In situ deep-sea surface-enhanced Raman scattering sensor reveals cyanide as a key factor in cold seep nitrogen...

Area of Science:

• Marine Biology
• Geochemistry
• Microbial Ecology

Background:

• Deep-sea vents and seeps are carbon-rich but nitrogen-limited ecosystems.
• Nitrogen cycling is crucial for microbial life in these extreme environments.
• Previous studies lacked direct in situ evidence for nitrogen fixation pathways.

Purpose of the Study:

• To develop a sensor for in situ detection of key molecules in deep-sea environments.
• To provide direct evidence for nitrogen fixation mechanisms in cold seep microbial communities.
• To understand the role of cyanide in deep-sea biogeochemical cycles.

Main Methods:

• Development of a robust surface-enhanced Raman scattering sensor for extreme deep-sea conditions (≥350°C, ≥2000m depth).
• In situ deployment of the sensor at a cold seep ecosystem.
• Detection of cyanide (CN) and analysis of its concentration gradients.

Main Results:

• The sensor successfully detected cyanide (CN) at concentrations above 5.7 μM in situ.
• Direct evidence was provided for an energy-efficient nitrogen fixation pathway involving cyanide.
• Cyanide was observed to be consumed as a microbial "circulating currency".

Conclusions:

• This study offers critical in situ evidence for nitrogen cycling in cold seeps.
• The findings advance our understanding of carbon, nitrogen, and sulfur cycle coupling.
• The developed sensor represents a breakthrough in deep-sea sensing technology.