# Picoplankton nitrogen guilds in the tropical and subtropical oceans: From the surface to the deep

## TL;DR

This study explores how different types of tiny ocean organisms contribute to the nitrogen cycle from the surface to deep ocean layers in tropical and subtropical regions.

## Contribution

The study quantitatively compares the stability of nitrogen acquisition and nitrogen-redox guilds across depths and environmental conditions.

## Key findings

- Nitrogen acquisition guilds are more stable and redundant than nitrogen-redox guilds across depths.
- Environmental factors like nitrogen depletion and oxygen availability affect the two guild types differently.
- The findings improve understanding of global nitrogen fluxes and functional diversification in the ocean.

## Abstract

Ecological guilds quantify the incidence and extent of resource transformation functions, irrespective of the species involved. Therefore, tackling the microbial nitrogen guilds is key to our understanding of the oceanic nitrogen cycle, but quantitative estimates of guild contribution across varying depths and under specific environmental conditions have yet to be accomplished. In this study, we examine the main picoplankton guilds participating in nitrogen cycling within the low and mid-latitude ocean ecosystems, from the surface down to 4000 m, using data obtained from 75 samples belonging to 11 stations in the Malaspina dataset. In particular, we used a quantitative approach to investigate the stability of nitrogen acquisition and nitrogen-redox guilds separately. Our results showed that nitrogen acquisition guilds are more stable and redundant than nitrogen-redox guilds across depths and site specific conditions. For example, differential conditions such as nitrogen depletion and oxygen availability affected the two groups of guilds in different ways. These findings have implications for the understanding of global nitrogen fluxes and the biosphere’s functional diversification.