Microbial mercury methylation in Antarctic sea ice

Area of Science:

• Environmental Science
• Microbiology
• Oceanography

Background:

• Mercury deposition in polar regions leads to methylmercury bioaccumulation in marine food webs.
• Controls on microbial mercury methylation in polar marine systems are poorly understood.
• Mercury methylation occurs with reduction and volatilization processes.

Purpose of the Study:

• To investigate mercury methylation and volatilization pathways in Antarctic marine environments.
• To identify microbial communities involved in mercury cycling in sea ice and seawater.
• To understand the role of sea ice in methylmercury production.

Main Methods:

• Mercury speciation measurements (total and methylated mercury).
• Metagenomic analysis of microbial DNA from Antarctic snow, brine, sea ice, and seawater.
• Combined chemical and genetic analyses to elucidate mercury cycling pathways.

Main Results:

• The marine bacterium Nitrospina was identified as a potential mercury methylator in Antarctic sea ice.
• Microaerophilic bacteria, like Nitrospina, appear significant in mercury methylation within sea ice.
• Known anaerobic mercury-methylating bacteria were absent in sea-ice metagenomes, suggesting alternative pathways.

Conclusions:

• Antarctic sea ice acts as a potential habitat for microbial methylmercury production in the Southern Ocean.
• Nitrospina represents a key player in mercury methylation within the sea ice environment.
• Further research is needed to fully understand mercury methylation and volatilization in polar marine ecosystems.