Distribution patterns of subsurface copepods and the impact of environmental parameters

The 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.