Cascading trophic effects on aquatic nitrification: Experimental evidence and potential implications
Cascading trophic effects on aquatic nitrification: Experimental evidence and potential implications
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对水生硝化作用的级联营养效应：实验证据和潜在影响
DOI：
10.3354/ame013161
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发表时间：
1997
影响因子：
1.4
通讯作者：
J. Johnson
中科院分区：
文献类型：
--
作者：
P. Lavrentyev;Wayne S Gardner;J. Johnson
使用从休伦湖萨吉诺湾（美国）富营养化地点和伊利湖南部（美国）富营养化湿地收集的天然浮游生物进行实验，以检验食菌可以控制水生硝化速率的假设。这些实验中氮和原生生物的动态揭示了一个一致的模式：由于NH氧化而导致硝酸盐浓度增加，总是伴随着食菌纳米浮游生物种群的崩溃。反过来，这种崩溃是由较大的纤毛虫和后生浮游生物的捕食压力引起的。使用维持在接近环境浓度的 NH 的富集分批培养物进行的实验表明，食菌原生生物可以通过减少细菌数量直接抑制硝化作用，并通过促进细菌聚集间接抑制硝化作用。后面的实验还表明微生物食草动物的进食策略，例如悬浮喂养的 Spumella sp.与表面进食的博多盐沼相比，可能决定它们的放牧对硝化菌的影响。最后，萨吉诺湾天然浮游生物群对荧光标记硝化细菌（FLNB）的摄入率表明，纳米鞭毛虫能够有效捕食低浓度的 FLNB。我们的研究表明，以前被忽视的营养因子可能对调节远洋环境中的硝化速率具有潜在的重要性。
Experiments, using natural plankton collected from a eutrophic site in Saginaw Bay, Lake Huron (USA) and from a hypereutrophic wetland of southern Lake Erie (USA), were conducted to test the hypothesis that bacterivory can control aquatic nitnfication rates. The dynamics of nitrogen and protists in these experiments revealed a consistent pattern: an increase in concentrations of nitrates due to oxidation of NH,' always followed the collapse of bacterivorous nanoplankton populations. This collapse was, in turn, caused by predation pressure of larger ciliates and metazooplankton. Experiments, using enrichment batch cultures maintained at near-ambient concentrations of NH,', indicated that bacterivorous protists can inhibit nitnfication directly by reducing bacterial numbers and indirectly by promoting bacterial aggregation. The latter experiments also suggest that feeding strategies of microbial grazers, e.g. suspension-feeding Spumella sp. versus surface-feeding Bodo saltans, may determine their grazing impacts on nitrifiers. Finally, ingestion rates of fluorescently labeled nitrifying bacteria (FLNB) by the natural planktonic assemblage from Saginaw Bay demonstrated that nanoflagellates were able to efficiently prey on low concentrations of FLNB. Our study suggests that previously neglected trophic factors may be of potential importance for mediating nitrification rates in the pelagic environment.