Macroinvertebrates, a forgotten player in the nutrient dynamics of riparian buffer zones

One of the main causes of poor ecological surface water quality in Europe is nutrient enrichment due to agricultural activities. Riparian buffer zones, the vegetative zones between agricultural land and surface waters, have proven to retain and remove nutrients, yet with highly variable effectivity. So far, the role of invertebrates as an explanation for this variability remains severely overlooked. Therefore, this study aimed to assess the contribution of invertebrates to nutrient retention and removal processes of riparian buffer zones. Only four articles on invertebrate activity in riparian buffer zones were found, which focused on their role in denitrification and nitrate leaching, ignoring the variety of other processes that contribute to buffer zone effectivity. Therefore, knowledge on the role of invertebrates available from other ecosystems was synthesized and extrapolated to riparian buffer zones. It is concluded that the effects of invertebrates on nutrient retention and removal processes often depend on specific species or functional groups, the intensity of bioturbation and feeding activity, as well as on the soil and sediment characteristics. We have made a strong case here that these same invertebrate-environment interactions are also likely to occur in buffer zone ecosystems, mediating nutrient dynamics. To efficiently tackle the most pressing knowledge gaps, the three most important components of future research should be: (1) the quantification of species-specific contribution of invertebrates, (2) the effects of lumbricid communities, and (3) the effects of their large-scale behavior on nutrient dynamics in hydrologically dynamic riparian buffer zones.