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首页> 外文期刊>Estuarine Coastal and Shelf Science >Benthic metabolism and nitrogen dynamics in an urbanised tidal creek: Domination of DNRA over denitrification as a nitrate reduction pathway
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Benthic metabolism and nitrogen dynamics in an urbanised tidal creek: Domination of DNRA over denitrification as a nitrate reduction pathway

机译：城市化潮汐小溪中的底栖生物代谢和氮动力学：DNRA在反硝化作用中占主导地位，作为硝酸盐还原途径

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摘要

Benthic oxygen and nutrient fluxes and nitrate reduction rates were determined seasonally under light and dark conditions at three sites in a micro-tidal creek within an urbanised catchment (Saltwater Creek, Australia). It was hypothesized that stormwater inputs of organic matter and inorganic nitrogen would stimulate rates of benthic metabolism and nutrient recycling and preferentially stimulate dissimilatory nitrate reduction to ammonium (DNRA) over denitrification as a pathway for nitrate reduction. Stormwaters greatly influenced water column dissolved inorganic nitrogen (DIN) and suspended solids concentrations with values following a large rainfall event being 5-20-fold greater than during the preceding dry period. Seasonally, maximum and minimum water column total dissolved nitrogen (TDN) and DIN concentrations occurred in the summer (wet) and winter (dry) seasons. Creek sediments were highly heterotrophic throughout the year, and strong sinks for oxygen, and large sources of dissolved organic and inorganic nitrogen during both light and dark incubations, although micro-phytobenthos (MPB) significantly decreased oxygen consumption and N-effluxes during light incubations due to photosynthetic oxygen production and photoassimilation of nutrients. Benthic denitrification rates ranged from 3.5 to 17.7 μmol N m~2 h~(-1), denitrification efficiencies were low (＜1-15%) and denitrification was a minor process compared to DNRA, which accounted for ～75% of total nitrate reduction. Overall, due to the low denitrification efficiencies and high rates of N-regeneration, Saltwater Creek sediments would tend to increase rather than reduce dissolved nutrient loads to the downstream Gold Coast Broadwater and Moreton Bay systems. This may be especially true during wet periods when increased inputs of paniculate organic nitrogen (PON) and suspended solids could respectively enhance rates of N-regeneration and decrease light availability to MPB, reducing their capacity to ameliorate N-effluxes through photoassimilation.
机译：在城市化集水区（Saltwater Creek，澳大利亚）的小潮河中的三个地点，在明暗条件下，季节性确定底栖氧气和养分通量以及硝酸盐还原率。据推测，雨水中有机物和无机氮的输入将刺激底栖生物代谢和养分循环的速率，并优先刺激异化硝酸盐还原为铵（DNRA），而不是反硝化作为硝酸盐还原的途径。暴雨极大地影响了水柱中的溶解性无机氮（DIN）和悬浮固体的浓度，发生大降雨之后的值比前一个干旱时期大5-20倍。季节性地，最大和最小水柱总溶解氮（TDN）和DIN浓度发生在夏季（湿）和冬季（干）。尽管微植物底栖动物（MPB）显着降低了光孵化期间的耗氧量和氮流量，但全年的克里克沉积物都是高度异养的，并且在明亮和黑暗的孵化过程中都大量吸收氧气，并溶解了大量有机和无机氮。光合作用的氧气生产和养分的光吸收。底栖生物的反硝化率在3.5至17.7μmolN m〜2 h〜（-1）之间，与DNRA相比，反硝化效率低（＜1-15％），反硝化是次要的过程，后者占硝酸盐总量的〜75％减少。总体而言，由于反硝化效率低和氮再生率高，咸水克里克沉积物倾向于增加而不是减少下游黄金海岸宽水域和摩顿湾系统的溶解养分负荷。在潮湿时期尤其如此，当增加颗粒状有机氮（PON）和悬浮固体的输入会分别提高N再生速率并降低MPB的光利用率，从而降低它们通过光吸收作用改善N排放的能力时。

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