GIS-assisted revealing of spatio-temporal dynamics in phycological indices of the Danube river delta

With the aim to predict shifts in water quality in the Danube river delta, a geographic information system (GIS) for environmental monitoring with additional functions for analyzing time-dependent series of observation results was developed. Using the developed GIS, the main trends of shifts in phycological indices of water quality for the period starting from 2005 were revealed. The topicality of these studies is dictated by the need to determine the impact of shifts in aquatic chemistry on the biotic component of the ecosystem. According to data on the Pantle-Buck saprobity index, there was a trend to improving water quality during the study period. A downward trend in species diversity was found using the Shannon diversity index calculated from the abundance of phytoplankton. The revealed trends in phycological indices were observed already in the inlet section of the Danube river delta (above Reni), i.e. they are due to factors operating outside the Danube delta. The obtained results on the trends of phycological parameters correlate with the previously obtained data of the analysis of the results of monitoring of aquatic chemistry parameters. The revealed downward trend in the saprobity index stems from a trend of improving water quality in terms of: BOD5 (correlation coefficient, R=0.68; significance level, α=6 %), phosphate phosphorus (R=0.70; α=5 %), suspended solids (R=0.80; α=2 %). The downward trend in the Shannon diversity index calculated from the abundance of phytoplankton is explained by an upward trend in manganese concentration (R=–0.75; α=3 %). The decrease in phytoplankton diversity according to the Shannon diversity index calculated from the phytoplankton abundance is explained by a sharp increase in the abundance of cyanophytes. The results obtained are of significant interest for predicting shifts in the ecological condition of the Danube river delt