Ecological health assessment of karstic springs based on the biological integrity of benthic fauna

The springs represent a crucial groundwater resource and are highly sensitive and vulnerable to human-induced environmental changes. To implement effective conservation activities, it is essential to conduct a bioassessment of the condition of these springs. In the present study, we used benthic macroinvertebrates to evaluate the ecological conditions of upland karstic springs in eastern Europe. We attended to answer whether environmental variables (hydrological, physical, or chemical) impact the density and taxonomic structure of benthic fauna and whether the responses are taxon-specific. We studied nine karstic spring habitats, limnocrenes and rheocrenes, during three seasons (spring, summer, autumn) of 2020. The mean molar ratio of bicarbonate to calcium (HCO₃⁻/Ca²⁺) ranged from 2.80 to 3.57, indicating stable geochemical conditions in the springs. The concentrations of sulfate (6.89-27.36 mg dm⁻³) and chloride (4.37-14.62 mg dm⁻³), along with nutrient levels of nitrates (5.74-31.16 mg dm⁻³) and orthophosphates (0.02-0.056 mg dm⁻³), showed no significant differences across spring types or seasons, suggesting that there were no noticeable anthropogenic impacts. The density of invertebrates varied between 208 and 776 ind. m -2 , with a significantly higher density observed in limnocrenes. Three taxa dominated the macrofauna: Gammaridae (7-84%), larvae of Chironomidae (5-57%), and Trichoptera (6-32%). According to redundancy analysis, the primary factors that influenced the structure and abundance of macroinvertebrates were substrate type, water current, and dissolved oxygen levels. Our analysis of the composition of benthic fauna concerning key environmental variables indicates that the studied karstic springs are in good ecological condition. The structure of the benthic fauna reflects natural habitat conditions and is not significantly affected by human activity. • Macroinvertebrates were used to assess the ecological integrity of karstic springs • Bottom substrate, water current and dissolved oxygen determined benthic communities • Gammaridae, Chronomidae and Trichoptera dominated karstic spring habitats • The structure of benthic fauna indicates a negligible human impact on the springs