A comprehensive bioassessment of karst aquifer flow paths 

Current challenges in the assessment of groundwater characteristics in karst areas result from the difficulties to effectively identify episodes of high water discharge and flow paths rates. The characteristics of karst aquifers formed by interconnected network of pores, fissures, fractures and conduits, with an alternation of high and low permeability zones and distinct water residence time, makes contamination difficult to be detected and monitored over underground flow paths. Groundwater’s have a high variability in recharge and flow rates, influenced by weather and climate patterns. At high flow, resulting from intense precipitations and/or significant snowmelt, karst groundwater’s moves rapidly through the rock, carrying effectively pollutants in and through the host rock. In contrast, during periods of drought and/or reduced surface inflow, groundwater moves slowly and diffuses more effectively within the primary/secondary pores of the rocks. In karst, the base flow is associated with long-term storage of the groundwater that creates a relatively stable environment for strictly subterranean dwellers organisms. Stable conditions in groundwater creates biodiversity hotspots where temperature, chemical composition highly influenced by lithology and potential contaminants acts together to ensure healthy habitats that supports a suite of associations of organisms indicative for the overall groundwater health. In contrast, a high discharge and a rapid flow path are associated with disturbances of groundwater habitats, associated with a shift in community patterns structure and dynamics. In this presentation, we combine water chemistry monitoring, stable isotope analyses (indicators of water source, recharge patterns and timing), identification of microbial communities (i.e., E. coli, enterococci, enterobacteria) and of groundwater fauna monitoring (indicative of both contamination and as biomarkers for groundwater flowpath) to identify episodes of high and base flow in a karst aquifer in the Padis karst area in NW Romania. We assume that a fine tune evaluation of groundwater communities (microbes and meiofauna biodiversity) can be used to: 1) understand the pattern of water flow variation across seasons, acting as disturbances for groundwater communities; and 2) detect the contaminated groundwater spots and potential degraded habitats. From this perspective, we used the microbes and groundwater fauna as biomarkers models to describe the potential causal linkages among groundwater karst flow and flow-path variation, groundwater habitat diversity/stability and quality, and groundwater community diversity in disturbed/undisturbed habitats.