Microbial ecological insights from estuarine sediments revealed by temporal and spatial network analysis

Association network analyses performed on microbial abundance data provides information regarding ecosystems functioning, quality and potential keystone taxa. Samples for network analyses can be collected spatially, temporally or both. Here, we compare the microbiomes and the reconstructed association networks resulting from temporal vs spatial sampling regimes from the Oka estuary in the Spanish Basque Country. The taxonomic composition although similar at Phylum level, diverged more at lower taxonomic levels such as Family. The dissimilarity of spatial replicates was higher than the temporal replicates; however, the dispersion of OTU abundances across samples was similar in the two datasets, indicating that OTU abundances varied similarly across samples. Moreover, the topological properties and keystones differed between networks. The number of edges and the connectance were higher in the spatial network, and keystones were more taxonomically diverse in the temporal network. Among those correlations present in the spatial and temporal networks, we identified potential interactions involved in the sulphur and nitrogen cycles, and in the degradation of organic matter. We conclude that network analyses reveal ecological aspects of the ecosystems functioning, nevertheless, the sampling must be thoroughly planned according to the aim of the study, since different sampling strategies may result in different outcomes.