As ecosystem engineers, bivalves play a key role in nutrient cycling, water quality and phytoplankton composition in aquatic ecosystems. However, the effect of different species of bivalves on phytoplankton composition and water quality may vary due to size-selective feeding as small bivalves generally prefer smaller particles than large bivalves. A 70-day outdoor experiment was carried out in mesocosms with and without a large bivalve Cristaria plicata (13.90 +/- 0.27 cm) to test the hypothesis that the bivalve C. plicata decrease microphytoplankton (> 20 mu m) more than nano- (2-20 mu m) and picophytoplankton (0.2-2 mu m) thereby changing the phytoplankton composition. Nitrogen, phosphorus, total suspended solids (TSS), organic suspended solids (OSS), benthic algal biomass and light intensity at the sediment surface were monitored. Three size groups of phytoplankton (microphytoplankton, nanophytoplankton, picophytoplankton), and abundance of cladocerans and rotifers were also measured. We found that the bivalve decreased the concentrations of total nitrogen (TN), TSS and OSS, but not total phosphorus (TP); increased light intensity and increased benthic algal biomass. Contrary to our hypothesis, we did not find decreased microphytoplankton biomass in the mesocosm with bivalves. However, bivalves reduced nanophytoplankton and picophytoplankton thus changing the phytoplankton composition towards larger rather than smaller phytoplankton groups. In addition, the abundance of rotifers, but not cladocerans was decreased in the bivalve mesocosms. Our results showed that the large bivalve C. plicata can decrease the phytoplankton biomass thereby improving water quality, but have limited effects on larger phytoplankton.

Based on long-term monitoring of the water bodies of the Naroch Lakes ecosystem (Belarus), we assessed the gross primary production (GPP) and the growth rate of phytoplankton under conditions of various nutrient loads. To estimate the growth rate of phytoplankton, we used both the ratio of primary production to biomass (P/B) and the results of mathematical modeling using the knowledge-and-data-driven (KDD) approach. Both estimates, the P/B ratio, and the results of the KDD approach turned out to be well consistent with each other. We identified periods of high (1978–1986) and low (2006–2018) phosphorus concentrations in lake water. Gross primary production of plankton naturally increased with increasing phosphorus load, while no relationship between the nutrient load and the phytoplankton growth rate was found. In the period between 1987 and 2005, the invasive filter-feeding zebra mussel Dreissena polymorpha colonized the Naroch Lakes. During the Dreissena polymorpha invasion, changes in the photosynthetic capacity of phytoplankton were clearly manifested. The growth of phytoplankton under varying nutrient conditions was assessed. The KDD approach and P/B ratio were used to estimate the phytoplankton growth rate. Gross primary production of plankton increased with increasing phosphorus load. No relationship between nutrient load and phytoplankton growth rate was found.

The problem of predator interference and the associated choice between two types of functions describing the functional response in mathematical modeling of population dynamics are widely discussed. It is the choice between predator-dependent and prey-dependent functions. Here we present the results of comparing a wide range of the functions describing the functional response, which are used in modeling trophic interactions, with the functional response that is characteristic of interactions between phytoplankton and zooplankton populations in the ecosystem of the Naroch Lakes (Belarus). We apply the knowledge-and-data-driven, or KDD, approach, which allows us to use the results of the monitoring of the Naroch Lakes ecosystem, to identify the time-dependent functional response in each of the reservoirs of this ecosystem. The KDD approach provides for direct input of monitoring data into the mathematical description of population dynamics. As a result, we show that predator-dependent functional responses best match the environmental processes in the ecosystem of the Naroch Lakes. At the same time, we have identified predator-dependent functions that meet the monitoring data even worse than prey-dependent functions.

Antimicrobial resistance (AMR) poses a severe threat to global health. The wide distribution of environmental antibiotic resistance genes (ARGs), which can be transferred between microbiota, especially clinical pathogens and human commensals, contributed significantly to AMR. However, few databases on the spatiotemporal distribution, abundance, and health risk of ARGs from multiple environments have been developed, especially on the absolute level. In this study, we compiled the ARG occurrence data generated by a high-throughput quantitative PCR platform from 1,403 samples in 653 sampling sites across 18 provinces in China. The database possessed 291,870 records from five types of habitats on the abundance of 290 ARGs, as well as 8,057 records on the abundance of 30 mobile genetic elements (MGEs) from 2013 to 2020. These ARGs conferred resistance to major common types of antibiotics (a total of 15 types) and represented five major resistance mechanisms, as well as four risk ranks. The database can provide information for studies on the dynamics of ARGs and is useful for the health risk assessment of AMR.

We present an approach (knowledge-and-data-driven, KDD, modeling) that allows us to get closer to understanding the processes that affect the dynamics of plankton communities. This approach, based on the use of time series obtained as a result of ecosystem monitoring, combines the key features of both the knowledge-driven modeling (mechanistic models) and data-driven (DD) modeling. Using a KDD model, we reveal the phytoplankton growth-rate fluctuations in the ecosystem of the Naroch Lakes and determine the degree of phase synchronization between fluctuations in the phytoplankton growth rate and temperature variations. More specifically, we estimate a numerical value of the phase locking index (PLI), which allows us to assess how temperature fluctuations affect the dynamics of phytoplankton growth rates. Since, within the framework of KDD modeling, we directly include the time series obtained as a result of field measurements in the model equations, the dynamics of the phytoplankton growth rate obtained from the KDD model reflect the behavior of the lake ecosystem as a whole, and PLI can be considered as a holistic parameter.

Lake Sevan is one of the largest high-altitude freshwater lakes in Eurasia and Armenia’s largest reservoir. A 20 m drop in the Sevan level has led to intense eutrophication of the lake. Accordingly, raising the water level by the planned 6 m is considered a radical measure to preserve the lake's ecosystem. The main goal of this research was to develop a system of water quality indices as an important component of science-based management of lake Sevan water resources. The problem was solved using a quantitative modification of the expert panel method (Delphi). A set of state variables was selected and a procedure was developed for converting environmental values of state variables into qualitative (rating) values; the assessment was done of the desired reference state, and the water quality index (SWQI) was calculated. The application of the developed system for assessing the water quality of lake Sevan made it possible to quantify the trend of improving water quality in recent years and to identify the significant relationship of SWQI with the water level and epilimnetic water temperature. Highlights A system of indicators of water quality is developed. The reference state for the lake is established. Using SWQI water quality is assessed. The relationship between SWQI and potential threats is discussed.

We used macrozoobenthos data (abundance, biomass, and community structure) spanning 69 years including annual surveys from 1997 to 2016 in three connected lakes with different trophic states located in the north-west of Belarus (lakes Naroch, Myastro, and Batorino) to investigate the relationships between Carlson’s trophic state indices (TSI) and macrozoobenthos. We studied the response of the macrozoobenthos both over time and by depth zone. We found that there is an inverse relationship between lake productivity as measured by chlorophyll-based TSI and macrozoobenthos abundance and biomass both when comparing the three Narochianskie lakes and in the long-term dynamics within each lake. Lake-wide and littoral zone benthic biomass decreased significantly with increasing trophic state. Macrozoobenthos community structure also differed among lakes, with Chironomidae dominating in the most productive lake (Batorino), Chironomidae and Mollusca dominating in Lake Myastro, which had an intermediate trophic state, and Mollusca dominating in the lake with the lowest TSI (Naroch). We found significant differences both in the average benthos biomass and in the composition of macrozoobenthos between the profundal (silt and lack of macrophytes) and littoral zones (presence of macrophytes) within each lake. We argue that bottom substrates, macrophytes, and dreissenid mussels were more important for macrozoobenthos than trophic state in these lakes. Several benthic invertebrate taxa differed among lakes and are potential indicators of trophic state.

Nile tilapia [ Oreochromis niloticus (Linnaeus, 1758)] is a widespread invasive fish, now present in lakes, rivers, and reservoirs around the world, and its dominance has led to serious ecological problems in many freshwater systems. However, little is known about its effect on macrophyte-dominated lake ecosystems. We conducted a 10-week mesocosm experiment to test the impact of tilapia on phytoplankton and water quality in model ecosystems with submerged macrophytes [ Vallisneria natans (Lour.) Hara] and the presence and absence of tilapia. Tilapia led to an increase in concentrations of total phosphorus, total nitrogen, total dissolved nitrogen, ammonia nitrogen, and total suspended solids and had negative impact on submerged macrophyte and light intensity, thus causing an overall deterioration in water quality. Tilapia increased the abundance of rotifers and changed the zooplankton community structure. Tilapia increased the total biomass of phytoplankton but the effect depended on the phytoplankton size, i.e., the overall proportion of micro-phytoplankton increased, while that of pico-phytoplankton decreased. Thus, tilapia also caused changes in the phytoplankton community structure. Our research shows that tilapia deteriorates water quality and modifies phytoplankton and zooplankton Communities of shallow lakes.

The role of phytoplankton as one of the main sources of energy entering the water food network is especially evident in fish-rearing ponds. Indeed, in these comparatively small ponds (unlike many lakes), variations in the abundance of phytoplankton can be extremely sensitive to the action of external factors, including human activity. Here, we present results of the analysis of the phytoplankton dynamics in adjacent fishponds and in supplying/recipient river courses upstream and downstream of the ponds during a growing season. In the grow-out ponds, phytoplankton biomass is shown to reach maximums in spring and in early autumn, while in the nursery pond, the phytoplankton dynamics is characterized by one long peak. The specificity of fish-rearing ponds as the human-regulated reservoirs clearly manifests itself under comparison of phytoplankton biomass of ponds with the biomass of phytoplankton inhabiting a nearby river. The averaged phytoplankton biomass in the ponds was 6.2–10.1 times higher than in the river. Besides, we show here that the taxonomic composition of phytoplankton in the river differs significantly from the composition of phytoplankton in the fish-rearing ponds. In particular, Cyanobacteria and Chlorophyta were revealed as the major portion of the phytoplankton in the fish-rearing ponds, while in the river their abundances were low.

The impacts of species invasions can subside over time as ecosystems ‘adapt’ and invaders decline or increase over time as additional species invade. The character and timescales of invasion impacts provide important insights into ecosystem dynamics and management. Yet long-term studies of invasion impacts remain rare and often confound invasive species impacts with coincident environmental change. One way to address this challenge is to ask: what ecological changes over time since invasion are recapitulated in ecosystems that span a range of conditions, are located in different regions, and were invaded in different decades? We synthesize many-decade time series across seven ecosystems to resolve shared changes in seven key ecosystem features following invasion by zebra mussels and subsequent invasion by quagga mussels. These two congeners are among the most widespread invasive species that re-engineer and increasingly co-invade freshwater ecosystems. Seven polymictic shallow lakes with long-term data sets reveal remarkably similar trends, with the strongest ecosystem impacts occurring within 5–10 years of zebra mussel invasion. Surprisingly, plankton communities then exhibited a partial, significant recovery. This recovery was absent, and impacts of initial invasion amplified, in four lakes where quagga mussels outcompeted zebra mussels and more completely depleted phytoplankton. Thus, we show that the ecosystem impacts of invasive species can subside over time but amplify with serial introductions of competing, even closely similar, taxa.

The data of continuous monitoring of the Naroch Lakes system, which includes eutrophic Lake Batorino, mesotrophic Lake Myastro, and oligo-mesotrophic Lake Naroch, are used to search for the factors most affecting the long-term dynamics of the state of a lake ecosystem under a changing nutrient load. The set of continuous series of seasonal mean values of eight parameters of each ecosystem obtained in 1978–2015 is analyzed by singular spectrum analysis (SSA) and principal component analysis (PCA). The third principal component (F3), which contributed 8.2, 9.8, and 13.3% to the dynamics of ecosystems of Lake Batorino, Lake Myastro, and Lake Naroch, respectively, turns out to be connected with phyto- and zooplankton biomass, as well as with the parameters characterizing the processes of destruction and biochemical decomposition of organic matter. A comparison of statistical relationships and periods of the dominant cyclic components of principal components F3 and the associated parameters of ecosystems allow us to conclude that the interpretation of the third main factor under conditions of changing nutrient load depend on the characteristics of a particular ecosystem. In nutrient-rich ecosystems, it can be interpreted as the transfer of produced primary organic matter to consumers of the next trophic level, related to the structure of the food chain in the ecosystem. In the ecosystems where the process of primary production is limited by nutrient(s), this factor is represented by the available amount of nutrients, which is the third main factor affecting its long-term dynamics.

Since the second half of the 1970s, the ecosystems of lakes Batorino, Myastro, and Naroch have undergone anthropogenic eutrophication, targeted deeutrophication, and benthification caused by the introduction of the filter-feeding mollusk Dreissena polymorpha Pallas. The set of continuous series of seasonal mean values of eight parameters of each ecosystem obtained in 1978–2015 have been analyzed by mathematical-statistical methods of principal components (PCA) and singular spectra (SSA). The analysis showed that the complicated long-term dynamics of the set of the chosen parameters of the ecosystems was described during this period of time by three principal components by 92% and 90% for Lake Batorino and Lake Myastro, respectively, and by five principal components by 94% for Lake Naroch. We propose a biological interpretation of these principal components, i.e., a hypothesis of the factors exerting the greatest effect on the ecosystem dynamics during those years. The first main factor, which determines the dynamics of the ecosystems of lakes Batorino, Myastro, and Naroch by 63, 65, and 43%, respectively, is interpreted as the resistance of the lake ecosystem to a variable biogenic load, which is inversely related to the trophicity of the reservoir. The second main factor, which contributes 21, 15, and 22% to the dynamics of the ecosystem parameters of Naroch lakes (in the same order), was interpreted as solar radiation activity. The interpretation of the third main factor depends on the properties of a particular ecosystem. For ecosystems that are not deficient in biogenic elements (lakes Batorino and Myastro, with a contribution of the factor to the ecosystem dynamics of 8 and 10%), this may be the transfer of the primary organic matter to consumers of the next trophic level related to the structure of the food chain in the ecosystem. For an ecosystem in which the process of primary production formation is limited by the available amount of biogenic elements (Lake Naroch, in which the contribution of the third main factor to ecosystem dynamics is 13%), this very factor is the third main one, affecting the ecosystem long-term dynamics. The fourth main factor, which determines the dynamics of the Lake Naroch ecosystem by 9%, is also related to the process of primary production formation. Only the fifth main factor, which determined 7% of the dynamics of the ecosystem of Lake Naroch during the analyzed time period, controls the transfer of primary production to consumers of the first trophic level. Thus, our statistical study not only confirmed empirical regularities of the functioning of lake ecosystems, but for the first time enabled us to obtain quantitative assessments of the importance of each main factor for ecosystem development under specific conditions, depending on the trophicity of the water body.

The ecosystem of the Naroch Lakes (Belarus) includes three water bodies, Lake Batorino, Lake Myastro and Lake Naroch. These lakes have a common catchment area. At the end of the 80 s, the ecosystem of the Naroch Lakes underwent a transformation, during which the nutrient load on the catchment area decreased, and the concentration of phosphorus as a limiting factor in these water bodies decreased significantly. At the same time, the Naroch Lakes were exposed to zebra mussel ( Dreissena polymorpha Pallas) invasion. In the mid-90 s, the biological and hydrochemical characteristics of the ecosystem of the Naroch Lakes stabilized. We show here that complex processes associated with the transformation of the lake ecosystem and affecting both trophic interactions in the Naroch Lakes and the influence of environmental factors on them can be represented using a single parameter, the phase-locking index, PLI . In this case, a statistically significant numerical value of PLI characterizes the phase synchronization of two processes, oscillations of the concentration of total phosphorus, TP, and oscillations of the concentration of chlorophyll, Chl. We show that the phase synchronization of these processes occurs only after the stabilization of the ecosystem of the Naroch Lakes. In the period preceding the transformation of the lake ecosystem, there was no synchronization. Numerical evaluation of PLI as a holistic parameter allows us to characterize the transformation of the lake ecosystem as a whole without resorting to study of complex interactions of various factors involved in this transformation.

The impacts of species invasions can subside or amplify over time as ecosystems “adapt” or additional invaders arrive. These long-term changes provide important insights into ecosystem dynamics. Yet studies of long-term dynamics are rare and often confound species impacts with coincident environmental change. We synthesize many-decade time-series across ecosystems to resolve shared changes in seven key features following invasion by quagga and zebra mussels, two widespread congeners that re-engineer and increasingly co-invade freshwaters. Six polymictic shallow lakes with long-term data sets reveal remarkably similar trends, with the strongest ecosystem impacts occurring within 5-10 years of zebra mussel invasion. Surprisingly, plankton communities then exhibited a partial, significant recovery. This recovery was absent, and impacts of initial invasion amplified, in lakes where quagga mussels outcompeted zebra mussels and more completely depleted phytoplankton. Thus, invasion impacts subside over time but can amplify with serial introductions of competing, even closely similar, taxa.

The 2011–2012 data on the hydrochemical mode of the transboundary River Viliya (Neris) and two of its tributaries in the territory of the Republic of Belarus and on structure of the phytoplankton community therein are presented. High phytoplankton biomass was determined in the summer period. For the first time, the presence of microcystin synthase genes (mcyE) was detected in the River Viliya (Neris), and four variants of microcystins were determined employing the MALDI-TOF method. Similarities in the species composition (including toxic species) of cyanobacteria from the River Viliya (Neris) and from the Curonian Lagoon of the Baltic Sea were noted. It can be assumed that the phytoplankton community structure of rivers can influence algal community formation in the downstream areas as well as in the coastal estuarine lagoons that eventually receive water from these rivers.

Results of the continuous monitoring of the Naroch lake system, which includes eutrophic Lake Batorino, mesotrophic Lake Myastro, and oligomesotrophic Lake Naroch, have been used to study the factors that largely affect the long-term dynamics of the lakes ecosystem under variable nutrient loading. A set of continuous series of average seasonal values of eight parameters from each ecosystem over 1978–2015 is analyzed using the SSA and PCA methods. The second principal component (F2), which contributes 15.3, 20.5, and 22.1% to the dynamics of the ecosystems of lakes Myastro, Batorino, and Naroch, respectively, is associated with three parameters that reflect the processes of formation and decomposition of the organic matter. A comparison of the periods of the dominant cyclical components of principal component F2 and related ecosystem parameters allows us to interpret the second main factor behind these components as activity from solar radiation.

An analysis of the long-term dynamics of hydroecological characteristics of the Naroch lake system (Belarus) for the period from 1979 to 2018 is presented. During this period, there was a sharp change in the anthropogenic load on the watershed of the Naroch ecosystem, associated with the implementation of measures for its ecological improvement, as well as the invasion of the Dreissena polymorpha Pallas mollusk. It is shown that the change in the external load on the lake ecosystem led to significant changes in the amplitude of fluctuations in the concentrations of hydroecological characteristics, while the predictability of such fluctuations changed insignificantly.

Climate change and other anthropogenic stressors have led to long-term changes in the thermal structure, including surface temperatures, deepwater temperatures, and vertical thermal gradients, in many lakes around the world. Though many studies highlight warming of surface water temperatures in lakes worldwide, less is known about long-term trends in full vertical thermal structure and deepwater temperatures, which have been changing less consistently in both direction and magnitude. Here, we present a globally-expansive data set of summertime in-situ vertical temperature profiles from 153 lakes, with one time series beginning as early as 1894. We also compiled lake geographic, morphometric, and water quality variables that can influence vertical thermal structure through a variety of potential mechanisms in these lakes. These long-term time series of vertical temperature profiles and corresponding lake characteristics serve as valuable data to help understand changes and drivers of lake thermal structure in a time of rapid global and ecological change.

The threat posed by invasive non-native species worldwide requires a global approach to identify which introduced species are likely to pose an elevated risk of impact to native species and ecosystems. To inform policy, stakeholders and management decisions on global threats to aquatic ecosystems, 195 assessors representing 120 risk assessment areas across all six inhabited continents screened 819 non-native species from 15 groups of aquatic organisms (freshwater, brackish, marine plants and animals) using the Aquatic Species Invasiveness Screening Kit. This multi-lingual decision-support tool for the risk screening of aquatic organisms provides assessors with risk scores for a species under current and future climate change conditions that, following a statistically based calibration, permits the accurate classification of species into high-, medium- and low-risk categories under current and predicted climate conditions. The 1730 screenings undertaken encompassed wide geographical areas (regions, political entities, parts thereof, water bodies, river basins, lake drainage basins, and marine regions), which permitted thresholds to be identified for almost all aquatic organismal groups screened as well as for tropical, temperate and continental climate classes, and for tropical and temperate marine ecoregions. In total, 33 species were identified as posing a 'very high risk' of being or becoming invasive, and the scores of several of these species under current climate increased under future climate conditions, primarily due to their wide thermal tolerances. The risk thresholds determined for taxonomic groups and climate zones provide a basis against which area-specific or climate-based calibrated thresholds may be interpreted. In turn, the risk rankings help decision-makers identify which species require an immediate 'rapid' management action (e.g. eradication, control) to avoid or mitigate adverse impacts, which require a full risk assessment, and which are to be restricted or banned with regard to importation and/or sale as ornamental or aquarium/fishery enhancement.

The scientific materials of ichthyological, piscicultural and hydrobiological research conducted in Republic of Belarus on over regions are published in the collection. The main focus on the development of new technologies of pond pisciculture, selection and breeding work with carp and studies of the new perspective pisciculture objects. The problems of fish feeding, diseases prophylaxis, estimation of the quality habitat of the natural ponds and rational nature management are discussed as well. The edition is purposed for fish industry experts, scientific workers, teachers and students of the biological and agricultural educational institutions.