Establishment of relationships between some biological, chemical and hydromorphological variables in the rivers of the lielupe basin

The goal of this study was to find relationships between some biological, chemical and hydro-morphological variables in the rivers of the Lielupe basin in 2001 – 2004 period. Spearman correlation, simple and multiple stepwise regression analysis were used. Close relations between river discharge and total nitrogen, HCO3– ions concentrations were established. Rivers pollution by biogenic matters was affected the loss of dissolved oxygen concentration until 61,4 %. Drastic increase of the concentration of Fe was characterized by low pH. Close relations between Ca2+, Mg2+ and HCO3– concentrations showed that the karst processes were determined water quality in the rivers of the Lielupe basin. Abundance of the Chironomidae species was good indicator of rivers water pollution by biogenic matters, but BI and DIUF indices were more sensitive to concentrations of these compounds. Comparison of sensibility of BI and DIUF indices to abundance of Ephemeroptera and Trichoptera species showed that DIUF index was more sensitive to abundance of Ephemeroptera species, but BI index was more sensitive to abundance of Trichoptera species. Established model, which was characterized the dependence between abundance of macroinvertebrates and abundance of Oligochaeta and Chironomidae taxons, was explained 99,7 % of the variation of the abundance of macroinvertebrates, thus benthic organisms which are less sensitive to pollutants were dominants in the rivers of the Lielupe basin in investigated period