RELATIONSHIPS BETWEEN TROPHIC STATE AND PHYSICOCHEMICAL VARIABLES OF SOME STANDING WATER BODIES ON THE TERRITORY OF EAST-AEGEAN RIVER BASIN DIRECTORATE, BULGARIA

M. Vladimirova, I. Traykov

Abstract: The objectives of the study were to describe the physicochemical variables and to assess the trophic state of the reservoirs Ovcharitsa, Byal Kladenets, Skalitsa, Zhrebchevo and the fishponds of Nikolaevo. Sampling was conducted at four occasions between April and August 2013. The concentrations of nutrients and the Carlson’s trophic state indices were used to assess the trophic state of the water bodies. The trophic state spans over several trophic categories – from oligo-mesotrophic to hypertrophic, with majority of the water bodies being eutrophic. Very strong positive correlation was observed between the transparency and the chlorophyl trophic state indices. Weaker, but still strong correlation was observed between the transparency and the phosphorus trophic state indices. The relationships between the trophic state indices depended on the depth of the water body and the influence of the heated waters from the thermal power station “Maritsa Iztok-2”. The trophic state of the water bodies depends not only on the amount of the available nutrients, but also on the circulation pattern and the length of the vegetation period. The thermal pollution from large steam electric power plants not only changes the environmental factors, but also the relationships between the physicochemical variables and the biological communities in the water bodies. Our results
show the different response of the studied variables in thermally influenced water bodies, compared to different unaffected by heated waters systems.

Keywords: chlorophyll-a; phytoplankton; reservoirs; thermal pollution; trophic state indices

Date published: 2017-09-29