Study of the long-term BVRcIcBVR_{c}I_{c} photometric variability of eight PMS stars in the young open cluster Trumpler 37

This paper reports results from our long-term $BV(RI)_{c}$ photometric CCD observations of eight pre-main-sequence stars collected from June 2008 to October 2022. These stars are located in the young open cluster Trumpler 37, in the field of GM Cephei. The observational data indicate that all stars from our study exhibit variability in all-optical passbands, typical for young stars. In this paper, we describe and discuss the photometric behavior of the stars and the possible reasons for their variability. For two of the objects, we identified periodicity in their light variation.Comment: 13 pages, 11 figures, 4 tables, accepted for publication in Research in Astronomy and Astrophysics (RAA

The genus <i>Nitzschia</i> on the South Shetland Islands and James Ross Island

The purpose of this study was to present LM and SEM observations of Nitzschia taxa encountered on the South Shetland Islands and James Ross Island. During the ongoing taxonomical revision of the freshwater and limno-terrestrial diatom flora on the South Shetland Islands and James Ross Island (Maritime Antarctic Region) eight unknown taxa belonging to the genus Nitzschia were found. These taxa were previously force-fitted into European names such as N. commutata or N. perminuta, but detailed light and scanning electron microscopical observations allowed their separation from the already known taxa and resulted in the description of eight new species. The paper discusses all twelve Nitzschia taxa found in the Maritime Antarctic Region. New taxa are compared to the morphologically most similar taxa and their ecology and biogeography are discussed. Although the genus Nitzschia is present worldwide, a large number of Nitzschia taxa have a restricted distribution within the Antarctic Region, showing a clear bioregionalism

Long term (1985–2018) changes of the habitat suitability of European souslik assessed by Maxent modelling based on Landsat satellite imagery – a case study from a mountain landscape of Central Bulgaria

The spatial and temporal aspects of the habitat suitability of the European souslik (Spermophilus citellus L.) in an area of Sredna Gora Mountain (Bulgaria) were studied. We used Landsat satellite imagery data to model changes in the habitat suitability of the species from 1985 to 2018. The obtained results demonstrate that the habitat suitability of the European souslik increased during the studied period, presumably due to raised temperatures and the accompanying drought during summertime, as well as the human-caused modifications in pasture livestock breeding. Based on statistical modelling, the employed procedure applies to long-term monitoring and assessment of the role of land cover change because of climate change and human activity on the habitat suitability of the European souslik. This approach can be useful for conservation planning

Patterns of craniometric variability of six common species of shrews (Soricidae: Crocidura, Neomys, Sorex)

The morphometric variability of the skull and the lower jaw of 6 species of shrews (Crocidura suaveolens s. l., C. leucodon, Neomys anomalus, N. fodiens, Sorex minutus, and S. araneus) from Bulgaria, Romania, Hungary, and Austria was analyzed. The results from the PCA and the unsupervised model-based clustering showed that morphological geographic intraspecific variation was clearly expressed in Crocidura suaveolens and C. leucodon, poorly pronounced in Neomys anomalus and N. fodiens, and almost missing in Sorex minutus and S. araneus. Our data provide a morphological confirmation of the recent molecular data, which indicate a division of both Crocidura species to western and eastern lineages. The geographical location of their boundaries was discussed

Microbes influence the biogeochemical and optical properties of maritime Antarctic snow.

Snow melt in the Antarctic Peninsula Region has increased significantly in recent decades, leading to greater liquid water availability across a more expansive area. As a consequence, changes in the biological activity within wet Antarctic snow require consideration if we are to better understand terrestrial carbon cycling on Earth's coldest continent. This paper therefore examines the relationship between microbial communities and the chemical and physical environment of wet snow habitats on Livingston Island of the maritime Antarctic. In so doing, we reveal a strong reduction in bacterial diversity and autotrophic biomass within a short (<1 km) distance from the coast. Coastal snowpacks, fertilized by greater amounts of nutrients from rock debris and marine fauna, develop obvious, pigmented snow algal communities that control the absorption of visible light to a far greater extent than with the inland glacial snowpacks. Absorption by carotenoid pigments is most influential at the surface, whilst chlorophyll is most influential beneath it. The coastal snowpacks also indicate higher concentrations of dissolved inorganic carbon and CO2 in interstitial air, as well as a close relationship between chlorophyll and dissolved organic carbon (DOC). As a consequence, the DOC resource available in coastal snow can support a more diverse bacterial community that includes microorganisms from a range of nearby terrestrial and marine habitats. Therefore, since further expansion of the melt zone will influence glacial snowpacks more than coastal ones, care must be taken when considering the types of communities that may be expected to evolve there