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Catfish have spread across Europe and several countries out of this region within the last decades. Basic knowledge of this apex predator has revealed concerns of invasive behaviour and questions regarding its utilization as a biomanipulation species. However, a method enabling its regulation to a required level has not yet been developed. We simulated the impact of angling on the catfish population by method of hook-lines in two post-mining lakes with a monitored population consisting of tagged individuals and in two reservoirs as reference sites. Further, the efficiency of hook-lines as a reducing device was examined and the economic aspects were determined. Catfish population in localities where the species is unwanted or invasive may be efficiently reduced to a harmless level by hook-lines and angling (depending on the approach of anglers). The most efficient time of the year seems to be spring to early summer with catch efficiency of 5.4 individuals per 10 baits in one day. The catch efficiency markedly decreased during the second part of the year and did not exceed 2.8 individuals per 10 baits in one day. Mean size of catfish had negative impact whereas catfish biomass had positive impact on the catch efficiency. Trophic status and number of catfish in the locality had no impact on the catch efficiency. According to model, 11–18 bait-days per 1 ha per season is efficient to decrease catfish population to 10% of the original size. Both angling and hook-lines are very simple, they are financially and time bearable mechanisms of catfish regulation in any condition. However, catfish play an important role as a biomanipulative species in many localities. In this case where catfish is beneficial, angling presents a real threat of population collapse and loss of the biomanipulative effect. Image 1 • Hook-lines and angling are methods that efficiently reduce a catfish population. • Relatively low effort resulted in a reduction of the catfish population. • Angling presents a real threat of population collapse, where catfish is beneficial. • Where catfish species is unwanted, both methods may be efficiently provided. [ABSTRACT FROM AUTHOR]

Long-term cyanobacterial blooms and hypereutrophic state have been typical for the shallow, urban Swarzędzkie Lake for many years. Diversion of sewage did not change its trophic status, so restoration began in autumn 2011 using the sustainable approach based on three methods. The aim of the study was to analyse how sustainable restoration affects zooplankton. We hypothesised that bottom-up and top-down methods reconstructed zooplankton composition. Thus, the abundance of large-size cladocerans increased and controlled phytoplankton effectively. The elimination of cyanobacteria bloom, the decrease of rotifer abundance and the twofold increase of filter-feeder effectiveness were observed in summer 2012. However, high phosphorus concentration, lack of regular cyprinid removal and insufficient fish stocking together with high temperature prevented zooplankton from controlling cyanobacteria bloom in summer 2013. Rotifer domination with high trophy species was noted, as before restoration. The number of rotifers decreased in 2014, while crustaceans increased due to the significant decrease of nutrient concentrations and an intensification of biomanipulation treatments. Therefore, summer phytoplankton growth was low, without cyanobacteria dominance. The rebuilding of zooplankton in Swarzędzkie Lake was observed during sustainable restoration. However, the treatments should be intensified when adverse changes were observed to obtain better results for the improvement of water quality. [ABSTRACT FROM AUTHOR]

Highlights • Simplified community and body size diminution occurred in the zooplankton community. • Unusual dynamics of diversity and biomass coincide well with carps' feeding rhythm. • Community traits related significantly to carp releasement in history. • Community traits related weakly to environmental factors. • Zooplankton-based indicators tend to overestimate trophic level under feeding stress. Abstract Zooplankton is widely used in indicating environmental changes and energy flow efficiency in aquatic ecosystems. Species composition and body size spectrum of zooplankton assemblage are sensitive to the changes of physico-chemical variability and fish feeding stress, and thus have in turn a prime bearing on water quality and cultured fishes. To study the response of zooplankton community to the introduction of planktivorous carps, monthly surveys were conducted in 2015 at six traditionally monitored locations in Miyun Reservoir, the unique surface drinking water of Beijing. There was a decrease in species richness, diversity, density and biomass, suggesting simplification of the community structure. Species diversity, density, and biomass declined significantly through the growth season, illustrating the great pressure imposed on the zooplankton. Regression and canonical correspondence analysis (CCA) showed low relationships between community traits and environmental variables. Zooplankton biomass had a significantly negative relationship with the stocking intensity of the filter-feeding carp. The different responses of the subgroups of Protozoa, Rotifera, Cladocera and Copepoda indicated that they responded differently to environmental stress. Seasonal variations in the density and biomass of the four subgroups and biomass size spectrum (BSS) indicated that planktons with medium and large body sizes were more sensitive and suffered more stress from the filter-feeding carp. The filter feeding by the silver and bighead carp disrupted the natural equilibrium of the zooplankton community, decreased diversity and stocks, altered the seasonal dynamics of all quantitative traits and suppressed the dominance of medium- and large-sized species or functional groups. The impacts of the fishery mode and the responses of different functional groups of zooplankton must be considered in ecological assessments and biomanipulation studies based on the zooplankton community structure and dynamics. [ABSTRACT FROM AUTHOR]

• Combining conventional and ecohydrological restoration maintained good water status. • Limiting nutrient inflow reduced the number of days with cyanobacteria bloom. • Sediment removal increased the phosphate level and induced overgrowth of Hydrodictyon reticulatum. • Trapping external nutrient loads was the most cost-effective restoration measure. • The SSBS and hybrid system reduced the cost of siltation treatment. The study presented in this paper aimed to improve the water quality of a small, stormwater-fed urban river and a cascade of ponds and reservoirs (Łódź, Poland) that are intensively used for recreation. We tested a combination of conventional restoration methods (bottom sediment removal and biomanipulation) and comprehensive ecohydrological restoration methods (hybrid systems, sequential sedimentation-biofiltration systems (SSBS), floating islands, landform-adjusted shoreline vegetation and plant harvesting). As a result of sediment removal (9795 m3, cost: €80761), almost 12.5 tons of nitrogen and 197 kg of phosphorous were eliminated from the reservoirs. The hybrid systems and SSBSs reduced the nutrient transport and suspended solid levels by 49%–98.5% and 89.6%–98.6%, respectively, from the upstream catchments to the reservoirs (investment cost: €63929). Generally, restoration improved most of the water quality indicators, although an increase in the phosphate concentration was observed from 0.06 to 0.17 mg L−1 before restoration to 0.13–0.28 mg L−1 immediately after restoration as a result of disturbances resulting from bottom sediment removal. Four years after restoration, the concentrations of the total forms of nutrients and ammonium were still considerably lower than before restoration. The number of summer days with microcystins and with chlorophyll a concentrations above the WHO limits for recreational waters decreased. However, there was a gradual decline in the physicochemical parameters of the water due to the local impacts of human use (swimming and duck and fish feeding), rather than from other external or internal loads, which were effectively controlled. [ABSTRACT FROM AUTHOR]

Increasing temperatures in aquatic ecosystems have resulted in changes in the proliferation patterns and persistence of cyanobacteria, particularly Microcystis sp.. In temperate lakes, large-sized herbivores such as Daphnia magna are used to control cyanobacterial blooms. The cladoceran, Simocephalus mixtus and the amphipod, Hyalella azteca are common in tropical and sub-tropical aquatic systems. Since both species are generalist feeders, we tested their ability to consume uni-cellular Microcystis sp. and Chlorella at different temperatures. Feeding rates and filtration rates at different temperatures (20, 25 and 30 °C) were quantified on diets of Chlorella vulgaris and Microcystis sp.; each diet separately at different concentrations (0.2, 0.5, 1.0 and 2.0 × 106 cell mL−1). Both the crustaceans were able to consume C. vulgaris and Microcystis sp. although at different rates depending on the food concentration and temperature. At 25 °C and a Microcystis sp. concentration of 2.0 × 106 cells mL−1, H. azteca fed up to 60 × 104 cells ind−1 h−1 of Microcystis sp. which was even greater than its feeding rate on C. vulgaris. Simocephalus was able to consume Microcystis sp. although at significantly lower rates as compared to C. vulgaris. Our experiments show that H. azteca can feed well on Microcystis sp.. Combined with control in fish predation pressure, both crustacean species could be used in top-down control, but further investigation on a large scale with these organisms is necessary to propose new alternatives. [ABSTRACT FROM AUTHOR]

We present a methodology for building biologically inspired, soft microelectromechanical systems (MEMS) devices. Our strategy combines several advanced techniques including programmable colloidal self-assembly, light-harvesting with plasmonic nanotransducers, and in situ polymerization of compliant hydrogel mechanisms. We synthesize optomechanical microactuators using a template-assisted microfluidic approach in which gold nanorods coated with thermoresponsive poly(N-isopropylmethacrylamide) (pNIPMAM) polymer function as nanoscale building blocks. The resulting microactuators exhibit mechanical properties (4.8 ± 2.1 kPa stiffness) and performance metrics (relative stroke up to 0.3 and stress up to 10 kPa) that are comparable to that of bioengineered muscular constructs. Near-infrared (NIR) laser illumination provides effective spatiotemporal control over actuation (sub-micron spatial resolution at millisecond temporal resolution). Spatially modulated hydrogel photolithography guided by an experimentally validated finite element-based design methodology allows construction of compliant poly(ethylene glycol) diacrylate (PEGDA) mechanisms around the microactuators. We demonstrate the versatility of our approach by manufacturing a diverse array of microdevices including lever arms, continuum microrobots, and dexterous microgrippers. We present a microscale compression device that is developed for mechanical testing of three-dimensional biological samples such as spheroids under physiological conditions. [ABSTRACT FROM AUTHOR]

This study aimed to characterise the composition, structure and trophic organisation of the macroinvertebrate communities of two pasture ponds - one natural and one artificial - in the Italian Prealps. Faunal composition was studied during the snow-free period in 2003-2004 and compared with data collected in 1984-1985. Insects (i.e., Coleoptera, Diptera and Heteroptera) prevailed (58%), followed by Tubificidae (40%). Overall, higher taxonomic diversity was assessed in the natural pond, which was less disturbed by livestock and humans. The invertebrate assemblages also had different inter- and intra-pond functional characteristics based on the substrate type (e.g., silt-mud sediments were dominated by collector-gatherers, burrowers and drought-tolerant taxa), vegetation cover and hydrological regime. The faunal composition of the two ponds was different from that reported 20 years prior due to the meteorological conditions (e.g., 2003 was exceptionally hot and dry), human activities (e.g., biomanipulation practices) and natural factors (e.g., siltation); these results emphasise the high vulnerability and resilience of alpine ponds. [ABSTRACT FROM AUTHOR]

The use of aquatic plants has recently become a popular technique for ecological restoration and purification of eutrophic rivers and lakes. In this paper, various technologies were studied and designed against the background of research and demonstration projects for pollution control in Dianchi Lake and comprehensive improvement of water quality. Different technical units were designed in the horizontal and vertical spaces of the water body. Horizontal spaces included plant buffers on the surface, algae enrichment and diversion, innovative floating beds, and emerging plant zones at the shoreline. Vertical spaces include ecological floating beds, ecological jellyfish, and ecological membrane coverings. Spatial growth patterns of aquatic plants were constructed with rational use of water space and integration with various techniques to maximize the absorption of nutrients in the lake, increase the transparency of the water, and alleviate lake eutrophication. The previous technologies were combined, and technical demonstrations were conducted using experiments. We set up an integrated technical demonstration district with an area of 0.25 km2 on the north shore of Dianchi Lake, and the results demonstrated the following: water transparency increased by >50 cm; algae biomass decreased by >70%; and the percent removal of total phosphorous (TP), total nitrogen (TN), and chemical oxygen demand (CODMn) was >30%. [ABSTRACT FROM AUTHOR]

Waajen, G, Lürling M, van de Sande R. The unfulfilled promise of urban Lake Kleine Melanen (The Netherlands): diagnostics, experiment on reduction of sediment P-release and in-lake restoration. Lake Reserv Manage. 35:8–24. Lake Kleine Melanen (The Netherlands) experienced cyanobacterial blooms during the summertime, causing public health risks, turbid water, and lack of macrophytes. To improve the situation, we determined the underlying causes of the poor water quality. Our diagnosis included the water and phosphorus (P) budget of the lake and showed the need for the reduction of both the external and internal P loads. The external P load (7.5 mg P/m2/d) exceeded the transition between the clear water state and the turbid state by 44–121%, mainly due to the discharges from the separated stormwater sewer system in the adjacent neighborhood. Due to political and financial considerations of the managing authorities, the restoration (2010–2012) was restricted to internal management. To reduce the high internal P load (3.8 mg P/m2/d), we tested 3 sediment capping options in an enclosure experiment, showing the best results when we combined sand capping with the P fixative Phoslock® and flocculant polyaluminumchloride. A 0.6–1.3 m thick layer of soft sediment was dredged from the lake. Thereafter, the sediment was capped with a 0.2 m thick layer of sand to which Phoslock® was added. Additional in-lake measures including fish removal and shoreline reconstruction were also conducted to support improvement. We compared water quality before (2008–2010) and after (2012–2014) interventions. Although the mean concentration of total P was reduced from 0.30 to 0.11 mg P/L, and cyanobacterial chlorophyll a from 52 to 6 μg/L, cyanobacterial blooms still occurred. For further water quality improvement, the reduction of the external P load caused by stormwater runoff is required. [ABSTRACT FROM AUTHOR]

Abstract The presented research is part of the LIFE project ("EH-REK" LIFE08 ENV/PL/000517) on innovative restoration methods for small urban impoundments in the city of Łódź (Poland). The objective was to evaluate the usefulness of zooplankton as a biological quality element, when assessing the effectiveness of restoration efforts in three urban reservoirs and a one pond. The fifth unrestored pond was used as an example of the progressive eutrophication of an urban ecosystem. Studies were conducted during two periods: before (2010−2012) and after (2013–2016) restoration. A selection of zooplankton indices, including the rotifer trophic state index (TSI ROT), was used. The influence of the supplying river resulted in the negligible responses of biological parameters to the restoration efforts in the Upper Arturówek (UA) reservoir, which is the first in cascade of reservoirs. However, clear symptoms of water quality improvements were observed in the other two reservoirs (the Middle Arturówek, MA; the Lower Arturówek, LA) and in the Bzura-17 (B17) pond. After restoration, the contribution of species indicative of high trophic levels decreased in these ecosystems. The TSI ROT was strongly positively correlated with the trophic state index based on chlorophyll a , and both parameters significantly decreased in the MA, LA and B17. In the unrestored pond (B11), the successive increase in the concentrations of chemical parameters indicated progressing eutrophication. Interestingly, since 2013, the TSI ROT values clearly decreased in B11, but the strong negative correlation between ammonium concentration and rotifer density indicated that the reduced TSI ROT values didn't result from improvements in water quality; rather, they resulted from the increases in pollution and the associated harmful impacts on Rotifera. In conclusion, the TSI ROT can be a useful tool for assessing the ecological quality of small urban ecosystems; however, the use of biological indices must be supported by also monitoring physicochemical parameters. Graphical abstract Unlabelled Image Highlights • Zooplankton can be a useful indicator of ecological conditions in restored ecosystems. • Rotifer trophic state index was positively correlated with trophic state index based on chlorophyll a. • The biological indices should be used along with physicochemical monitoring when assessing water quality. • Rotifer trophic state index was not reliable in ponds with high concentrations of ammonium. [ABSTRACT FROM AUTHOR]

Removal of cyprinid fish is a widely used biomanipulation tool to transform turbid shallow eutrophic lakes in north temperate regions into a clear water state. We here evaluate the removal of cyprinids from streams as a supplement to lake fishing. Since cyprinids often aggregate in high densities in lake inlet/outlet streams during winter migration, removal of fish in this space-confined habitat may be cost-efficient as compared to fish removal in the lake habitat. In two consecutive years, we annually removed up to 35% of the dominant cyprinids from an inlet stream to a lake and argue that this could easily be increased with a more targeted fishing effort. Concurrently, we monitored species- and length-specific variation in migration propensity, to explore how this relates to efficient fish removal. Smaller planktivores generally had a much higher migratory propensity than larger benthivores. Hence, stream fishing specifically targets species and size groups that are less efficiently controlled with traditional lake fishing methods. As a rule of thumb, stream fishing is most efficient when water temperature is 2-6°C. Prior to implementing fish removals from streams, the potential evolutionary consequences of the targeted removal of migratory phenotypes should be considered. [ABSTRACT FROM AUTHOR]

We investigated the roles of a benthivorous (Prochilodus brevis, Steindachner 1875) and a planktivorous (Oreochromis niloticus, Linnaeus, 1758) fish in translocating phosphorus from the benthic to the pelagic habitat of a tropical eutrophic shallow lake and its impact on phytoplankton biomass and water transparency. We performed two field experiments in 20 mesocosms (6 m3) with a 2 × 2 factorial design. Fish presence/absence was manipulated in combination with the presence/absence of a fish cage (4 m3) that prevented fish accessing the sediment. Benthivorous fish increased total phosphorus and chlorophyll a concentrations and decreased water transparency, but only when they had access to the sediment. Planktivorous fish increased the concentration of chlorophyll a without changing total phosphorus concentrations, whether or not they had access to the sediment. Results suggest that only the benthivorous fish increased phytoplankton biomass by translocating phosphorus from benthic to pelagic habitats. However, the planktivorous fish increased phytoplankton biomass by removing zooplankton and recycling nutrients within the pelagic zone. We conclude that removal of either fish species can improve the water quality of eutrophic shallow lakes in tropical regions, but only the removal of benthivorous fish will reduce the internal loading of phosphorus. [ABSTRACT FROM AUTHOR]

The knowledge of prey small fish stock, distribution and abundance is necessary to guide stocking of piscivorous fish for the biomanipulation in domestic tap water lakes. This study describes the current status of small fish community in Lake Kuilei (China), and examines the spatial and seasonal variations of the community in relation to key environmental factors. Based on submerged macrophyte cover and water depth, the lake was divided into five major habitats: (1) macrophyte covered shallow habitat of water depth < 2.00 m, (2) uncovered or less-covered shallow habitat (2.00 m–3.50 m), (3) uncovered medium shallow habitat (3.50 m–5.00 m), (4) uncovered medium deep habitat (5.00 m–6.50 m) and (5) uncovered deep habitat (6.50 m–8.50 m). The abundance and composition of small fish were monitored by benthic fykenet sampling from April 2013 to January 2014. A total of 2881 individuals belonging to 5 families and 21 species were collected. Based on their abundance (accounted for 88.96% of the total) and occurrence (more than 33.33%), Acheilognathus chankaensis, Acheilognathus macropterus, Microphysogobio microstomus, Pseudorasbora parva and Rhinogobius giurinus were recognized as dominant small fish species. The results of correlation analysis identified that species richness (Sr), Shannon-Wiener diversity index (H′) and Margalef′s richness index (D) were significantly negatively correlated with water depth, but positively correlated with biomass of submerged macrophytes.Redundancy analysis (RDA) revealed that the spatial distributions of most small fishes were negatively associated with water depth. The details of these findings are beneficial to understanding the adaptation of the small fishes in degraded environments, and to developing suitable biomanipulation strategies for the management of fish resources and water quality in the lakes along the lower reach of the Changjiang (Yangtze) River basin. [ABSTRACT FROM AUTHOR]

Human impacts on freshwater ecosystems are pervasive, but the short and discontinuous nature of most datasets limits our ability to understand the controls on water quality and effectively manage freshwater resources. We examine change in Lake Mendota (Madison, Wisconsin) over the last two centuries by pairing analyses of a sedimentary archive with the site's > 100 yr limnological record. We show that eutrophication of the lake, evident as an abrupt shift in sediment composition, began in the late 19th century following the intensification of urban and agricultural land use in the watershed. Efforts to address deterioration of lake water quality, including the removal of point‐source pollutants and biomanipulation, have had a measurable influence on sediment composition and water clarity. Since the early 1980s, quasi‐seasonal cycles of phytoplankton blooms have induced calcite precipitation, leaving distinct laminations in the sedimentary record. These "whiting events" evidently did not accumulate in lake sediments until the late 20th century, indicating that efforts to remediate water quality have shifted the lake to a new ecosystem state. Calcite whitings can improve water quality in eutrophic lakes by coprecipitation with phosphate, increasing phosphorus (P) burial in lake sediments. Using long‐term limnological records, we report negative correlations between calcite saturation indices and P in lake surface waters and show that calcite whitings could partially explain recent P decline in Lake Mendota surface waters. Our study reveals a previously uncharacterized potential control on water quality in this eutrophic lake and demonstrates the benefit of coupling long‐term limnological data with sedimentary records. [ABSTRACT FROM AUTHOR]

Abstract Fish manipulation has been used to restore lakes in the temperate zone. Often strong short-term cascading effects have been obtained, but the long term-perspectives are less clear. Fish manipulation methods are far less advanced for warm lakes, and it is debatable whether it is, in fact, possible to create a trophic cascade in warm lakes due to the dominance and high densities of fast-reproducing omnivorous fish. However, removal of benthic feeding fish also reduce disturbance of the sediment, which not only affects the nutrient level but also the concentration of suspended organic and inorganic matter with enhanced water clarity and potentially better growth conditions for submerged macrophytes. We conducted a biomanipulation experiment in one of the basins in Chinese Huizhou West Lake that have remained highly turbid after extensive nutrient loading reduction. Another basin was used as control (control-treatment pairing design). Removal of a substantial amount of plankti-benthivorous fish was followed by planting of submerged macrophytes and stocking of piscivorous fish. We found strong and relatively long-lasting effects of the restoration initiative in the form of substantial improvements in water clarity and major reductions in nutrient concentrations, particularly total phosphorus, phytoplankton and turbidity, while only minor effects were detected for crustacean zooplankton grazers occurring in low densities before as well as after the restoration. Our results add importantly to the existing knowledge of restoration of warm lakes and are strongly relevant, not least in Asia where natural lakes frequently are used extensively for fish production, often involving massive stocking of benthivorous fish. With a growing economy and development of more efficient fish production systems, the interest in restoring lakes is increasing world-wide. We found convincing evidence that fish removal and piscivores stocking combined with transplantation of submerged macrophytes may have significant effects on water clarity in warm shallow lakes even if the zooplankton grazing potential remains low, the latter most likely as a result of high predation on the zooplankton. Graphical abstract Image 1 Highlights • Biomanipulation was used to restore a eutrophic shallow lake in tropical China. • Substantial reduction in TP and Chl a concentrations, and turbidity were observed. • Low densities in crustacean zooplankton indicated minor grazing effects on phytoplankton. • The increased bottom-up effect is likely the mechanism for success in restoration in this warm lake. [ABSTRACT FROM AUTHOR]

A field simulation experiment was conducted to test the hypothesis that altering bivalve aquaculture methods could promote the restoration of eutrophic waterbodies. We used three aquaculture methods - benthic aquaculture, suspended aquaculture, and macrophytes/bivalve combined aquaculture - to (1) investigate their effects on seston removal through monitoring water turbidity, pelagic and benthic algae, and (2) compare their impacts on the phosphorus (P) balance at the water-sediment interface by determining different forms of P contents in the water and sediments. The results showed that the seston removal effects did not differ significantly among these three aquaculture methods. Furthermore, the changes of all investigated P parameters in the water and sediments showed that P release occurred in the benthic and suspended aquaculture treatments. The suspended aquaculture strengthened the regeneration of P from sediments into the water compared with the benthic aquaculture. In addition, the results of a principal component and classification analysis showed that macrophytes/bivalve combined aquaculture promoted the maintenance of restoration effects and P balance at the water-sediment interface. In conclusion, benthic aquaculture coupled with replanting submerged macrophytes is a better choice for water managers when using biomanipulation of bivalves to remedy eutrophic waterbodies. [ABSTRACT FROM AUTHOR]

• A calibrated zooplankton groups module was utilized to estimate seasonal dynamics. • Macrophyte reestablishment indicated on improvement of balance in SWE. • Zooplanktivorous fish manipulation had a seasonal heterogenous impact on zooplankton. • Fish-zooplankton-macrophyte-phytoplankton biomanipulation mitigated eutrophication. Eutrophication leads to algae blooms and reduces the transparency of water bodies, which seriously affects water quality and ecosystem equilibrium, especially in shallow water body ecosystems (SWE). Controlling foodwebs by manipulating fish and macrophytes provides a feasible method to mitigate the effects of eutrophication. The response of zooplankton as the primary consumer to biomanipulation is mostly conceptualized and lacks detailed observation. Mesocosm experiments that altered the biomass of planktivorous fish and macrophytes were set up and their boundary conditions were extended into a series of scenarios for modeling biomanipulation. Thus, this study utilizes a one-dimensional lake ecosystem model Water Ecosystems Tool (WET) which considered each zooplankton group: rotifers, cladocerans, and copepods, to predict the seasonal dynamic effects of biomanipulation on zooplankton in SWE, and the model results are analyzed in comparison with the mesocosm results. Observed data from mesocosm experiments set up in a temperate pond, including water temperature, dissolved oxygen (DO), total nitrogen (TN), total phosphorus (TP), chlorophyll a (Chl a), macrophytes, zooplankton, and fish, were used to calibrate and validate the models. The modeled results showed that in spring and summer zooplanktivorous fish removal would increase all three categories of zooplankton and consequently cause a decrease of phytoplankton, whilst an increase in fish biomass would increase phytoplankton, and concomitantly water turbidity. However, in autumn, rotifers and phytoplankton increased in response to fish removal, but cladocerans and copepods decreased, 27% and 41%, respectively. Across all three vegetated seasons, increasing the biomass of macrophytes revealed a similar pattern: all three categories of zooplankton increased and phytoplankton subsequently decreased. Our study proposes a "fish-zooplankton-macrophyte-phytoplankton" trophic cascade and quantitatively predicts the dynamics of each zooplankton group under biomanipulation through this pathway, and provides support for establishing macrophyte beds and removing zooplanktivorous fish (in spring and summer) as an effective approach to mitigate eutrophication. [Display omitted] [ABSTRACT FROM AUTHOR]

The research was carried out on Karczemne Lake, a water reservoir located in Kartuzy (northern Poland, Pomeranian Lake District). Monitoring of the water and bottom sediment of Karczemne Lake showed a very high level of contamination of the reservoir by a long-term inflow of untreated municipal sewage. The trophic status index of total phosphorus (TP) was unusually high at 101, and the TP content in the bottom sediments—31 mg g−1 (dry weight)—was the highest value recorded worldwide in a lake. Based on the monitoring results, to achieve constant improvement of the water quality, we recommend a completely new, safe and economically justified method of bottom sediment removal and management. A very important aspect of this method is the prevention of uncontrolled sewage discharge back into the lake basin. Removed sediment with interstitial water will be pumped through a pipeline and transported to a sewage treatment plant. In the sediment mining field in which the sludge will be removed, the first phase of phosphorus inactivation will be carried out to chemically precipitate pollutants distributed in the water column as a result of sediment resuspension. After the deepening of the entire lake basin, the method of phosphorus inactivation will be carried out on the entire surface of the lake as the next stage of restoration. A supporting activity will be biomanipulation. Before the restoration is started, the municipal sewerage system will be modernized.

Abstract Aim To evaluate the impact of a biomanipulation experiment on the feeding of fish species from a neotropical semiarid reservoir, before and after the removal of the exotic species Oreochromis niloticus. Methods The values of Food Index were analyzed for six species: Oreochromis niloticus , Prochilodus brevis Steindachner,1875, Hypostomus cf. paparie Fowler,1941, Hoplias gr. malabaricus Bloch,1794, Astyanax bimaculatus Linnaeus,1758 and Leporinus piau Fowler,194. All data were obtained in two periods, before of the removal O. niloticus (May 2012 to January 2013) and after its removal (April 2013 to November 2013). The Morisita-Horn index was used to evaluate the feeding similarity among the six species and determine trophic categories (insectivorous, omnivorous, iliophaga and piscivora). To establish the probable variations due the presence of O. niloticus species, the Food Index of the six species was used in a Bray-Curtis similarity matrix. Through the Non-metric Multidimensional Scaling (NMDS) we could not observe any differences among items consumed by different species. The Canonical Correspondence Analysis (CCA) was used to assay the influence of environmental variables on the dietary, from the Food Index data. Results All species were classified in four trophic categories that do not shown any variation among the formed groups during studied periods. After the removal of Nile tilapia some species showed changes in food items, according to NMDS. The CCA indicated low association among the monthly Food Index of species and the environmental changes. Conclusion The process of biomanipulation on the Ecological Station from Serra Negra reservoir, which compares the dietaries from five local species before and after removal of exotic species Oreochromis niloticus, resulted in modification of dietary composition from three of five studied species.

Submerged macrophytes play a key role in north temperate shallow lakes by stabilizing clear-water conditions. Eutrophication has resulted in macrophyte loss and shifts to turbid conditions in many lakes. Considerable efforts have been devoted to shallow lake restoration in many countries, but long-term success depends on a stable recovery of submerged macrophytes. However, recovery patterns vary widely and remain to be fully understood. We hypothesize that reduced external nutrient loading leads to an intermediate recovery state with clear spring and turbid summer conditions similar to the pattern described for eutrophication. In contrast, lake internal restoration measures can result in transient clear-water conditions both in spring and summer and reversals to turbid conditions. Furthermore, we hypothesize that these contrasting restoration measures result in different macrophyte species composition, with added implications for seasonal dynamics due to differences in plant traits. To test these hypotheses, we analyzed data on water quality and submerged macrophytes from 49 north temperate shallow lakes that were in a turbid state and subjected to restoration measures. To study the dynamics of macrophytes during nutrient load reduction, we adapted the ecosystem model PCLake. Our survey and model simulations revealed the existence of an intermediate recovery state upon reduced external nutrient loading, characterized by spring clear-water phases and turbid summers, whereas internal lake restoration measures often resulted in clear-water conditions in spring and summer with returns to turbid conditions after some years. External and internal lake restoration measures resulted in different macrophyte communities. The intermediate recovery state following reduced nutrient loading is characterized by a few macrophyte species (mainly pondweeds) that can resist wave action allowing survival in shallow areas, germinate early in spring, have energy-rich vegetative propagules facilitating rapid initial growth and that can complete their life cycle by early summer. Later in the growing season these plants are, according to our simulations, outcompeted by periphyton, leading to late-summer phytoplankton blooms. Internal lake restoration measures often coincide with a rapid but transient colonization by hornworts, waterweeds or charophytes. Stable clear-water conditions and a diverse macrophyte flora only occurred decades after external nutrient load reduction or when measures were combined.

Biomanipulation of filter-feeding bivalves or fish can serve as complementary measures to zooplankton manipulation approach in lakes dominated by large-sized algae. A laboratory grazing experiment was conducted to compare the selective grazing of benthic bivalves (Hyriopsis cumingii) and planktivorous fish (silver carp) on particle size and algae species. Their combination grazing effects were also detected. The results showed that the clearance rates of silver carp were higher than that of H. cumingii, and that silver carp preferred particles in the 30-50 and 50-100 μm size fraction whereas H. cumingii did not show a significant selective grazing on seston size. Furthermore, the differences between the selective grazing of H. cumingii and silver carp on algae species were detected. Some algae species, which had not been digested well by silver carp, were not detected in H. cumingii’s pseudofeces. Similarly, some algal species in the pseudofeces of bivalves were not detected in the feces of fish. Moreover, the combined clearance rates of H. cumingii and silver carp (ranging from 12.14 to 95.99 mL g DW−1 h−1) were higher than that of single filter feeder (0.47 to 10.18 mL g DW−1 h−1). We suggest therefore that when using biomanipulation measures to control large-sized algal overgrowth, a combination of different filter feeders may be a better way considering their collaborative grazing in both particle size and algae species selectivity. [ABSTRACT FROM AUTHOR]

In many ecosystems, apex consumers (top predators) play a crucial role in food web dynamics. Their top-down impacts are known to spread downwards through the food webs in a cascading fashion. Trophic cascades manifest when top predators are excluded from an ecosystem or introduced into a system lacking them. Two such case studies are described here. Trophic cascades are generally more pronounced in the aquatic than in the terrestrial ecosystems, which in turn is related to the differences in the average body sizes of herbivores relative to the plant resources they feed upon and in the structure of their food webs. Scientists express concern that human activities have been leading to planet-wide trophic downgrading (loss of apex consumers) which could affect vital ecological processes of the biosphere. [ABSTRACT FROM AUTHOR]

The aquatic vegetation in nutrient-rich shallow lakes and ponds is structured by the interplay of multiple biotic and abiotic drivers. We tested the contribution of the macrophyte propagule bank and the delayed as well as direct impact of waterbirds on submerged aquatic vegetation in a peri-urban pond system. To clarify the functional hierarchy of predictor variables, effects of herbivorous waterfowl and propagule bank potential were ranked relative to environmental, phytoplankton, and zooplankton indicators. Two aspects of the aquatic vegetation – community composition and total pond-scale cover – were discriminated. Within vegetation communities, phytoplankton biovolume and waterfowl herbivory during summer were linked to low macrophyte abundance, whereas propagule density of angiosperms was positively associated with specific assemblages of submerged macrophytes. High algal biovolume and summer waterfowl grazing seemed to affect maximal pond-scale cover of submerged aquatic vegetation. The presence of waterfowl in cold and spring periods was unrelated to vegetation structure in the consecutive main growth season. In addition, availability of propagules in the sediment did not automatically prompt pond-wide vegetation cover (especially when overruled by high waterfowl densities), nor did it guarantee a position in the submerged macrophyte community. Nonetheless, propagule bank potential was related to the waterbody's general ecological status, since turbid ponds exhibited impoverished propagule reserves compared to ponds residing in a clear, macrophyte-dominated state. Inadequate recruitment therefore represents a plausible bottleneck for macrophyte establishment. We conclude that phytoplankton-caused turbidity and high waterfowl biomass densities greatly restrict submerged macrophyte abundance. Propagule banks also participate in structuring submerged aquatic vegetation, though a stronger role is reserved for herbivorous waterfowl. [ABSTRACT FROM AUTHOR]

Ecological networks are useful for describing the complex trophic interactions within an ecosystem and hold great potential for ecosystem-based management. However, owing to the complexity and limited knowledge on the trophic interactions of natural food webs, it is challenging to make quantitative predictions about ecological community response to management interventions. Here, we use stable isotope mixing models in conjunction with Bayesian Belief Networks (BBN) to develop and examine the trophic interactions for six empirically determined aquatic food webs in tropical reservoirs. Using BBN, we predicted potential trophic cascade outcomes to predator removals, validated the predictions against data observed from in-situ biomanipulation experiments, and identified influential species using sensitivity analyses. Comparisons among various food web modelling frameworks demonstrated the importance of weighted connectance and network-centric approach for quantitative predictions, suggesting that the Bayesian Belief Network framework can play an important role in ecosystem-based management. [ABSTRACT FROM AUTHOR]

For this study we applied a biological restoration technology combined with introducing filterfeeding bivalves (Hyriopsis cumingii), stocking planktivorous fish (silver carp), and replanting submerged macrophytes (Ceratophyllum demersum L.) in order to treat eutrophic water. The effects of this combined biological restoration measure on remedying eutrophic water were investigated, and the main mechanisms of this combined measure for nutrient transportation and transformation were revealed. The results showed this combined biological restoration measure effectively reduced nutrient nitrogen (N) and phosphorus (P) loads in the water. The assimilation and absorption of submerged macrophytes and the nutrient transformation from water to the sediments were the main mechanisms for water N and P removal. In conclusion, the combination of different biological restoration measures may be a potential choice for water managers in eutrophic water restoration. [ABSTRACT FROM AUTHOR]

Due to sea water eutrophication and global warming, the harmful Phaeocystis blooms outbreak frequently in coastal waters, which cause a serious threat to marine ecosystem. The application of rotifer to control the harmful alga is a promising way. To investigate the influence of initial rotifer density and temperature on the ability of rotifer Brachionus plicatilis to eliminate Phaeocystis globosa population, we cultured P. globosa with different initial rotifer densities (1, 3, 5 inds mL −1 ) at 19, 22, 25, 28, and 31 °C for 9–16 d. Results showed that the population of rotifer feeding on Phaeocystis increased rapidly and higher temperatures favored the growth of P. globosa and B. plicatilis . With increased initial rotifer density and temperature, both the clearance rate of rotifer and the reduction rate of P. globosa increased, and thus P. globosa were eliminated earlier. Both temperature and initial rotifer density had significant effects on clearance rate of rotifer and the time to Phaeocystis extinction, and there was a significant interaction between the two factors on the two parameters, i.e., the effect of initial rotifer density on eliminating Phaeocystis decreased with increasing temperature. The rotifer in 5 inds mL −1 at 28 °C eliminated P. globosa in 4 d, whereas the rotifer in 1 ind mL −1 at 19 °C spent about 16 d on eliminating P. globosa . In conclusion, higher temperature and bigger initial rotifer density promote rotifer to eliminate the harmful P. globosa , and the optimal temperature for rotifer to clear P. globosa is 28 °C. [ABSTRACT FROM AUTHOR]

Sustainable restoration using three methods – water aeration, phosphorus inactivation, and biomanipulation – was applied in Swarzędzkie Lake to slow progressive eutrophication. The treatments were limited to wind aeration alone after three years of restoration as a result of lack of funding. The research was carried out in a period of limited restoration. Phytoplankton was sampled monthly from the surface layer. Samples were preserved with Lugol's solution and counted using a Sedgewick-Rafter chamber with a light microscope. The fluctuation of phytoplankton abundance and biodiversity were determined, comparing data before (2011), during (2012-14), and after the main restoration measures (2015-16). Mean phytoplankton abundance ranged from ca. 31.0×103 spec. ml-1 (2011) by 23.6×103 spec. ml-1 (2012-2014) to 17.5×103 spec. ml-1 (in 2016). Although cyanobacterial bloom occurred in 2013, the average amount of cyanobacteria decreased at least three times during the restoration and one year after the limitation of treatments. The abundance of cyanobacteria again increased sharply in 2016 (ca. 18×103 spec. ml-1). H' index was rising from 1.29 in 2011 to 2.63 in 2015 and started to decrease in 2016. Despite the fact that the total phytoplankton abundance decreased during the restoration processes (2012-16), the abundance of cyanobacteria, which was the main problem of Swarzędzkie Lake, increased when the restoration was limited to wind-aeration (2015-16). An increase of biodiversity and low abundance of cyanobacteria prognosticated the stabilization of the lake's ecosystem. However, a drastic limitation of restoration treatments resulted in another increase of cyanobacteria abundance, which ruined the lake repair. Restoration should not be ceased before the end of the stabilization phase of the ecosystem. [ABSTRACT FROM AUTHOR]

While fish communities have been studied in Czech reservoirs for decades, monitoring has increased since implementation of the EU Water Framework Directive (2000 / 60 / EC). Despite this, many smaller drinking water reservoirs have yet to be surveyed. Between May and July 2016, we undertook a pilot-study examining the fish communities of five Moravian reservoirs (Ludkovice, Bojkovice, Hubenov, Nová Říše and Landštejn). Fish were sampled using boat electrofishing along the littoral zone and Nordic gill nets in the pelagic zone. Both methods were evaluated separately and combined as CPUE and relative abundance and biomass ( %). Nineteen fish species and one hybrid were recorded, with roach Rutilus rutilus dominating overall by abundance, but carp Cyprinus carpio, pike Esox lucius and wels Silurus glanis dominating by biomass in electrofishing samples. Predatory species represented up to 60 % of biomass in the combined sample, with an F / C index ranging from 0.5 - 3, implying a high abundance of predators. Electrofishing tended to underestimate the abundance of bleak and ruffe, while gill nets underestimated the biomass of predatory species. In some reservoirs, the abundance of pike and wels was high (though it is difficult to say if these fish were stocked or the result of natural reproduction). In others (e.g. Landštejn), zander Sander lucioperca were not registered by either sampling method, despite intensive stocking. Overall, gill netting alone appears inadequate for gaining a true picture of the fish community in reservoirs and we suggest a combination of electrofishing and gill netting in future. [ABSTRACT FROM AUTHOR]

Feldberger Haussee (NE Germany) was polluted for almost a century. During the late 1970s, the nutrient input reached a maximum of approximately 1.9/11.5 g TP/TN m −2  yr −1 . As a result, the lake became a hypertrophic ecosystem and had largely lost its recreational value. In 1980, the sewage discharge was stopped, decreasing the external loading by approximately 90%. Because of vast amounts of phosphorus stored in the sediment, the lake remained highly eutrophic until 1985 with a TP concentration of ca. 1 mg L −1 . To accelerate recovery, biomanipulation was applied from 1985 to 2002 but was successful to only a minor extent. Eventually, due to sediment sequestration and discharge to downstream lakes the TP spring maximum (2006–2010) dropped to 0.112–0.078 mg L −1 . However, given the trend, it was obvious that it would take another 10–15 years for the concentration to approach the desired mesotrophic level. Thus, it was suggested to inactivate the surplus phosphorus by treating the lake with poly-aluminium chloride (PAC) as precipitant. To ensure good water quality, the objective was to decrease concentrations below 0.035 mg TP L −1 , while optimising the amount of PAC applied (as much as needed, but as little as possible). As a prerequisite, the status of the lake was carefully studied; external phosphorus loading and the amount of mobile phosphorus stored in the sediment being of specific interest. Laboratory experiments, modelling studies and field observations eventually resulted in an estimated dosage of 27 g Al m −2 (molar Al/P 12). Following the treatment in April 2011, prime water quality parameters showed two opposing trends: (1) TP concentration immediately dropped below the restoration target (≤0.025/0.035 mg L −1 ), primary production and phytoplankton biomass declined substantially. (2) However, water clarity did not improve for another four years. The likely reason for the delay was the structure of the phytoplankton community. It was dominated by cyanobacteria with the potential to trigger intensive calcite precipitation and thus impair transparency. In spring 2015, the cyanobacteria suddenly disappeared and transparency increased significantly. We speculate that these changes of the planktonic community shifted the ratio of assimilation and respiration in favour of the latter. This allowed an increase of free CO 2 * (dissolved CO 2 & dissociated carbonic acid) altering the carbonate buffering system and thus halting the formation of calcite crystals. Also, the phytoplankton, now represented by small readily ingestible taxa, promoted a flourishing Daphnia population inflicting heavy grazing losses, resulting in clear water stages (2015 June, 4.20 m; 2016, August 3.70 m; 2017 August, 4.5 m). We conclude that the drastic decrease of phosphorus availability in concert with structural and functional changes of the plankton community eventually improved the water quality of Haussee significantly. The lake is now in a mesotrophic status; well in accordance with the aim of the restoration project. [ABSTRACT FROM AUTHOR]

Ergasilosis is a common parasitic disease of fish caused by species of the family Ergasilidae. During the fish growing season, parasitic abundance (including developmental stages) changes in relation to zooplankton development. In this study, we evaluated the seasonal dynamics of ergasilosis in relation to zooplankton development at two reservoirs (Hubenov, Koryčany) in the Morava River Basin (Czech Republic). Samples of fish and zooplankton were obtained at monthly intervals between April and October 2014. In total, 189 fish of 11 species were caught using electrofishing and seine nets. Overall, epidemiological characteristics were higher in the Hubenov reservoir, which also hosted higher numbers of pelagic Copepods. Hubenov also supported a higher number of predatory fish species, which presumably helped to reduce the number of zooplanktonophagic cyprinids. Our results suggest that each reservoir represents a unique ecosystem with its own pattern of ergasilosis seasonal development. Differences between reservoirs are closely related to zooplankton development, which is in turn affected by the fish stock in each reservoir. As the nauplius and copepod stages of arthropods form part of the zooplankton assemblage, they will be found at highest numbers in reservoirs where predatory fish suppress zooplanktonophagic fish species. We suggest to analyse zooplankton with the determination of the genus Ergasilus. [ABSTRACT FROM AUTHOR]

Submerged macrophytes play a key role in north temperate shallow lakes by stabilizing clear-water conditions. Eutrophication has resulted in macrophyte loss and shifts to turbid conditions in many lakes. Considerable efforts have been devoted to shallow lake restoration in many countries, but long-term success depends on a stable recovery of submerged macrophytes. However, recovery patterns vary widely and remain to be fully understood. We hypothesize that reduced external nutrient loading leads to an intermediate recovery state with clear spring and turbid summer conditions similar to the pattern described for eutrophication. In contrast, lake internal restoration measures can result in transient clear-water conditions both in spring and summer and reversals to turbid conditions. Furthermore, we hypothesize that these contrasting restoration measures result in different macrophyte species composition, with added implications for seasonal dynamics due to differences in plant traits. To test these hypotheses, we analyzed data on water quality and submerged macrophytes from 49 north temperate shallow lakes that were in a turbid state and subjected to restoration measures. To study the dynamics of macrophytes during nutrient load reduction, we adapted the ecosystem model PCLake. Our survey and model simulations revealed the existence of an intermediate recovery state upon reduced external nutrient loading, characterized by spring clear-water phases and turbid summers, whereas internal lake restoration measures often resulted in clear-water conditions in spring and summer with returns to turbid conditions after some years. External and internal lake restoration measures resulted in different macrophyte communities. The intermediate recovery state following reduced nutrient loading is characterized by a few macrophyte species (mainly pondweeds) that can resist wave action allowing survival in shallow areas, germinate early in spring, have energy-rich vegetative propagules facilitating rapid initial growth and that can complete their life cycle by early summer. Later in the growing season these plants are, according to our simulations, outcompeted by periphyton, leading to late-summer phytoplankton blooms. Internal lake restoration measures often coincide with a rapid but transient colonization by hornworts, waterweeds or charophytes. Stable clear-water conditions and a diverse macrophyte flora only occurred decades after external nutrient load reduction or when measures were combined. [ABSTRACT FROM AUTHOR]

Accelerated eutrophication and requirements of the Water Framework Directive impose searching for effective restoration methods Recently positive effects are achieved by means of sustainable restoration methods that are cheap because they are limited to activities initiating natural changes in the ecosystem. Despite previous research, there is still not enough accurate data on ecosystem response (i.e. changes in the physico-chemical variables and phytoplankton composition in shallow lakes) to the sustainable restoration based on simultaneous application of several methods The restoration of shallow urban hypertrophic Swarzędzkie Lake started in autumn 2011. Three methods: were applied: (i) aeration of waters above the bottom sediments using a wind-driven aerator, (ii) phosphorus inactivation in water column using small doses of iron sulphate and magnesium chloride and (iii) biomanipulation with cyprinids catching and pike fry stocking. The aim of the study was to analyse the phytoplankton succession as well as physico-chemical variables of water quality in a shallow urban lake as a response to restoration measures. Samples were taken monthly from 2012 to 2014 at the deepest place of the lake, every 1m in the depth profile. Due to the restoration process, the Secchi depth increased to 1.00m. The oxygenation improved, as the anaerobic period in the deep water layer shortened to one month. The concentration of nutrients slightly decreased (mainly total nitrogen, from 5.5 to 4.0 mg N l −1 ), especially above the bottom. These changes had an impact on phytoplankton, which decreased twofold. The dominating cyanobacteria was eliminated or reduced and an increase in the number of chlorophytes, chrysophytes and cryptophytes has been observed. Nevertheless, the observed changes were not stable yet, so the restoration process should be continued to achieve permanent improvement. [ABSTRACT FROM AUTHOR]

Rapid recruitment of small fish after biomanipulation in warm lakes may delay the reestablishment of submerged macrophytes, not least at high nutrient concentrations. Success has recently been obtained in controlling phosphorus (P) loading to many lakes, but nitrogen (N) inputs often remain high. To determine the interactive effects of N loading and the abundance of small-sized fish on the growth of the submerged macrophyte Vallisneria natans , we conducted an outdoor mesocosm experiment with a factorial design on the north shore of Lake Taihu, China. The experiment involved two densities of small crucian carp – low (10 g m − 2 ) and high (40 g m − 2 ) – crossed with two levels of N loading – present-day external nutrient loading (P: 5 μg L − 1 day − 1 , N: 130 μg L − 1 day − 1 ) and P: 5 μg L − 1 day − 1 with a three times higher N loading (N: 390 μg L − 1 day − 1 ). The results showed that nitrogen-fish interactions significantly hindered the growth of V. natans , particularly at the high N loading. At low N loading, high densities of fish decreased the relative growth rate, mean leaf length, leaf mass and root mass of V. natans by 16%, 5%, 8%, and 23%, respectively, compared with these measures at low fish densities. The effect of fish was even stronger when N loading was high, with decreases of 232%, 32%, 57%, and 47% for the respective plant growth measures. The stronger effect at high N loading was attributed to higher turbidity due to enhanced phytoplankton biomass and to increased consumption or damage of plants by the fish in response to the more nutrient-enriched plant tissue. Our results indicate that high abundance of small crucian carp in warm lakes may reduce the resilience of submerged macrophytes to external N loading, thereby lowering the chances of successful restoration by biomanipulation. [ABSTRACT FROM AUTHOR]

Since 1967, the temperate, shallow, pond-type Lake Warniak has been subjected to different biomanipulation methods including the introduction of common carp, Cyprinus carpio L., grass carp, Ctenopharyngodon idella (Val.), silver carp, Hypophthalmichthys molitrix (Val.), and bighead carp, Hypophthalmichthys nobilis (Richardson) and then their removal in an effort to control macrophytes and phytoplankton. Recently, pilot stocking with predatory fish, particularly pike, Esox lucius L., has also been conducted. Hence, an examination of the long-term response patterns of phytoplankton to multiple fish-induced stressors was undertaken. In recent years, Chara domination (2000-2004) has helped to stabilize a clear-water state, high/good ecological status, and meso-eutrophic conditions. After the disappearance of Charales in 2004, the rapid, unstable changes in phytoplankton biomass, structure, and biodiversity suggested a shift toward a turbid-water state. As a result, the phytoplankton assemblages changed from those dominated by cryptophytes Y+X2+X1+LO (2000-2004) through those dominated by cyanobacteria K (2005-2008), dinoflagellates LO+Y (2009-2011), and cryptophytes Y+LO+F+X2 (2012), to those dominated by diatoms D+K+P+A (2013-2014) with representative taxa that occur in nutrient-rich and/or nutrient-poor water bodies. The 1967-2014 changes indicated that four periods, two with clear-water state and two with turbid-water state, alternately, one after the other, resulted from different fish pressure. Higher autochthonous fish biomass was usually accompanied by lower phytoplankton biomass. In contrast, the introduction of Cyprinidae fish had a stimulating effect on summer phytoplankton dominated by cyanobateria. Among the nutrients, only phosphorus played an important role. [ABSTRACT FROM AUTHOR]

Biomanipulation, or management actions aimed to structure biological communities to achieve certain goals, has often been used in the restoration of aquatic ecosystems. In 2000, The Nature Conservancy acquired the Emiquon Preserve, which included two former Illinois River floodplain lakes, to restore these ecosystems. Restoration included stocking to establish a native fish community commensurate with historical records. Largemouth bass ( Micropterus salmoides, bass) were also introduced to control poor water clarity and invasive common carp ( Cyprinus carpio, carp). We summarized fish community characteristics and tested whether bass contributed to water clarity maintenance and limited carp during 2007-2014. The fish community was dominated by species stocked in greatest abundance, 13 of 32 species initially stocked have not been collected, and species diversity increased. No carp were observed in bass diets, water clarity declined significantly, and carp relative abundance increased. Increasing water levels during 2008-2009 diffused bass predation potential upon zooplanktivorous fishes and carp and weakened potential trophic cascading interactions. Our findings suggest that water level management, greater stocking of piscivores to maintain predator densities, prevention of gizzard shad ( Dorosoma cepedianum) introduction, and/or a more diverse fish community including other native piscivores may be required to achieve long-term restoration goals. [ABSTRACT FROM AUTHOR]

Reclaimed water is an effective method for addressing water pollution and shortages. However, its use may contribute to the collapse of receiving water (algal blooms and eutrophication) owing to its unique characteristics. A three-year biomanipulation project was conducted in Beijing to investigate the structural changes, stability, and potential risks to aquatic ecosystems associated with the reuse of reclaimed water in rivers. During the biomanipulation, the proportion of Cyanophyta in the community structure of phytoplankton density in river supplied with reclaimed water decreased, and the community composition shifted from Cyanophyta and Chlorophyta to Chlorophyta and Bacillariophyta. The biomanipulation project increased the number of zoobenthos and fish species and significantly increased fish density. Despite the significant difference in aquatic organisms community structure, diversity index and community stability of aquatic organisms remained stable during the biomanipulation. Our study provides a strategy for minimizing the hazards of reclaimed water through biomanipulation by reconstructing the community structure of reclaimed water, thereby making it safe for large-scale reuse in rivers. [Display omitted] • Biomanipulation resulted in lower phytoplankton and cyanobacterial biomass. • Biomanipulation enriched the number of zoobenthos and fish. • Biomanipulation reconstructing aquatic community structure in reclaimed water. [ABSTRACT FROM AUTHOR]