Linking Hydrogeology and Ecology in Karst Landscapes: The Response of Epigean and Obligate Groundwater Copepods (Crustacea: Copepoda)

Mattia Di Cicco,Diana Maria Paola Galassi,Ilaria Vaccarelli,Tiziana Di Lorenzo,Barbara Fiasca,Mattia Iannella

doi:10.3390/w13152106

Abstract

Groundwater invertebrate communities in karst landscapes are known to vary in response to multiple environmental factors. This study aims to explore the invertebrate assemblages’ composition of an Apennine karst system in Italy mainly described by the Rio Gamberale surface stream and the Stiffe Cave. The stream sinks into the carbonate rock and predominantly feeds the saturated karst into the cave. For a minor portion, groundwater flows from the epikarst and the perched aquifer within it. The spatial distribution of the species belonging to the selected target group of the Crustacea Copepoda between the surface stream and the groundwater habitats inside the cave highlighted a different response of surface-water species and obligate groundwater dwellers to the hydrogeological traits of the karst unit. Our results suggest that fast endorheic infiltration routes promoted the drift of epigean species from the surface to groundwater via the sinking stream while most of the obligate groundwater dwellers come from the perched aquifer in the epikarst from diffuse infiltration pathways.

Highlights

Groundwater invertebrate communities in karst landscapes are known to vary in response to multiple environmental factors over a wide range of spatial and temporal scales [1,2,3,4,5,6]
The purpose of this study was (i) to explore species distribution patterns across a hydrological continuum of a stream flowing in the recharge area of a karst aquifer fed by the same stream; (ii) to assess which species were able to disperse from the surface to the underground; (iii) to evaluate which species may have followed an alternative route for the colonization of the saturated karst or the dripping pools in the unsaturated karst
Significant differences in hydrochemistry were observed between RG and Stiffe Cave (SC) in the relative concentration of Particulateorganic organicmatter matter (POM) and DOC, and in the overall variation in temperature, the fastflowing of the surface stream water did not allow an enrichment in Ca2+, Na+ and K+, suggesting that the main drains are represented by fast-flowing conduits [5,6,32]

Summary

Introduction

Groundwater invertebrate communities in karst landscapes are known to vary in response to multiple environmental factors over a wide range of spatial and temporal scales [1,2,3,4,5,6]. A mature karst aquifer shows a heterogeneous spatial distribution of hydraulic conductivities in the range of 10−10 –10−1 ms−1. The coexistence of low conductivities of the rock matrix (10−10 ms−1 ) and the highest ones of large conduits draining the system (10−1 ms−1 ) [8,9,10] are reflected in geomorphological features acting as preferential pathways of intensive groundwater circulation, with turbulent flow in karst conduits, and low water speed in the capacitive subsystems. The concept was refined by Pipan and Culver [15,16] and Kozel and Pipan [17] under an integrated ecohydrological perspective due to the role of epikarst invertebrates for their potential role as tracers of water movement from the recharge area to the karst groundwaters [2,15,18]

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