Between darkness and light: spring habitats provide new perspectives for modern researchers on groundwater biology.

Raoul Manenti,Beatrice Piazza

doi:10.7717/peerj.11711

Abstract

Springs are interfaces between groundwater and surface habitats and may play an important role in the study of subterranean animals. In this systematic evidence review and meta-analysis, we explore whether observations of stygobionts in springs are relevant and more common than observations of epigean animals in groundwater. We searched the Web of Science database for papers on groundwater fauna and spring fauna. For each paper we found, we recorded whether the paper reported the occurrence of typical stygobionts in springs, of surface animals in groundwater, or of the same taxa in both habitats. If so, we recorded how many such species were reported. We also recorded the scientific discipline of each study and the year of publication. Our search yielded 342 papers. A considerable number of these papers reported stygobionts in springs: 20% of papers dealing with groundwater fauna and 16% of papers dealing with spring fauna reported the occurrence of stygobionts in spring habitats. Both the number of papers that mentioned stygobionts in springs, and the number of stygobiont species that were documented in springs, were higher than equivalent measures for the occurrence of surface fauna underground. We also detected a positive relationship between year of publication and the number of reports of stygofauna in springs. To broaden the insights from biological research on underground environments, we suggest that springs should be considered not only as simple sampling points of stygobionts but also as core stygobiont habitats.

Highlights

The zoologist Botosaneanu (1998) defined springs as the “doors on River Styx,” the river of the Greek mythological underworld
As some studies have already suggested, transition zones are important for regulating ecosystem processes and the flow of organic matterand organisms between surface and underground habitats (Moseley, 2009; Plenet & Gibert, 1995; Prous, Ferreira & Martins, 2004). With this opinion paper based on a systematic review of the recent scientific literature, we aim to stimulate a change in the conception of and in the approach to springs by studies dealing with stygobionts and groundwater fauna
We followed the Preferred Reporting Items for Systematic Reviews (PRISMA) guidelines (Page & Moher, 2017), and we searched the Web of Science database for peer-reviewed papers on both stygofauna and fauna living in spring habitats (Fig. 2)

Summary

Introduction

The zoologist Botosaneanu (1998) defined springs as the “doors on River Styx,” the river of the Greek mythological underworld. Other biologists who study subterranean environments and groundwaters consider springs to be openings that allow them to see the inhabitants of an otherwise inaccessible environment (Culver, Holsinger & Feller, 2012; Fiasca et al, 2014; Galassi et al, 2014; Pipan & Culver, 2012; Pipan et al, 2012). This view of spring habitats as windows into a different environment is true in. The drawing is modified from Andrea Melotto and Benedetta Barzaghi

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Conclusion