Features of the seasonal succession of phytoplankton in the Crimean coastal area (Black Sea) in years with different climatic conditions (2009–2014)

Under conditions of climatic changes, it is of great interest to study the dynamics of various functional complexes of phytoplankton species. The long-term influence of previous cold winters on the course of the seasonal succession of phytoplankton, as well as the intensity of blooms in the open waters of the Black Sea, were shown earlier. In the coastal zone, this relationship has not yet been sufficiently studied. Based on regular monitoring studies in the coastal area of Sevastopol from 2009–2014, features of the course of seasonal succession of phytoplankton in years with different climatic conditions were revealed: the “cold” years differed from the “warm” ones by a longer dominance of diatom complexes in terms of cell abundance, especially of small-celled species, which characterize the initial stage of seasonal succession of phytoplankton. The level of development of both diatoms and dinoflagellates was minimal compared to other years, with a shift in the periods of maxima to later months. In contrast, the "warm" years were characterized by the predominance of dinoflagellates for most of the study period, with a shift in timing of the maxima to earlier months. Both diatoms and dinoflagellates reached their maximal development in “warm” years in spring and autumn. In the “moderate” years, phytoplankton development proceeded either by analogy with the “cold” (2009) or “warm” (2011) years. The seasonal succession described above is typical for the northwestern Black Sea, in particular, the Sevastopol coastal area, and differs from the average pattern for the northwestern part described earlier for 1992–1993. The difference consisted of an increase in the proportion of stages I and III due to a decrease in stage II compared to 1992–1993.

Upper pliocene diatom complexes and its significfnce to establish lower boundary of quarter (South of the Far East)

An analysis of the evolutionary distribution of diatoms in the outcrops of the Late Cenozoic shows that, upon reaching the level of the Annensky Horizon (Gelazian stage), the extinct species disappear almost completely. A predominance of the alluvial type of sedimentogenesis and reduction in the lake basins areas are clearly registered for deposits of the diatom zone Aulacoseira praegranulata var. praeislandica f. praeislandica. A cooling in the Late Pliocene with the pronounced temperature minimum at the level about 2,58 million years is fairly bright reflected in the ecological structures of diatomic associations (upper complex): the benthic arcto- and north-boreal flora predominates. Of that time, a total absence of the pollen of the broad-leaved species is also characteristic and paleo-landscapes become close to the Eopleistocene ones. From this moment on, the coexistence and expansion of the polar ice sheets begin (transition of planet from the “Green house” mode to the “Ice house” mode) which determine the formation of the modern climatic system of the Earth which emphasizes the globality of the palaeoclimatic event. From the lithological point of view, the bottom of the red rocks strata of the Annensky Horizon corresponding to the Gelazian stage bottom (2,58 million years) coincides with this boundary in the southern Primorye. The age changes of the Quarter boundary to this chronostratigrahic level is well founded.

Таксономическое разнообразие диатомовых комплексов голоценовых донных отложений малых водоемов депрессии озера Имандра

A study of the taxonomic diversity of diatom algae in Holocene bottom sediments of two small water basins at the western coast of the lake Babinaskaya Imandra (Murmansk Region) has demonstrated the historical transformations of the species compositions of structures of diatom complexes associated with environmental changes in the Holocene. The water basins studied featured the predominance of the benthic and adhesive algae in the algal communities throughout the Holocene. The most drastic changes in the diatom complexes were associated with a tectonic event nearby the Imandra depression.

Assessment of trophic status long-term transformations in Rybinsk and Ivankovo reservoirs (diatom analysis)

The studies were conducted under the integrated monitoring of the Rybinsk and Ivankovo reservoirs. The work is devoted to the assessment of long-term environmental changes under the influence of natural and anthropogenic factors. It was suggested to combine the two traditional methods of analysis. Initially, diatom complexes from bottom sediments were analyzed layer by layer. Then the results obtained were compared with the available information database on the species composition of phytoplankton complexes. Information about phytoplankton was avalible as a result of biomonitoring of reservoirs. The possibility of carrying out the work was determined by the fact that monitoring in the water area of the Rybinsk and Ivankovsky reservoirs was carried out for several decades. It was proposed to assess the reliability and comparability of the results obtained in assessing changes in the trophic status of reservoirs. The saprobity index (S) was calculated for diatom complexes from sediments. The data obtained was compared with similar calculations for the species structure of phytoplankton complexes.

Diatomic flora of Lake Tikozero in the Holocene

Preliminary data of micropaleontological (diatom) study of sediments of Lake Tikozero located on the eastern coast of Lake Yokostrovskaya Imandra (Murmansk region) are presented. Based on the results of diatom analysis, the taxonomic composition and structure of diatom complexes were studied, the stages of the development of the ecosystem of the lake were established. The studied lake was characterized by the dominance of benthic forms and fouling in the composition of paleosocial communities. Upward in the column of sediments, there is a change in indicator groups with respect to pH: the proportion of acidophils decreases from 62% to 18%, and the proportion of alkaliphiles increases from 5% to 40%. A change in the dominant diatom complex was revealed: the acidophilic benthic species Brachysira zellensis (Grunow) Round & D.G. Mann is replaced by the littoral species Staurosira construens Ehrenberg, which prefers slightly alkaline waters.

Comprehensive monitoring of the Klyazma reservoir

The research was carried out during the comprehensive monitoring of the Klyazma reservoir in 2019. The work is devoted to the assessment of long-term environmental changes under the influence of natural and anthropogenic factors. The research combines two traditional methods of analysis. A layer-by-layer study of diatomic complexes and chemical composition in the bottom sediments of the reservoir was carried out. The results obtained were compared with the results of comprehensive monitoring on the taxonomic composition of phytoplankton and the chemical composition of water in the reservoir's water area. The results of previous studies on the chemical composition of water in the reservoir were used. In addition to the traditional forms of chemical and hydrobiological analysis, an innovative method of graphical analysis was applied to phytoplankton complexes and the principle of unification of bioindication methods was applied for diatom complexes from sediment columns. The main scenarios of taxonomic proportions transformations in phytoplankton and diatom complexes were determined using the method of graphical analysis for the Klyazma reservoir water area. The transformations are caused by the influence of water from the Moscow channel and the planned annual lowering of the water level in the reservoir. Bottom sediments showed a regular increase in the reservoirs level of saprobisation. Presumably, this is due to a non-linear increase in the number of tourists and an cahnges in recreational load. Pronounced accumulation of Cu, Zn and other heavy metals in the coastal zone of the reservoir was confirmed.

Paleoenvironmental reconstructions and a sedimentological evidence of paleoseismic activity ca 9000 yr BP in Karelia, NW Russia, based on lake sediment studies on Mount Vottovaara

Karelia, like the entire Fennoscandian Shield, is a region with a low seismic activity. An example of the best-studied locality is a paleoseismic dislocation on Mount Vottovaara, which bears traces of disastrous Holocene geological events following the degradation of the last ice sheet. The evolution of the study area falls into three stages. At pre-Quaternary stage I, an uplifted block broken by numerous fractures and faults was formed. At glacial stage II, coarse clastic moraine was formed, the moving ice polished the crystalline basement surface and glacial scars were formed. At final deglaciation stages, the mountain top remained a nunatak. As Salpausselkä II marginal sediments retreated by about 70 km from the mountain, a postglacial stage in the region’s evolution, at which an earthquake occurred, began. It could have been triggered mainly by the consequences of the degradation of the Late Weischelian glaciations such as the rapid removal of the glacial load that contributed to the rejuvenation of various old faults. Changes in paleoecological conditions for the Mount Vottovaara area were reconstructed based on the results of lithological, palynological, diatom and radiocarbon studies of bottom sediments from a small lake on the mountain top. Vegetation dynamics from the Younger Dryas to the Subboreal period is presented. Small lake evolution stages were distinguished based on analysis of diatom complexes and the pollen and spores of aquatic and aquatic-subaquatic plants and Pediastrum algae. The data obtained show that minerogenic sediments were abruptly succeeded by organic in the late Preboreal-early Boreal period. The thickness of Boreal sediments and changes in the composition of diatom complexes and spore-and-pollen spectra suggest a depositional hiatus triggered by a strong earthquake which changed the water level of the pond and its basin structure. The earthquake is also indicated by numerous dismembered, displaced, thrown-away and shifted rock blocks and seismogravity downfalls. Deflation and other types of weathering are responsible for the formation of seide-shaped piles of blocks and boulders on the mountain top.