When Nutrients Become Contaminants in Aquatic Systems: Identifying Responses to Guide Terrestrial-Derived Detrital Endpoint Development for Managers

Abstract

This chapter evaluates the case for inclusion of terrestrial-derived detrital endpoints, which are those metrics that describe changes to detrital pathways in freshwater ecosystems, into the regulatory framework for US wadeable streams. Terrestrial detritus consisting of dead plant and animal matter is an important resource subsidy to forested-aquatic stream ecosystems, and detrital form and function can be negatively modified by elevated nutrient and salt contaminants in aquatic ecosystems. Of concern to regulators, a large proportion of US wadeable streams with poor water quality and biological condition due to nutrient and salt contamination occur in temperate-forested biomes where detritus is essential for aquatic life. This chapter reviews existing US water quality endpoint response characteristics and proposes a suite of endpoints derived from a literature review that can be used to detect changes in detrital-based wadeable streams caused by elevated nutrient and salt contaminants. These detrital endpoints may serve as sentinels of impending species loss and better allow managers to detect and prevent changes to critical ecosystem functions. Furthermore, this review illustrates how research on contaminants and ecological subsidies in linked aquatic-terrestrial ecosystems can be used to inform management of these ecosystems.