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<p>Bivalves play a key role in regulating the biogeochemistry of coastal systems, particularly by enhancing nitrogen recycling in sediments. However, the impact of these processes on sediment nitrous oxide (N<sub>2</sub>O) emissions—a potent greenhouse gas—remains poorly understood, limiting our ability to develop effective mitigation strategies. This study investigated N<sub>2</sub>O fluxes at the sediment–water interface in a 120&#xa0;day land-based enclosure experiment with Pacific oysters (<i>Crassostrea gigas</i>) at four stocking densities and a control group. The results showed that sediments consistently acted as N<sub>2</sub>O sources, with the highest stocking density exhibiting significantly greater N<sub>2</sub>O fluxes due to increased particulate organic carbon (POC) and nitrogen (PON) deposition. Oyster aquaculture significantly altered sediment biogeochemistry, and random forest modeling identified pore water nitrate as a strong predictor of N<sub>2</sub>O flux. The <i>nirK</i> gene abundance increased while <i>nosZ</i> gene abundance decreased in the highest stocking density group, resulting in an elevated <i>nir/nosZ</i> ratio. Structural equation modeling further indicated that oyster density indirectly increased N<sub>2</sub>O flux by altering pore water physicochemical properties. Although local environmental conditions modulate N<sub>2</sub>O fluxes, this study elucidates how stocking density drives N<sub>2</sub>O emissions via biogeochemistry and microbial pathways, highlighting that managing stocking density is a key consideration for mitigating the climate footprint of aquaculture.</p>

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Pacific oyster (Crassostrea gigas) stocking density as a regulator of nitrous oxide emissions: connecting sediment biogeochemistry and microbial functional genes

  • 期刊论文

  • 发表日期：

    2026年5月13日

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  • Shengjie Xu,
  • Li Li,
  • Xuan Dong,
  • Miaojun Pan,
  • Wenwen Jiang,
  • Xiangli Tian,
  • Yunwei Dong,
  • Shuanglin Dong,
  • Ramón Filgueira

摘要

Bivalves play a key role in regulating the biogeochemistry of coastal systems, particularly by enhancing nitrogen recycling in sediments. However, the impact of these processes on sediment nitrous oxide (N2O) emissions—a potent greenhouse gas—remains poorly understood, limiting our ability to develop effective mitigation strategies. This study investigated N2O fluxes at the sediment–water interface in a 120 day land-based enclosure experiment with Pacific oysters (Crassostrea gigas) at four stocking densities and a control group. The results showed that sediments consistently acted as N2O sources, with the highest stocking density exhibiting significantly greater N2O fluxes due to increased particulate organic carbon (POC) and nitrogen (PON) deposition. Oyster aquaculture significantly altered sediment biogeochemistry, and random forest modeling identified pore water nitrate as a strong predictor of N2O flux. The nirK gene abundance increased while nosZ gene abundance decreased in the highest stocking density group, resulting in an elevated nir/nosZ ratio. Structural equation modeling further indicated that oyster density indirectly increased N2O flux by altering pore water physicochemical properties. Although local environmental conditions modulate N2O fluxes, this study elucidates how stocking density drives N2O emissions via biogeochemistry and microbial pathways, highlighting that managing stocking density is a key consideration for mitigating the climate footprint of aquaculture.