Projects / Programmes
Effects of environmental changes on organisms and processes in Lake Bohinj
| Code |
Science |
Field |
Subfield |
| 1.03.03 |
Natural sciences and mathematics |
Biology |
Ecosystems |
| Code |
Science |
Field |
| B260 |
Biomedical sciences |
Hydrobiology, marine biology, aquatic ecology, limnology |
| B270 |
Biomedical sciences |
Plant ecology |
| B280 |
Biomedical sciences |
Animal ecology |
Lake Bohinj, ecology, temperature, climate, eutrophication, trophic relations
Researchers (6)
Organisations (2)
Abstract
Lake Bohinj is the largest glacial lake in Slovenia. It is oligotrophic lake with relatively low concentration of total phosphorous, nitrogen and chlorophyll a, and an average Secchi disc transparency over 8 m. In proposed project we will investigate the relations between different trophic levels in lake community in order to estimate the susceptibility of ecosystem to global environmental trends, such as increasing temperature and pollution. It is known that changes in environmental factors affect community structure. Additionally, changes in community structure influence on relationship between primary and secondary producers, and are reflected in energy flow and functioning of the ecosystem. As planktonic crustaceans as grazers of phytoplankton may constitute an important link in the energy flow within lake ecosystem, the effect of food quality and temperature on zooplankton will be studied. Measurements will be done in the field and in laboratory under controlled conditions. Energy demands measurements in dominant group of organisms in lake (microplankton, zooplankton, macrobenthos, macrophytes and microbial community in sediment) will provide the basis for assessment of food web relations and the dynamics in ecosystem. Biochemical and physiological parameters will be determined in order to indicate conditions of experimental organisms in relation to selected environmental factors.
Significance for science
Metabolic properties of the lake are important index of its function. Productivity and community respiration are two important components of ecosystem dynamics and carbon budget. These metabolic rates are considered fundamental ecological and water quality information. Primary production by phytoplankton, macrophytes, and benthic algae forms the autochthonous basis of the food web. Terrestrial input of particulate and dissolved organic carbon is a potential allochthonous basis of the food web. Therefore, we estimated the primary production and carbon loss in the process of respiration in the major groups of organisms in oligotrophic Lake Bohinj. The results have shown the role of each group of organisms in the functioning of the ecosystem and have allowed insight into the relations between the trophic levels (using comparable methods), and thus better estimation of the trend of the ecosystem changes. Knowledge on the contribution of particular group of organisms to the total metabolism of the lake and the knowledge of the relationship between trophic levels serve as a basis for assessing the vulnerability of lake ecosystems to environmental change, and allow us to assess the direction of changes in the functioning of the ecosystem. Based on the results, we have also evaluated the adequacy of particular groups of organisms for the purpose of monitoring of lake status and as an indicator for the early detection of changes in the structure and functioning of lake ecosystems.
For the assessment and monitoring of the lake status it is important to get an insight into the potential intensity of metabolic processes in both the water column and the sediment compartment. Such a combined approach to ecosystem health assessment enables trends of changes in functioning of lake ecosystems to be predicted. Therefore, the biological oxidation capacity of sediments, measured as electron transport system (ETS) activity, is a valuable information about the lake ecosystem, its functioning and its health, in combination with other indicators or information about the system. Additional investigations on different types of the lakes would be needed to find out the possibility of the use of ETS activity as a part of an index, that could be used as the only estimator of the lake ecosystem status.
Research on the influence of temperature changes for a few degrees Celsius on the metabolic potential of key groups of organisms in the lake have shown that even a small change in temperature leads to a change in metabolic activity of communities. Since the previous studies have mainly investigated the response of organisms to global warming in the eutrophic lake, the results of our project contribute to the knowledge about the influence of the temperature changes on the communities in low productive lakes.
The results that were obtained in the framework of the research project have contributed new knowledge on energy flow and recycling of material through the different trophic levels in the oligotrophic lake. Using the universal method of measuring ETS activity enabled us to investigate the communities of organisms belonging to different trophic levels, and to evaluate their role in the functioning of ecosystems. The results have contributed new knowledge about the influence of global changes on the ecosystem level.
Significance for the country
The results of the research project have shown that the monitoring of metabolic activity of organisms from different trophic levels can be used as an indicator of the changes in the trophic state of Lake Bohinj. Knowledge of the carbon loss in the process of respiration in the various groups of organisms on the one hand, and the assessment of primary production on the other hand provided important information about the vulnerability of the Lake Bohinj to climate changes and direct human impacts.
The relationship between respiratory carbon loss through different components in the lake and estimated carbon productivity in littoral and pelagial showed that the daily respiratory carbon loss was, on average, greater than the estimated primary productivity. Unproductive aquatic ecosystems have been reported to support a disproportionately higher respiration rate than productive aquatic ecosystems, and to act as carbon dioxide sources. Thus, Lake Bohinj is net heterotrophic, meaning that respiration exceeds gross primary production. Our results revealed that the respiratory carbon loss through zooplankton, microplankton, zoobenthos, sediments and macrophytes in Lake Bohinj exceeded carbon productivity by about 55 t of carbon per year. Moreover, this value is probably even greater because of organic carbon degradation by fish and by bacterioplankton smaller than 1µm that are not retained on filters. It should be noted that this value represents only a rough estimate of metabolic activity in the lake, because the conversion factors used in calculations of respiration and primary productivity could provide only approximate values. Nevertheless, it can be assumed that the carbon that supports respiration in Lake Bohinj is derived from within-lake primary production as well as from allochthonous sources in the watershed. Estimation of primary productivity in littoral and pelagial showed that macrophytes and phytoplankton in the littoral contributed 10% more to whole-lake productivity of autochthonous carbon than did phytoplankton in the pelagic zone. Areal carbon productivity in littoral was greater than in pelagial. The reason is the presence of macrophytes which contributed significantly to estimated carbon productivity in the littoral zone. Although intensive degradation of organic matter was observed especially in sediments of Lake Bohinj, the concentrations of nutrients were low due to rapid recycling.
The results of our research can serve as a basis for more efficient protection of Lake Bohinj and planning the activities in the area of Triglav National Park.
Most important scientific results
Annual report
2008,
final report,
complete report on dLib.si
Most important socioeconomically and culturally relevant results
Annual report
2008,
final report,
complete report on dLib.si
