Department of Hydrochemistry and Ecosystem Modelling (HEM)

The Department of Hydrochemistry and Ecosystem Modelling (HEM) of the Institute of Hydrobiology of the Biology Centre CAS studies biogeochemical cycles and processes that control composition and quality of surface waters. This interdisciplinary research is focused on the structure, functions, problems and management of aquatic environments like reservoirs, natural lakes and their catchments.

The staff also provide lecturing of aquatic and environment sciences at the University of South Bohemia and are engaged in advisory services on water quality and aquatic ecosystem functioning for water policy and water management.

The main subjects of studies include:

  • recovery of mountain lakes and their catchments after atmospheric acidification;
  • eutrophication of water ecosystems as a result of external and internal nutrient loading;
  • reconstruction and modelling of historical trends in biogeochemical cycling of the macronutrients in aquatic ecosystems;
  • photochemical processes involved in the transport of macro- and micronutrients via dissolved organic matter from soils to aquatic systems;
  • the role of sediments and organic matter in the internal cycling of nutrients in lakes;
  • the environmental characteristics which can best explain the patterns of nutrient flux to waters in complex catchments.

Current research projects

Drinking WAter Readiness for the Future

Project No.: TO01000202

Principal Investigator: doc. Ing. Petr Porcal, Ph.D.

Financial support: TAČR and Norway Grants

Duration: 2021 - 2024

Increasing levels of Dissolved Organic Matter (DOM) is a large challenge for Drinking Water Treatment Plants. Surface water is the source for more than 50% of drinking water in the Czech Republic. In the region of South Bohemia surface water supports drinking water for more than 350 thousand people from the reservoirs (Římov, Husinec, Jordán) and Otava River. Catchments of these sources will be characterized with respect to the sources of DOM and their temporal and spatial variability resulting in a map of DOM sources with future predictions. A methodology for outflow control in reservoirs to minimize the effect of flood events with high DOM levels will be developed. A cooperation among basin authorities, drinking water producers and Czech and Norway research partners will be established.

Life at the Edge: The Limits of Occurrence of Insect Larvae

Project No.: 20-00892L

Principal Investigator: Evžen Stuchlík

Financial support: Czech Science Foundation

Duration: 2020 - 2022

Survival of animals under extreme environmental conditions has always been intriguing to ecologists and physiologists. Examples for an extreme environment are brooks in mountainous areas with different degrees of harshness. Despite the harsh conditions, these rivers are densely populated by chironomids (Diptera: Chironomidae) who are even found close to the mouth of glaciers. We hypothesize that i) different pathways of metabolism are differently affected by very low temperature, ii) carbohydrate metabolism may be more flexible than e.g. lipid metabolism, and iii) these differences are based on subspeciation and not a pure metabolic phenomenon. The study sites for this project are high alpine streams with a harshness gradient located in the Alps and the Tatra Mts. We assume that the harshness gradient must be strong enough to limit the occurrence of chironomid larvae and energy stores of an animal are a good proxy for its health. To study thresholds for survival of the high alpine stream chironomids in the past, lake sediments cores from 3 sites in the Bohemian Forest will be used.

The aim of the project is the characterization of the harshness gradients; quantification of energy stores in individuals from different sites; tracing of selected genes from endocrine to metabolic regulation; characterization of genetic homogeneity; paleolimnological evidence of past populations' response to the deglaciation.

Palaeoecological reconstruction of global environmental changes at the Younger Dryas onset

Principal Investigator: Evžen Stuchlík

Financial support: Ministry of Education, Youth and Sport of the Czech Republic

Duration: 2019 - 2022

Scientific goals of the project:
1. To test the hypothesis that the Laacher See volcanic explosion (12900 calibrated years BP) changed freshwater communities in the Bohemian Forest lakes.
2. To test the hypothesis that the Younger Dryas Boundary (YDB) layer (well-known from many North American sedimentary sequences) is also present in sediments of the Bohemian Forest lakes. If yes, this layer has characteristic geochemical and geophysical signal, contains impact-related micro-spherules (MSPs), and could be used as an important tool for regional chronostratigraphy.
3. To test the hypothesis that YDB is present in selected Alaska lakes. If yes, YDB will be compared with YDB found at the Czech sites.
4. To test the hypothesis that the Younger Dryas (YD) onset was characterized by changes in environmental chemistry, a decrease in biota abundances and biodiversity, or a shift in composition of ecological groups in the studied palaeoecosystems. If yes, which factors were responsible for the ecosystem damage and transformation? Was the YD onset more pronounced in Alaska lakes or in the Czech lakes?
5. To determine the timing of the presumed sudden environmental changes at the YD onset in both regions (central Europe and Alaska) and compare the results with the geochemical data from the Greenland ice (especially with the North Greenland Ice Core Project record).

Paleo-records of global range events from lake sedimentary sequence

Project No.: 20-08294S

Principal Investigator: Evžen Stuchlík

Financial support: Czech Science Foundation

Duration: 2020 - 2022

A multiple evidence from increasing number of sites shows that a major cosmic impact occurred at the end of the Pleistocene. The so-called Younger Dryas Boundary layer (YDB) supports the hypothesis that a fragmented cosmic body slammed into the Earth ~12,800 cal. BP at the time of the Younger Dryas cooling onset. This layer contains a characteristic assemblage of impactrelated particles and elemental composition. Simultaneously, megafaunal extinctions, changes in vegetation cover, human population cultural shifts, and widespread wildfires were documented. In Europe, YBD records are still rare and most of them are known from paleosoils. We have focused on lake sediment sequences and identified the presence of YDB markers in Bohemian Forest lakes, Czech Republic. Our first results suggest environmental contamination of the region by long-range atmospheric transport of pollutants. In the proposed project, we will study history of three selected lake-catchment ecosystems with focus on the YDB transition and identification of Late Glacial and Early Holocene tephra layers.

The aims of the project are: 1) Testing of uniqueness of the YBD proxies within the postglacial sedimentary records. 2) Identification of volcanic ash (tephra) layers in lake sediments of Late Glacial and Early Holocene age. 3) Reconstruction of ecosytems' reaction on the YDB environmental contamination.

Phosphorus leaching from undeveloped alpine soils: Biotic or abiotic control?

Project No.: 20-19284S

Principal Investigator: Jiří Kaňa

Financial support: Czech Science Foundation

Duration: 2020 - 2022

We will identify major environmental factors controlling P leaching from undeveloped soils in natural, unmanaged areas. We will evaluate effects of soil recovery from acidification, increasing dust deposition, and climate-accelerated physical erosion of rocks on chemistry and ability of soils to retain/release P. The most pronounced increases in lake water P concentrations (besides USA) have occurred in the Tatra Mountains, mainly in catchments with high proportion of scree and undeveloped till soils. Using local rocks, we will experimentally assess effects of climate change on their physical erosion. Then, we will evaluate effect of increased rock weathering on soil chemistry and P retaining ability. Special attention will be paid to composition of microbial community of till soils, and activity and role of its major components in P mobilization from rock and dust. Using long-term trends in chemistry and biology of lakes, we will evaluate individual and synergetic effects of recovery from acidification and climate change on the ongoing changes in their nutrient status and trophy.

The aims of the project ate to evaluate effects of (1) chemistry and microbial community of till and alpine meadow soils on P cycling, and (2) climate changes (increasing physical erosion and dust deposition) and recovery from acidification on increasing P leaching from soils and the related eutrophication of receiving waters.

Quantifying water and phosphorus fluxes in disturbed vs. intact mountain forest catchments by hydrological, isotopic and hydrochemical methods

Project No.: 19-22276Y

Principal Investigator: Yuliya Vystavna

Financial support: Czech Science Foundation

Duration: 2019 - 2021

Changes in catchment hydrology can result in nutrients losses from catchments with following reduction of soil fertility but increasing primary production and eutrophication of water bodies. Applying hydrological models, stable water isotopes (O-18, H-2) and hydrochemical measurements we will trace and quantify phosphorus fluxes in a pair of forest catchments - with a healthy stand and stand in early stage of recovery after deforestation. This paired catchment study is focused on (i) determination of recharge patterns and water balance, including snowmelt and rain runoff; groundwater-surface water interactions; partitioning of evaporation and transpiration by plants; estimation of water residence time; (ii) quantification of phosphorus leaching with different hydrological pathways under contrasted hydrological conditions. Results of these analyses will be demonstrated on modelled scenarios linking water and phosphorus fluxes. This multidisciplinary project will fill a gap in knowledge on possibilities of complex application of isotope hydrology, hydrology and hydrochemistry.

The project goal is to develop and apply multidisciplinary paired catchment study to quantify phosphorus fluxes under contrasted hydrological conditions and model scenarios to predict effects of hydrology on the nutrient dynamic in catchments.

An interdisciplinary study on element cycling in mountain catchment-lake systems regenerating from tree dieback

Project No.: 19-16605S

Principal Investigator: Jiří Kopáček

Financial support: Czech Science Foundation

Duration: 2019 - 2021

Bark beetle outbreak killed many mature spruce trees in unmanaged, acidified catchments of the Bohemian Forest lakes (BF, Central Europe), with the most pronounced tree loss (>90% in 2004–2008) in the Plešné catchment. The tree dieback significantly changed element cycling in soils and waters and affected their biogeochemistry. At present, forest has been rapidly regenerating. Our >20-year long environmental research on the BF catchments (forest, soil, water, climate) provides a worldwide unique opportunity for a complex ecosystem study on the effects of natural forest dieback and regeneration of the individual ecosystem parts. We propose an integrated laboratory and field mass budget studies on (1) C and N cycling in soils and their effects on leaching of other elements (P, S, Ca, Mg, K, and Al) and (2) how these changes affect regeneration of forest and soil microbial community, and chemical and biological recovery of waters from acidification. Modelling will enable projection of these changes to other similarly affected mountain areas and different forestry practices.

We will evaluate (1) pools and fluxes of ecologically important elements (N, P, C, S, Ca, Mg, K, Al) in catchment-lake systems regenerating from natural tree dieback, (2) how nutrient availability in soil and deadwood affects tree grows, and (3) how this grow affects soil and water biogeochemistry.

Life on the edge: Biogeochemical factors driving transition from lotic to lentic microbial community in headwaters

Project No.: 19-00113S

Principal Investigator: Petr Porcal

Financial support: Czech Science Foundation

Duration: 2019 - 2021

Planktonic microbial communities of lotic and lentic headwater environments substantially differ. Until now, the transformation of bacterial community from lotic to lentic has been poorly studied and the role of stream-originated microbes in the formation of the lentic bacterial assemblies is not clear. Mechanisms of initial assembly of microbial communities in large water bodies are difficult to understand due to long water residence times and large pool of local species. Small lentic water bodies, with short water residence time, located on headwater streams represent promising model ecosystems of combined highly plastic characteristics of lotic vs. lentic microbial communities, depending on hydrological conditions and environmental (terrestrial & aquatic) chemistry. In our project, using such an ecosystem as a study site, we would like to address the general mechanisms driving microbial consortia transformation and reassembly, especially the role of alternation of hydrological conditions together with the changes in the pool of dissolved organic matter in this process.

This study will address the mechanisms responsible for assembly of lotic microbial communities by identification of: I) chemical and bacterial interactions relevant for their metabolic pathways; II) key environmental parameters driving the community shift; III) the role of stream microbial inoculum.


Biology Centre CAS
Institute of Hydrobiology
Na Sádkách 702/7
370 05 České Budějovice

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