Increased supply of ambient nitrogen has minimal effect on salt marsh bacterial production
Increased supply of ambient nitrogen has minimal effect on salt marsh bacterial production
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DOI：
10.4319/lo.2009.54.3.0713
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发表时间：
2009-05-01
影响因子：
4.5
通讯作者：
Hobbie, J. E.
中科院分区：
文献类型：
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作者：
Bowen, J. L.;Crump, B. C.;Hobbie, J. E.
我们通过沼泽施肥实验，研究了长期低水平的营养物富集对异养沼泽细菌生产力的作用。在该实验中，我们通过将整个盐沼富集到大约153个背景营养物浓度，模拟了广泛的沿海富营养化条件。我们测量了在四个盐沼的低沼泽和高沼泽生境中氚化亮氨酸的吸收，作为细菌生产的代理，其中两个富含营养物质。我们假设在这些富含碎屑的系统中添加氮会直接刺激沼泽泥炭的细菌分解。与我们的预期相反，我们发现在高沼泽栖息地添加营养物质没有反应，那里有大量的沼泽植被有机质供应。在低沼泽生境中，细菌产量确实增加了，在那里施肥增加了底栖生物叶绿素的存量。施肥并没有通过提供额外的养分来直接增加细菌的产量，这些养分可以用来分解来自营养贫乏的沼泽草的有机物。相反，低沼泽生境中不稳定的底栖微藻的增加间接刺激了细菌的生产力。因此，盐沼的分解对慢性富营养化的威胁可能具有比以前认识到的更大的复原力。
We examined the role of chronic low-level nutrient enrichment on the productivity of heterotrophic marsh bacteria via a marsh fertilization experiment in which we mimicked the conditions of widespread coastal eutrophication by enriching entire salt marshes to approximately 153 background nutrient concentrations. We measured the uptake of tritiated leucine, as a proxy for bacterial production, in both low and high marsh habitats in four salt marshes, two of which were enriched with nutrients. We hypothesized that adding nitrogen in these detritus-rich systems would directly stimulate bacterial decomposition of marsh peat. Contrary to our expectations, we found no response to added nutrients in high marsh habitats, where there is a significant supply of organic matter from marsh vegetation. Bacterial production did increase in the low marsh habitats, where fertilization increased the standing stock of benthic chlorophyll. Fertilization did not directly increase bacterial production by providing added nutrients that could be used to decompose organic matter derived from nutrient-poor marsh grasses. Rather, bacterial productivity was indirectly stimulated by the concomitant increase in labile benthic microalgae in low marsh habitats. Decomposition of salt marshes may therefore have a greater resilience to the threat of chronic eutrophication than has been previously recognized.