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During 2009–2011, 50 points of the Daube River Basin were surveyed. In 23 of them, seven species of Unionidae were recorded: U. pictorum, U. tumidus, U. crassus sensu lato, A. anatina, A. cygnea, P. сomplanatа and S. woodiana, which is an invasive species. Th e index of occurrence of freshwater mussels in general was 100 % in the Lower Danube River (5 study areas), 42 % in Tisa River (31 study areas), 33.3 % in Seret River (3 study areas), 36 % in Prut River (11 study areas). Th e index of occurrence of species was rather low: 24 % of A. anatina, 22 % of U. tumidus, 22 % of U. crassus, 16 % of U. pictorum, 14 % of P. complanata, 14 % of S. woodiana, and 2 % of A. cygnea. U. crassus was not found in the Lower Danube river, while A. cygnea was found only there outside the main watercourse. Th e invasive species S. woodiana occurred in the Lower Danube River and in the sub-basin of Tisa River (with 83 % and 20 % frequency, respectively. Th e mean values of population densities ranged from 1.00 (A. cygnea) to 6.14 ind./m2 (S. woodiana), and the mean biomass varied from 1.14 (P. сomplanatа) to 797.54 g/m2 (S. woodiana).

In wetlands, a distinct zonation of plant species composition occurs along moisture gradients, due to differential flooding tolerance of the species involved. However, "flooding" comprises two important, distinct stressors (soil oxygen demand [SOD] and partial submergence) that affect plant survival and growth. To investigate how these two flooding stressors affect plant performance, we executed a factorial experiment (water depth x SOD) for six plant species of nutrient-rich and nutrient-poor conditions, occurring along a moisture gradient in Dutch dune slacks. Physiological, growth, and biomass responses to changed oxygen availability were quantified for all species. The responses were consistent with field zonation, but the two stressors affected species differently. Increased SOD increased root oxygen deprivation, as indicated by either raised porosity or increased alcohol dehydrogenase (ADH) activity in roots of flood-intolerant species (Calamagrostis epigejos and Carex arenaria). While SOD affected root functioning, partial submergence tended more to reduce photosynthesis (as shown both by gas exchange and 13C assimilation), leaf dark respiration, 13C partitioning from shoots to roots, and growth of these species. These processes were especially affected if the root oxygen supply was depleted by a combination of flooding and increased SOD. In contrast, the most flood-tolerant species (Juncus subnodulosus and Typha latifolia) were unaffected by any treatment and maintained high internal oxygen concentrations at the shoot : root junction and low root ADH activity in all treatments. For these species, the internal oxygen transport capacity was well in excess of what was needed to maintain aerobic metabolism across all treatments, although there was some evidence for effects of SOD on their nitrogen partitioning (as indicated by 865N values) and photosynthesis. Two species intermediate in flooding tolerance (Carex nigra and Schoenus nigricans) responded more idiosyncratically, with different parameters responding to different treatments. These results show that partial submergence and soil flooding are two very different stressors to which species respond in different ways, and that their effects on physiology, survival, and growth are interactive. Understanding species zonation with water regimes can be improved by a better appreciation of how these factors affect plant metabolism independently and interactively.

Changes in the concentration and spectral absorption of chromophoric dissolved organic matter (CDOM) may strongly condition the optical properties of tropical and subtropical water bodies. We examined the spatial distribution of CDOM-related absorption, spectral slope and vertical attenuation of solar radiation in two shallow lakes in the Esteros del Iberá wetland system. In situ measurements were made to examine spatial variations in photobleaching yields in natural lake conditions. The results showed that "fresh" allochthonous CDOM is more susceptible to phototransformations than either "aged" allochthonous organic matter or autochthonous sources, if the distances from sources are considered as proxies for residence time. Based on measured changes in absorption spectral slope in relation to solar ultraviolet irradiance, a model was developed which used CDOM as a non-conservative tracer of water masses. Spatial changes in CDOM absorption within the lake were then used to compare photo related transformations to those associated with conservative mixing.

The production of aquaculture products in closed water supply plants is becoming more widespread, and the volume of cultivation with such systems of freshwater fish is increasing. The use of closed water supply plants is the most promising global trend. When growing in closed water supply facilities, all parameters of the technological process are supported by automated devices, and the influence of natural factors on the process of the process is minimal. However, such systems require complex technological support, which needs constant improvement. When working in closed water supply plants, a precipitate is formed that needs to be recycled. It is expedient to utilize these sediments using methods that allow to receive additional heat and electricity for the needs of closed water supply plants in the production of aquaculture. On the basis of generalization and analysis of literary sources, it was found that the average value of the coefficient of conversion of mixed fodder during fattening of pigs is from 2.8 to 3.2 kg of feed per kg of weight gain. The average value of the coefficient of conversion of mixed fodder during fattening cattle is from 6.3 to 7.2 kg of feed per kg of weight gain. When growing broilers, the feed conversion rate is from 1.6 to 2 kg per kg of weight gain. The average value of the coefficient of conversion of mixed fodder during the cultivation of trout was 1.6 kg of feed per kg of weight gain, and at feeding sows – 1.2 kg of feed per kg of weight gain. The results of the development of block diagrams for the installation of closed water supply for the production of aquaculture with the provision of partial energy autonomy due to heat and electricity generated during the cogeneration of biogas generated during methane digestion of organic constituents of the sediment formed during the operation of the closed water supply system are presented.

POTAMON is a unidimensional, non-stationary model, designed for simulating potamoplankton from source to mouth. The forcing variables are discharge, river morphology, water temperature, available light and nutrient inputs. Given the description of several algal categories, POTAMON allows to simulate algal "successions" at a particular site, as well as longitudinal changes of potamoplankton composition and biomass. The algal categories differ by their physiology, their loss rates, and their sensitivity to grazing by zooplankton. Two zooplankton categories were considered, Brachionus-like and Keratella-like, which differ by their clearance rate, their incipient limiting level, their selectivity towards phytoplankton, and their growth yield. The model simulates satisfactorily the onset and the magnitude of the phytoplankton spring bloom in the Belgian part of R. Meuse, the biomass decrease in early summer, and the autumn bloom. It also renders the major variations of algal assemblages along the river. The model allows to confirm that the main driving variables of potamoplankton dynamics in a eutrophic river are physical factors: discharge and related variables (e.g. retention time), light and temperature. In addition, the simulations confirm that the zooplankton-phytoplankton interaction may result in phytoplankton biomass fluctuations and compositional changes. POTAMON can be useful to explore plankton dynamics in a large river, and it may become a tool to test various management measures.

AbstractPotential toxic effects of thiamethoxam on nontarget organisms and the community structure of a generic Midwestern farm pond and emergent wetland were assessed using 2 versions of the comprehensive aquatic system model: CASMGFP, a generic farm pond model, and CASMGWL, a generic wetland model. The CASMGFP and CASMGWL are integrated bioenergetics‐based and habitat quality models that describe the daily biomass values of selected producer and consumer populations representative of generalized Midwestern farm ponds and emergent wetlands. The CASMGFP demonstrated the ability to reproduce values of population biomass reported for Midwestern (and other) pond ecosystems; the CASMGWL provided a similar modeling capability for Midwestern emergent wetlands. Lethal and sublethal effects of thiamethoxam were modeled as extrapolations of laboratory toxicity assays using the CASMGFP and the CASMGWL. Time series of daily environmental concentrations of thiamethoxam constructed for 6 regional pesticide applications across the United States failed to produce any calculated impacts on modeled population biomass or changes in community structure of modeled trophic guilds in the CASMGFP or the CASMGWL. However, evaluation of systematically increased daily concentrations demonstrated the ability of both models to simulate direct and indirect toxic effects of this pesticide. The present model study suggests that process‐based food web/ecosystem models can be used to characterize the potential ecological effects of thiamethoxam on generalized farm pond and emergent wetland ecosystems. Environ Toxicol Chem 2018;37:738–754. © 2017 SETAC

'Trophic state' is often used to classify aquatic ecosystems according to biotic productivity. Carlson trophic state indices were used to assess the trophic situation in Gheshlagh reservoir (North-Western Iran), on which a dam was constructed three decades ago. Using data from a one-year surface sampling, a comparison of the trophic state index (TSI), between four sampling points in the reservoir and one sampling point under the dam, was performed. The results of the TSI calculated based on chlorophyll a (chl. a) concentration and Secchi depth showed that the aquatic environment in the reservoir is eutrophied (50 < TSI < 80), while it is mesotrophic (40 < TSI < 50) under the dam. Moreover, the measured concentrations of chl. a and phosphate were consistent with the available data ranges on eutrophication. In addition, it was shown that algal biomass bloom occurred at the end of spring, all over the sampling points.

This study aims to ascertain the effects of CO2 induced water acidification and leaks from Carbon Capture and Storage activities on the South American amphipod Hyale youngi. A 10-day acute toxicity test was performed using sediments from two sites located inside the Santos Estuarine System. They were subjected to five pH treatments (8.1, 7.6, 7.0, 6.5, and 6.0). Metals (Cd, Cu, Cr, Pb, Ni and Zn) and the metalloid As were analyzed to determine the influence of their acidification-related mobility on the amphipods mortality. The results showed that mortality becomes significant when compared to control in pH 6.5 in the Canal de Piaçaguera sediment (contaminated) and at pH 6.0 in Ilha das Palmas sediment (reference).