Baikal gastropods described by W.A. Lindholm

The molluscan fauna of Lake Baikal is currently known to comprise about 150 species of gastropods, of which approximately 70% are endemics. Baikal gastropods include 8 families: Baicaliidae, Benedictiidae, Bithyniidae (Caenogastropoda), Valvatidae (Heterobranchia), Acroloxidae, Planorbidae, Lymnaeidae and Physidae (Panpulmonata). By studying the samples collected during a three-year expedition supervised by A.A. Korotneff, professor of the Kiev University, W.A. Lindholm described 55 new species, varieties (= subspecies) and forms (= morphs) that belonged to all families of gastropods (except Physidae) living in Baikal and in the connected shallow water bodies (sors). Lindholm was the first to note a wide spectrum of conchological variability of Baikal gastropods and their heterogeneous geographic distribution in the lake. Using collection of naturalist Petr Mikhno, Lindholm described two new species from Lake Hövsgöl (= Khubsugul) in Mongolia that has the hydrological connection to Lake Baikal via the Selenga River. Despite more than a century of studying the gastropod fauna in lakes Baikal and Hövsgöl, some species and subspecies described by Lindholm are rare, with only a few specimens subsequently being reported, and some have never been found again. The present study is a brief review of 46 species, subspecies and morphs of gastropods described by Lindholm. The review includes photographs of type specimens, main synonyms and references, detailed information on the type localities, diagnoses, and information on distribution in Baikal including depth zones and substrate types. All type specimens (except those of one species) are well preserved and are currently stored in the collection of the Zoological Institute of the Russian Academy of Sciences (St. Petersburg).

Infrasound signals from earthquakes of December 5, 2014 in the water area of lake Hovsgol, Northern Mongolia

A comprehensive analysis of waveforms of seismic and infrasonic vibrations from the earthquake that occurred on December 5, 2014, in the water area of Lake Hovsgol was performed. The analysis showed that the infrasonic signal recorded at the Tory station (Geophysical Observatory of the Institute of Solar-Terrestrial Physics, Russian Academy of Sciences) was formed by the sources of three generation types: local, secondary, and epicentral. The obtained results allow us to propose the model of epicentral infrasonic signal generation by flexural waves from an elastic ice membrane on the surface of Lake Hovsgol.

Caddisflies of Mongolia: Distribution and diversity

In Mongolia, there are 198 caddisfly species belonging to 69 genera in 16 families. An updated species list also indicates the species that have been DNA barcoded. The distributions of species in the Mongolian aimags (provinces) are presented. Most species records are results from the Mongolian Aquatic Insect Survey (2002–2011, northcentral and western Mongolia) and Hovsgol_GEF projects (2002–2006, Lake Hovsgol and vicinity), and personal collections; other records are from the literature. The Mongolian caddisfly fauna is characteristic of central Asia and includes only 1 endemic species. Over half of the known Mongolian species occur in Hovsgol Aimag.

Unusual occurrence of a Didymosphenia bloom in a lentic habitat: Observation of Didymosphenia laticollis blooming on the eastern shore of Lake Hövsgöl (Mongolia)

The stalked diatom Didymosphenia is being thoroughly studied because it can cause serious nuisance blooms. The species most commonly involved is D. geminata. Although Didymosphenia species occur in running waters and lakes, published reports generally refer to lotic habitats. Given the applied interest in Didymosphenia, as well as its suitability for fundamental ecological studies, here we report an observation of a Didymosphenia bloom occurring on the southern part of the eastern shore of the large oligotrophic Lake Hövsgöl (Mongolia). LM and SEM observations revealed that the bloom was formed by Didymosphenia laticollis. The bloom extended for a long stretch of the eastern shore whilst on the opposing lake margin no bloom was visible, where a different Didymosphenia species was collected (D. mongolica). We interpreted the Lake Hövsgöl D. laticollis bloom in light of the most updated knowledge on Didymosphenia blooms ecophysiology. Lake Hövsgöl meets all main environmental requirements for Didymosphenia bloom formation: conditions are oligotrophic and phosphorus is the limiting factor, waters are very transparent and benthic light availability is consequently high, alkalinity is relatively high, and stable rocky substrata in a hydrologically-turbulent environment are widespread. The light-brown color of the bloom is in good agreement with experimental results suggesting that low-SRP conditions promote bloom formation in the presence of high light and alkalinity, because energy is converted to stalk material (the primary site of alkaline phosphatase production in Didymosphenia) rather than in cells. We speculate that the occurrence of the bloom on the eastern shore and its absence on the western shore might depend upon morphology, land use, and climate change causing alkalinity and organic phosphate inputs on the eastern side.