Microbial diversity and nitrogen cycling across oxygen gradients in the eastern tropical Pacific during two La Niña years.

Microbial diversity and nitrogen cycling in the eastern tropical Pacific OMZs show minimal interannual variation between two La Niña years despite ENSO fluctuations.

• Why it matters: Understanding how microbial communities and nitrogen processes respond to oxygen variability is crucial for predicting the impacts of expanding OMZs driven by climate change, yet this remains poorly understood.
• What they did: Metagenomic analysis was conducted across oxygen gradients during the 2022 La Niña and compared with data from 2011, focusing on microbial diversity, community composition, and nitrogen cycling genes.
• The result: Vertical oxygen thresholds influence microbial community shifts and nitrogen pathways more than interannual differences, with only slight variations in diversity and nitrogen gene abundance observed between the two years.