Lake-wide assessment of microplastics in the surface waters of Lake Baikal,Siberia

Limnology - Small microplastic particles < 330 µm, sometimes called mini-microplastics (MMP), are far more abundant than those larger than 330 µm....     

Description of the lake baikal microorganism communities growing on a steel plate and in the natural water surrounding this substratum

This article presents an analysis of the microbial community growing on a stainless steel plate. A sample from this plate has been tested for the rpoC gene. Dominant biofilm species (clones) were identified with the help of molecular cloning and nucleotide sequencing of a 16S rRNA gene fragment. The activities of planktonic microorganisms and biofilm microorganisms attached to the plate were compared. Seven of nineteen sequences (37%) were found to belong to the Sphingobacteria group. Analysis of 16S rRNA gene sequences cloned from natural biofilms sampled from Lake Baikal showed a great variety of microorganisms in the biofilm. The following taxonomic groups were revealed among them: sphingobacteria, α-proteobacteria, cyanobacteria, verrucomicrobia, bacilli, γ-proteobacteria, flavobacteria, and β-proteobacteria. This kind of analysis was done in Lake Baikal for the first time.     

Molecular-phylogenetic analysis of cyclopoids (Copepoda: Cyclopoida) from Lake Baikal and its water catchment basin

Baikalian cyclopoids represent one of the richest endemic faunas of freshwater cyclopoid copepods. The genus Diacyclops Kiefer, 1927 is the most numerous by species number in the lake. In this work, molecular-phylogenetic analysis of 14 species and 1 sub-species from Lake Baikal and its water catchment basin is performed. The regions of mitochondrial cytochrom-oxydase I (COI) and of nuclear small-subunit 18S rRNA were used as evolution markers. In the obtained set of COI gene sequences, an effect of synonymous substitution saturation is revealed. Baikalian representatives of the genus Diacyclops form at phylogenetic schemes by two markers a monophyletic group, it suggest their origin from a common ancestral form. Preliminary estimate of this group age is 20–25 My.     

Microcystins in Cyanobacterial Biofilms from the Littoral Zone of Lake Baikal

Some species of cyanobacteria synthesize toxins whose concentration during water bloom can reach values dangerous for human and animal health. Planktonic cyanobacteria are the most common and well-studied microcystins producers, hepatotoxic cyclic heptapeptides, whereas microcystin-producing benthic cyanobacteria are less known. In recent years, the mass development of benthic cyanobacteria forming extensive fouling on different substrates has been detected in the littoral zone of Lake Baikal. We found microcystins produced by benthic cyanobacteria in the biofouling on different natural and artificial substrates, including diseased and dead endemic sponges Lubomirskia baicalensis and Baikalospongia spp. collected from the littoral area of Lake Baikal. Microscopic analysis of the biofouling revealed prevalence of representatives of Nostocales and Oscillatoriales with predominance of Tolypothrix distorta that is likely the main microcystin producer in Lake Baikal. According to enzyme-linked immunosorbent assay (ELISA), microcystin concentrations in biofouling were 29.8–3050 μg/kg dry weight. We identified eight microcystin variants using MALDI-TOF/TOF; [Dha7]MC-YR was detected in most samples. The presence of microcystins in biofilms formed on the surface of the artificial substrate by Phormidium autumnale was also recorded. The data obtained demonstrated the necessity to monitor potentially toxic species and concentrations of cyanotoxins in plankton and benthos in the littoral zone of Lake Baikal, especially in the regions with intense tourist and recreational activities.     

Ultrastructure of the ciliary pits in the Geocentrophora group (Platyhelminthes,Lecithoepitheliata)

The ultrastructure of the paired lateral ciliary pits in several endemic species of Geocentrophora from Lake Baikal and in one cosmopolitan species, G. baltica, has been compared and the possible functional significance is discussed. The pit is composed of two distinctive parts; the bottom of the pit is an extensive sensitive area, filled with uni-and biciliary sensory receptors with reduced rootlets and numerous neurotubules. The walls of the pit are formed by several large dark cells, characterized by a dark cytoplasm with numerous mitochondria, a large nucleus, intracellular canaliculi, basal infoldings of the cell membrane, glycogen granules and a varying number of cilia. A protruding, densely ciliated ridge occurs along the anterior wall of the pit. The cilia have a strengthened rootlet system and seem to provide a strong water current into the pit. Dark cell processes penetrate the basement membrane of the pit and come into the vicinity of large cells with a cytoplasm similar to that of the dark cells of the pit. These large cells in their turn come close to the terminal parts of the protonephridial canals, containing a weir. Smaller protonephridial capillaries without a weir seem to open directly into the pit lumen. The morphological data obtained suggest that the ciliary pit in not only a sensory structure, but plays a part in osmoregulation and ion exchange as well.     

The role of water lichens in the biogeochemical processes in the Lake Baikal stony littoral

Water crustose lichens of g. Verrucaria (V. scabra Vězda, V. rheitrophyla Zsch., V. maura Wahlenb. in Ach., and V. hydrela Ach.) and water foliose lichen Collema ramenskii Elenk. were studied in the stony littoral of the western coast of Lake Baikal in 2002–2006. Their densities were highest at depths of 1.5 to 2 m; 95–100% of rock fragments collected from the depths of 1.5–2.2 m were covered by plentiful crustose thalli of Verrucaria spp. Lichens make a large contribute to the destruction of the stony ground in the shallow-water zone. Unlike water, foliose and crustose lichens concentrate Ti, La, Ce, Y, Mn, and Th. Thalli of Collema ramenskii differ from Verrucaria species in their ability to accumulate Zn, Co, and Ni. Compared to the bottom sediments, all the studied water lichen species concentrate Zn, while Collema ramenskiiconcentrate Zn and Mo.     

Interspecific variability of telomeric DNA length in some Siberian and endemic Baĭkal planarians (Plathelminthes, Tricladida)

The length of the telomeric DNA in nine species of planarians inhabiting Lake Baikal and one Siberian species from Baikal rivers was determined using Southern hybridization. According to preliminary estimations, it varied in the range of 25-30 kb (Rimacephalus arecepta, Rimacephalus pulvinar, Sorocelis hepatizon, Sorocelis nigrofasciata, Protocotylus sp., Baikalobia guttata, Bdellocephala baikalensis, Phagocata sibirica) and 50 kb (Baikaloplana valida, Baikalobia copulatrix). It is the first estimation of the values of telomeric region lengths for Baikal free-living flat worms.