State Key Laboratory of Freshwater Ecology and Biotechnology, Institute of Hydrobiology, Chinese Academy of Sciences, Wuhan 430072, China; National-Regional Joint Engineering Research Center for Soil Pollution Control and Remediation in South China, Guangdong Key Laboratory of Integrated Agro-environmental Pollution Control and Management, Institute of Eco-environmental and Soil Sciences, Guangdong Academy of Sciences, Guangzhou 510650, China.
State Key Laboratory of Freshwater Ecology and Biotechnology, Institute of Hydrobiology, Chinese Academy of Sciences, Wuhan 430072, China; University of Chinese Academy of Sciences, Beijing 100049, China.
Sci Total Environ. 2024 May 20;926:172108. doi: 10.1016/j.scitotenv.2024.172108. Epub 2024 Mar 30.
Global aquaculture production is expected to rise to meet the growing demand for food worldwide, potentially leading to increased anthropogenic greenhouse gases (GHG) emissions. As the demand for fish protein increases, so will stocking density, feeding amounts, and nitrogen loading in aquaculture ponds. However, the impact of GHG emissions and the underlying microbial processes remain poorly understood. This study investigated the GHG emission characteristics, key microbial processes, and environmental drivers underlying GHG emissions in low and high nitrogen loading aquaculture ponds (LNP and HNP). The NO flux in HNP (43.1 ± 11.3 μmol m d) was significantly higher than in LNP (-11.3 ± 25.1 μmol m d), while the dissolved NO concentration in HNP (52.8 ± 7.1 nmol L) was 150 % higher than in LNP (p < 0.01). However, the methane (CH) and carbon dioxide (CO) fluxes and concentrations showed no significant differences (p > 0.05). NO replaced CH as the main source of Global Warming Potential in HNP. Pond sediments acted as a sink for NO but a source for CH and CO. The △NO/(△NO + △N) in HNP (0.015 ± 0.007 %) was 7.7-fold higher than in LNP (0.002 ± 0.001 %) (p < 0.05). The chemical oxygen demand to NO-N ratio was the most important environmental factor explaining the variability of NO fluxes. Ammonia-oxidizing bacteria driven nitrification in water was the predominant NO source, while comammox-driven nitrification and nosZII-driven NO reduction in water were key processes for reducing NO emission in LNP but decreased in HNP. The strong CH oxidization by Methylocystis and CO assimilation by algae resulted in low CH emissions and CO sink in the aquaculture pond. The Mantel test indicated that HNP increased NO fluxes mainly through altering functional genes composition in water and sediment. Our findings suggest that there is a significant underestimation of NO emissions without considering the significantly increased △NO/(△NO + △N) caused by increased nitrogen loading.
全球水产养殖产量预计将上升，以满足全球对食品不断增长的需求，这可能导致人为温室气体（GHG）排放的增加。随着鱼类蛋白需求的增加，养殖池塘的放养密度、投喂量和氮负荷也将增加。然而，GHG 排放的影响及其潜在的微生物过程仍知之甚少。本研究调查了低氮和高氮负荷养殖池塘（LNP 和 HNP）中 GHG 排放的 GHG 排放特征、关键微生物过程和环境驱动因素。HNP 中的硝态氮通量（43.1±11.3 μmol m d）显著高于 LNP（-11.3±25.1 μmol m d），而 HNP 中的溶解态硝态氮浓度（52.8±7.1 nmol L）比 LNP 高 150%（p<0.01）。然而，甲烷（CH）和二氧化碳（CO）通量和浓度没有显著差异（p>0.05）。NO 取代 CH 成为 HNP 中全球变暖潜势的主要来源。池塘沉积物既是 NO 的汇，也是 CH 和 CO 的源。HNP 中的△NO/（△NO+△N）（0.015±0.007%）比 LNP（0.002±0.001%）高 7.7 倍（p<0.05）。NO-N 化学需氧量与 NH4+-N 化学需氧量的比值是解释 NO 通量变化的最重要环境因素。水相氨氧化菌驱动的硝化作用是主要的 NO 来源，而水相 comammox 驱动的硝化作用和 nosZII 驱动的 NO 还原作用是降低 LNP 中 NO 排放的关键过程，但在 HNP 中减少。Methylocystis 强烈氧化 CH 和藻类同化 CO 导致养殖池塘中 CH 排放量低和 CO 汇。Mantel 检验表明，HNP 主要通过改变水和沉积物中的功能基因组成来增加 NO 通量。我们的研究结果表明，如果不考虑氮负荷增加导致的△NO/（△NO+△N）显著增加，NO 排放可能会被严重低估。
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