Measuring Alloxanthin as a Proxy Approach in a Study of Trophic Relationships between Zooplankton and Cryptophyte Algae in Lake Shira

Cryptophyte algae are an important trophic link in many aquatic ecosystems, but they remain insufficiently studied in terms of trophic interactions with other components of ecosystems. They are better quality food than most other algae and, therefore, can be subject to selective grazing by zooplankton; thus, direct measurements of the dynamics of their concentration in lakes may give very low productivity indicators. One way to assess the consumption of cryptophyte algae by zooplankton is to determine the content of alloxanthin, a carotenoid specific for cryptophyte algae, in zooplankton. The present study investigated the alloxanthin content of sedimentary silts, sedimentation traps, and zooplankton of Lake Shira using high performance liquid chromatography. A significant correlation was found between the abundance of some zooplankton species capable of consuming cryptophyte algae and the flux of precipitated alloxanthin recorded in sedimentation traps. Analysis of zooplankton samples (the largest contribution to the biomass of which was made by the copepod Arctodiaptomus salinus (Daday, 1885)) for the content of carotenoids during the spring-summer season showed the presence of alloxanthin amounts reaching 80 μg/g, which decreased by the end of the season, and that correlated with the biomass of cryptophyte algae in the lake. Carotenoids associated with other groups of algae were observed in considerably smaller amounts. Thus, the copepod A. salinus exhibits high selective consumption of cryptophyte algae, which may serve as a confirmation of a close trophic relationship between them

Comparative Characterization of the Cellular Composition of the Black Scorpionfish (Scorpaena porcus L.) Hematopoietic Organs during the Spawning Season and the Period of Reproductive Inactivity

Hematopoiesis in teleosts has a number of characteristics that are not fully understood. In the present work, the cellular composition of the hematopoietic organs (head kidney and spleen) of the black scorpionfish during the spawning season and the period of reproductive inactivity was studied using light microscopy. The morphology and the percentage of blood cells were described. The head kidney was shown to be the main hematopoietic organ of the black scorpionfish: immature blood cells of all hematopoietic lines at the different stages of differentiation were observed there. They were divided into 3 clusters depending on the average cell diameter. Lymphocytes, thrombocytes and colony-forming cells, the precursors for all types of blood cells, were observed within the cluster of small cells. The intermediate-size cluster comprised blast forms (erythroblasts and blasts of white blood cells). The large-size cluster consisted of maturing granulocytes, monocytes, macrophages, plasma cells, and mature erythrocytes. The spleen mainly contained mature erythrocytes, showing signs of senescence, and erythrocyte ghosts. Therefore, it was concluded that the spleen of the black scorpionfish performs the function of depositing and utilizing erythrocytes. The study also demonstrated the seasonal dynamics of hematopoiesis. The increase in the number of erythroblasts was recorded in the head kidney of spawning individuals. Erythroblasts were also found in the spleen, in spite of their total absence in the reproductively inactive fish. Consequently, the spleen of the black scorpionfish is an organ of secondary erythropoiesis, which functions when the hematopoietic capacity of the kidneys is insufficient

Bottom Communities and Abiotic Factors: Analysis of Statistical Relationship Using the Instability Index and Virtual Species Distribution

Statistical procedures for quantifying the relationships between the community structure and abiotic variables start with selecting a minimum set of uncorrelated environmental factors that determine the ecological conditions essential for each of the species. This is especially important when constructing models of spatial distribution of species which are key to ecology of communities and conservation of nature. The aim of the study is to explore whether some applications of information theory can be used to rank environmental factors with respect to their contribution to the formation of the ecological structure of aquatic communities. We consider the applicability of the instability index, which is a special case of the Kullback-Leibler entropy divergence and reflects the information gain from the displacement of a particular realization of a random variable relative to its mean value. Using of instability indices allows to reduce multidimensional data sets on species structure of communities and abiotic factors to lower dimension sets of commensurate standardized variables and to explore the relationships between the latter. The initial data we used were the results of the long-term (1990–2019) hydrobiological survey of benthic communities in small and medium-sized rivers in the Middle and Lower Volga regions. We consider the indices of instability calculated for each of 147 taxa of macrozoobenthos and 8 geophysical and hydrochemical indicators. Based on these data, we constructed random forest regression models and calculated potential weights of environmental factors that determine ecological preferences of species. The most significant explanatory variables were used to construct distribution maps of «virtual species», which were compared with the corresponding empirical data. A habitat suitability map of chironomids (Diptera, Chironomidae), the Prodiamesinae subfamily, is presented. Instability indices can be effectively used for exploratory analysis of various ecosystems, e. g. ranking habitats according to the degree of environmental instability and / or species associations, selecting the most informative abiotic variables that determine the population density of the taxa, etc.

Growth and Development of the Introduced Picea L. (Karst.) Species in the Taiga Zone (Karelia)

The study was conducted in the Botanical Garden of Petrozavodsk State University (South Karelia, the middle taiga subzone) from April to October during 1988–2016. The following representatives of the genus Picea were investigated: four introduced species (Picea glauca (Moench) Voss [syn. P. canadensis Britt.], P. pungens Engelm. f. viridis Regel., P. obovata Ledeb., and P. mariana Britt.) and one native species (P. abies (L.) Karst.). The growth of P. abies shoots starts 1–4 weeks earlier and ends 1–3 weeks later compared to the introduced species. The earliest culmination of shoot growth is observed in P. glauca and P. obovata and the latest in P. abies. The longest shoots are formed by P. abies. The growth dynamics of shoots differs considerably between the introduced species and the native species. The dates of the beginning and the culmination of the shoot growth in the studied species are to a certain extent affected by the temperature of the air. P. abies needles begin to grow 1–2 weeks earlier than the needles of the introduced species. The earliest culmination of needle growth is observed in P. obovata and P. glauca and the latest in P. pungens. P. abies and P. pungens show the largest needle length increment, while in the other species, it is 2–4 times smaller. The longest needles are formed in P. pungens and P. abies. There is a noticeable difference in needle growth dynamics between the introduced species and the native species. The dates on which needles begin to grow are largely determined by the temperature of the air. The temperature of the air and solar radiation produce a substantial effect on the time of occurrence of most phenophases in the studied Picea species. P. pungens and P. glauca were found to be the most promising spruce species for residential landscaping and creation of artificial plant communities in Karelia

Spatial Distribution, Population Structure, and Predatory Impact of Gelatinous Predators on Zooplankton Community in Inshore Waters off Crimean Coast of the Black Sea

The study reports the data on the distribution and predatory impact of the gelatinous macroplankton on mesozooplankton in the inshore waters of Crimea in April 2016. In the study areas, gelatinous macroplankton comprised Scyphomedusae Aurelia aurita (Linnaeus, 1758) and three ctenophore species (Mnemiopsis leidyi A. Agassiz, 1865, Beroe ovata Bruguire, 1789, and Pleurobrachia pileus (O. F. Müller, 1776). The biomass of A. aurita dominated everywhere and varied from ~ 62 to 330 g·m‑2 in different areas. The largest A. aurita biomass was observed in the South Coast of Crimea and the smallest in Karkinitsky Bay, where the number of jellyfish was high, suggesting the predominance of small individuals in the population. The size structure of A. aurita population differed by region: the proportion of large animals increased from the West to the East. The abundance and biomass of M. leidyi were rather low: 0.33–1.45 ind·m‑2 and 1–51.7 g·m‑2, respectively (the exception was the position in the Kerch Strait, where M. leidyi abundance reached 2 ind. m‑2 and biomass 126.3 g·m‑2); that species occurred only at 33–45 % of the stations (the exception was Karkinitsky Bay – 17 %), with the maximum values in the South Coast of Crimea. Large, 55–70-mm, adult individuals predominated. P. pileus biomass was lower than the biomass of A. aurita and M. leidyi in all areas, but its abundance was much higher. The daily rations of A. aurita varied widely both in the entire area and from one region to another. The daily ration values correlated with the carbon content in A. aurita body. The predation pressure of A. aurita on zooplankton in the inshore waters of Crimea was very low and did not result in a crucial decrease in mesozooplankton abundance. The effect of M. leidyi, even with its low abundance and biomass, was much stronger

Morphological and Functional Characterization of Hemocytes of the Black Sea Bivalves: Pacific Oyster (Crassostrea gigas) and Mussel (Mytilus galloprovincialis)

To understand the role that hemocytes play in processes of cellular immunity of bivalve mollusks, they should be accurately classified based on their morphological and physiological characteristics. The circulating hemocytes of the cultured Pacific oyster (Crassostrea gigas) and marine mussel (Mytilus galloprovincialis) were investigated using light microscopy and flow cytometry. In the mussel, two cell types, granulocytes and agranulocytes, were identified based on the presence of two subpopulations of cells differing by size and granularity level on light scatter plots. Light microscopic examination confirmed the presence of cells with cytoplasmic granules and cells without granulation in hemolymph of the mussel. In the oyster, light microscopy and flow cytometry revealed three types of hemocytes: agranulocytes, hyalinocytes, and granulocytes. The cells in the hemolymph of both species were mainly represented by agranular cells, which constituted 78.4 ± 8.9 % in the mussel and 86.7 ± 2.7 % (agranulocytes and hyalinocytes) in the oyster. Agranulocytes were the smallest cell type in the mussel and oyster. They were round-shaped and had large nuclei and narrow cytoplasm. Hyalinocytes of the oyster were larger and irregularly shaped, with eccentric nuclei. Granulocytes of both species contained numerous eosinophilic, basophilic, and mixed granules and formed pseudopodia. Flow cytometry showed that the agranular hemocytes of both species produced considerably fewer reactive oxygen species compared to granulocytes. Morphological and functional characterization of hemocytes of cultivated species improves the analysis of physiological state of bivalve mollusks farmed in the Black Sea region

The Effect of Salinity and Nutrient Load on the Ecosystems of Selected Lakes in the South of Siberia

Salinity largely determines the species diversity and structure of the food web in lake ecosystems. Many studies have been focused on the salinity tolerance of various plankton species. There are fewer studies investigating the modifications in the food web interactions under the effect of salinity. An appropriate system for such studies is closely located lakes of different salinity. We took samples during the summer stratification and analyzed the physicochemical and biological characteristics of 20 lakes (salinity 0.1-35 g/l) in southern Siberia in order to provide general description of this system and to test a number of hypotheses about the effect of salinity on the structure of the food web. The analysis revealed two key factors structuring ecosystems of the studied lakes. The species composition of zooplankton was determined by salinity, with a decrease in the number of species and the transformation of the community from a diverse community of zooplankton (salinity up to 3 g/l) to the dominance of large daphnia (3-8 g/l), copepods (> 8 g/l), small cladocerans and rotifers (20-30 g/l), and Artemia (> 30 g/l). The top predator (fish) was eliminated at salinity above 10 g/l. The biomass of zooplankton did not depend on salinity, but significantly increased in lakes with an increased nutrient load. The nutrient load also had a significant effect on the concentration of total phosphorus, turbidity and transparency of water, and the concentration of chlorophyll “a”. Thus, we recorded the structuring effect of the nutrient load (bottom-up control) on the biomass of the trophic levels and the parameters of water transparency, while salinity transformed the trophic chain from the top, leading to the disappearance of fish and a change in the dominant species of zooplankton. At the same time, salinity did not affect the biomass of the trophic levels. In order to detect top-down effects in the ecosystems of saline lakes, it is necessary to perform a comparative analysis of the seasonal dynamics of ecosystems of lakes with different salinity

Effect of Anthropogenic Factors on the Ecosystem of the Yenisei River Anabranch within the City of Krasnoyarsk

In recent decades, freshwater ecosystems have regularly experienced blooms of green algae (green tides), causing environmental and economic damage. Blooms of green alga Spirogyra sp. occur in the ‘Abakanskaya’ anabranch of the Yenisei River in summer months. The anabranch is influenced by several anthropogenic factors: construction of a dam in the upper reaches; heated water discharge from a thermal power plant; fish farming. The aim of this study was to assess the impact of anthropogenic factors on the ecosystem of the Abakanskaya anabranch and to identify the main factors favoring Spirogyra sp. blooms. Samples were taken in May-September 2018-2019 at four sites: 1 – upstream of the dam (control), 2 – downstream of the dam, 3 – near the point of heated water discharge, 4 – downstream of the fish farm. Physical and chemical parameters, biomass and species composition of phytoplankton, phytoperiphyton, zooplankton, zoobenthos, and higher water plants, gross primary production (GPP), nitrogen content in biomass of periphyton, higher plants, and zoobenthos were studied. The main factor that caused changes in the community was that there was no water flow in the anabranch because of the low capacity of the dam drainage pipes. While upstream of the dam most ecosystem features were within the limits typical for this part of the Yenisei River, downstream of the dam, the system seemed to change from lotic to lentic: percentage of motile forms of phytoplankton, biomass of zooplankton, percentage of true zooplankton species, taxon number and taxonomic diversity of zooplankton and zoobenthos became higher; phytoperiphyton primary production rose (because of Spirogyra sp. bloom); higher water plants thrived. The other investigated factors, namely, thermal, nutrient, and organic pollution evidently produced combined effect on the ecosystem because of the absence of water flow, and their specific effects were not obvious

Growth and Development of Introduced Larix Mill. Species in the Taiga Zone (Karelia)

The study reports results of research carried out from April to October during 1988–2016 at the Botanical Garden of Petrozavodsk State University (South Karelia, middle taiga subzones). Three introduced species of the genus Larix (Larix sibirica Ledeb., L. leptolepis (Sieb. et Zucc.) Gord, and L. dahurica Turcz. ex Trautv.) were studied. The growth of shoots and needles in different species begins, reaches its culmination, and ends almost simultaneously, differing by no more than one week across the species. L. sibirica shows the highest growth rate. The timing of growth, culmination, and the dynamics of growth of shoots and needles are largely determined by variations in precipitation, temperature, and humidity. The direction and strength of such an effect may vary from year to year. The dates of phenological phases of the Larix species studied here are chiefly determined by the air temperature in the current growing season and the dates of formation of wintering buds in the previous growing season. Bud swelling and opening begins almost simultaneously in the studied species. Most of the other phenological phases begin and end earliest in L. sibirica and latest in L. leptolepis. All the studied species, primarily L. sibirica, are promising for residential landscaping and creation of artificial plant communities in Karelia

What Quantitative Anatomy Can Provide for Kinetics of Xylogenesis: Analysis of Cell Radial Diameters

A theoretical and experimental verification of a simple hypothesis was carried out in this study to determine if features of the anatomical structure of coniferous annual rings (in a case study of pine trees from moisture-deficient growth conditions in the steppe zone) quantified in tracheidograms of annual rings can be used to reconstruct the kinetics of seasonal growth. During two sharply different growth seasons, sampling was performed periodically, and seasonal growth of tree rings was measured where the forming annual ring was separated into zones (cambium, extension zone, zone of cell wall thickening, zone of mature tracheids). Based on these data and total tracheidograms, a simple scheme for converting the variability of the radial cell sizes into cumulative and differential cell production curves was proposed. Statistical analysis revealed both correspondence and discrepancies between theoretical and experimental data, showed the prospects of the proposed approach, and suggested the need for longer seasonal observations