Do composition and diversity of bacterial communities and abiotic conditions of spring water reflect characteristics of groundwater ecosystems exposed to different agricultural activities?

Karczewski K, Göbel P, Meyer EI

Abstract

Modern agricultural practices have undeniably increased global food production. Onthe other hand, agricultural practices not only lead to a degradation of natural ecosystemsbut also affect the functioning of ecosystems and the related services theyprovide. Even though impacts of anthropogenic activities vary across ecosystems,freshwater ecosystems are among those affected to a higher degree. In comparisonto surface water ecosystems, groundwater ecosystems are less affected by anthropogenicpollutants, as the overlaying soil retains organic and inorganic substances.However, it has become evident that the excessive use of fertilizers has led to theeutrophication of many aquifers. Bacterial communities, which significantly contributeto the cycling of matter due to their metabolic capacities, are prone to environmentalperturbations, and structural variation of bacterial communities mayconsequently affect the functioning of groundwater ecosystems. Our present paperintends to evaluate the impact of anthropogenic activities on environmental conditionsas well as on the structural properties of bacterial communities in groundwater.We repeatedly sampled emerging groundwater at five spring sites belonging to differentcatchments and determined the concentration of abiotic variables as well asthe diversity and composition of bacterial communities on a local scale. We hypothesizedthat anthropogenic activities influence the concentration of abiotic variables,especially of nitrate, as well as the composition and diversity of bacterial communitiesin groundwater. Our results show that underground spring catchment areas onlyslightly differ regarding the concentration of abiotic variables as well as the structureof bacterial communities. Furthermore, abiotic variables, presumably influenced byanthropogenic activities, do not correlate with the diversity and composition of bacterialcommunities. Although supported only by circumstantial evidence, we suggestthat upwelling groundwater from the deeper aquifer affects the diversity and compositionof bacterial communities, and we argue that bacterial communities act asuseful indicators for environmental changes.