The Marine Nitrogen Cycle

Bioturbation: impact on the marine nitrogen cycle.

Sediments play a key role in the marine nitrogen cycle and can act either as a source or a sink of biologically available (fixed) nitrogen. This cycling is driven by a number of microbial remineralization reactions, many of which occur across the oxic/anoxic interface near the sediment surface. The presence and activity of large burrowing macrofauna (bioturbators) in the sediment can significan...

The Marine Nitrogen Cycle: Overview and Challenges

A Neoproterozoic Transition in the Marine Nitrogen Cycle

The Neoproterozoic (1000-542 million years ago, Mya) was characterized by profound global environmental and evolutionary changes, not least of which included a major rise in atmospheric oxygen concentrations [1, 2], extreme climatic fluctuations and global-scale glaciation [3], and the emergence of metazoan life in the oceans [4, 5]. We present here phylogenomic (135 proteins and two ribosomal ...

Marine archaea take a short cut in the nitrogen cycle.

S eeing “nitrification” and “Archaea” in the title of the paper in PNAS by Alonso-Sáez et al. (1) will not surprise anyone following the story about the role of these microbes in an important pathway of the nitrogen cycle. What will puzzle, if not surprise, everyone is the other key word, “urea.” That nitrogenous compound never comes up in discussions of nitrification and Archaea, and even othe...

Marine nitrogen: Phosphorus stoichiometry and the global N:P cycle

Nitrogen supply is often assumed to limit marine primary production. A global analysis of total nitrogen (N) to phosphorus (P) molar ratios shows that total N:P is low (<16:1) in some estuarine and coastal ecosystems, but up to 100:1 in open oceans. This implies that elements other than N may limit marine production, except in human impacted, estuarine or coastal ecosystems. This pattern may re...