Does land use impact on groundwater invertebrate diversity and functionality in floodplains?

- We study the effect of land use on groundwater invertebrate communities.
- Groundwater invertebrate communities changed between land use types.
- Invertebrate diversity and ecosystem services increased with forest occupancy.
- Agriculture had a negative influence on groundwater invertebrate communities.
- Water quality controlled groundwater invertebrate diversity and ecosystem services.

Land use change, especially the transformation of riparian forest to agricultural fields, plays an important role in groundwater quality, yet little is known about the effects of land use change on groundwater invertebrate assemblages and diversity. This study assesses for the first time the effect of land use (agricultural vs. forest use) on the groundwater invertebrate community of four river floodplains representative of variable conditions across SW Europe (the Garonne River in France, and the Bidasoa, Ebro and Tajo Rivers in Spain). Groundwater invertebrate and water samples were collected quarterly in 8-12 piezometers located in each floodplain over a year. Taxonomic and functional diversity indices and ecosystem services (i.e. biogeochemical filtration and particulate organic matter breakdown) were calculated. The taxonomic and functional diversity of groundwater invertebrate communities increased linearly with the increasing surface occupied by riparian forests and decreased under intensified agriculture use. Moreover, the provision of key ecosystem services related to the biogeochemical filtration and particulate organic matter breakdown also increased 2-fold under more natural forest land. According to regression models, this is likely due to the pressure of agricultural practices on groundwater quality, with high concentrations of nitrates and sulphates exerting a negative influence over groundwater invertebrate diversity and their associated ecosystem services. The results of this study have important management implications, and suggest that the presence of large riparian corridors enhances groundwater invertebrate diversity and functionality in floodplains deeply disturbed by agricultural practices.