长江河口水体暗碳固定的温度适应性

Temperature adaptability of dark carbon fixation in seawater from the Yangtze River Estuary

为了明确全球增温如何影响富营养化河口中基于碳氮耦合过程产生的暗碳固定,以长江河口作为典型研究区域,分别在河口近岸和近海不同盐度区域设置采样断面,利用14C(NaH14CO3)标记方法结合烯丙基硫脲(allylthiourea,ATU)抑制剂法,对不同温度和氮营养盐添加条件下的水体总暗碳固定(dark carbon fixation,DCF)和由氨氧化微生物驱动的暗碳固定(DCFAOB)速率进行了研究.结果表明,长江河口水体中的DCF速率介于0.23~0.33µmolC·L^(-1)·d^(-1)之间,其中氨氧化微生物驱动的暗碳固定约占总暗碳固定的4.13%~43.61%.在最适温度范围内,水体中的DCF速率随着环境温度的增加而显著上升,但整体上低盐度条件下DCF速率受环境温度的影响更明显.此外,低盐度和高盐度水体的DCF速率最大值分别出现在30℃和25℃,在该温度条件下添加氨氮可明显促进水体DCF速率的增加.研究结果揭示了河口水体暗碳固定对环境温度变化的响应过程,能够为全面认识和科学评估河口生态系统碳固定与碳汇通量提供理论支持与数据参考.

To clarify the effects of global warming on dark carbon fixation(DCF)in eutrophic estuaries,the rates of total DCF and DCF driven by ammonia-oxidizing microorganisms(DCFAOB)were studied under various water temperatures and nitrogen concentrations using 14C labeling(NaH14CO3)and the allylthiourea(ATU)inhibitor method.The Yangtze River Estuary was used as a study area and sampling locations were set up in the estuary and offshore locations.The DCF rates in the Yangtze River Estuary ranged from 0.23 to 0.33µmolC·L^(-1)·d^(-1) and that DCFAOB rates accounted for 4.13%to 43.61%of the DCF.Although DCF rates increase significantly under optimum temperatures,the increase was more obvious with changes in ambient temperature under low salinity.The optimum temperatures for DCF in areas of low and high salinity were found to be 30℃and 25℃,respectively,with the addition of ammonia-nitrogen at these conditions significantly increasing the DCF rates.The results of this study reveal how dark carbon fixation in estuarine water can change when subjected to environmental temperature changes,thereby providing theoretical support and data references to aid in the comprehensive understanding and scientific assessment of carbon fixation and carbon sink flux in estuarine ecosystems.