俄勒冈州亚奎纳湾（Yaquina Bay）——一个北太平洋温带河口的反硝化率。
Denitrification rates across a temperate North Pacific estuary, Yaquina Bay, Oregon.
作者信息
Sigleo A C
机构信息
Western Ecology Division, US Environmental Protection Agency, 2111 SE Marine Science Drive, Newport, Oregon 97365-5260, USA.
出版信息
Estuaries Coast. 2019;42(3):655-664. doi: 10.1007/s12237-019-00516-2.
The extent and temporal variability of denitrification activity was measured in Yaquina Bay, Oregon, over a year using sediment cores collected approximately monthly from August 2003 through August 31, 2004. Denitrification rates in sediments from a marine-dominated intertidal sand flat near the mouth of the estuary averaged 0.181 ±0.114 mmol m d whereas sediments in the estuary (5 stations) and river averaged 0.626 ±0.141 mmol m d. Sediment cores from all estuarine sites indicated denitrification activity throughout the year and were within the values reported for other temperate estuaries. Denitrification rates decreased with depth from 0.4 mmol m d in the upper 2 to 5 cm of sediment to 0.006 mmol m d at 28 cm sediment depth, indicating denitrification occurred primarily in the upper 5 cm. There was no relationship between denitrification rate and nitrate concentrations in the overlying water column (r = 0.16). Denitrification rates were lowest in areas with low sediment carbon content, particularly in the sandy intertidal areas at the mouth of the estuary (r = 0.78). The results suggest that denitrification rates in this estuary were influenced primarily by the availability of organic carbon. The amount of nitrogen removed by denitrification was estimated to be 8.7 percent of the annual Yaquina River load for August 2003 through August 2004. The relatively low percent lost via denitrification may be due to high river discharge when the nitrogen load was greatest during winter storm events and dissolved nitrogen was exported directly from the estuary into the Pacific Ocean. Stable isotopes were used to investigate the carbon source. The carbon isotope data increased from -27 δC in the freshwater river to -21.5 δC at the seawater site, reflecting a typical change from terrestrial plant vegetation to phytoplankton carbon sources. Similar values for δC between suspended and benthic sediments indicated resuspension and mixing occurred during tidal inflow.
2003年8月至2004年8月31日期间，大约每月从俄勒冈州的亚奎纳湾采集沉积物岩芯，对该区域反硝化作用的范围和时间变化进行了为期一年的测量。河口附近以海洋为主的潮间带沙滩沉积物中的反硝化速率平均为0.181±0.114 mmol m⁻² d⁻¹，而河口（5个站点）和河流中的沉积物平均为0.626±0.141 mmol m⁻² d⁻¹。所有河口站点的沉积物岩芯显示全年都有反硝化活动，且在其他温带河口报道的值范围内。反硝化速率随深度降低，从沉积物上部2至5厘米处的0.4 mmol m⁻² d⁻¹降至沉积物深度28厘米处的0.006 mmol m⁻² d⁻¹，表明反硝化主要发生在上部5厘米。反硝化速率与上覆水柱中的硝酸盐浓度之间没有关系（r = 0.16）。在沉积物碳含量低的区域，特别是河口口的砂质潮间带区域，反硝化速率最低（r = 0.78）。结果表明，该河口的反硝化速率主要受有机碳可用性的影响。2003年8月至2004年8月期间，通过反硝化作用去除的氮量估计为亚奎纳河年负荷的8.7%。通过反硝化作用损失的比例相对较低，可能是由于冬季风暴事件期间氮负荷最大时河流流量大，溶解态氮直接从河口排入太平洋。使用稳定同位素研究碳源。碳同位素数据从淡水河流中的-27‰δC增加到海水站点的-21.5‰δC，反映了从陆地植物植被碳源到浮游植物碳源的典型变化。悬浮沉积物和底栖沉积物之间相似的δC值表明在涨潮期间发生了再悬浮和混合。
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