Recent advances in marine N-cycle studies using ¹⁵N labeling methods.

Area of Science:

• Marine microbial ecology
• Biogeochemistry
• Stable isotope geochemistry

Background:

• Nitrogen (N) is crucial for marine ecosystems.
• Microbial N-transformations drive marine N-cycling.
• 15N stable isotopes are key tracers for N-cycle research.

Purpose of the Study:

• To summarize recent methodological advances in 15N stable isotope applications for marine N-cycle research.
• To discuss how these advances provide new insights into marine N-cycling.
• To highlight progress in studying nitrification and N-fixation.

Main Methods:

• Direct application of 15N stable isotopes (e.g., 15N-ammonium, 15N-nitrate, 15-15N2 gas).
• Improved experimental designs for tracing N-transformations.
• Single-cell studies utilizing 15N stable isotopes.

Main Results:

• Methodological advancements enhance the study of complex N-transformations.
• New approaches facilitate tracing microbially mediated processes (nitrification, denitrification, anammox, N-fixation).
• Recent insights have been gained into marine nitrification and N-fixation.

Conclusions:

• 15N stable isotope techniques are continuously evolving.
• These evolving methods are critical for understanding marine N-cycling.
• Advances offer powerful tools for investigating microbial roles in marine biogeochemical cycles.