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Identification and toxic potential of Cyanoprokaryota in the Bulgarian water bodies. Environmental health risks

Final Report Summary - CYANOIT (Identification and toxic potential of cyanoprokaryota in the Bulgarian water bodies. Environmental health risks.)

Our project was conducted during a key period for Bulgaria, i.e. during 2007-2010 when, as a member of the European Union, the country had to meet the obligations for monitoring surface water as a part of the European Union Water Framework Directive (2000/60/EC) for water protection and management. Bulgaria had to apply an integrated approach to assess the water quality and harmonise the national legislation with the European Union in this direction.

In the course of the project, normatively defined key indicators that were used in monitoring and evaluation of the water quality were determined, consisting of taxonomic composition, abundance and biomass of the phytoplankton with emphasis on representatives of cyanoprokaryota. Concerning the taxonomic composition, an inventory list of cyanoprokaryotic species for each investigated period and dam was prepared. These data were used to evaluate the total species' richness, as well as for the calculation of some taxonomic indices of diversity and the proportion of the major taxonomic groups. The presence of toxic species was also analysed for the selected dams. On the basis of the performed research it was clear that all examined dams had a stable taxonomic composition and relatively low diversity of phytoplankton. Green algae, i.e. chlorophyta, were dominant for summer phytoplankton and the group of cyanoprokaryota was relatively poor in terms of species' composition. 'Algal blooms' were determined by using the biomass and density, respectively.

Based on the average physicochemical data for the water transparency that were obtained using the Secchi disk, the amount of total chlorophyll-a and total biomass as well as the amount of total nitrogen and total phosphorus and their ratio (TN/TP) were determined. In addition, the trophic status of each dam was defined and the trophic state index (TSI) and Catalan index were calculated. For the case of the 'Studen Kladenets' reservoir, which is the second largest dam in Bulgaria after the Iskar dam, the value of TSI index was 50, the amount of chlorophyll-a was equal to 2.44 mg/l, the total biomass was 1.16 mg/l and the ratio of TN/TP was calculated equal to 66. This data showed a transition from a mesotrophic environment to a state of eutrophy and limitation of phosphorus at community level.

The relevance and innovation of the project was also determined by the monitoring of surface water used for drinking, fishing or recreation regarding the cyanotoxins which was launched in Bulgaria. Cyanotoxins were recognised as a factor representing a danger to the flora, fauna and people. The presence of cyanotoxins, e.g. microcystins, nodularins, saxitoxins and anatoxin-a, in all dams that were included in this investigation was analysed using biological, i.e. in vivo and in vitro, immunological (enzyme-linked immunosorbent assay (ELISA)) and physicochemical (high-performance liquid chromatography (HPLC)) methods.

In addition, an assessment of the water of the 11 monitored Bulgarian dams for the presence of heavy metals was conducted. Water samples, collected during the summer of 2008 and 2009 were tested for the levels of five heavy metals, namely zinc, lead, manganese, copper and cadmium. The most frequently elevated values were determined for zinc, lead and cadmium. Alarming data on the lead content was obtained for the water of the reservoirs Vacha and Studen Kladenets. The detected levels of lead in the reservoir Vacha, equal to 0.24 mg/L for 2008 and 0.29 mg/L for 2009, were 30 times more than the maximum permitted concentration of 0.01 mg/L, which was set by the World Health Organization (WHO). The reported elevated concentrations of lead in the water of Vacha reservoir were dangerous to the aquatic ecosystem as well as to people who chose this place for recreation or fishing. Moreover, this dam was used as a source of drinking water.

All these data suggested that a continuous control and monitoring of water quality and timely awareness of potential risks for both aquatic ecosystems and human health was required. The relationship between the phytoplankton structure of a water basin, the presence of cyanotoxins and the water quality rendered it possible to create a good system for monitoring the phytoplankton and its toxic potential.