Algae decomposition released dissolved organic matter subfractions on dark abiotic mercury methylation

Area of Science:

• Environmental Chemistry
• Aquatic Toxicology
• Biogeochemistry

Background:

• Mercury methylation is a critical process in aquatic ecosystems, converting inorganic mercury into toxic methylmercury.
• Algae-derived dissolved organic matter (DOM) plays a significant role in mercury methylation, but its specific components and their effects are not fully understood.
• Effective management of mercury risks in aquaculture requires detailed knowledge of mercury methylation mechanisms.

Purpose of the Study:

• To investigate the influence of algae (Ulothrix sp.)-derived DOM subfractions on dark abiotic mercury methylation.
• To identify key DOM components responsible for promoting or inhibiting mercury methylation.
• To provide insights for managing mercury methylation in aquaculture areas.

Main Methods:

• Investigated mercury methylation using subfractions of DOM from decomposed algae (Ulothrix sp.).
• Analyzed methylmercury (MeHg) production and the rate of MeHg formation (%MeHg) under varying mercury concentrations.
• Compared mercury methylation potential between decomposed and undecomposed algal DOM.

Main Results:

• The hydrophobic basic component (HOB) of DOM significantly promoted mercury methylation.
• Methylmercury production rate (%MeHg) decreased with increasing mercury concentration, indicating limited binding sites and methyl donors.
• Decomposed algal DOM significantly reduced MeHg production compared to undecomposed DOM, with peak reduction observed after 20-30 days of decay.
• Hydrophilic acid (HIA) components showed an inhibitory effect on mercury methylation.

Conclusions:

• Algae-derived DOM subfractions, particularly HOB and HIA, critically influence mercury methylation processes.
• DOM decomposition weakens mercury methylation ability, suggesting a potential bioremediation strategy.
• Understanding these DOM-Hg methylation interactions is crucial for mitigating mercury pollution in aquaculture environments.