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Nedyalkov N.,Bulgarian Academy of Science | Koshev Y.,Bulgarian Academy of Science | Raykov I.,Museum of Natural History Varna
North-Western Journal of Zoology

During field surveys for small mammals in Bulgaria we found specimens of Crocidura leucodon, Talpa europaea and a Mus sp with color variation. We reviewed the national scientific collections and the available literature for cases of small mammals with color variations. Color variation in small mammals is very rare, so far we found nine cases only, five cases of T. europaea and one case each of C. leucodon, C. suveolens, Sorex araneus and Mus sp. The albino C. leucodon is one out of 143 white-toothed shrews (Crocudra sp.) or 0.69%. The form of the partialy leucistic Mus sp. is one out of 633 mice (0.15%), caught between 2001 and 2007. © NwjZ, Oradea, Romania, 2014. Source

Tonkov S.,Sofia University | Marinova E.,Catholic University of Leuven | Marinova E.,Royal Belgian Institute Of Natural Sciences | Filipova-Marinova M.,Museum of Natural History Varna | Bozilova E.,Sofia University
Quaternary International

The environmental changes (vegetation history, human impact and land use, influence of the Black Sea) in the area of Lake Durankulak, northeastern Bulgaria, were reconstructed and synthesized for the last ca. 8000 years. The palaeoecological information derived from various proxies (pollen, plant macrofossils, molluscs, sediments) was compared on a regional scale with the evidence from the nearby coastal lakes Shabla-Ezeretz and Bolata. The Early Holocene xerothermic steppe vegetation, dominated by Chenopodiaceae, Artemisia and Poaceae species, and accompanied by stands of trees in moister habitats, was transformed after 6000 cal. BP into a forest-steppe, comprising oak woods with Carpinus betulus, Ulmus, Tilia, Acer. This vegetation pattern has been periodically modified, depleted and replaced by arable land or xerothermic herbaceous communities enriched with anthropophytes and ruderals, particularly after the intensification of human activities since 3300 cal. BP. The archaeobotanical evidence from the region has provided valuable information about the occupation phases and subsistence strategy of the local people since the Late Neolithic (5300 cal. BC/7250 cal. BP). Periods with cultivation of cereals (Triticum, Hordeum) and/or stock-breeding activity were interrupted by abandonment of the settlements and the arable land due to unfavourable environmental changes. The periodical connection/isolation of Lake Durankulak with the Black Sea and the periods of marine influence were recorded by changes in the composition of the fossil molluscan fauna and the lithology of the sediments, and chronologically confirmed by radiocarbon dates. The development of the coastal lakes throughout the largest part of the Holocene has been also considerably influenced by the fluctuations of the Black Sea level. © 2013 Elsevier Ltd and INQUA. Source

Filipova-Marinova M.,Museum of Natural History Varna | Pavlov D.,Society of Innovative Ecologists of Bulgaria | Coolen M.,Woods Hole Oceanographic Institution | Giosan L.,Woods Hole Oceanographic Institution
Quaternary International

Spores, pollen and dinoflagellate cysts of Late Pleistocene and Holocene sediments were analyzed from Giant Gravity Core 18 from the Black Sea continental slope, recovered from a water depth of 971 m. The investigated length of the core is 203.5 cm. It includes 3 lithological units: light grey clay, sapropels and coccolith-bearing ooze. The core was sampled at 5-10 cm intervals. Sampling of the interval 141.5-126 cm was carried out at every cm. AMS radiocarbon dating of bulk organic carbon was performed on 18 selected sediment layers. This chronological data allowed the first high-resolution pollen stratigraphy of Late Quaternary sediments from the western Black Sea area to be presented. The percentage spore-pollen diagram is divided into 6 local pollen assemblage zones. The trends in the vegetation dynamics and climate changes and the early history of migration of the majority of the arboreal taxa that nowadays occur in the Eastern Balkan Range were traced out. The palynological record suggests that open oak forests were spread in the Eastern Balkan Range at the beginning of the Holocene and shows early migration of the major temperate arboreal species such as Quercus, Ulmus, Tilia and Carpinus betulus. This vegetation palaeosuccession continues with the spreading of mixed oak forests from 8950 until 2620 cal. BP (8650 ± 40 until 3120 ± 35 14C BP) followed by destructive changes due to human impact and climate deterioration. A cooling of Holocene climate that is well known in the North Atlantic region as the " 8200 yrs cold event" is identified for the first time in marine records from the Bulgarian Black Sea area. The assemblages of dinoflagellate cysts and acritarchs were investigated to provide a reconstruction of surface seawater salinity and surface seawater temperature changes. Two main dinoflagellate cyst assemblages, one dominated by fresh- to brackish water species such as Spiniferites cruciformis and Pyxidinopsis psilata and a subsequent one, that is characterized by euryhaline marine Mediterranean species such as Lingulodinium machaerophorum, Spiniferites belerius, Spiniferites bentorii, Operculodinium centrocarpum and acritarchs Cymatiosphaera globulosa testified a change in SSS from low salinity (<7‰) to present day conditions after 7990 cal. BP. Substantial freshening of Black Sea surface waters at 2570 cal. BP is established and connected with the transition from a relatively dry and warm to relatively cold and wet climate. © 2012 Elsevier Ltd and INQUA. Source

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