Exploring the marine microbial interactome over 10 years

Abstract

There is a multitude of microbes that populate the oceans, but we still have a limited knowledge about their ecological interactions. Here we have constructed microbial association networks using monthly samples from a 10-year time-series in the North-Western Mediterranean (Blanes Bay Microbial Observatory). Community 18S and 16S rDNA amplicons from two size fractions (pico-plankton [0.2-3m] and nano-plankton [3-20m]) were sequenced with Illumina MiSeq. Positive or negative correlations between Operational Taxonomic Units (OTUs) were determined using extended Local Similarity Analyses (eLSA), including 18 environmental parameters. A co-occurrence network for the pico-eukaryotic OTUs present in >20% of the samples comprised 40,004 significant edges and 401 OTUs. Most edges (99.1%) were positive (co-occurrences), while 0.9% were negative (co-exclusions), suggesting cooperative associations or similar habitat preferences. The network was highly connected, featuring a mean number of node neighbours of 198.0 and a clustering coefficient (C) of 0.8, which was considerable larger than what is obtained from a random network of the same size (C=0.4). The network also had a small characteristic path length (L=1.56), pointing to small-world characteristics. So far, our results suggest that multiple ecological interactions are taking place among pico-eukaryotes over a time period of 10 years. Ongoing work including other community components as well as network deconvolution will allow us to predict diverse ecological interactions increasing our knowledge of the marine microbial interactome