Validation study of the acute biotic ligand model for silver

Area of Science:

• Environmental toxicology
• Aquatic toxicology
• Computational toxicology

Background:

• The biotic ligand model (BLM) is crucial for predicting metal toxicity in aquatic ecosystems.
• Validating the BLM for silver is essential for accurate environmental risk assessment.
• Previous BLM development utilized diverse organism data, raising questions about acclimation and age effects.

Purpose of the Study:

• To validate the acute biotic ligand model for silver using natural waters.
• To assess the model's predictive accuracy for fish and invertebrates.
• To investigate the influence of water chemistry, organism acclimation, and size on silver toxicity.

Main Methods:

• Characterization of eight North American natural waters (ionic composition, pH, DOC, sulfide).
• Acute toxicity testing (48-h for Ceriodaphnia dubia, 96-h for Pimephales promelas) to determine silver LC50s.
• Measurement of Na(+) and Cl(-) influx rates in P. promelas of varying sizes.

Main Results:

• The BLM adequately predicted silver toxicity to C. dubia, though some predicted LC50s exceeded measured values.
• BLM predictions for P. promelas were less accurate, particularly in low ionic strength waters.
• No significant difference in silver toxicity was observed between acclimated and non-acclimated P. promelas.
• Na(+) and Cl(-) influx rates were inversely related to fish mass and positively correlated with silver sensitivity.

Conclusions:

• The biotic ligand model for silver requires further refinement for accurate prediction of fish toxicity, especially in dilute waters.
• Organism acclimation to test waters does not appear to significantly influence acute silver toxicity predictions.
• Fish size, linked to ion transport rates, is a critical factor influencing silver sensitivity and BLM accuracy.