In freshwater ecosystems, snails can significantly influence the competition between primary producers through grazing of periphyton. This activity can potentially be modified by trematodes, a large group of parasites which mostly use molluscs as the first intermediate host. Available studies, however, show contradictory effects of trematodes on snail periphyton grazing. Here, we used four different freshwater snail-trematode systems to test whether a general pattern can be detected for the impact of trematode infections on snail periphyton grazing. In our experimental systems, mass-specific periphyton grazing rates of infected snails were higher, lower, or similar to rates of non-infected conspecifics, suggesting that no general pattern exists. The variation across studied snail-trematode systems may result from differences on how the parasite uses the resources of the snail and thus affects their energy budget. Trematode infections can significantly alter the grazing rate of snails, where, depending on the system, the mass-specific grazing rate can double or halve. This underlines both, the high ecological relevance of trematodes and the need for comprehensive studies at the species level to allow an integration of these parasite-host interactions into aquatic food web concepts.

• Klíčová slova
• Freshwater snails, Grazing rates, Host–parasite interaction, Periphyton, Trematodes,
• MeSH
• ekologie MeSH
• ekosystém MeSH
• hlemýždi parazitologie   MeSH
• infekce červy třídy Trematoda parazitologie   MeSH
• interakce hostitele a parazita fyziologie   MeSH
• perifyton * MeSH
• potravní řetězec MeSH
• přijímání potravy fyziologie   MeSH
• sladká voda parazitologie   MeSH
• Trematoda izolace a purifikace   MeSH
• zvířata MeSH
• Check Tag
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH

Polarization microscopy, possibly together with some contrast techniques (dark field and color phase contrast), was used to study the periphyton (microbiome) growing on filamentous green algae. The material containing filamentous algae with periphyton on the surface was collected in the villages of Sýkořice and Zbečno (Křivoklátsko Protected Landscape Area). The objects were studied in a LOMO MIN-8 St. Petersburg polarizing microscope and a Carl Zeiss Jena NfpK laboratory microscope equipped with an In Ph 160 basic body with variable dark field or color phase contrast and a Nikon D70 DSLR digital camera. Cells of filamentous algae of the genera Cladophora, Vaucheria, and Oedogonium were studied and the periphyton attached to them formed by cyanobacteria of the genera Chamaesiphon and Pleurocapsa and algae of the genera Characium, including diatoms of the genera Eunotia and Synedra. In all cases, the cell walls of the host algae showed a very strong birefringence. In contrast, the walls of cyanobacteria of the genera Chamaesiphon and Pleurocapsa were characterized by a much weaker birefringence (Pleurocapsa somewhat thicker), and the diatom frustules of the genera Eunotia and Synedra were almost without a birefringence. Strongly birefringent granules were found in the cytoplasm of the green alga of the genus Characium, which forms periphyton on the filamentous green algae of the genus Vaucheria. The periphyton on the filamentous alga of the genus Oedogonium, formed by cyanobacteria of the genus Pleurocapsa and diatoms of the genera Eunotia and Synedra, deposited in a massive layer of mucus containing birefringent crystals, showed a particularly strong birefringence. At the end of the vegetation of filamentous algae, their parts and remnants of periphyton (diatom frustules and crystals) became part of the detritus at the bottom of the culture vessel. The use of polarization microscopy in the study of filamentous algae with periphyton on the surface allows us not only to determine the birefringence of the observed structures, but also to partially deduce their chemical composition, or regular arrangement of particles, so-called shape birefringence.

• Klíčová slova
• Algae, Color phase contrast, Cyanobacteria, Dark field technique, Development, Microbiome, Periphyton, Polarization microscopy,
• MeSH
• Chlorophyta * chemie   MeSH
• cytoplazma MeSH
• perifyton * MeSH
• polarizační mikroskopie MeSH
• rozsivky * chemie   MeSH
• sinice * metabolismus   MeSH
• Publikační typ
• časopisecké články MeSH

The utilization of food resources by aquatic consumers reflects the structure and functioning of river food webs. In lotic water systems, where food availability and predator-prey relationships vary with gradient changes in physical conditions, understanding diet assimilation by local communities is important for ecosystem conservation. In the subtropical Liuxi River, southern China, the relative contribution of basal resources to the diet assimilation of functional feeding groups (FFGs) was determined by stable carbon (13C) and nitrogen (15N) isotope analyses. The output of Bayesian mixing models showed that diatom-dominated periphyton (epilithic biofilm), aquatic C3 plants (submerged hydrophytes), and suspended particulate organic matter (SPOM) associated with terrestrial C3 plants contributed the most to the diet assimilation of FFGs in the upper, middle, and lower reaches, respectively. The relative contribution of consumer diet assimilation was weighted by the biomass (wet weight, g/m2) of each FFG to reflect resource utilization at the assemblage level. From the upper to the lower reaches, the spatial variation in the diet assimilation of fish and invertebrate assemblages could be summarized as a longitudinal decrease in periphyton (from 57%-76% to <3%) and an increase in SPOM (from <7% to 51%-68%) with a notable midstream increase in aquatic C3 plants (23%-48%). These results indicate that instream consumers in the Liuxi River rely more on autochthonous production (e.g., periphyton and submerged hydrophytes) than on terrestrially derived allochthonous matter (e.g., terrestrial plants). The pattern of resource utilization by consumers in the mid-upper Liuxi River is consistent with findings from other open subtropical and neotropical rivers and provides evidence for the riverine productivity model. Our study indicates that protecting inherent producers in rivers (e.g., periphyton and submerged hydrophytes) and restoring their associated habitats (e.g., riffles with cobble substrate) are conducive to aquatic ecosystem management.

• Klíčová slova
• MixSIAR, carbon source, diet assimilation, food web, periphyton, submerged hydrophyte,
• Publikační typ
• časopisecké články MeSH

Stable isotopes are increasingly used to detect and understand the impacts of environmental changes on riverine ecological properties. The δ13C and δ15N signatures of fish with different feeding habits were measured in a large subtropical river to evaluate how fish isotopic niches respond to environmental gradients and human disturbance. From basal resources to fish consumers, the high values of epilithic periphyton (biofilm) δ13C and suspended particulate organic matter δ15N concurrently determined the niche ranges and space (e.g., convex hull area) of fish communities. Along a longitudinal gradient (except in the industrial zone), the number of fish trophic guilds identified by Bayesian ellipses continuously increased; meanwhile, higher trophic diversity and less redundancy were observed near the lower reaches and estuary. Variance inflation factors were estimated to detect the multicollinearity of 40 environmental variables, 14 of which were selected as indicators. Relative importance (RI) analysis was used to evaluate the explanatory power of these indicators for the spatial variation in isotopic niche metrics; the results showed that riffle habitat area, water nitrate concentration, gravel-cobble substrate, and riparian buffer width were the 4 key environmental indicators (average RI > 12%) that determined the longitudinal pattern of fish isotopic niches. These findings suggested that community-level δ13C signatures are more responsive to changes in habitats (e.g., riffle) and substrates (e.g., gravel-cobble) supporting the productivity of autochthonous diatoms while δ15N signatures respond to water quality altered by nitrogen pollution from manure-fertilized farming and poultry livestock effluent. Furthermore, δ15N may be more robust and interpretable than δ13C as an isotopic indicator of ecosystem change in rivers exposed to multiple or complex anthropogenic stressors.

• Klíčová slova
• Epilithic periphyton, Layman metrics, MixSIAR, Nitrogen pollution, SIBER, Trophic guilds,
• MeSH
• Bayesova věta MeSH
• ekosystém * MeSH
• environmentální indikátory MeSH
• izotopy dusíku analýza   MeSH
• izotopy uhlíku analýza   MeSH
• lidé MeSH
• monitorování životního prostředí MeSH
• řeky * MeSH
• zvířata MeSH
• Check Tag
• lidé MeSH
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• Geografické názvy
• Čína MeSH
• Názvy látek
• izotopy dusíku MeSH
• izotopy uhlíku MeSH

Epilithon contributes to phosphorus (P) cycling in lakes, but its P uptake traits have been rarely studied. We measured the chemical composition of epilithon and its inorganic P uptake kinetics using isotope 33P in three deep oligo- to mesotrophic post-mining lakes in April, July, and October 2019. Over the sampling period, epilithon biomass doubled, while the P content in biomass dropped to 60% of the April values, and the seasonal changes in P content expressed per epilithon area were only marginal and statistically not significant. High epilithic C:P molar ratios (677 on average) suggested strong P deficiency in all investigated lakes. Regarding the kinetic parameters of phosphorus uptake, maximum uptake velocity (V max , seasonal range 1.9-129 mg P g OM-1 h-1) decreased by an order of magnitude from April to October, while half-saturation constant (K S , seasonal range 3.9-135 mg P L-1) did not show any consistent temporal trend. Values of epilithic specific P uptake affinity (SPUA E , seasonal range 0.08-3.1 L g OM-1 h-1) decreased from spring to autumn and were two to four orders of magnitude lower than the corresponding values for seston (SPUA sest ), which showed an opposite trend. Considering our results, we suggest a possible mechanism underlying a stable coexistence of planktonic and epilithic microorganisms, with plankton prospering mostly in summer and autumn and epilithon in winter and spring season. Additionally, a phenomenon of reversible abiotic P adsorption on epilithon was observed.

• Klíčová slova
• epilithon, hydric recultivation, oligotrophic lakes, periphyton, phosphorus uptake, specific P affinity,
• Publikační typ
• časopisecké články MeSH

BACKGROUND AND AIMS: Rootless carnivorous plants of the genus Utricularia are important components of many standing waters worldwide, as well as suitable model organisms for studying plant-microbe interactions. In this study, an investigation was made of the importance of microbial dinitrogen (N2) fixation in the N acquisition of four aquatic Utricularia species and another aquatic carnivorous plant, Aldrovanda vesiculosa. METHODS: 16S rRNA amplicon sequencing was used to assess the presence of micro-organisms with known ability to fix N2. Next-generation sequencing provided information on the expression of N2 fixation-associated genes. N2 fixation rates were measured following (15)N2-labelling and were used to calculate the plant assimilation rate of microbially fixed N2. KEY RESULTS: Utricularia traps were confirmed as primary sites of N2 fixation, with up to 16 % of the plant-associated microbial community consisting of bacteria capable of fixing N2. Of these, rhizobia were the most abundant group. Nitrogen fixation rates increased with increasing shoot age, but never exceeded 1·3 μmol N g(-1) d. mass d(-1). Plant assimilation rates of fixed N2 were detectable and significant, but this fraction formed less than 1 % of daily plant N gain. Although trap fluid provides conditions favourable for microbial N2 fixation, levels of nif gene transcription comprised <0·01 % of the total prokaryotic transcripts. CONCLUSIONS: It is hypothesized that the reason for limited N2 fixation in aquatic Utricularia, despite the large potential capacity, is the high concentration of NH4-N (2·0-4·3 mg L(-1)) in the trap fluid. Resulting from fast turnover of organic detritus, it probably inhibits N2 fixation in most of the microorganisms present. Nitrogen fixation is not expected to contribute significantly to N nutrition of aquatic carnivorous plants under their typical growth conditions; however, on an annual basis the plant-microbe system can supply nitrogen in the order of hundreds of mg m(-2) into the nutrient-limited littoral zone, where it may thus represent an important N source.

• Klíčová slova
• 15N2 labelling, Aldrovanda vesiculosa, N nutrition, U. australis, U. intermedia, U. reflexa, Utricularia vulgaris, aquatic carnivorous plants, daily nitrogen gain, nitrogen fixation, periphyton, traps,
• MeSH
• amoniové sloučeniny analýza   MeSH
• Bacteria genetika   izolace a purifikace   metabolismus   MeSH
• bakteriální RNA chemie   genetika   MeSH
• Droseraceae metabolismus   mikrobiologie   MeSH
• dusík metabolismus   MeSH
• ekologie MeSH
• ekosystém MeSH
• fixace dusíku * MeSH
• izotopy dusíku MeSH
• Magnoliopsida metabolismus   mikrobiologie   MeSH
• molekulární sekvence - údaje MeSH
• RNA ribozomální 16S chemie   genetika   MeSH
• sekvence nukleotidů MeSH
• sekvenční analýza RNA MeSH
• voda metabolismus   MeSH
• výhonky rostlin metabolismus   MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• srovnávací studie MeSH
• Názvy látek
• amoniové sloučeniny MeSH
• bakteriální RNA MeSH
• dusík MeSH
• izotopy dusíku MeSH
• RNA ribozomální 16S MeSH
• voda MeSH

Parallel adaptive radiations have arisen following the colonization of islands by lizards and lakes by fishes. In these classic examples, parallel adaptive radiation is a response to the ecological opportunities afforded by the colonization of novel ecosystems and similar adaptive landscapes that favour the evolution of similar suites of ecomorphs, despite independent evolutionary histories. Here, we demonstrate that parallel adaptive radiations of cichlid fishes arose in South American rivers. Speciation-assembled communities of pike cichlids (Crenicichla) have independently diversified into similar suites of novel ecomorphs in the Uruguay and Paraná Rivers, including crevice feeders, periphyton grazers and molluscivores. There were bursts in phenotypic evolution associated with the colonization of each river and the subsequent expansion of morphospace following the evolution of the ecomorphs. These riverine clades demonstrate that characteristics emblematic of textbook parallel adaptive radiations of island- and lake-dwelling assemblages are feasible evolutionary outcomes even in labile ecosystems such as rivers.

• Klíčová slova
• Crenicichla, cichlid, convergence, diversification, parallel evolution, species flock,
• MeSH
• biologická adaptace genetika   MeSH
• biologická evoluce * MeSH
• cichlidy anatomie a histologie   genetika   MeSH
• ekosystém MeSH
• fenotyp MeSH
• fylogeneze MeSH
• jednonukleotidový polymorfismus genetika   MeSH
• jezera MeSH
• ostrovy MeSH
• řeky * MeSH
• sekvenování celého genomu MeSH
• zvířata MeSH
• Check Tag
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Research Support, U.S. Gov't, Non-P.H.S. MeSH
• Geografické názvy
• ostrovy MeSH
• Uruguay MeSH

During the period 1996-1997, three constructed wetlands with sub-surface horizontal flow were investigated. All systems are designed to treat municipal sewage from small villages (150, 200 and 300 PE). The survey included microscopical identification of organisms in both wastewater and filtration substrate. The organisms were used as an indication of oxygen conditions (aerobic, anoxic and anaerobic) in the particular microenvironment. Saprobiological terms characterizing different levels of saprobity were employed to characterize inflowing wastewater, filtration bed and outflowing water. The occurrence of organisms was correlated with BOD5 values in particular profiles. It has been found that the biocenosis in the inflowing wastewater differs from those found in the filtration bed and water outflowing from the vegetated beds. The organisms were grouped into those living under anaerobic and anoxic conditions and those living under aerobic conditions. More than 70 species of bacteria, amoebae, ciliates, rotifers, colorless flagellates, cyanobacteria and algae were found and the most important 45 species were figured in a plate together with saprobiological information for each species. Biota of the inflowing water is usually restricted to bacteria, ciliata and colorless flagellata while the organisms found in outflowing water as well as in periphyton growing on outflow structures indicate 2-3 levels better quality.

• MeSH
• Bacteria MeSH
• ekosystém * MeSH
• Eukaryota MeSH
• filtrace MeSH
• kyslík metabolismus   MeSH
• mikrobiologie vody MeSH
• monitorování životního prostředí * MeSH
• odpad tekutý - odstraňování metody   MeSH
• odpadní vody * MeSH
• pohyb vody MeSH
• populační dynamika MeSH
• půdní mikrobiologie MeSH
• vířníci MeSH
• zvířata MeSH
• Check Tag
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• Názvy látek
• kyslík MeSH
• odpadní vody * MeSH

Simultaneous application of polarization microscopy and dark field techniques has been used to study the internal structure of microbial cells. The dark field technique displays subtle cell structures like glowing objects on a dark background. In the polarizing microscope, cross polarizing filters along with the first-order quartz compensator and a rotary table show the maximum birefringence of the individual structures. The material containing microorganisms was collected in the villages of Sýkořice and Zbečno (Křivoklátsko Protected Landscape Area). The objects were studied in a laboratory microscope Carl Zeiss Jena type NfpK equipped with In Ph 160 basic body with variable dark field, special condenser with interchangeable diaphragm apertures, a rotary table, Meopta Praha polarizer, analyzer, first-order quartz compensator from LOMO Sankt Petersburg, and a digital Nikon D 70 DSLR camera. Three orders of microorganisms were studied: Siphonocladales, Chlorococcales, and Peritricha. Anisotropic structures in different amounts and sizes (e.g., granules and microfibrils) or in different configurations (e.g., cell walls or pellicle) have been found in all Protista organisms under study. Filamentous algae of the genus Cladophora (Cladophoraceae, Siphonocladales, Ulvophyceae) featured a strongly birefringent cell wall (shape birefringence) surrounded by less birefringent periphyton (microbial biofilm), at the edges of which cyanobacterial fibers could be recognized-a very important finding. The coccal algae of the genus Scenedesmus (Scenedesmataceae, Chlorococcales, Chlorophyceae) exhibited not only strongly birefringent granules, but also strongly birefringent microfibrils in the cytoplasm outside the strongly birefringent cell walls-very important finding. Of all the studied microorganisms, the weakest birefringence was shown in the surface membrane (pellicle) of the Vorticella (Vorticellidae, Peritricha, Ciliata). On the other hand, the ring of cilia on the top of the body had a somewhat stronger birefringence-an important finding. In conclusion, the dark field technique provides a high contrast image in the microscope and, if supplemented simultaneously by polarization microscopy, will allow us to partially infer the composition of the examined structures.

• MeSH
• anizotropie MeSH
• Chlorophyta * MeSH
• cytoplazma MeSH
• dvojitý lom MeSH
• polarizační mikroskopie MeSH
• Publikační typ
• časopisecké články MeSH

Tropical and subtropical rivers are being subjected to multiple stressors from human disturbance (e.g., water pollution and habitat degradation). Understanding the relationship between environmental conditions and the river ecosystem is important for improving river management. We built 14 Ecopath models composed of 28 functional groups (trophic levels [TLs] of 1.0-3.8) along a subtropical urban river to explore the influence of environmental changes on system attributes. From headwaters to downstream, the model outputs showed that the transfer efficiency (TE), energy flow parameters, and ecosystem theory indices exhibited significant (P < 0.05) differences across a longitudinal gradient of disturbance, indicating heterogeneous attributes of local river segments. The high TE values of TLs I, II, and III separated the upper, middle, and lower reaches, respectively, which could be attributed to the shift in dominant consumption flows from upstream 'periphyton - aquatic insects - insectivorous fish' to midstream 'detritus - shrimp - crustaceavorous fish' and to downstream 'phytoplankton - filter-feeding invertebrates/fish'. Structural equation modelling was used to test the causal relationships among environmental variables and demonstrated that abiotic factors directly influenced biomass composition and indirectly influenced trophic networks. Water quality, including dissolved oxygen and flow velocity; habitat characteristics, such as riffles, cobble-gravel substrate, and seasonal floodplain; and biological indicators, including the relative contributions (%) of decapods, insectivorous fish, and insect scrapers to biomass composition, had significant (P < 0.05) positive impacts on system maturity (evaluated by omnivory, connectance, and cycling indices). In the future, it will be possible to evaluate the health of river ecosystems by monitoring representative environmental factors, which could be a cost-effective approach to system-level improvement.

• Klíčová slova
• Biological indicators, Ecopath, Ecotrophic efficiency, Habitat characteristics, Longgang River, River management, Transfer efficiency,
• MeSH
• bezobratlí MeSH
• ekosystém * MeSH
• lidé MeSH
• potravní řetězec * MeSH
• řeky MeSH
• zvířata MeSH
• Check Tag
• lidé MeSH
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• Geografické názvy
• Čína MeSH