Ecological control of nitrite in the upper ocean

Area of Science:

• Marine microbial ecology
• Biogeochemical cycles
• Oceanography

Background:

• Nitrite, an intermediate in nitrogen oxidation, forms a primary nitrite maximum at the base of the sunlit ocean layer.
• Nitrite accumulation varies with latitude, occurring throughout the sunlit layer at higher latitudes.

Purpose of the Study:

• To model nitrifying chemoautotrophs in marine ecosystems.
• To explain nitrite distributions using microbial community interactions.
• To investigate the influence of phytoplankton nutrient and light limitation on nitrifying microorganisms.

Main Methods:

• Theoretical framework development for chemoautotroph interactions.
• Modeling of nitrifying chemoautotrophs within marine ecosystems.
• Integration with ocean circulation models to simulate microbial responses.

Main Results:

• Microbial community interactions can explain observed nitrite distributions.
• Differences in redox chemistry and cell size between ammonia- and nitrite-oxidizing chemoautotrophs allow nitrite accumulation over ammonium.
• Nitrifying microorganisms are excluded from the sunlit layer under nitrogen limitation but thrive at depth under light limitation, leading to nitrite accumulation.
• Coexistence of nitrifying microorganisms in the sunlit layer is possible under iron or light limitation.

Conclusions:

• Microbial processes and community interactions are key drivers of marine nitrite distribution.
• Phytoplankton limitation (nitrogen, light, iron) significantly influences nitrifying microorganism distribution and nitrite accumulation.
• The study provides a framework for incorporating chemoautotrophs and their biogeochemical impacts into ocean models.