TROPHIC STATE AND MACROPHYTE BASED ASSESSMENT OF THE ECOLOGICAL STATUS OF SELECTED RESERVOIRS IN BULGARIA

I. Traykov, A. Tosheva

Abstract: The objectives of the study were to assess the trophic state and to compare it to the ecological potential of the water bodies according to the macrophyte assemblages within selected reservoirs. The studied reservoirs varied greatly in their trophic status, as well as in species composition and abundance. Sampling was conducted between 2009 and 2014. The concentrations of nutrients and the Carlson’s trophic state indices were used to assess the trophic state of the reservoirs. The trophic state varied between oligo-mesotrophic to hyper-eutrophic, with the majority being eutrophic. A discrepancy between the expected trophic state and the measured one was observed for each water body type. No correlation was observed between the trophic state and the ecological status of the water bodies. Trophic state assessment, traditionally, is focused on the “open water” conditions and not so on the littoral aquatic plant communities. The latter, on the other hand, can modify the trophic state by reducing the nutrient inputs to the water bodies. The two assessment schemes have different ecological meanings as the former assesses the algal biomass and the latter – the deviation from reference conditions. Our results show the need to further investigate the relationship between the different biological quality elements, and their response to the changes in the supporting physicochemical parameters.

Keywords: bioindication; BQEs; eutrophication; macrophytes; monitoring; reservoirs; WFD

Date published: 2017-09-29