Predicting dietborne metal toxicity from metal influxes

Area of Science:

• Environmental Toxicology
• Ecotoxicology
• Aquatic Ecology

Background:

• Dietborne metal uptake is a primary exposure route for aquatic organisms.
• Understanding the relationship between dietary metal exposure and toxicity is crucial but challenging.
• Quantifying metal exposure and bioaccumulation in aquatic invertebrates requires precise methods.

Purpose of the Study:

• To characterize dietborne copper (Cu), nickel (Ni), and cadmium (Cd) influxes in the freshwater gastropod Lymnaea stagnalis.
• To investigate the relationship between dietary metal concentrations and metal uptake rates.
• To assess the capacity of L. stagnalis to detoxify accumulated metals.

Main Methods:

• Utilized stable metal isotopes to label diatoms for exposure experiments.
• Quantified metal influxes and uptake rate constants (k(uf)) in L. stagnalis.
• Determined detoxification (k(detox)) and efflux (K(e)) rate constants for Cu, Ni, and Cd.

Main Results:

• Metal influxes correlated linearly with dietborne metal concentrations within environmentally relevant ranges.
• Uptake rate constants were highest for Cd and Ni, followed by Cu.
• Detoxification rate constants were significantly higher than efflux rate constants for all metals.
• High copper concentrations reduced feeding rates, causing uptake to plateau.

Conclusions:

• Lymnaea stagnalis efficiently absorbs Cu, Cd, and Ni from its diet.
• The snail primarily relies on detoxification rather than reduced uptake or increased excretion to manage metal loads.
• Detoxification mechanisms are overwhelmed at very high metal uptake rates, indicating a toxicity threshold.