UC San Diego

In marine ecosystems, eelgrasses have proven to be influential to their surrounding environments through their many ecosystem functions, ranging from the provisioning of food and shelter to serving as a natural defense against pollution and pathogenic bacteria. In the marine waters of San Diego, CA, USA, eelgrass beds comprised of Zostera spp. are an integral part of the coastal ecosystem. To evaluate the impact of eelgrass on bacterial and archaeal community structure we sequenced the 16S rRNA gene from paired eelgrass-present and eelgrass-absent sites. We applied mixed effects models to the gene sequencing results and bacterial abundance data derived by flow cytometry to test the hypothesis that microbial community structure is influenced by the presence of eelgrass. This approach allowed us to identify specific microbial taxa that were differentially present at eelgrass-present and eelgrass-absent sites. Principal component analysis (PCA) revealed that PC1 and PC2 accounted for a 93.1 % of the variance in microbial community structure among the samples. Microbial taxa that were differentially present between eelgrass present and eelgrass absent sites were identified, along with microbial taxa that were differentially present between samples from the inner and outer San Diego Bay sampling sites. Differentially present bacterial taxa included potential pathogens of order Rickettsiales, family Flavobacteriaceae, Tenacibaculum maritimum and members of the order Pseudomonadales.