Temporally intensive observations of sediment biogeochemical fluxes were used to examine the effects of water column oxygen depletion and associated loss of sediment bioirrigation on denitrification rates. In the tidal Choptank River, a subestuary of the Chesapeake Bay, coupled nitrification/denitrification was identified as the main pathway for the production of N2 gas in the sediment. Although denitrification rates were stimulated by high rates of bioirrigation, the overall efficiency of the process sharply declined as temperature increased and bottom water O2 declined. Consequently, there was a transition from nitrogen remineralization resulting in N2 gas production in winter to complete recycling of remineralized NH4+ back to the water column in summer. Bioirrigation rate estimates using a bromide tracer showed the same pattern as those derived from combining diffusive pore water O2 fluxes with intact core incubations. These bioirrigation estimates were consistent with peak abundance of small spionid polychaetes in early spring with populations declining sharply into summer. Following deposition of the spring algal bloom, bioirrigation was more important than diffusive oxygen transport, increasing the depth of habitat for microbial denitrification. Low bottom water oxygen (~ 3 mg L−1) in summer was accompanied with a loss of bioirrigation and very low denitrification efficiency. Denitrification efficiency was shown to be sensitive to bottom water oxygen concentrations even in the absence of hypoxia or anoxia.

中文翻译：

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生物灌溉河口沉积物中反硝化作用的时间增强

沉积物生物地球化学通量的时间密集观测被用于检查水体氧耗竭和沉积物生物灌溉相关损失对反硝化率的影响。在潮汐 Choptank 河（切萨皮克湾的一个亚河口）中，耦合硝化/反硝化被确定为沉积物中产生 N2 气体的主要途径。尽管高速率生物灌溉刺激了反硝化速率，但随着温度升高和底部水 O2 下降，该过程的整体效率急剧下降。因此，从冬季产生 N2 气的氮气再矿化过渡到夏季将再矿化的 NH4+ 完全循环回水体。使用溴化物示踪剂估算的生物灌溉速率显示出与通过将扩散孔隙水 O2 通量与完整核心孵化相结合而得出的模式相同的模式。这些生物灌溉估计值与早春的小型棘皮多毛类动物的峰值丰度一致，进入夏季时种群数量急剧下降。在春季藻华沉积之后，生物灌溉比扩散氧运输更重要，增加了微生物反硝化的栖息地深度。夏季低底水氧（~ 3 mg L-1）伴随着生物灌溉的损失和非常低的反硝化效率。即使在没有缺氧或缺氧的情况下，反硝化效率也对底水氧浓度敏感。这些生物灌溉估计值与早春的小型棘皮多毛类动物的峰值丰度一致，进入夏季时种群数量急剧下降。在春季藻华沉积之后，生物灌溉比扩散氧运输更重要，增加了微生物反硝化的栖息地深度。夏季低底水氧（~ 3 mg L-1）伴随着生物灌溉的损失和非常低的反硝化效率。即使在没有缺氧或缺氧的情况下，反硝化效率也对底水氧浓度敏感。这些生物灌溉估计值与早春的小型棘皮多毛类动物的峰值丰度一致，进入夏季时种群数量急剧下降。在春季藻华沉积之后，生物灌溉比扩散氧运输更重要，增加了微生物反硝化的栖息地深度。夏季低底水氧（~ 3 mg L-1）伴随着生物灌溉的损失和非常低的反硝化效率。即使在没有缺氧或缺氧的情况下，反硝化效率也对底水氧浓度敏感。生物灌溉比扩散氧运输更重要，增加了微生物反硝化的栖息地深度。夏季低底水氧（~ 3 mg L-1）伴随着生物灌溉的损失和非常低的反硝化效率。即使在没有缺氧或缺氧的情况下，反硝化效率也对底水氧浓度敏感。生物灌溉比扩散氧运输更重要，增加了微生物反硝化的栖息地深度。夏季低底水氧（~ 3 mg L-1）伴随着生物灌溉的损失和非常低的反硝化效率。即使在没有缺氧或缺氧的情况下，反硝化效率也对底水氧浓度敏感。