%0 Journal Article %A Luke R. Thompson %A Gareth J. Williams %A Mohamed F. Haroon %A Ahmed Shibl %A Peter Larsen %A Joshua Shorenstein %A Rob Knight %A Ulrich Stingl %T Metagenomic Covariation Along Densely Sampled Environmental Gradients in the Red Sea %D 2016 %R 10.1101/055012 %J bioRxiv %P 055012 %X Oceanic microbial diversity covaries with physicochemical parameters. Temperature, for example, explains more than half of global variation in surface taxonomic abundance. It is unknown, however, whether covariation patterns hold over narrower parameter gradients and spatial scales, extending to mesopelagic depths and across water masses. We collected 45 epipelagic and mesopelagic samples spanning the Red Sea, capturing latitudinal and depth-dependent gradients. From metagenomes we calculated relative abundances of taxonomic groups, gene ortholog groups, and pathways, and modeled their responses to environmental parameters. Gene ortholog group and pathway functional metrics and species- and genus-level taxonomic metrics were equally well explained (75–79%) by environmental parameters. However, only functional and not taxonomic covariation patterns were conserved when comparing with an intruding water mass with different physicochemical properties. Temperature explained the most variation in each metric, followed by nitrate, chlorophyll, phosphate, and salinity. That nitrate explained more variation than phosphate suggested nitrogen limitation, consistent with low surface N:P ratios. Covariation of gene ortholog groups with environmental parameters revealed patterns of functional adaptation to the challenging Red Sea environment: high irradiance, temperature, salinity, and low nutrients. Nutrient acquisition gene ortholog groups were anticorrelated with concentrations of their respective nutrient species, recapturing trends previously observed across much larger distances and environmental gradients. This dataset of metagenomic covariation along densely sampled environmental gradients includes online data exploration supplements, serving as a community resource for marine microbial ecology. %U https://www.biorxiv.org/content/biorxiv/early/2016/05/24/055012.full.pdf