Bentosne silikatne alge (Bacillariophyta) u proceni ekološkog statusa reka Velike Morave i Save.
Benthic diatoms (Bacillariоphyta) in assessment of the ecological status of the Velika Morava and the Sava rivers
Abstract:
Diatoms are dominant group in a phytobenthos community of freshwater ecosystems, widely distributed, present throughout the year and they inhabit diverse habitats. Considering to be good bioindicators, many countries developed assessment of the ecological status of waters and monitoring of changes in aquatic ecosystems based on diatom indices. In accordance with the guidelines of the Water Framework Directive, the legislation of the Republic of Serbia formalized the assessment of ecological status/potential on the bases of biological water quality elements, which include benthic diatoms.
Until now algological investigations of the Velika Morava River and the Sava River primarily concerned the phytoplankton community, while the studies of the benthic diatoms communities recently began. Studies that include the assessment of the ecological status of large rivers based on benthic diatoms have not been done on the territory of Serbia so far.
The goals of our research were: qualitative and quantitative analysis of the benthic diatoms community composition, to determine their spatial and seasonal dynamics, to determine the values of physical and chemical parameters at sampling sites and the most important environmental parameters that affect the investigated communities, assessment of the water quality based on the diatom indices values using OMNIDIA software, assessment of the ecological potential of the Velika Morava River and the Sava River (part of the flow through Serbia), in accordance with the legislation of the Republic of Serbia, consideration of the efficiency of benthic diatoms as indicators in the water monitoring and the effectiveness of selected ecological indices, evaluation of environmental potential and identification of the specific indicator taxa and forms.
Phytobenthos samples from the Velika Morava River were collected annually (from 2010 to 2011) at five sampling sites, while samples from the Sava River were collected each September during a period of four years (2011, 2012, 2014 and 2015) at a total of 33 sites along the entire watercourse. After processing the material, the analysis of the benthic diatoms community was carried out according to the research objectives.
In the Velika Morava River presence of 162 taxa was detected, while in the Sava River presence of 184 taxa was registered. The dominant and frequent taxa of the Sava and the Velika Morava rivers are considered as eutrophic and hypereutrophic taxa.
The greatest influence on seasonal dynamic of benthic diatoms of the Velika Morava have environmental parameters pH, temperature and arsenic. The most important environmental parameters affecting the community of benthic diatoms of the Sava are arsenic and silicon, with the greatest influence on sites in the lower course of the river.
Along the Sava River, the composition of the benthic diatoms communities changes from the dominance of the forms closely attached to the substrate (upstream) to the dominance of the motile forms (middle and lower flow), which is in accordance with the general changes in the Sava River, from the sub-alpine river to the lowland river, with the dominance of the smaller fractions of the substrate.
The high water levels recorded in September 2014 on the Sava River, didn't result in decrease of Shannon's diversity index values, which confirms the resistance of benthic diatoms to this type of pressure. Our research suggests that large rivers are an important habitat for benthic diatoms.
The species Mayamaea cahabaensis, first time identified in the Sava and the Velika Morava rivers (and therefore in diatom flora of the Serbia), was recorded with a high abundance. Two potentially invasive taxa ‒ Didymosphenia geminata and Diadesmis confervacea are present in the Sava River with a low abundance. Teratological forms of diatoms have been recorded at all sites in the Velika Morava River and at several sites on the Sava River. It has been confirmed that the share of teratological forms in diatom community has a bioindicator potential.
In the case of the Velika Morava River, our research indicate that assessment according to national legislation is more reliable using IPS index in comparison to CEE. It is necessary to consider changing class boundaries for the CEE index for type 2 watercourses.
Diatom indices are sensitive to increased concentrations of arsenic and iron, although indices were primarily designed as indicators of organic pollution and nutrient load. Having this in mind, benthic diatoms can be considered as a reliable indicator of the presence of multiple pressures in the case of large lowland rivers, and they can be used as a parameter of general degradation.
The reliability of the standard methodology for benthic diatoms sampling in routine monitoring, in the case of the Velika Morava and Sava rivers, is confirmed.
Source:
Faculty of Science, University of Kragujevac, 2017, 1-170Funding / projects:
- Evolution in Heterogeneous Environments: Adaptation Mechanisms, Biomonitoring and Conservation of Biodiversity (RS-MESTD-Basic Research (BR or ON)-173025)
- Monitoring and Modeling of Rivers and Reservoirs (MORE) - Physical, Chemical, Biological and Morphodynamic Parameters (RS-MESTD-Technological Development (TD or TR)-37009)
- Managing the effects of multiple stressors on aquatic ecosystems under water scarcity (EU-FP7-603629)