Groundwater biodiversity patterns in the Lessinian Massif of northern Italy

Abstract

SUMMARY1. The distribution patterns of stygobiotic invertebrates were examined with a stratified sampling design at 197 sites selected among four hydrogeographic basins in the Lessinian Massif (northern Italy). The sites were approximately evenly distributed among four hydrogeological zones: unsaturated and saturated zone of karstic aquifers, and hyporheic and saturated zone of porous aquifers. 2. Outlying Mean Index (OMI) analysis which assesses deviation of habitat conditions from reference conditions, was used to evaluate the importance of 14 selected environmental variables in shaping groundwater biodiversity patterns in the region (total of 89 stygobiotic species). The measured variables explained 80% of the variability in the data set. 3. Sampling sites were distributed along the environmental gradients defined by OMI analysis. Significant differences were detected between karstic and porous site, as well as among sites located in the four hydrogeological zones. Differences among the four hydrogeographic basins were not observed. 4. Ordination of stygobiotic species along the environmental gradients was best explained by historical variables (mainly Wü rmian glaciation and age of the underlying geological formation), while variables related to hydrogeology (mainly pH, calcium concentration and habitat fragmentation) influenced species distributions in the hydrogeological zones. An Environmental Integrity Index and nitrate concentration were significantly correlated with altitude, but appeared not to play a significant role in determining stygobiotic biodiversity patterns at the regional scale. 5. Results of the OMI analysis were highly significant for all taxa, suggesting that stygobiotic species are sensitive to the environmental factors studied. Thirty-five species showed high habitat specialisation (OMI index > 10). These species were usually rare and endemic to the Lessinian Massif. Most of them were found in a single hydrogeological zone. 6. Quaternary glaciations appear not to have lowered stygobiotic species richness in the Lessinian Massif. This may be because of the marginal location of the region with respect to the Wü rmian glacier limit and because of extensive networks of fractures in the vadose zone of the karst, which may have allowed stygobionts to move deep down in the aquifers to seek refuge during surface freezing and to recolonise ancestral habitats after the glaciers retreated.

Differences in aquatic microcrustacean assemblages between temporary and perennial springs of an alpine karstic aquifer

“…In contrast, the benthic species rarely occurred in the temporary springs but the species abundantly present in the drift of the perennial spring were often collected also in the drift from the temporary springs, what is indicative of interconnectivity of the two zones. Galassi et al (2009b) observed a higher regional distributional rarity of the species from the vadose zone compared to that in the phreatic zone, which was not the case in this study where only one site was investigated. Here the species richness was the highest in the drift from the perennial spring.…”

“…At a regional scale, historical variables (glaciations and the age of geological formations), altitude and geology (pore size) primarily determined the hypogean community composition and species richness (Dole-Olivier et al, 2009a). A comparison of the vadose and phreatic zones revealed higher regional species richness in the former (Dole-Olivier et al, 2009b;Galassi et al, 2009b;Galassi et al, 2013), most probably due to higher habitat heterogeneity and habitat fragmentation.…”

“…of harpacticoid Lessinocamptus, Paramorariopsis, Parastenocaris genus and the cyclopid species Speocyclops infernus (Brancelj, 2002;Pipan, 2005;Brancelj, 2009;Galassi et al, 2009b). Previously, Speocyclops infernus was shown to be widespread over broader geographical areas in the epikarst and vadose zones (Pipan, 2005;Brancelj, 2009;Papi and Pipan, 2011), while Lessinocamptus pivai was reported to be collected only from one karstic site (the vadose zone) in the northern Italy (Stoch, 1997).…”

“…In caves, investigations are usually focused on selected hypogean habitats that are either cave streams (Sket and Bole, 1981;Fong and Culver, 1996;Schneider and Culver, 2004), puddles and pools filled with percolating water (Brancelj, 2002;Fišer and Zagmeister, 2009), or trickles of percolating water (Pipan and Brancelj, 2004;Sket et al, 2004). In the last decade, regional assessment of hypogean biodiversity using a hierarchical approach was carried out across Europe that also made a comparison of species richness between the vadose and phreatic zone of the same karstic aquifers possible (PASCALIS project;Dole-Olivier et al, 2009b;Galassi et al, 2009b;Stoch et al, 2009). At a regional scale, historical variables (glaciations and the age of geological formations), altitude and geology (pore size) primarily determined the hypogean community composition and species richness (Dole-Olivier et al, 2009a).…”

Effect of Temperature Rising on the Stygobitic Crustacean Species Diacyclops belgicus: Does Global Warming Affect Groundwater Populations?

“…Diurnal temperature fluctuations are typically found at depths of less than 1 m, but seasonal fluctuations may be detectable at depths up to 15 m [10]. The annual amplitude of temperature is typically less than 2 • C in porous aquifers that are deeper than 5 m below the soil surface [11][12][13][14][15]. Yet, shallow porous aquifers are not immune to global warming, because the annual mean temperature of groundwater closely tracks the ambient air temperature [11].…”