Sampling fauna in aquifers: a comparison of net-sampling and pumping

Abstract

Two devices frequently used for sampling groundwater fauna in aquifers were compared: the phreatobiological net-sampler and the centrifugal pump. These two methods were tested in a French Pyrenean alluvial aquifer during two contrasting seasons. Macrocrustacean (amphipods, isopods) and microcrustacean taxa (cyclopoids) were collected from 15 wells with different characteristics (piezometric level, depth, water extraction, hydrogeological settings) in order to compare the relative abundance patterns obtained with the two methods. Very similar patterns were observed using either the phreatobiological net or the pump, whatever the taxa considered, Species characteristics (size, ecological preferences, locomotory behaviour) did not influence the results. The global efficiency of the methods appeared to depend on sample size, i.e. on the abundance of the species collected. The advantages and disadvantages of the two methods are discussed relative to the sampling criteria (field framework, damage to fauna, ease of use, convenience). Under some conditions, the phreatobiological net-sampler can be considered a valuable alternative to pumping in aquifers.