Multimetric approach for ecological integrity assessment: conceptual foundations and applications.

Abstract

The use of multimetric indices (MMIs) to assess ecological conditions in aquatic environments has been applied globally. These indices are practical tools that incorporate various biotic metrics at different levels of biological organization. However, criticism has been directed to the use of MMIs, especially regarding the methodological criteria applied in the process such as related to metric selection and scoring and identification of reference conditions that consider all sources of ecological integrity disturbance. A review of the scientific literature was carried out to evaluate processes of creation and validation of MMIs worldwide. The criteria used by scientists to identify reference conditions, metric selection and scoring, the main metrics globally used in MMIs, and the challenges in applying these indices were verified. It was identified whether nonnative species have been considered as a source of degradation of ecological integrity in the MMIs application. The results indicated that there are no common criteria for determining reference conditions, for metric selection and scoring, which makes it difficult to compare different programs and regions, and to develop or improve future MMIs. The results showed that metrics related to species richness were most frequently used in MMIs applied worldwide, thus, it represents a consistent response pattern in the assessment of ecological conditions. The results also indicate that differentiating natural variability from anthropogenic impacts was evidenced as the major challenge in the MMIs creation and application. The review of the scientific literature indicated that biological invasions are neglected in ecological integrity assessments, as nonnative species are rarely considered as a disturbing factor in identifying reference conditions and species origin metrics are not widely used in MMIs. The results presented in this review may promote the advancement and improvement of MMIs as bioassessment tools.