Cao Yiping, Green Peter G, Holden Patricia A
Donald Bren School of Environmental Science and Management, University of California, Santa Barbara, CA 93106-5131, USA.
Appl Environ Microbiol. 2008 Dec;74(24):7585-95. doi: 10.1128/AEM.01221-08. Epub 2008 Oct 31.
Denitrifying microbial communities and denitrification in salt marsh sediments may be affected by many factors, including environmental conditions, nutrient availability, and levels of pollutants. The objective of this study was to examine how microbial community composition and denitrification enzyme activities (DEA) at a California salt marsh with high nutrient loading vary with such factors. Sediments were sampled from three elevations, each with different inundation and vegetation patterns, across 12 stations representing various salinity and nutrient conditions. Analyses included determination of cell abundance, total and denitrifier community compositions (by terminal restriction fragment length polymorphism), DEA, nutrients, and eluted metals. Total bacterial (16S rRNA) and denitrifier (nirS) community compositions and DEA were analyzed for their relationships to environmental variables and metal concentrations via multivariate direct gradient and regression analyses, respectively. Community composition and DEA were highly variable within the dynamic salt marsh system, but each was strongly affected by elevation (i.e., degree of inundation) and carbon content as well as by selected metals. Carbon content was highly related to elevation, and the relationships between DEA and carbon content were found to be elevation specific when evaluated across the entire marsh. There were also lateral gradients in the marsh, as evidenced by an even stronger association between community composition and elevation for a marsh subsystem. Lastly, though correlated with similar environmental factors and selected metals, denitrifier community composition and function appeared uncoupled in the marsh.
盐沼沉积物中的反硝化微生物群落和反硝化作用可能受到许多因素的影响，包括环境条件、养分有效性和污染物水平。本研究的目的是考察在一个营养负荷高的加利福尼亚盐沼中，微生物群落组成和反硝化酶活性（DEA）如何随这些因素而变化。在代表不同盐度和养分条件的12个站点，从三个海拔高度采集沉积物样本，每个海拔高度具有不同的淹没和植被模式。分析内容包括细胞丰度、总群落和反硝化菌群落组成（通过末端限制性片段长度多态性分析）、DEA、养分和洗脱金属。通过多变量直接梯度分析和回归分析，分别分析了总细菌（16S rRNA）和反硝化菌（nirS）群落组成以及DEA与环境变量和金属浓度之间的关系。在动态的盐沼系统中，群落组成和DEA变化很大，但二者均受到海拔高度（即淹没程度）、碳含量以及特定金属的强烈影响。碳含量与海拔高度高度相关，在对整个盐沼进行评估时，发现DEA与碳含量之间的关系具有海拔特异性。盐沼中也存在横向梯度，这在一个盐沼子系统中群落组成与海拔高度之间更强的关联中得到了证明。最后，尽管反硝化菌群落组成和功能与相似的环境因素和特定金属相关，但在盐沼中它们似乎是解耦的。
