Department of Entomology, College of Agriculture and Life Sciences, Virginia Tech University, 216 Price Hall, Blacksburg, VA 24061, USA.
Environ Monit Assess. 2010 Feb;161(1-4):517-30. doi: 10.1007/s10661-009-0765-4. Epub 2009 Feb 28.
Investigating relationships of benthic invertebrates and sedimentation is challenging because fine sediments act as both natural habitat and potential pollutant at excessive levels. Determining benthic invertebrate sensitivity to sedimentation in forested headwater streams comprised of extreme spatial heterogeneity is even more challenging, especially when associated with a background of historical and intense watershed disturbances that contributed unknown amounts of fine sediments to stream channels. This scenario exists in the Chattahoochee National Forest where such historical timber harvests and contemporary land-uses associated with recreation have potentially affected the biological integrity of headwater streams. In this study, we investigated relationships of sedimentation and the macroinvertebrate assemblages among 14 headwater streams in the forest by assigning 30, 100-m reaches to low, medium, or high sedimentation categories. Only one of 17 assemblage metrics (percent clingers) varied significantly across these categories. This finding has important implications for biological assessments by showing streams impaired physically by sedimentation may not be impaired biologically, at least using traditional approaches. A subsequent multivariate cluster analysis and indicator species analysis were used to further investigate biological patterns independent of sedimentation categories. Evaluating the distribution of sedimentation categories among biological reach clusters showed both within-stream variability in reach-scale sedimentation and sedimentation categories generally variable within clusters, reflecting the overall physical heterogeneity of these headwater environments. Furthermore, relationships of individual sedimentation variables and metrics across the biological cluster groups were weak, suggesting these measures of sedimentation are poor predictors of macroinvertebrate assemblage structure when using a systematic longitudinal sampling design. Further investigations of invertebrate sensitivity to sedimentation may benefit from assessments of sedimentation impacts at different spatial scales, determining compromised physical habitat integrity of specific taxa and developing alternative streambed measures for quantifying sedimentation.
研究底栖无脊椎动物与沉降物之间的关系具有挑战性，因为细沉积物既是自然栖息地，又是在过量水平下的潜在污染物。在由极端空间异质性组成的森林集水区中，确定底栖无脊椎动物对沉降物的敏感性更加困难，特别是当与历史和强烈的流域干扰相关联时，这些干扰会向溪流输送未知数量的细沉积物。这种情况存在于 Chattahoochee 国家森林中，在那里，历史上的木材采伐和与娱乐相关的当代土地利用可能已经影响了源头溪流的生物完整性。在这项研究中，我们通过将 30 个、100 米的河段分配到低、中或高沉降类别，调查了森林中 14 条源头溪流的沉降物和大型无脊椎动物组合之间的关系。在这些类别中，只有 17 个组合指标中的一个（附着百分比）有显著差异。这一发现对生物评估具有重要意义，表明受到沉降物物理影响的溪流可能没有受到生物影响，至少使用传统方法是这样。随后进行了多元聚类分析和指示物种分析，以进一步调查不受沉降类别影响的生物模式。评估沉降类别在生物河段聚类中的分布情况表明，在河段尺度上存在内部水流的变异性，并且在聚类中通常存在沉降类别变化，反映了这些源头环境的整体物理异质性。此外，单个沉降变量和指标在生物聚类组中的分布关系较弱，这表明在使用系统纵向采样设计时，这些沉降措施是底栖无脊椎动物组合结构的不良预测指标。进一步研究无脊椎动物对沉降物的敏感性可能受益于评估不同空间尺度上的沉降物影响，确定特定类别的物理栖息地完整性受损情况，并开发替代的河床措施来量化沉降物。
