Biological toxicity of lanthanide elements on algae

Area of Science:

• Marine Biology
• Environmental Toxicology
• Inorganic Chemistry

Background:

• Lanthanides are rare earth elements with increasing environmental presence.
• Understanding their ecotoxicity is crucial for marine ecosystem health.
• Monocellular algae form the base of marine food webs and are sensitive indicators of water quality.

Purpose of the Study:

• To investigate the biological toxicity of individual and mixed lanthanides on marine monocellular algae.
• To determine the relationship between lanthanide seawater abundance and their toxicity.
• To assess the applicability of existing toxicity rules (e.g., Harkins rule) to lanthanides.

Main Methods:

• Exposure of Skeletonema costatum to varying concentrations of 13 individual lanthanide elements.
• Assessment of growth inhibition using 96-hour EC50 (Effective Concentration causing 50% inhibition).
• Comparison of toxicity data with natural abundance of lanthanides and evaluation against the Harkins rule.

Main Results:

• All tested lanthanides exhibited similar toxic effects on Skeletonema costatum.
• A concentration of approximately 29.04 µmol L⁻¹ of any single lanthanide caused a 50% reduction in algal growth after 96 hours.
• Lanthanide toxicity was not correlated with their natural abundance, and the Harkins rule was not applicable.
• A mixture of lanthanides had an equivalent inhibitory effect to individual lanthanides at the same total concentration.

Conclusions:

• The biological toxicity of lanthanides on marine monocellular algae is element-independent.
• Monocellular algae appear unable to distinguish between chemically similar lanthanide elements.
• This suggests a non-specific toxicity mechanism for lanthanides in these organisms.