Silver is being buried under the sea, due to climate change

Researchers have made a significant connection between silver burial in marine sediments and human-induced climate change, reports Live Science. This study indicates that global warming is leading to increased silver deposition in the South China Sea.

Since 1850, the quantity of silver found in marine sediments off Vietnam has significantly grown, corresponding with the beginning of the Industrial Revolution. This period marked a surge in greenhouse gas emissions, which contributes to global warming. Liqiang Xu, the study's lead author and an associate professor at Hefei University of Technology, remarked that the research demonstrates a potential relationship between global warming and silver cycles in the ocean. This discovery implies that climate change may also impact other trace elements in the marine environment.

Silver, like many other elements, originates on land. It travels to oceans mainly through processes like weathering, where rainwater dissolves elements from rocks and transports them into rivers. In various ocean regions, silver concentrations rise due to river runoff, atmospheric dust, human activities, and hydrothermal vents. While ionic silver (Ag+) is hazardous to marine life, its interactions within ocean ecosystems remain poorly understood.

Investigating Silver's Behavior in Marine Environments

To explore silver’s behavior in the ocean, Xu and colleagues examined a sediment core from the Vietnam upwelling area in the eastern South China Sea. Upwelling zones are significant due to cold water rising from the seafloor, bringing important nutrients that nourish rich surface ecosystems. The latest study, published in Geophysical Research Letters on August 13, revealed two distinct zones within the sediment core.

Researchers found that silver concentrations decreased from a depth of approximately 3 inches (7 centimeters) up to about 1200 B.C. From around 1850, the core displayed a dramatic increase in silver burial. This timing aligns with the atmospheric CO2 levels, suggesting that climate change may enhance silver entrapment in certain marine sediments.

Regional Variations and Implications of Silver Levels

The study highlights that silver concentrations in upwelling areas tend to be high, especially in regions where human activities contribute additional silver through pollution. Coastal locations like Massachusetts and San Francisco Bay are referred to as "silver estuaries" due to similar observations. Originating silver levels off Vietnam were naturally elevated and comparable to concentrations found in Canada, Mexico, Peru, and Chile. However, prior studies did not link these elevated levels with climate change.

With rising global temperatures, enhanced coastal winds can intensify upwellings. This uptick in nutrient availability leads to a surge in algae growth, benefiting the entire marine food web. Consequently, these environments could potentially experience increased dissolved silver absorption by organisms. When these organisms die, they carry silver to the seafloor along with organic matter.

Broader Context and Potential Environmental Effects

The interactions between dead marine life and silver transport to sediments have gained attention in broader studies. A 2021 review affirmed that dead organisms might play a role in silver accumulation on the ocean floor. Low oxygen environments may additionally support silver retention through various chemical processes. The expansion of such low-oxygen areas highlights the potential for increased silver trapping across more marine habitats.

If these trends hold true globally, the implications could pose a threat to oceanic ecosystems. Xu expressed concern that the silver amassed in sediments could potentially leach back into seawater, endangering aquatic life. Furthermore, if the silver stores do not re-enter the water, they may eventually return to land. As the review authors aptly put it, "Nothing is truly lost, only relocated."

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