In 1980th, in the course of systematic study of phytobenthos in the Lake Baikal, L. A. Izhboldina collected material on the structure and distribution of meio- and macrophytobenthos in the littoral zone of Posolsky Sor Bay, the shallow water lagoon on the eastern lake coast. The main part of the bay, where data was sampled, known as Bolshoi Sor, is 9.7 km long and till 4.9 km wide; the depth is usually doesn’t exceed 3–4 m; the bottom is formed by sandy sediments. The research has been conducted due to introduction and fast spreading of Elodea canadensis through Lake Baikal in 1980^th. In the paper, we present description of 15 benthic profiles from 7 sections of the bay. Data was collected in June and September of 1984, as well as in August of 1986. Verbal description of profiles is supplemented by drawn schemes with indication of prevailing sediments, dominant species and biomass of benthic coenoses (gr/sq. m). Sand, sometimes silted sand of the bottom is not conductive for development algae and cyanobacteria. In total, there are 15 species registered in phytobenthos of the bay. None of the numerous endemic for Baikal aglae species was noted in the Posolsky Sor Bay. There are cyanobacteria Gloetrichia pisum and Aphanothece stagnina among coenoses dominants. Communities with dominance of G. psium develop in first half of summer on the depth of 3–3.5 m. Occurrence of A. stagnina in phytobenthic samples from Posolsky Sor reaches 69 %, whereas in other parts of Lake Baikal, this species registered usually not more than in 5 % of samples. Most frequent vascular plants are Potamogeton perofliatus and Elodea canadensis but communities with dominance of these species did not occupy significant areas. In September of 1984, E. canadensis was a dominant in many localities, especially in southern part of the bay. Although in 1986, most of these patches were not revealed. It was substituted by coenoses of P. perfoliatus.

Chepinoga Victor Vladimirovich, Doctor of Sciences (Biology), Leading Research Scientist, V. B. Sochava Institute of Geography SB RAS, 1, Ulan-Batorskaya st., Irkutsk, 664033, Russian Federation, tel.: (3952) 42–70–95, Professor, Irkutsk State University, 1, K. Marx st., Irkutsk, 664003, Russian Federation, tel.: (3952) 24–18–55, e-mail: victor.chepinoga@gmail.com 

Izhboldina Ludmila Aleksandrovna, Candidate of Sciences (Biology), Scientific Research, Institute for Biology, Irkutsk State University, 1, Karl Marx st., Irkutsk, 664003, Russian Federation, tel.: (3952) 24–18–55 

Mincheva Elena Vyacheslavovna, Candidate of Sciences (Biology), Research Scientist, Limnological Institute SB RAS, 3, Ulan-Batorskaya st., Irkutsk, 664033, Russian Federation, tel.: (3952) 42–29–23, e-mail: elenakuznetsova01@gmail.com

Chepinoga V.V., Izhboldina L.A., Mincheva E.V. Distribution of Meio- and Macrophytobenthos in the Littoral Zone of some Parts of the Lake Baikal Coasts According to Profiling Data from 1963–1986. Part 1. Posolsky Sor Bay. The Bulletin of Irkutsk State University. Series Biology. Ecology, 2019, vol. 27, pp.16-29. https://doi.org/10.26516/2073-3372.2019.27.16 (in Russian)

Azovsky M.G., Chepinoga V.V. Vysshie vodnye rasteniya ozera Baikal [Aquatic higher plants of Baikal Lake]. Irkutsk, Irkutsk St. Univ. Publ., 2007, 157 p. (in Russian)

Barashkov G.K. O metodike kolichestvennogo ucheta litoral'nykh vodoroslei [On the method of quantitative accounting of littoral algae]. Raspredelenie i sostav promyslovykh vodoroslei Barentsova morya [Distribution and composition of commercial algae in Barents Sea]. Moscow, St.-Petersb., 1965, pp. 8-12. (in Russian)

Bogorov V.G. Kolichestvennaya otsenka zhivotnogo i rastitelnogo naseleniya okeana [Quantitative assessment of the oceanic animal and plant populations]. Doklady Akademii Nauk, 1965, vol. 162, no. 5, pp. 1181-1183. (in Russian)

Gagarin P.K. Elodeya kanadskaya na Baikale [Elodea canadensis in Lake Baikal]. Geography and Natural Resources, 1995, no. 2, pp. 66-73. (in Russian)

Grachev M.A. «Avoska i avos». Ekologicheskii krizis na Baikale: zagadka veka [“Avoska and Avos”. The ecological crisis on Baikal]. Nauka iz pervykh ruk [Science First Hand], 2016, vol. 68, no. 2, pp. 6-19. (in Russian)

Izhboldina L.A. Meio- i makrofitobentos ozera Baikal (vodorosli) [Meio- and macrophytobenthos of Baikal Lake (algae)]. Irkutsk, Irkutsk St. Univ. Publ., 1990, 176 p. (in Russian)

Izhboldina L.A. Atlas i opredelitel' vodoroslei bentosa i perifitona ozera Baikal (meio- i makrofity) s kratkimi ocherkami po ikh ekologii [Atlas and key to benthic and periphyton of Lake Baikal (meyo- and macrophytes) with short essays on their ecology]. Novosibirsk, Science Center Publ., 2007, 248 p. (in Russian)

Izhboldina L.A., Takhteev V.V. Donnye vodorosli - meio- i makrofity [Benthic algae - meio- and macrophytes]. Baikalogy. Rusinek O.T. et al. (eds.). Novosibirsk, Nauka Publ., 2012, vol. 2, pp. 532-538. (in Russian)

Izhboldina L.A., Chepinoga V.V., Mincheva E.V. Raspredelenie meio- i makrofitobentosa v litoral'noi zone otkrytykh pribrezhii oz. Bai-kal po dannym profilirovaniya 1963–1988 gg. Chast' 1. Zapadnyi bereg [Meio- and Macrophytobenthos Distribution in the Littoral Zone along the Open Coasts of Lake Baikal According to Profiling Data from 1963–1988. Part 1. Western Coast]. Bull. Irkutsk St. Univ. Ser. Biol. Ekol., 2017a, vol. 19, pp. 3-35. (in Russian)

Izhboldina L.A., Chepinoga V.V., Mincheva E.V. Raspredelenie meio- i makrofitobentosa v litoral'noi zone otkrytykh pribrezhii oz. Bai-kal po dannym profilirovaniya 1963–1988 gg. Chast' 2. Vostochnyi bereg [Meio- and Macrophytobenthos Distribution in the Littoral Zone along the Open Coasts of Lake Baikal According to Profiling Data from 1963–1988. Part 1. Eastern Coast]. Bull. Irkutsk St. Univ. Ser. Biol. Ekol., 2017b, vol. 19, pp. 35-56. (in Russian)

Kazenkina G.A., Ladokhin N.P. Donnye otlozheniya i nekotorye osobennosti geomorfologii Posol'skogo sora na Baikale [Bottom sediments and some features of the geomorphology of Posolsk Sor Bay on Baikal]. Issledovaniya beregov vodokhranilishch na oz. Baikal [Studies of reservoirs coasts on the Lake Baikal]. Moscow, Nauka Publ., 1964, pp. 92-104. (in Russian)

Konstantinov A.S. Obshchaya gidrobiologiya [General hydrobiology]. Moscow, Vysshaya shkola Publ., 1986, 472 p. (in Russian)

Maistrenko S.G., Neronov Yu.V. Rasprostranenie elodei kanadskoi (Elodea sanadensis Michaux) v basseine ozera Baikal (18 let nablyudenii) [Distribution of Elodea canadensis Michaux in the Lake Baikal basin (Results of 18 years monitoring)]. Sostoyanie vodnykh ekosistem Sibiri i perspektivy ikh ispol'zovaniya [The state of Siberian aquatic ecosystems and their management prospects]. Proc. Sci. Read. in memory of B.G. Ioganzen, Tomsk, Russia, 1998, pp. 331–333. (in Russian)

Kravtsova L.S., Izhboldina L.A., Khanaev I.V., Pomazkina G.V., Domysheva V.M., Kravachenko O.S., Grachev M.A. Narushenie vertikalnoi zonalnosti zelenykh vodoroslei v otkrytom Listvennichnom zalive ozera Baikal kak sledstvie lokal'nogo antropogennogo vozdeistviya [Disturbances of the vertical zoning of green algae in the coastal part of the Listvennichnyi Bay of Lake Baikal]. Doklady Biol. Sci., 2012, vol. 447, no. 2, pp. 227-229. (in Russian)

Rogozin A.A. Beregovaya zona Baikala i Khubsugula. Morfologiya, dinamiki i istoriya razvitiya [The coastal zone of Baikal and Hovsgol. Morphology, dynamics and development history]. Novosibirsk, Nauka Publ., 1993, 168 p. (in Russian)

Chepinoga V.V. Rasteniya-neofity v gidrofil'noi flore Baikal'skoi Sibiri [Neophyte plant species in hydrophilous flora of Baikal Siberia]. Bull. Tomsk St. Univ. Ser. Biol., 2015, no. 1(29). pp. 8-85. https://doi.org/10.17223/19988591/29/6 (in Russian)

Shimaraev M.N. Kuimova L.N. Temperaturnyi rezhim i teplovoi balans [Temperature and thermal balance]. Limnologiya pribrezhno-sorovoi zony Baikala [Limnology of the coastal zone of Baikal]. N.A. Florensov (ed.). Novosibirsk, Nauka Publ., 1977, pp. 82-106. (in Russian)

Potemkina T.G., Potemkin V.L., Kotsar O.V., Fedotov A.P. Climate factors as a possible trigger of modern ecological changes in shallow zone of Lake Baikal (Russia). Int. J. Environ. Stud., 2018, vol. 75, no. 1, pp. 86-98. https://doi.org/10.1080/00207233.2017.1406727

Khanaev I.V., Kravtsova L.S., Maikova O.O., Bukshuk N.A., Sakirko M.V., Kulakova N.V., Butina T.V., Nebesnykh I.A., Belikov S.I. Current state of the sponge fauna (Porifera: Lubomirskiidae) of Lake Baikal: Sponge disease and the problem of conservation of diversity. J. Great Lakes Res., 2018, vol. 44, no.1, pp. 77-85. https://doi.org/10.1016/j.jglr.2017.10.004

Timoshkin O.A., Moore M.V., Kulikova N.N., Tomberg I.V., Malnik V.V., Shimaraev M.N., Troitskaya E.S., Shirokaya A.A., Sinyukovich V.N., Zaitseva E.P., Domysheva V.M., Yamamuro M., Poberezhnaya A.E., Timoshkina E.M. Groundwater contamination by sewage causes benthic algal outbreaks in the littoral zone of Lake Baikal (East Siberia). J. Great Lakes Res., 2018, vol. 44, no. 2, pp. 230-244. https://doi.org/10.1016/j.jglr.2018.01.008

Timoshkin O.A., Bondarenko N.A., Volkova Ye.A., Tomberg I.V., Vishnyakov V.S., Malnik V.V. Mass development of green filamentous algae of the genera Spirogyra and Stigeoclonium (Chlorophyta) in the littoral zone of the southern part of Lake Baikal. Hydrobiol. J., 2015, vol. 51, no. 1, pp. 13-23. https://doi.org/10.1615/HydrobJ.v51.i1.20

Timoshkin O.A., Samsonov D.P., Yamamuro M., Moore M.V., Belykh O.I., Malnik V.V., Sakirko M.V., Shirokaya A.A., Bondarenko N.A., Domysheva V.M., Fedorova G.A., Kochetkov A.I., Kuzmin A.V., Lukhnev A.G., Medvezhonkova O.V., Nepokrytykh A.V., Pasynkova E.M., Poberezhnaya A.E., Potapskaya N.V., Rozhkova N.A., Sheveleva N.G., Tikhonova I.V., Timoshkina E.M., Tomberg I.V., Volkova E.A., Zaitseva E.P., Zvereva Y.M., Kupchinsky A.B., Bukshuk N.A. Rapid ecological change in the coastal zone of Lake Baikal (East Siberia): Is the site of the world’s greatest freshwater biodiversity in danger? J. Great Lakes Res., 2016, vol. 42, no. 3, pp. 487-497. https://doi.org/10.1016/j.jglr.2016.02.011

Bondarenko N.A., Ozersky T., Obolkina L.A., Tikhonova I.V., Sorokovikova E.G., Sakirko M.V., Potapov S.A., Blinov V.V., Zhdanov A.A., Belykh O.I. Recent changes in the spring microplankton of Lake Baikal, Russia. Limnologica, 2019, vol. 75, pp. 19-29. https://doi.org/10.1016/j.limno.2019.01.002

Volkova E.A., Bondarenko N.A., Timoshkin O.A. Morphotaxonomy, distribution and abundance of Spirogyra (Zygnematophyceae, Charophyta) in Lake Baikal, East Siberia. Phycologia, 2018, vol. 57, no. 3, pp. 298–308. https://doi.org/10.2216/17-69.1