Koriyama M, Koga A, Seguchi M, Ishitani T
Organization for General Education, Saga University, 1 Honjo-machi, Saga, 840-8502, Japan.
Marine Biological Research Institute of Japan Co., Ltd., 1-7-7 Shinagawa-ku, Tokyo, 141-0033, Japan.
Environ Monit Assess. 2016 Feb;188(2):96. doi: 10.1007/s10661-016-5101-1. Epub 2016 Jan 16.
To investigate the seasonal variation of denitrification rate (DR) and clarify the controlling factors of denitrification in the mudflat sediments of Ariake Bay, we conducted field surveys biweekly each month from April 2006 to January 2008. NH4(+)-N porewater concentration increased from summer to autumn due to the organic material mineralization under higher sediment temperatures. The seasonal pattern of NH4 (+)-N flux between sediments and overlying water interface indicated that the mudflat sediments were a source of NH4(+)-N in summer. NO3(-)+NO2(-)-N porewater concentrations were low, ranging from 0.53 to 11.46 μM, and mudflat sediments were sinks of NO3(-)+NO2(-)-N throughout the year. The mean number of denitrifiers tended to increase in July-September (2188-75,057 MPN g(-1)) and to decrease in March-May (500-3740 MPN g(-1)). DR tended to increase in summer, ranging from 76.03 to 990.21 μmol m(-2) day(-1), and to decrease in winter, ranging from 25.01 to 206.07 μmol m(-2) day(-1). There was no significant correlation between DR and denitrifier number. Environmental factors influencing DR during the investigation period were determined by multiple regression analysis with the stepwise method. The results indicated that NO3(-)+NO2(-)-N flux was an important factor in denitrification of mudflat sediments in Ariake Bay. Denitrification was depended on nitrate diffusing from overlying water into sediments under reduced sediment conditions during summer-mid-autumn. On the other hand, in late autumn-winter at Eh>+200 mV and sediment temperature >10 °C, nitrate produced by sediment nitrification was thought to be denitrified subsequently; that is, the coupled nitrification-denitrification may have taken place in the upper layer of mudflat sediments.
为了研究有明湾滩涂沉积物中反硝化速率（DR）的季节变化并阐明反硝化作用的控制因素，我们于2006年4月至2008年1月每月每两周进行一次实地调查。由于在较高沉积物温度下有机物质的矿化作用，NH4(+)-N孔隙水浓度从夏季到秋季增加。沉积物与上覆水界面之间NH4(+)-N通量的季节模式表明，滩涂沉积物在夏季是NH4(+)-N的来源。NO3(-)+NO2(-)-N孔隙水浓度较低，范围为0.53至11.46 μM，滩涂沉积物全年都是NO3(-)+NO2(-)-N的汇。反硝化细菌的平均数量在7月至9月趋于增加（2188 - 75,057 MPN g(-1)），在3月至5月趋于减少（500 - 3740 MPN g(-1)）。DR在夏季趋于增加（范围为76.03至990.21 μmol m(-2) day(-1)），在冬季趋于减少（范围为25.01至206.07 μmol m(-2) day(-1)）。DR与反硝化细菌数量之间没有显著相关性。在调查期间，通过逐步多元回归分析确定了影响DR的环境因素。结果表明，NO3(-)+NO2(-)-N通量是有明湾滩涂沉积物反硝化作用的一个重要因素。反硝化作用在夏末秋初期间，依赖于在沉积物还原条件下从覆盖水扩散到沉积物中的硝酸盐。另一方面，在深秋至冬季，当Eh > +200 mV且沉积物温度 > 10 °C时，沉积物硝化作用产生的硝酸盐随后被认为发生了反硝化作用；也就是说，在滩涂沉积物的上层可能发生了耦合硝化 - 反硝化作用。
