Rivanna Conservation Alliance, Charlottesville, VA, USA.
Trout Unlimited, Klamath Falls, OR, USA.
Environ Monit Assess. 2021 Nov 3;193(12):765. doi: 10.1007/s10661-021-09556-3.
Benthic macroinvertebrate community assessments are used commonly to characterize aquatic systems and increasingly for identifying their impairment caused by myriad stressors. Yet sampling and enumeration methods vary, and research is needed to compare their abilities to detect macroinvertebrate community responses to specific water quality variables. A common assessment method, rapid bioassessment, uses subsampling procedures to identify a fixed number of individual organisms regardless of total sample abundance. In contrast, full-enumeration assessments typically allow for expanded community characterization resulting from higher numbers of identified organisms within a collected sample. Here, we compared these two sampling and enumeration methods and their abilities to detect benthic macroinvertebrate response to freshwater salinization, a common stressor of streams worldwide. We applied both methods in headwater streams along a salinity gradient within the coal-mining region of central Appalachia USA. Metrics of taxonomic richness, community composition, and trophic function differed between the methods, yet most metrics exhibiting significant response to SC for full-enumeration samples also did for rapid bioassessment samples. However, full-enumeration yielded taxonomic-based metrics consistently more responsive to the salinization gradient. Full-enumeration assessments may potentially provide more complete characterization of macroinvertebrate communities and their response to increased salinization, whereas the more cost-effective and widely employed rapid bioassessment method can detect community alterations along the full salinity gradient. These findings can inform decisions regarding such tradeoffs for assessments of freshwater salinization in headwater streams and highlight the need for similar research of sampling and enumeration methodology in other aquatic systems and for other stressors.
底栖大型无脊椎动物群落评估通常用于描述水生系统，并越来越多地用于识别由众多胁迫因素造成的水生系统损害。然而，采样和计数方法各不相同，需要进行研究来比较这些方法检测底栖大型无脊椎动物群落对特定水质变量的响应能力。一种常见的评估方法，即快速生物评估，使用抽样程序来识别固定数量的个体生物，而不管总样本丰度如何。相比之下，全计数评估通常允许对更大数量的已识别生物进行扩展的群落特征描述，这是在采集样本中实现的。在这里，我们比较了这两种采样和计数方法及其检测底栖大型无脊椎动物对淡水盐度变化响应的能力，淡水盐度变化是全球溪流的一种常见胁迫因素。我们在美国阿巴拉契亚中部煤炭开采区的一条沿盐度梯度的源头溪流中应用了这两种方法。分类丰富度、群落组成和营养功能的指标在两种方法之间存在差异，但大多数对全计数样本的 SC 表现出显著响应的指标也对快速生物评估样本表现出显著响应。然而，全计数法产生的基于分类的指标对盐度梯度的响应更为一致。全计数评估法可能能够更全面地描述大型无脊椎动物群落及其对盐度增加的响应，而成本效益更高、应用广泛的快速生物评估法则可以在整个盐度梯度上检测到群落变化。这些发现可以为评估源头溪流淡水盐度变化时的这些权衡提供信息，并强调在其他水生系统和其他胁迫因素下需要对采样和计数方法进行类似的研究。
