Distribution patterns of subsurface copepods and the impact of environmental parameters

Abstract

a b s t r a c tThe ecosystem dynamics in the vadose zone, the unsaturated layer between the surface and the groundwater table, was studied in five caves located in northwestern Romania. Hypogean and epigean copepod assemblages collected in drip water and in the associated pools were analyzed over a period of 12 and 7 months, respectively. The temporal variation of fauna in both habitats was related to a series of environmental parameters (pH, temperature, electrical conductivity, forest cover, precipitation, type of limestone, hydrographic basin, substrate and volume of the pools). Canonical Correspondence Analysis was used to explore the relationships. Over the year, total abundances in pools were much lower than the abundances observed in drips and showed steep raising values in December only. It is shown that forest cover might be one of the most important driving factor influencing the copepod diversity and abundance. Occurrence of epigean species underground was influenced by precipitation and drip rates. The occurrence of hypogean species was related to electrical conductivity, as an indicator of residence time of water in the vadose zone. Pools on limestone harbored a more diverse and abundant fauna than those with clay sediments. Pools with calcite precipitation were preferred by hypogean species.

Drip heterogeneity and the impact of decreased flow rates on the vadose zone fauna in Ciur‐Izbuc Cave, NW Romania

“…It means that species will migrate towards the vadose zone where water maintains for longer periods of time by continuous refilling from the epikarst zone. Extending this assumption to flow rates, we can postulate that only the most constant drip points, maintained by more stable flow paths through the vadose zone, will be constantly productive, in terms of both faunal abundance and diversity; however, the results of Moldovan et al (, ) and Meleg et al (, , ) suggest that this is not true because a general reduction in flow rates triggers the active dispersal of fauna in the vadose zone. During periods of high water input into the vadose zone, fauna flourish and reproduce in an environment that receives nutrients from the surface.…”

“…The aquatic fauna of the unsaturated zone has only been studied in the last few decades, by sampling dripping water inside caves (see review in Pipan & Culver, ). Studies have attempted to correlate biodiversity and abundance to environmental factors, such as the physicochemical characteristics of the water, thickness of the rock above the cave, intensity of dripping, and time of water residence (Camacho et al, ; Liu, Zhou, Ellis Burnet, & Brancelj, ; Meleg, Fiers, Robu, & Moldovan, ; Meleg, Moldovan, Iepure, Fiers, & Brad, ; Pipan & Culver, ). Except for the presence of pollutants being found to be a factor in such biodiversity and abundance, the rest of the results have been inconclusive, with conclusions being merely speculative because the samples were either taken occasionally, or monitoring was only conducted over short timeframes.…”

“…Dripping points with common surface origin follow different paths underground and cross different voids that harbour different subcommunities (Moldovan et al, ). Therefore, even spatially close subcommunities might have different species composition in space and time as a consequence of (a) physical features of the karst (void topography and interconnectivity); (b) water flow (influenced by porosity, rainfall seasonality or randomness, and the occurrence of extreme rainfall events); (c) seasonal variations in water chemistry; (d) human activities on the surface (Bottrell & Atkinson, ; Kogovšek & Šebela, ; Meleg et al, ; Meleg et al, ); and (e) microbial activity (Benavente et al, ; Wood, Keller, & Johnstone, ). All of these factors can drastically impact on both the abundance and diversity of fauna at the analysed drip points, even if they are located close to each other (Meleg et al, ; Meleg et al, ; Meleg, Battes, Fiers, & Moldovan, ; Moldovan et al, ).…”

“…In the upstream stations, a less fractured limestone or a lower secondary porosity and a lower connectivity explained the observed stability in terms of isotope composition of drip water. However, no correlation was found between flow rates and the abundance or diversity of aquatic fauna collected directly from the drips; the drastic decrease in the flow that started during summer 2008, which peaked during autumn of the same year, was not followed by a decrease in the fauna collected under the drips (Meleg et al, ; Meleg et al, ). The combined information on isotopes and the aquatic fauna in drips in Ciur‐Izbuc Cave has been used to explain the heterogeneity of groundwater communities (Moldovan et al, ) that sustained previous conclusions concerning extreme heterogeneity in space and time of the fauna that colonize the voids network (Moldovan et al, ; Moldovan, Pipan, Iepure, Mihevc, & Mulec, ; Rouch & Danielopol, ; Sket, Trontelj, & Žagar, ).…”

Hard rock aquifers and free‐living nematodes – an interdisciplinary approach based on two widely neglected components in groundwater research

“…In general, arthropods, nematodes and annelids are common groundwater animals (e.g. Humphreys, 2009;Meleg et al, 2012;Gutjahr et al, 2013). Nevertheless, research focuses have been, and still clearly are, on arthropod communities (e.g.…”