Contrasting Dynamics and Biotic Association Networks in Estuarine Microbenthic Communities Along an Environmental Disturbance Gradient

Estuarine ecosystems experience a range of anthropogenic pressures. Consequently, robust monitoring tools are essential for their management and protection. Utilizing environmental DNA in routine monitoring programs enables the inclusion of benthic microorganisms, which are not only good indicators of environmental condition, but also play critical roles in ecosystem functioning. We collected eDNA sediment samples in six estuaries from the Basque coast (Spain) with different levels of disturbance: first, to better understand the dynamics of microbial communities and their ecological associations; and second, to unveil how contamination affects them. For the first time in estuarine sediments, time series data were used to examine consensus networks to identify potential indicators of biotic integrity and to compare their topology (network structure). In general, sediment communities were relatively temporally stable, with the moderately and heavily disturbed sites showing more variation. The consensus networks also differed significantly in their topologies, with more impacted estuaries having fewer nodes, edges, and connectance, among others, and higher modularity compared to those less impacted. Moreover, the potential keystone taxa and predicted functional profiles differed between consensus networks. This illustrates how modeled association networks can reveal new insights regarding the state of estuarine ecosystems and their potential functional processes.