Spatial, temporal, and experimental: three study design cornerstones for establishing defensible numeric criteria in freshwater ecosystems

1.Nutrient over‐enrichment increasingly threatens global water resources. Stressor‐response studies specifically designed to identify levels of nutrients strongly associated with undesirable ecological conditions are needed to inform numeric nutrient criteria that protect inland waters.

2.Diatoms are important components of aquatic life, which support higher trophic levels and are sensitive to nutrient enrichment. We tested a framework that relies on stressor‐response modelling of phosphorus (P) enrichment and stream diatom assemblages across many field locations, multiple years and seasons within years, and under controlled experimental conditions to inform nutrient criteria development.

3.Diatom species composition was nonlinearly correlated with total phosphorus (TP) throughout the two‐year field study. This occurred despite temporal shifts in species composition between two hydrologically distinct years and over eight seasons.

4.Species assemblages on rocks transplanted fro...