Petr Znachor

Institute of Hydrobiology CAS · Department of Aquatic Microbial Ecology

Freshwater reservoirs are water bodies of special interest, as they provide various ecosystem services such as the supply of drinking water, agricultural irrigation, industrial and cooling water supplies, power generation, flood control and recreation. Reservoirs share many features with natural lakes but differ from them in several important aspec...

Telonemia are one of the oldest identified marine protists that for most part of their history have been recognized as a distinct incertae sedis lineage. Today, their evolutionary proximity to the SAR supergroup (Stramenopiles, Alveolates, and Rhizaria) is firmly established. However, their ecological distribution and importance as a natural predat...

Zooplankton communities are the primary conduit of energy from phytoplankton to planktivorous fish in freshwater ecosystems and play key roles in the functioning of these systems. Therefore, they are often proposed as ecological indicators. However, most zooplankton research focuses on a single waterbody or region, and insights from such studies ma...

Background Protists are essential contributors to eukaryotic diversity and exert profound influence on carbon fluxes and energy transfer in freshwaters. Despite their significance, there is a notable gap in research on protistan dynamics, particularly in the deeper strata of temperate lakes. This study aimed to address this gap by integrating proti...

Photosynthetic cryptophytes are ubiquitous protists that are major participants in the freshwater phytoplankton bloom at the onset of spring. Mortality due to change in environmental conditions and grazing have been recognized as key factors contributing to bloom collapse. In contrast, the role of viral outbreaks as factors terminating phytoplankto...

Background Protists are essential contributors to eukaryotic diversity and exert profound influence on carbon fluxes and energy transfer in freshwaters. Despite their significance, there is a notable gap in research on protistan dynamics, particularly in the deeper strata of temperate lakes. This study aimed to address this gap by integrating proti...

Estimations of methane (CH4) emissions are often based on point measurements using either flux chambers or a transfer coefficient method, which may lead to strong underestimation of the total CH4 fluxes. In order to demonstrate more precise measurements of the CH4 fluxes from an aquaculture pond, using a higher resolution sampling approach we exami...

Body size is a key functional trait that affects many physiological and ecological processes. Among ectotherms, body size patterns are strongly influenced by temperature variation (temperature-size rule). Consequently, climate change is likely to alter body size patterns affecting ecosystem function, particularly in size-structured aquatic communit...

Background Planktonic microbial communities have critical impacts on the pelagic food web and water quality status in freshwater ecosystems, yet no general model of bacterial community assembly linked to higher trophic levels and hydrodynamics has been assessed. In this study, we utilized a 2-year survey of planktonic communities from bacteria to z...

Quillworts (Isoëtes) represent highly specialized flora of softwater lakes, that is, freshwater ecosystems potentially sensitive to acidification. In this paper, we combine a review of previous studies and our new results to address unrecognized reproduction strategies of quillworts to overcome long‐term environmental stresses. These strategies pla...

Background The phytoplankton spring bloom in freshwater habitats is a complex, recurring, and dynamic ecological spectacle that unfolds at multiple biological scales. Although enormous taxonomic shifts in microbial assemblages during and after the bloom have been reported, genomic information on the microbial community of the spring bloom remains s...

Estimations of methane (CH4) emissions are often based on point measurements using either flux chambers or a transfer coefficient method which may lead to strong underestimation of the total CH4 fluxes. In order to demonstrate more precise measurements of the CH4 fluxes from an aquaculture pond, using higher resolution sampling approach we examined...

Zoosporic parasites (i.e. fungi and fungi-like aquatic microorganisms) constitute important drivers of natural populations, causing severe host mortality. Economic impacts of parasitic diseases are notable in the microalgae biotech industry, affecting production of food ingredients, biofuels, pharma- and nutraceuticals. While scientific research on...

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 ³³ P in three deep oligo- to mesotrophic post-mining lakes in April, July, and October 2019. Over the sampling period, epilithon biomass doubl...

Biomonitoring of complex heterogeneous environments is highly challenging. Fish in deep water bodies occupy different habitats, so a combination of survey methods has traditionally been used. Environmental DNA (eDNA) metabarcoding is a novel monitoring tool that can overcome spatial heterogeneity in a highly sensitive and entirely non-invasive mann...

We evaluated long-term trends and seasonal variations in the major physical–chemical properties of the circum-neutral Slapy reservoir (Vltava, Czech Republic) from 1960 to 2019. Mean annual water temperature increased by 2.1 °C, flow maxima shifted by ~ 13 days from the early April to mid-March, and the onset of thermal stratification of water colu...

Small lakes and ponds occupy an enormous surface area of inland freshwater and represent an important terrestrial–water interface. Disturbances caused by extreme weather events can have substantial effects on these ecosystems. Here, we analysed the dynamics of nutrients and the entire plankton community in two flood events and afterwards, when quas...

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 double...

We evaluated long-term trends and seasonal variations in the major physical-chemical properties of the circum-neutral Slapy reservoir (Vltava, Czech Republic) from 1960 to 2019. Mean annual water temperature increased by 2.1 °C, flow maxima shifted by ~13 days from the early April to mid-March, and the onset of thermal stratification of water colum...

Using archived fish scale samples together with long-term monitoring data, this study investigates the potential of fish scales to record historical changes in the aquatic environment. We analysed stable carbon (δ¹³C) and nitrogen (δ¹⁵N) isotopes in the scales of two planktivorous cyprinid species collected from the meso-eutrophic Římov Reservoir,...

Highly abundant, small waterbodies contribute substantially to global freshwater shoreline and surface area. They are strongly interlinked with the terrestrial surrounding, thus controlling the flow of energy, nutrients and organisms through the landscape. Disturbance events can have severe consequences for these ecosystems and the entire downstrea...

Metabolic coupling between phytoplankton and bacteria determines the fate of dissolved organic carbon in aquatic environments, and yet how changes in the rate of primary production affect the bacterial activity and community composition remains understudied. Here, we experimentally limited the rate of primary production either by lowering light int...

The aquatic quillwort Isoëtes lacustris L. survived five decades of severe acidification in Černé Lake (Bohemian Forest, central Europe), but failed to reproduce. To detect which ontogenetic stage is more affected by water acidification and to identify water chemistry thresholds for successful recruitment, experiments were carried out on quillwort...

In this overview (introductory article to a special issue including 14 papers), we consider all main types of natural and artificial inland freshwater habitas (fwh). For each type, we identify the main biodiversity patterns and ecological features, human impacts on the system and environmental issues, and discuss ways to use this information to imp...

The anoxygenic phototrophic bacteria (APB) are an active component of aquatic microbial communities. While DNA-based studies have delivered a detailed picture of APB diversity, they cannot provide any information on the activity of individual species. Therefore, we focused on the expression of a photosynthetic gene by APB communities in two freshwa...

Environmental changes can exert strong pressure on freshwater biota and lead to unwanted alterations of local communities and deterioration of ecosystem services. Disentangling the links between environmental and community changes is, therefore, essential to understand and predict the impact of human activities on freshwater ecosystems. This is par...

In this study, a remote sensing-based method of mapping and predicting fish spatial distribution in inland waters is developed. A combination of Earth Observation data, in-situ measurements, and hydroacoustics is used to relate fish biomass distribution and water-quality parameters along the longitudinal transect of thě Rímov Reservoir (Czech Repub...

• Multiple factors operate simultaneously and interact in complex ways to shape community assembly. Understanding the organisation of communities including species interactions and the importance of driving factors (food, temperature, nutrients, oxygen concentration, etc.) is a central topic in ecology. Intra‐annual variation in zooplankton and the...

Freshwater environments teem with microbes that do not have counterparts in culture collections or genetic data available in genomic repositories. Currently, our apprehension of evolutionary ecology of freshwater bacteria is hampered by the difficulty to establish organism models for the most representative clades. To circumvent the bottlenecks inh...

Freshwater environments teem with microbes. Currently, our apprehension of evolutionary ecology of freshwater bacteria is hampered by the difficulty to establish organism models for the most representative clades. To circumvent the bottlenecks inherent to the cultivation-based techniques, we applied ecogenomics approaches in order to unravel the ev...

Man-made reservoirs are common across the world and provide a wide range of ecological services. Environmental conditions in riverine reservoirs are affected by the changing climate, catchment-wide processes and manipulations with the water level, and water abstraction from the reservoir. Long-term trends of environmental conditions in reservoirs t...

We studied the diversity of Limnohabitans using Reverse Line Blot Hybridization with Limnohabitans lineage-specific probes in the freshwater canyon-shaped Římov Reservoir (CZ). To examine the succession of distinct lineages we performed two studies: (i) an intensive spring sampling program at the lacustrine part of the Římov Reservoir (from ice mel...

p>The zooplankton community in a relatively small and mountain pond was studied during the spring growing season. To investigate which factors operate in the community structure, we explored several physical conditions, such as high inflows, and the biotic dynamics of the main zooplankton groups (i.e., rotifers, cladocerans and copepods). Two extre...

The ecological relevance and factors shaping dynamics of Limnohabitans sp. have been largely studied by fluorescence in situ hybridisation (CARD-FISH) with a 16S rRNA probe targeting the R-BT group (lineages LimBCDE), but not lineage LimA. Consequently, ecology and distribution of LimA remained unknown. We developed a double hybridisation strategy...

Ecological quality assessment of non-natural water bodies is, in contrast to natural systems, less developed and requires determining biological indicators that reliably reflect environmental conditions and anthropogenic pressures. This study was motivated to propose fish indicators appropriate for assessment of reservoir ecosystems in central Euro...

Algal population size may vary substantially over the season in response to varying growth and loss rates strongly affected by environmental drivers. In our study, we measured growth and viability of Fragilaria crotonensis, a dominant diatom of the summer phytoplankton in the small, meso-eutrophic, dimictic freshwater Rimov Reservoir (Czech Republi...

Despite the global importance of phytoplankton primary production, the ecological role of cell death as an important loss process in phytoplankton is poorly understood. To assess the significance of cell death in phytoplankton, we studied cell viability of dominant species in the canyon-shaped eutrophic Římov Reservoir (Czech Republic) at weekly an...

We employed high frequency sampling to determine the major factors modulating microbial food web composition and dynamics through the spring phytoplankton bloom and clear water phases in a freshwater reservoir. We examined effects of a changing trophic structure of the planktonic community cascading from the level of zooplankton, through phytoplank...

Isoëtes lacustris (quillwort) is an aquatic macrophyte commonly dominating oligotrophic softwater lakes in Europe. Reproductive ecology of a relic population of quillwort based on spore germination was studied in an acidified mountain lake in the Czech Republic. In a four-year experiment, we recorded temperature-related temporal changes in micro- a...

The impact of fish and cyclopoid copepod predation on zooplankton communities was evaluated using large-volume mesocosms (depth 9.5 m; volume 13 m3) in the Rˇ ı´mov reservoir (Czech Republic). Two yearling roach and perch individuals introduced into mesocosms represented the fish treatment, which was compared to cyclopoid copepods (initial abundanc...

Diatoms are one of the most important phytoplankton groups. As they grow, diatoms use silicon to produce a siliceous frustule, which protects the cell. During A pril– N ovember 2011, at 1–3 week intervals, we estimated diatom silicification rates at two distinct sites along the longitudinal profile of the canyon‐shaped eutrophic Římov Reservoir (Cz...

Mesocosms represent a helpful tool enabling in situ experiments within the pelagic zone of lakes and reservoirs. Experimental studies using mesocosms are widely used in shallow lakes. Here, we describe an improved method suitable for deep freshwater ecosystems. We use a metal supporting framework carrying four polyethylene bags (circular cross-sect...

Biological response of aquatic macrophytes to changes in water chemistry and temperature has been studied on a background of the long-term research of Bohemian Forest lakes recovery from acid stress. Isoëtes lacustris and I. echinospora are common aquatic macrophytes adapted for living in soft-water lakes widely distributed in European lake distric...

The recognition and discrimination of phytoplankton species is one of the foundations of freshwater biodiversity research and environmental monitoring. This step is frequently a bottleneck in the analytical chain from sampling to data analysis and subsequent environmental status evaluation. Here we present phytoplankton diversity data from 49 lakes...

Metadata of 259 lakes available to this study including 139 samples used in the analyses of this study. (XLS)

List of taxa found from Lakes Alinen Mustajärvi (AM), Erken (ER) and Římov (RI) when analyzing phytoplankton samples by microscopy. (DOC)