Elena S. Kravchuk

Comparative Analysis of Ecophysiological Characteristics of Stephanodiscus hantzschii Grun. in the Periods of Its Bloom in Recreational Water Bodies

In the periods of summer and autumn bloom of the Stephanodiscus hantzschii Crun. in recreational water bodies, studies on the vertical distribution of chlorophyll a, its contents per unit biomass, efficiency in using photosynthetically active radiation (EPhAR), and assimilative activity of microalgae were performed. The results confirmed the existence of two ecophysiological forms of St. hantzschii and provided evidence that both forms are typically autotrophic and can efficiently use low-intensity PhAR for photosynthesis.

Seasonal dynamics of amino acids in two small Siberian reservoirs dominated by prokaryotic and eukaryotic phytoplankton

The comparison of the dynamics of phytoplankton biomass and total amino acid composition was made for two water bodies: in one the phytoplankton were dominated by prokaryotes (i.e., there was a bloom of cyanobacteria) and by eukaryotic microalgae in the other. The dynamics of phytoplankton biomass and of total amino acid composition of water were investigated during the vegetation season. It was found that the only factor that significantly changed the percentages of amino acids in water was the bloom of cyanobacteria in the “blooming” water body. During the bloom of cyanobacteria, the absolute and relative content of the Leu-Glu group increased, while the contents of other acids generally dropped. Before and after the bloom, no significant variations in the total amino acid composition were recorded. In the reservoir where eukaryotic microalgae dominated, no significant variations in amino acid composition were recorded during the season.

Seasonal dynamics of akinetes of Anabaena flos-aquae in bottom sediments and water column of small Siberian reservoir

Seasonal dynamics of Anabaena flos-aquae (Lyngb.) Breb., including vegetative cells, akinetes and akinete envelopes, in bottom sediments and water column at both littoral and deeper central stations of a small Siberian reservoir was studied. Two types of akinetes were observed: in the first half of summer Anabaena formed akinetes, which served for vegetative reproduction and germinated in water column soon after differentiation, while in the second half of summer the akinetes produced served as a resting stages, which were deposited to bottom sediments. Canonical correlation analyses revealed that decrease of water temperature was the main environmental factor that stimulated the akinete formation. In contrast to the general opinion, concentration of inorganic phosphorus slightly, but positively influenced the akinete formation. Thus, akinetes formed in response to the temperature decrease, needs a certain level of this nutrient. At littoral and open-water stations abundance and seasonal dynamics of akinetes in water column and their sinking pattern were very similar. However, seasonal dynamics of abundance of akinetes in sediments in these two reservoir locations differed: whereas the abundance of akinetes in open water increased permanently during the summer, that in the littoral decreased soon after their sedimentation. The cause for decrease in abundance of akinetes in bottom sediments in winter is unknown.

Spatial distribution of resting stages (akinetes) of the cyanobacteria Anabaena flos-aquae in sediments and its influence on pelagic populations

Recruitment of pelagic populations of cyanobacteria from littoral bottom sediments is assumed to be one of the key factors for the development of harmful blooms. Therefore, it is necessary to obtain more information on the possible factors influencing the spatial distribution of the resting stages in littoral bottom sediments. To test the hypothesis that akinete abundances in littoral bottom sediments are associated with silt and the presence of higher water plants, we sampled spatial and vertical distribution and seasonal dynamics of akinetes of cyanobacterium Anabaena flos-aquae in a small Siberian reservoir. We found that akinetes accumulate in silt at stations located in macrophyte beds. Two experiments were carried out to test if there is relationship between size of inoculum and size of the pelagic population of A. flos-aquae. The proportion of A. flos-aquae in total phytoplankton biomass depended on the initial abundance of akinetes in bottom sediments. The model based on laboratory experiments gave good qualitative description of the field data. These findings can be useful to predict the location of the main akinete accumulation zones in a water body and plan the removal of sediment to prevent the cyanobacterial blooms.

Seasonal variations of metal concentrations in periphyton and taxonomic composition of the algal community at a Yenisei River littoral site

The concentrations of metals K, Na, Ca, Mg, Fe, Mn, Zn, Cu, Ni, Pb, Co and Cr, in the water and periphyton (epilithic algal communities) were studied at a site in the middle stream of the Yenisei River (Siberia, Russia) during three years using monthly sampling frequencies. Despite considerable seasonal variations in aquatic concentrations of some metals, there was no correlation between metal contents in the water and in periphyton. Seasonal concentration variations of some metals in periphyton were related to the species (taxonomic) composition of periphytic microalgae and cyanobacteria. Enhanced levels of Ni and Co in periphyton in late autumn, winter, and early spring were likely caused by the predominance of cyanobacteria in the periphytic community, and annual maximum levels of K in periphyton in late spring and early summer were attributed to the domination of Chlorophyta, primarily Ulothrix zonata.

Species-specific stimulation of cyanobacteria by silver carp Hypophthalmichthys molitrix (Val.).

ISSN 0012-4966, Doklady Biological Sciences, 2006, Vol. 408, pp. 223–225.

Distribution and migration of metals in trophic chains of the Yenisei ecosystem near Krasnoyarsk City

Methods of atomic absorption, flame photometry, and emission spectral analysis were used to study the concentrations of metals in water and major ecosystem components of the Yenisei River upstream of Krasnoyarsk City (conventionally background area). The mean bulk concentrations of Al and Cu in water exceeded the MAC for water bodies used for fishery. Cu concentration in freshwater shrimp was found to be reliably higher than that in the link of primary producers (periphyton), and Cd concentration in caddis fly larvae was found to exceed that in water moss. The maximal concentrations of metals among the examined aquatic organisms were recorded in periphyton. Cr concentration in the muscles of Arctic grayling was found to exceed some international standards.

Seasonal changes in the standing stock of essential polyunsaturated fatty acids in the biomass of phyto- and zoobenthos on a littoral station of the Yenisei River.

In the past decade, it was shown that polyunsaturated fatty acids (PUFAs) of the ω 3 family, primarily, eicosapentaenoic ( 20:5 ω 3 , EPA) and docosahexaenoic ( 22:6 ω 3 , DHA) acids, play a key role in the regulation of the cardiovascular system and other pivotal physiological and biochemical processes in humans and animals [1, 2]. These acids are essential, because humans and the majority of animals are not able to synthesize them in sufficient amounts and must receive them with food. Today, a number of foreign dietitian organizations have introduced the norms of daily consumption of PUFAs for population. In the biosphere, EPA and DHA are synthesized most effectively by microalgae. Therefore, the main source of these essential PUFAs are aquatic ecosystems. Because PUFAs pass the trophic chain algae → invertebrates → fish before getting to humans, the assessment of the standing stock of essential PUFAs in various aquatic ecosystems [2] and the efficiency of their passage along the trophic chain is a topical problem. We studied seasonal changes in the content of EPA and DHA in the biomass of primary producers (phytobenthos) and primary consumers (zoobenthos) at the littoral station on the Yenisei River upstream of Krasnoyarsk. Samples of zoobenthos were taken with the use of a kick-bottom sampler at a depth of at most 0.5 m after roiling benthic sediments (pebbles). A kick-bottom sampler is a frame ( 40 × 35 cm) with a net (opening, 40 × 40 cm; mesh, 0.25 mm) directed downstream. For quantitative estimation of the phytobenthos (phytoperiphyton) biomass, pebbles were taken from a frame ( 10 × 10 cm) fixed on the bottom, from which all biofouling organisms were brushed into a certain volume of water.

Potential effect of macrophyte beds on number of akinetes of blue-green algae in littoral of a body of water

The distribution of the resting stages of blue-green algae (akinetes) in bottom sediments of the littoral of a small Siberian water reservoir has been studied. The irregularity (mosaicism) of the distribution of akinetes in the bottom sediments of the littoral has been demonstrated and the possible mechanisms of its formation have been analyzed.

Seasonal dynamics of akinetes of Anabaena flos-aquae in the bottom sediments and water column of a small Siberian reservoir

Seasonal dynamics of akinetes of Anabaena flos-aquae (Lyngb.) Breb. was studied in the sediments and the water column in profundal and littoral zones of a small Siberian reservoir. It was hypothesized that even in a shallow mixed reservoir cyanobacterial bloom initiates in the littoral zone and only then distributes throughout the water body. Two types of akinetes have been recognized: one type ensures vegetative reproduction, and the other, survival during adverse growth conditions. Seasonal dynamics of abundance of akinetes and vegetative cells was quite the same in water column in the littoral and profundal zones. However, there were differences in the seasonal dynamics of abundance of akinetes in the bottom sediments of these two areas: in the central zone the abundance increased throughout the vegetation period, whereas in the littoral zone the abundance decreased after settling of akinetes. During winter, the abundance of akinetes decreased in the sediments in both profundal and littoral zones. The explanation to this fact has not been found yet.