Office of Research and Development, US Environmental Protection Agency, 26 W. Martin Luther King Dr., Mail Stop 591, Cincinnati, OH, 45268, USA,
Environ Monit Assess. 2014 Feb;186(2):949-59. doi: 10.1007/s10661-013-3426-6. Epub 2013 Oct 1.
Benthic macroinvertebrates are sampled in streams and rivers as one of the assessment elements of the US Environmental Protection Agency's National Rivers and Streams Assessment. In a 2006 report, the recommendation was made that different yet comparable methods be evaluated for different types of streams (e.g., low gradient vs. high gradient). Consequently, a research element was added to the 2008-2009 National Rivers and Streams Assessment to conduct a side-by-side comparison of the standard macroinvertebrate sampling method with an alternate method specifically designed for low-gradient wadeable streams and rivers that focused more on stream edge habitat. Samples were collected using each method at 525 sites in five of nine aggregate ecoregions located in the conterminous USA. Methods were compared using the benthic macroinvertebrate multimetric index developed for the 2006 Wadeable Streams Assessment. Statistical analysis did not reveal any trends that would suggest the overall assessment of low-gradient streams on a regional or national scale would change if the alternate method was used rather than the standard sampling method, regardless of the gradient cutoff used to define low-gradient streams. Based on these results, the National Rivers and Streams Survey should continue to use the standard field method for sampling all streams.
底栖大型无脊椎动物是美国环境保护署国家河流和溪流评估的评估要素之一，在溪流和河流中进行采样。在 2006 年的一份报告中，建议针对不同类型的溪流（例如低梯度与高梯度）评估不同但可比较的方法。因此，在 2008-2009 年国家河流和溪流评估中增加了一个研究内容，对标准底栖大型无脊椎动物采样方法与专门为低梯度可涉溪流和河流设计的替代方法进行了并列比较，该替代方法更侧重于溪流边缘生境。在位于美国大陆的 9 个综合生态区中的 5 个中，在 525 个地点使用每种方法采集样本。使用为 2006 年可涉溪流评估开发的底栖大型无脊椎动物多指标指数对方法进行比较。统计分析并未显示出任何趋势表明，如果使用替代方法而不是标准采样方法，无论用于定义低梯度溪流的梯度截止值如何，区域或国家尺度上对低梯度溪流的总体评估会发生变化。基于这些结果，国家河流和溪流调查应继续使用标准野外方法对所有溪流进行采样。
