, 1863) showed the lowest abundance (271,500 ind./m3). The cumulative biomass recorded during the study period was 258.97 g/m3, with the highest seasonal value observed in spring 2006. Biomass was dominated by Cyclops vicinus (175.05 g/m3), followed by Copepodites (74.32 g/m3), Nauplii (4.98 g/m3) and Thermocyclops oithonoides (4.62 g/m3). Cluster analysis based on the Bray–Curtis similarity index revealed more than 85% similarity among most sampling stations with respect to abundance. Station 12 was clearly separated from all other stations because of its exceptionally high biomass, dominated by C. vicinus and Copepodites, whereas stations 3, 4, 8, 1, 11, 2 and 6 showed approximately 87% similarity. Seasonal dynamics were characterized by contrasting patterns in juvenile and adult development: Nauplii and Copepodites reached maximum abundance during winter, whereas biomass peaked in spring due to the development of the dominant species C. vicinus.
Ecological and biochemical aspects of assessment of Cu and Ni pollution of freshwater bodies in the Region of Stara Zagora, Bulgaria – a review
(Plovdiv University "Paisii Hilendarski", 2026-04-08) Valkova, Elica; Atanasov, Vasil; Marinova, Margarita; Sirakov, Ivaylo; Velichkova, Katya; Raykov, Violin; Yakimov, Kristian; Kutsarov, Yordan; Kirilov, Kiril
The study aims to make an ecological assessment of Cu (copper) and Ni (nickel) pollution of freshwater bodies in the Stara Zagora industrial Region, Bulgaria. A literature reference has been prepared on the concentrations of Cu and Ni at all levels in the food chain: sediment, aquatic plants and fish in the studied region and worldwide. The results of our own research on the amounts of these metals in the sediment and organisms of aquatic biota from water bodies in the region have also been interpreted. When analyzing the obtained data, a negative correlation is established between the accumulation of Cu in the liver of carps inhabiting the Ovcharitsa and Topolnitsa Dams. A dependence of a similar nature is also observed for the element nickel. When comparing the amounts of copper and nickel within the framework of our study, as well as those from other research worldwide, a similar trend is observed regarding the levels of these metals in the liver and musculature of the tested fish. Studies conducted in the Region of Stara Zagora, Bulgaria, and other countries confirmed the ability of hydrobionts to accumulate heavy metals and to be excellent bioindicators for pollution with these toxicants. Global environmental pollution is a prerequisite for continuing research in this area, with other possible environmental markers.
Comparative analysis of the genetically determined isoenzyme polymorphism in populations of selected Crocus species distributed in Bulgaria
(Plovdiv University "Paisii Hilendarski", 2026-04-08) Stoyanov, Ivan; Vasileva, Penka; Stoyanov, Kiril; Raycheva, Tsvetanka
The genus Crocus is represented by 15 species in the flora of Bulgaria. The present research is based on isoenzyme analysis, and the genetic heterogeneity in populations of selected species was studied: C. adamioides, C. chrysanthus, C. flavus, C. olivieri, C. pallasii, C. pulchellus, and C. randjeloviciorum. The probable genetic control of four polymorphic enzyme groups - non-specific esterases (EST), malate dehydrogenases (MDH), malic enzymes (ME), and superoxide dismutases (SOD) was established, which appear as suitable markers for characterizing intra- and inter-population genetic variability. Fourteen variable loci were analyzed, and specific biochemical markers were established for distinguishing Crocus species. A comparative analysis of the studied populations' gene pool and genotypic structure was conducted. The results show that malate dehydrogenases, malic enzymes, superoxide dismutases, and non-specific esterases are polymorphic biochemical genetic markers suitable for inter-population comparisons and for studying intra-population heterogeneity in Crocus species.
Growth and physiological performance of walnut plants grafted during winter dormancy and grown in containers
(Plovdiv University "Paisii Hilendarski", 2026-04-01) Dimitrov, Angel; Akova, Vanya; Nacheva, Lilyana; Gandev, Stefan
The study was carried out at the Fruit Growing Institute of Plovdiv (Bulgaria) during the period 2019-2022. The growth and physiological performance of walnut plants (Juglans regia L. ‘Izvor 10’) propagated during winter dormancy by the methods of cleft and whip/tongue grafting, grown in containers, were monitored, comparing them with those of walnut plants grafted following the standard technology of patch budding, grown in a nursery. The plants grown in a nursery were 120.4 to 122 cm in height and those grown in containers were characterized by lower average values – from 76.2 to 111 cm. The values for the stem cross-sectional area of the plants grown in the nursery varied from 349.9 to 379.7 mm2 and they were higher than those grown in containers (from 88.2 to 221.8 mm2). Higher values for the root system volume were reported for the plants grown in containers (283 – 294.4 cm3), the differences being statistically significant. Plants grown in containers had a normally developed and functioning photosynthetic apparatus. No differences in chlorophyll fluorescence parameters were reported between patch-budded and container-grown plants.
Prey type influences predator–prey size relationship in Natrix natrix (Linnaeus, 1758) (Reptilia: Colubridae)
(Plovdiv University "Paisii Hilendarski", 2026-05-28) Mollov, Ivelin
In the current study the relationship between predator body length and prey body length in the Grass Snake (Natrix natrix) is examined, based on data from 39 individuals collected in the city of Plovdiv, Bulgaria. Prey items were classified into two categories - “fish” and “frog”. A significant positive relationship between snake length and prey length was registered, indicating size-mediated prey selection. The scaling relationship was stronger in snakes consuming frogs than in those consuming fish. Relative prey size differed significantly
between prey types, with fish representing proportionally larger prey.