Denitrification is a modular process that is mediated by an assemblage of microbes with varying denitrification gene combinations. The controls on these gene combinations, known as modularity, are poorly understood and marine observations are mostly limited to permanently anoxic systems. In this global metagenomic analysis representing 69 water column metagenome samples we report different modularity patterns associated with e...

Nitrification (microbial oxidation of ammonia to nitrite and nitrate) controls nitrogen speciation and is the main source of nitrous oxide (N 2 O) in the ocean. It was recently shown that the most abundant marine ammonia oxidizers, the ammonia‐oxidising archaea (AOA), are also capable of oxidising urea, providing a previously ignored source of nitrite. Here, we show that the relative magnitude of urea and ammonia oxidation rat...

Nitrogen (N) bioavailability affects phytoplankton growth and primary production in the aquatic environment. N bioavailability is partly determined by biological N cycling processes that either transform N species or remove fixed N. Reliable estimates of their kinetic parameters can help understand the distribution of N cycling processes. However, available estimates of kinetic parameters are often derived from microbial isola...

The three major oxygen deficient zones (ODZs) of the world oceans (eastern tropical North and South Pacific (ETNP and ETSP, respectively), and Arabian Sea (AS) host the vast majority of pelagic fixed nitrogen (N) loss and up to half of total marine N loss. The input of organic matter is an important control on the absolute and relative importance of the two main pathways of N removal (denitrification and anammox). We investiga...