Davies Susan P, Jackson Susan K
Maine Department of Environmental Protection, State House Station 17, Augusta 04333, USA.
Ecol Appl. 2006 Aug;16(4):1251-66. doi: 10.1890/1051-0761(2006)016[1251:tbcgad]2.0.co;2.
The United States Clean Water Act (CWA; 1972, and as amended, U.S. Code title 33, sections 1251-1387) provides the long-term, national objective to "restore and maintain the ... biological integrity of the Nation's waters" (section 1251). However, the Act does not define the ecological components, or attributes, that constitute biological integrity nor does it recommend scientific methods to measure the condition of aquatic biota. One way to define biological integrity was described over 25 years ago as a balanced, integrated, adaptive system. Since then a variety of different methods and indices have been designed and applied by each state to quantify the biological condition of their waters. Because states in the United States use different methods to determine biological condition, it is currently difficult to determine if conditions vary across states or to combine state assessments to develop regional or national assessments. A nationally applicable model that allows biological condition to be interpreted independently of assessment methods will greatly assist the efforts of environmental practitioners in the United States to (1) assess aquatic resources more uniformly and directly and (2) communicate more clearly to the public both the current status of aquatic resources and their potential for restoration. To address this need, we propose a descriptive model, the Biological Condition Gradient (BCG) that describes how 10 ecological attributes change in response to increasing levels of stressors. We divide this gradient of biological condition into six tiers useful to water quality scientists and managers. The model was tested by determining how consistently a regionally diverse group of biologists assigned samples of macroinvertebrates or fish to the six tiers. Thirty-three macroinvertebrate biologists concurred in 81% of their 54 assignments. Eleven fish biologists concurred in 74% of their 58 assignments. These results support our contention that the BCG represents aspects of biological condition common to existing assessment methods. We believe the model is consistent with ecological theory and will provide a means to make more consistent, ecologically relevant interpretations of the response of aquatic biota to stressors and to better communicate this information to the public.
美国《清洁水法》（《联邦水污染控制法》；1972年，经修订后编入美国法典第33编，第1251 - 1387节）规定了长期的国家目标，即“恢复和维护国家水体的……生物完整性”（第1251节）。然而，该法案并未界定构成生物完整性的生态组成部分或属性，也未推荐用于衡量水生生物群落状况的科学方法。25多年前曾有一种界定生物完整性的方式，将其描述为一个平衡、综合、适应性的系统。从那时起，美国各州设计并应用了各种不同的方法和指标来量化其水体的生物状况。由于美国各州使用不同的方法来确定生物状况，目前很难确定各州之间的状况是否存在差异，或者将各州的评估结果汇总起来进行区域或全国性评估。一个全国适用的模型，能够独立于评估方法来解读生物状况，将极大地帮助美国的环境从业者开展以下工作：（1）更统一、直接地评估水生资源；（2）更清晰地向公众传达水生资源的当前状况及其恢复潜力。为满足这一需求，我们提出了一个描述性模型——生物状况梯度（BCG），该模型描述了10种生态属性如何随着压力源水平的增加而变化。我们将这个生物状况梯度划分为六个层级，对水质科学家和管理人员很有用。通过确定一组来自不同地区的生物学家将大型无脊椎动物或鱼类样本归入这六个层级的一致性程度，对该模型进行了测试。33位大型无脊椎动物生物学家在54次分类中有81%的一致性。11位鱼类生物学家在58次分类中有74%的一致性。这些结果支持了我们的观点，即BCG代表了现有评估方法中生物状况的共同方面。我们认为该模型与生态理论一致，将提供一种手段，以便对水生生物群落对压力源的反应做出更一致、与生态相关的解读，并更好地向公众传达这些信息。
