King Ryan S, Richardson Curtis J
Nicholas School of the Environment and Earth Sciences, Duke University, Box 90328, Durham, North Carolina 27708, USA.
Environ Manage. 2003 Jun;31(6):795-809. doi: 10.1007/s00267-002-0036-4.
Ioassessment is used worldwide to monitor aquatic health but is infrequently used with risk-assessment objectives, such as supporting the development of defensible, numerical water-quality criteria. To this end, we present a generalized approach for detecting potential ecological thresholds using assemblage-level attributes and a multimetric index (Index of Biological Integrity-IBI) as endpoints in response to numerical changes in water quality. To illustrate the approach, we used existing macroinvertebrate and surface-water total phosphorus (TP) datasets from an observed P gradient and a P-dosing experiment in wetlands of the south Florida coastal plain nutrient ecoregion. Ten assemblage attributes were identified as potential metrics using the observational data, and five were validated in the experiment. These five core metrics were subjected individually and as an aggregated Nutrient-IBI to nonparametric changepoint analysis (nCPA) to estimate cumulative probabilities of a threshold response to TP. Threshold responses were evident for all metrics and the IBI, and were repeatable through time. Results from the observed gradient indicated that a threshold was > or = 50% probable between 12.6 and 19.4 microg/L TP for individual metrics and 14.8 microg/L TP for the IBI. Results from the P-dosing experiment revealed > or = 50% probability of a response between 11.2 and 13.0 microg/L TP for the metrics and 12.3 microg/L TP for the IBI. Uncertainty analysis indicated a low (typically > or = 5%) probability that an IBI threshold occurred at < or = 10 microg/L TP, while there was > or = 95% certainty that the threshold was < or = 17 microg/L TP. The weight-of-evidence produced from these analyses implies that a TP concentration > 12-15 microg/L is likely to cause degradation of macroinvertebrate assemblage structure and function, a reflection of biological integrity, in the study area. This finding may assist in the development of a numerical water-quality criterion for TP in this ecoregion, and illustrates the utility of bioassessment to environmental decision-making.
生物评估在全球范围内被用于监测水生生物健康状况，但很少用于风险评估目的，比如支持制定合理的数值水质标准。为此，我们提出一种通用方法，利用群落水平属性和多指标指数（生物完整性指数 - IBI）作为响应水质数值变化的终点，来检测潜在的生态阈值。为说明该方法，我们使用了来自南佛罗里达沿海平原营养生态区湿地的现有大型无脊椎动物和地表水总磷（TP）数据集，这些数据来自一个观测到的磷梯度和一个磷添加实验。利用观测数据确定了十个群落属性作为潜在指标，其中五个在实验中得到验证。这五个核心指标分别以及作为综合的营养 - IBI进行非参数变点分析（nCPA），以估计对总磷阈值响应的累积概率。所有指标和IBI都出现了阈值响应，并且随时间具有重复性。观测梯度的结果表明，对于单个指标，总磷在12.6至19.4微克/升之间时阈值出现概率大于或等于50%，对于IBI，总磷阈值为14.8微克/升。磷添加实验的结果显示，对于指标，总磷在11.2至13.0微克/升之间时响应概率大于或等于50%，对于IBI，总磷阈值为12.3微克/升。不确定性分析表明，总磷浓度小于或等于10微克/升时出现IBI阈值的概率较低（通常大于或等于5%），而有大于或等于95%的确定性认为阈值小于或等于17微克/升。这些分析得出的证据权重表明，总磷浓度大于12 - 15微克/升可能会导致研究区域内大型无脊椎动物群落结构和功能退化，这反映了生物完整性。这一发现可能有助于制定该生态区总磷的数值水质标准，并说明了生物评估在环境决策中的实用性。
