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Antarctic marine organisms are characterised by a significant level of endemism. This is due to geological, climatological and oceanographic reasons, such as the break-up of Antarctida from Gondwana during the Cretaceous; the formation of a circumpolar current; the extremely low water temperatures (close to freezing); the short summer seasons. The South Shetland Islands (West Antarctic Peninsula) are one of 29 known biogeographic areas in the Southern Hemisphere (Griffiths et al. 2009). King George Island is the largest island from the South Shetlands and eight countries have their polar bases there. Marine bottom macroinvertebrates from the surrounding seawaters are very well studied (Siciński et al. 2011). Less research was carried out in the region of the nearby Livingston Island. There are located two polar bases: "St. Kliment Ohridski" (Bulgaria) and "Juan Carlos I" (Spain). We can assume that in the seawaters of the South Bay we can also expect a rich bottom macroinvertebrate fauna because of the similar conditions and the close distance between the two islands. The aim of this study is to present the first Bulgarian results on the taxonomic composition of marine macroinvertebrates from the South Bay, Livingston Island. The samples were collected during the XXVII Bulgarian Antarctic Expedition (2018-2019 austral summer). Various sites in four areas were sampled: the coastal zone in front of the Bulgarian Polar Base (Costa Bulgara); a small bay south of Cape Hesperides (Reservnoto port); Johnsons Dock Bay near the Spanish research station and Walker Bay near Hannah Point. Samples were collected mainly through bottom trawling at depths of 2 to 20 meters on different types of bottom substrates using Zodiac boats. A total of 11 macrozoobenthos samples were collected. Our preliminary results show that the main macrozoobenthic species are well known in the seawaters of the South Shetlands and usually they have a circumpolar distribution. At the site with soft muddy bottoms (Johnsons Dock Bay), the corrugated ribbon worm Parborlasia corrugatus (McIntosh, 1876) (order Heteronemertea, class Pilidiophora, phylum Nemertea) as well as ascidians (order Phlebobranchia, class Ascidiacea, phylum Chordata) had the highest biomass. The most abundant in the Johnsons Dock Bay were the Antarctic bivalve Aequiyoldia eightsii (Jay, 1839) (order Nuculanida, class Bivalvia, phylum Mollusca); the scale worm Barrukia cristata (Willey, 1902) and the catworm Aglaophamus trissophyllus (Grube, 1877) (both of order Phyllodocida, class Polychaeta, phyllum Annelida). The seroid isopod Spinoserolis beddardi (Calman, 1920) (order Isopoda, class Malacostraca, phyllum Arthropoda) dominated in the muddy / sandy bottom of Hannah Point. The habitats of the rocky bottom (Costa Bulgara) were inhabited mainly by crustaceans (order Aphipoda, class Malacostraca, phyllum Arthropoda) and gastropods (phylum Mollusca). In the tidal zone of this habitat (0-2m), the predominant species was the Antarctic limplet Nacella concinna (Strebel, 1908) (order Patellogastropoda, class Gastropoda, phylum Mollusca). [ABSTRACT FROM AUTHOR]

Conservation of freshwater environments and assessment of their ecosystem services as a function of biodiversity are key research objectives with global importance. Additionally, the taxonomic composition of aquatic communities, including benthic macroinvertebrates, is crucial for the evaluation of the ecological status of the water bodies they inhabit. Numerous biotic indices and metrics have been developed based on freshwater benthic invertebrates. This contribution focuses on the order Trichoptera, as it includes diverse sensitive taxa with specific requirements to their environment. The aim was to summarise the current knowledge on morpho-taxonomy of adult and larval stages of Bulgarian caddisflies based on published and original data. The only checklist of Bulgarian caddisflies was published in the 1980s by Kumanski 1981 and included 218 species from 76 genera. This checklist was mostly based on adult Trichoptera. It was followed by two monographs (Kumanski 1985, Kumanski 1988) and numerous scientific papers (mostly by the same author, e.g. Kumanski 1993, Kumanski 2007) that by 2007 increased the number of known caddisflies from Bulgaria to 258 species. Based on the literature and on original data, the number of valid species of Trichoptera in Bulgaria is estimated to 255. They are from 78 genera, belonging to 20 families. Worldwide, adult forms are better studied, while not all of the larval stages of caddisflies are currently known or described. More than 100 of the Bulgarian caddisflies (almost 40%) lack larval description. This is likely owing to their limited geographical distribution and insufficient studies on the aquatic stages of Bulgarian Trichoptera over the last decades. Additionally, some of the representatives of the order are endemic for the Balkan Peninsula or Bulgaria. [ABSTRACT FROM AUTHOR]