Aquacultural source of nitrous oxide revealed by nitrogen isotopes

Area of Science:

• Environmental Science
• Aquaculture Science
• Biogeochemistry

Background:

• Coastal aquaculture expansion increases nitrogen loading and nitrous oxide (N2O) emissions.
• Understanding N2O production pathways in aquaculture is crucial for sustainability.

Purpose of the Study:

• To characterize N2O production pathways and rates in subtropical aquaculture ponds.
• To determine the relative contributions of water column and sediment to N2O emissions.

Main Methods:

• Utilized 15N-labeled dissolved inorganic nitrogen tracers.
• Quantified N2O production rates in ponds cultivating shrimp, seabass, and prawn.
• Analyzed water column and sedimentary N2O production.

Main Results:

• Total N2O production rates varied (6-70 µmol-N m-2 d-1), with shrimp ponds showing the highest emissions.
• Sediment accumulation significantly stimulated N2O production, exceeding water column contributions.
• Partial denitrification (>60%) was the dominant N2O production pathway, influenced by nitrite availability.

Conclusions:

• Sediment conditions and nutrient loading are key drivers of N2O emissions in aquaculture.
• Partial denitrification, fueled by nitrite, is the primary mechanism for N2O generation.
• Sustainable aquaculture practices should address nitrogen management in pond sediments.