Interannual dynamics of size, age composition and parameters of growth for japanese sardine Sardinops melanostictus in periods of its high abundance in the North-West Pacific

Interannual dynamics of size composition, age structure, and growth parameters are considered for japanese sardine Sardinops melanostictus in context of its recent and previous blooms and mass migrations to the Pacific waters at Kuril Islands and to the northern Japan Sea. Before the post-bloom catastrophic decline in the 1990s, in conditions of the highest density of the sardine population, small-sized fish with relatively slow growth rate became dominant, distinguished by lowered reproductive potential because of low population fecundity and reproduction rate. In the new, modern bloom of sardine population, two modal groups are observed in the year-classes size composition, in particular in the Japan Sea, with different exterior and biological parameters. There is assumed that they correspond with two morphological types, which alter each other at different stages of the demographic cycle, that determines total abundance of sardine population in the North-West Pacific and its long-term dynamics.

SEASONAL AND INTERANNUAL DYNAMICS OF CHLOROPHYLL IN PLANKTON OF THE RYBINSK RESERVOIR (2015–2019)

New data on chlorophyll content at standard stations in the Rybinsk reservoir, that continue series of long-term observations, were obtained in May–October 2015–2019. A fluorescent method is used in this study which makes it possible to determine the total amount of chlorophyll (ΣChl) by its content in cyanoprokaryotes, di-atoms, and green algae (ChlCyan, ChlBac, ChlChl, respectively). These taxa are the main contributors to ƩChl which show interannual and seasonal variation. In different years, the average content of ChlBac makes 2.4–6.6 μg/L or 24–50% of the ΣChl pool, ChlCyan – 3.1–10.9 μg/L (50–70%), ChlChl – 0.3–1.2 μg/L (3–12%). The distribution of ChlBac in the water column is generally uniform while the amount of ChlCyan decreases with depth. With the average ΣChl content for the growing season 14.8±1.0, 13.0±1.3, 7.8±0.6, 13.6±1.6, and 11.9±1.0 μg/L in 2015–2019, the trophic status of the reservoir varied from moderately eutrophic to mesotrophic.

STRUCTURE AND INTERANNUAL DYNAMICS OF THE REGIONAL ECOSYSTEMS RADIATION BALANCE OF THE PLAIN CRIMEA

The research team calculated the values of the radiation balance elements of the plain Crimea ecosystems on the bases of open databases of climate data and GIS-modeling and, moreover, analyzed their spatial and temporal differentiation. It is revealed that the spatial distribution of the radiation balance is characterized by an increase in values from the center to the coast of the peninsular. It correlates with the spatial differentiation of both total solar radiation and all other elements of the short-wave part of the radiation balance. There is a significant excess of radiation balance values of the plateau landscape level ecosystems over values of the hydromorphic landscape level ecosystems. This difference is determined by the location of selected key areas on the western coast of the Crimean Peninsula, which is characterized by the maximum values of total solar radiation supply. The elements of the long-wave part of the radiation balance change in the opposite direction, compared with the short-wave part of the radiation balance, which is associated with an increase of air temperature and climate continentality in the direction from the coast to the center of the peninsula. Two periods were identified in the interannual dynamics corresponding to the change of the circulatory periods of the Northern Hemisphere. In general, the considered ecosystems are characterized by trends of increasing radiation balance values in conditions of growth of all its elements. Such growth is provided by significant increase of values during the second period compared with the negative trends of radiation balance values for a number of ecosystems in the first one.

INTERANNUAL DYNAMICS OF PLANKTON COMMUNITIES IN THE CHANNEL SECTIONS OF THE KUIBYSHEV RESERVOIR

Based on the materials of hydro-biological studies in the Volga part of the Kuibyshev reservoir in 2018 and 2019, the authors evaluated changes in the quantitative indicators and taxonomic composition of phytoplankton and zooplankton. According to the results of the study, it was revealed that in 2019 the taxonomic diversity increased, but the abundance and biomass indices of phytoplankton decreased, while zooplankton decreased only in its abundance.

Interannual dynamics of breeding bird assemblage within the Central Botanical Garden of the National Academy of Sciences of Belarus (Minsk)

We studied the dynamics of the composition and diversity of breeding bird assemblage within the Central Botanical Garden of the National Academy of Sciences of Belarus in Minsk during 2016–2019 and compared with census data from breeding seasons of 1982–1985 and 1991–1992. Total 86 species were recorded and the breeding was confirmed for 59 of them. The interannual dynamics of breeding density for 42 species is analysed. Overall bird densities varied from 2.03 pairs/ha to 8.76 pairs/ha during single year; 16 species (Fringilla coelebs, Erithacus rubecula, Turdus merula, T. philomelos, T. pilaris, Parus major, Cyanistes caeruleus, Sylvia atricapilla, S. borin, S. curruca, Phylloscopus sibilatrix, Ph. collybita, Ph. trochilus, Sturnus vulgaris, Pica pica and Columba palumbus) were shown to be the dominants in assemblage during these years. We found that there was increased in species richness (17 new breeding species appeared, 2 breeding species disappeared) and the overall breeding bird density (by almost 3– 4 times) since 1982. The main factors explaining the dynamics of some assemblage characteristics such as synurbization of some bird species and change in habitat structure are discussed.