Measuring the attainment of biological integrity in the USA: a critical element of ecological integrity

The concept of ecological integrity has become a worldwide phenomenon and is firmly entrenched into the regulatory structure of environmental law in the United States of America (USA). The attainment of ecological integrity requires the attainment of its three elements: physical, chemical, and biological integrity. In the USA, measures of chemical integrity were implemented first into monitoring programs and were effective in reducing pollutant loadings to the nation's surface waters. Because biological communities integrate the effects of different stressors such as reduced oxygen, excess nutrients, toxic chemicals, increased temperature, excessive sediment loading, and habitat degradation, the advent of bioassessment in regulatory programs has provided a more comprehensive and effective monitoring and assessment strategy. Measures of biological integrity clearly have become a priority in the USA. The development of biological criteria (biocriteria) within regulatory programs to serve as thresholds by which to judge the attainment of designated aquatic life conditions of surface waters is a major focus of states and Indian tribes within the USA. The derivation of reference conditions for the nation's surface waters (i.e., streams, rivers, lakes, wetlands, estuaries, and marine waters) across different physiographic regions is a critical element in the design of biocriteria and is currently a primary initiative in the USA. Nearly all state water resource agencies have developed bioassessment approaches for streams; 1600 to 75 000 km of streams require assessment in each state. Bioassessment development for other water body types is not as advanced to date. The US Environmental Protection Agency (USEPA) has produced technical guidance for developing effective bioassessment programs; they include crucial elements such as defining objectives, classifying water bodies according to expected biological attributes, deriving the reference condition of the site classes, developing standardized protocols for sampling and data analysis, and implementing a quality assurance plan. Approaches to bioassessment in the USA follow a basic design of incorporating various attributes of the elements and processes of the aquatic community, which is either an aggregation into a multimetric index or a series of multivariate analyses using the attributes as input variables. The Clean Water Act of 1972 and its subsequent amendments mandate maintaining, restoring, and protecting the ecological integrity of surface waters. Through use of robust bioassessments and other measures of ecological integrity, the USA has developed a strategic plan to establish priorities to meet this goal.