Comparison of ecological state/potential assessment of 19 Bulgarian water bodies based on macrophytes and phytoplankton (2011 2012)

Nowadays, one of the most striking challenges for Bulgarian limnologists comes from the attempts to implement the requirements of Water Framework Directive (WFD) for assessment of the ecological status of the water bodies. This work represents results from the monitoring of the reservoirs Aleksandur Stamboliyski, Antimovo, Batak, Burzina, Gorni Dubnik, Zhrebchevo, Iovkovtsi, Krapets, Mandra, Ognyanovo, Rabisha, Suedinenie, Tsonevo and the lakes Alepu, Atanasovsko Ezero, Dourankoulak, Pomoriysko Ezero, Shabla and Sreburna. The studies were conducted simultaneously in the summer months of 2011 and 2012 on the following parameters: algal taxonomic composition and abundance, presence/absence of algal blooms and blooms of potential toxic species, algal group index, reference index for macrophytes, water temperature, transparency, pH, conductivity, chlorophyll a, total phosphorus, total nitrogen, phosphate phosphorus, ammonium nitrogen, nitrate nitrogen and chemical oxygen demand. The ecological status was registered in the five WFD categories. The set of data, based on the detected species composition of 236 algal taxa and 33 species of macrophytes, allowed us to compare statistically the values of the used parameters and the water bodies according to their biodiversity and abiotic features. The obtained results are important for clarifying the official classification of the surface water bodies of Bulgaria according to State Order N4/14.09.2012 and for making proposals for its improvement. Comparisons of the finally attributed ecological status/potential, based on macrophytes and phytoplankton, showed some significant differences and were used as a basis for discussion of the parameters and their weighted values, used up-to-now for the assessment of Bulgarian water bodies.