Expedition on board the R/V “Papanin” on July 2-11, 2024

The field works were carried out on board the R/V “Papanin” on July 2-11, 2024 within the State Assignments No. 0279-2021-0006 “Studies of functioning of hydrate, oil and gaseous hydrocarbon systems and associated microbial communities in Lake Baikal” (led by T.I. Zemskaya), No. 0279-2021-0007 “Comprehensive studies of the Lake Baikal coastal zone: long-term dynamics of communities under the influence of various environmental factors and biodiversity; causes and consequences of negative environmental processes” (led by O.A. Timoshkin), No. 0279-2021-0004 “Investigation of the advective and turbulent water exchange of Lake Baikal and its impact on the lake ecosystem, risks of catastrophic events” (led by I.A. Aslamov), No. 0279-2021-0014 “Investigation of the role of atmospheric fallout on water and terrestrial ecosystems of the Baikal Basin, identification of atmospheric pollution sources” (led by T.V. Khodzher). LIN SB RAS staff and a graduate student from MSU Geology Department participated in the expedition.

The aim of the field work is to reveal by specialists of different profiles the peculiarities of distribution and habitat conditions of the Baikal gastropods, including the zones of supposed mud volcanism and outlets of mineralized fluids at depths of 100-200m. The main attention was paid to representatives of the endemic family Benedictiidae inhabiting depths from 1.5 to 1400 m (Sitnikova et al., 2021) to continue integral (morpho-anatomical and molecular-genetic) studies. Based on the data of the previous expeditions in 2021-2023, molecular genetic analysis revealed the presence of species new to science in this family; information on the distribution of abyssal species was significantly expanded; and a rare species, Benedictia nana, was found for the first time since it was first described in 1975

Throughout the expedition, gastropods were collected at depths ranging from 6 to 200 meters using the teleoperated unmanned underwater vehicle “Rovbilder” RB-300 (TUUV) and a dredge. Twenty-four gastropod samples were collected from 7 sites of Lake Baikal: Solontsovaya Bay and Solontsovaya Banka; bays Malaya Kosa, Goryachinskaya, Ayaya, Tukaralagda, Sosnovka, and Aya. It is planned to study the morphology of the shell (teleoconch and protoconch) and teeth of the radula using scanning electron microscopy, the structure and topography of internal organs (including reproductive organs), to analyze the nucleotide sequences of fragments of two or three genes of mitochondrial and nuclear DNA, and at the final stage, to describe new species and to identify relationships between all known species.

Using TUUV and a benthic tube, soil samples were collected for chemical analysis of pore water and methane content in Malaya Kosa Bay and Goryachinskaya Bay in the North Baikal Depression. At the same time, samples were taken for zoobenthos analysis. To assess bacterial diversity by molecular biology methods, cone-shaped structure was sampled in Goryachinskaya Bay, and spherical conglomerates were sampled in Malaya Kosa Bay.

A colorless sulfur bacterium of the genus Thioploca was collected in the area of gas outlets near the settlement of Bolshoye Goloustnoye in order to isolate DNA for deciphering its complete genome. Samples were also taken here to analyze pore water, methane content, and zoobenthos diversity.

MSU graduate student collected sediment samples for grain size measurement at all sites investigated.

Samples of all collected material are currently being processed for further comprehensive ecological, morphological, and molecular genetic analysis.