Elevated N/P Ratios Enhance Arsenic Bioaccumulation and Biotransformation in Marine Microalgae

Area of Science:

• Marine microbial ecology
• Biogeochemistry
• Environmental toxicology

Background:

• Marine microalgae are key primary producers and efficient arsenic accumulators.
• Elevated nitrogen-to-phosphorus (N/P) ratios due to nutrient pollution alter marine biogeochemical cycles.
• The impact of changing N/P ratios on arsenic biogeochemistry in microalgae is poorly understood.

Purpose of the Study:

• To investigate how intensified N/P ratios affect arsenic uptake and transformation in marine microalgae.
• To elucidate the underlying molecular and metabolic mechanisms driving these changes.
• To assess the ecological implications for marine food webs and human health.

Main Methods:

• Controlled laboratory experiments exposing microalgae to varying N/P ratios.
• Transcriptome analysis to identify gene expression changes.
• Metabolomic flux analysis to track metabolic pathways.
• Analysis of the Tara Oceans database for global gene distribution.

Main Results:

• Increased N/P ratios significantly enhanced arsenic accumulation and promoted conversion of inorganic to organic arsenic species.
• Upregulation of arsenic transport genes and altered metabolic energy flow, favoring carbon fixation and ATP synthesis over amino acid metabolism.
• Arsenic metabolism-related genes are globally distributed in surface oceans.

Conclusions:

• Elevated N/P ratios reallocate metabolic energy in marine microalgae, boosting arsenic uptake and biotransformation.
• While beneficial for short-term cellular detoxification, this process may increase organic arsenic accumulation and trophic transfer.
• Long-term consequences include potential ecological and human health risks due to altered arsenic speciation and mobility.