Calibrating Predicted Mixture Toxic Pressure to Observed Biodiversity Loss in Aquatic Ecosystems

Area of Science:

• Environmental Chemistry
• Ecotoxicology
• Biodiversity Science

Background:

• Assessing chemical pollution's impact on biodiversity typically relies on laboratory toxicity tests for species sensitivity.
• A metric exists to quantify the toxic pressure of chemical mixtures on aquatic organisms using data from ~12,000 chemicals.
• A critical gap is the lack of calibration between this lab-based metric and observed biodiversity effects in natural environments.

Purpose of the Study:

• To bridge the gap between laboratory-derived chemical toxicity metrics and real-world biodiversity impacts.
• To calibrate a lab-based metric of toxic pressure with field-observed biodiversity changes.
• To establish a reliable method for assessing chemical mixture impacts on aquatic ecosystems.

Main Methods:

• Quantified mixture toxic pressure using water quality monitoring data from 1286 sites, expressed as multi-substance potentially affected fraction of species (msPAF).
• Quantified species abundance and richness loss at these same sites.
• Calibrated msPAF with observed biodiversity loss to derive a new biodiversity impact metric.

Main Results:

• A direct relationship was established between msPAF and the potentially disappeared fraction of species (PDF).
• Species abundance and richness showed a general decline with increasing toxic pressure.
• A near 1:1 relationship was derived between the potentially affected fraction of species (PAF) and the potentially disappeared fraction of species (PDF).

Conclusions:

• The lab-based mixture toxic pressure metric (msPAF) can be interpreted in terms of species loss in field conditions.
• "Safe" regulatory concentrations may not adequately protect all exposed species assemblages.
• Biodiversity impact assessments can be reliably conducted using mixture toxic pressure metrics, supporting a safer chemical economy.