ECOLOGICAL STATE ASSESSMENT OF AQUACULTURE PONDS BASED ON PHYTOPLANKTON

Purpose. Assessment of the ecological state of aquaculture ponds based on phytoplankton indices when using different organic fertilizers. Methodology. Collection and processing of algological material have been performed using generally accepted hydrobiological methods. Sampling was conducted before and after application of organic fertilizers and during entire vegetation period twice per month. Saprobity indices were determined by Pantle-Buck technique in Sladechek modification using the biomass of indicator species based on quantitative samples, indicator significance of individual algae species was conducted according to the list of saprobic organisms. Findings. Results of a complex study of phytoplankton and an assessment of water quality of nursery ponds after application of different fertilizers are presented. The performed studies showed that, phytoplankton was presented by 203 species and intraspecific taxa of algae. At the same time, experimental ponds treated with organic fertilizers were characterized by the presence of higher species diversity (102-138) than control ponds (82 taxa) without introduced fertilizers. An analysis of phytoplankton species composition in all ponds showed that the majority of alga-indicator species dominating in the alga flora of the examined ponds belong to the group of β-mesosaprobes (up to 68.4-77.1%), i.e. species inhabiting waters with moderate level of organic pollution. Values of saprobity indices during the entire vegetation period in both experimental and control ponds did not exceed the values of β' and β''-mesosaprobic zones. Average values of saprobity indices were within 1,97±0,01 ? 2,01±0,01. According to the composition of dominating phytoplankton species and their relation to saprobity, the investigated aquaculture ponds are assessed as moderately polluted with the III class of water quality and their ecological state is characterized as “relatively satisfactory”. Originality. Ecological state and water quality assessment of aquaculture ponds have been provided based on phytoplankton indices after application of different organic fertilizers. Practical value. The obtained results can serve as an informational and methodological basis for ecological monitoring of aquaculture ponds. The data on the composition, structure, level of development, and ecological peculiarities reveal the role of phytoplankton in the processes of formation of water quality and bioproductivity.