Role of invertebrates in groundwater ecosystem processes and services

Invertebrates in groundwater influence ecosystem processes through their trophic interactions with biofilms and nontrophic actions that engineer the physical environment. The relative contributions of trophic and ecosystem engineering activities of invertebrates are largely modulated by environmental attributes (sizes of interstices, substratum type, particle sizes) which determine the hydrological exchanges between surface water and groundwater. We review these processes in karst and alluvial groundwater ecosystems and propose a conceptual framework for understanding the interplay between invertebrate activities and physical properties at the surface water–groundwater interface and the influence of hydrological exchanges, organic matter processing, and biogeochemical processes in groundwaters. This framework highlights that there is potential for multiple ecosystem services to be fulfilled by invertebrates; however, environmental impacts affecting the physical properties of the interface (lowering of the groundwater table, artificial aquifer recharge, clogging) can alter the capacity of invertebrates to provide these services. Coherent field and laboratory tests based on our conceptual framework and a multidisciplinary approach remain necessary to evaluate hydrological exchanges, nutrient fluxes, microbial processes, functional traits of invertebrates, and biodiversity in groundwater ecosystems.