Details

Autor(en) / Beteiligte

• Sun, Yinan
• Jiang, Wei
• Yu, Kefu
• Xu, Shendong
• Feng, Chunmei
• Xie, Sirong
• Wei, Chaoshuai

Titel

High‐Resolution Coral Records of Cadmium in Surface Seawater: Biogeochemical Cycling and a Novel Proxy for Winter Monsoon

Ist Teil von

• Geochemistry, geophysics, geosystems : G3, 2022-11, Vol.23 (11), p.n/a

Ort / Verlag

Washington: John Wiley & Sons, Inc

Erscheinungsjahr

2022

Quelle

Wiley Online Library

Beschreibungen/Notizen

• Cadmium (Cd) geochemical cycle plays a significant role in the composition and function of the marine ecosystem. Skeletal cadmium‐to‐calcium (Cd/Ca) ratios in hermatypic corals have been applied to reconstruct the historical changes of oceanic and climatic processes, yet there was no systematic evaluation of this tracer's natural variability in high resolution over time. Here, we reported a coral skeletal Cd/Ca record in monthly resolution from 1999 to 2008 CE and reconstructed the history of Cd contents in surface seawater in the northern South China Sea. A significant seasonal variation (higher in the winter but lower in the summer) of Cd contents in surface seawater can be identified. We found that the seasonal variations in coral skeletal Cd/Ca ratios exhibited significant trends coupled with the surface wind speeds, indicating that strong winds had likely driven the vertical seawater mixing process and then induced the process of sediment remobilization on the shelf, which significantly increased Cd contents in surface seawater. The reduction in Cd contents in surface seawater due to biological processes might be masked by the impacts of surface winds. Importantly, we also observed that coral skeletal Cd/Ca records in the winter showed significant correlations with the winter monsoon index, highlighting the possibility as a new proxy of winter monsoon in the non‐upwelling shelf environments. Plain Language Summary Cadmium (Cd) is a nutrient element absorbed by phytoplankton in surface seawater, showing a distribution of low surface content and high bottom content. In order to determine the seasonal variations of Cd content in surface seawater in the northern South China Sea, we analyzed the coral skeletal Cd/Ca ratios in monthly resolution (1999–2008 CE) and finally concluded that the process of sediment resuspension and vertical mixing of seawater driven by winter monsoons is the main reason. The reduction of Cd contents in surface seawater due to biological processes was masked by the impacts of surface winds. In the past, Cd content in seawater/coral has been used to track the history of upwelling and El Niño Southern Oscillation, but the potential indicative on winter monsoon has not been reported so far. Considering that the trend between coral skeletal Cd/Ca ratios and average wind speeds showed a great agreement, we suggested that coral skeletal Cd/Ca ratios in the winter might be a potential proxy of winter monsoon. Key Points Coral skeletal Cd/Ca ratios in monthly resolution were first reported Seawater mixing process and sediments resuspension caused by winter monsoon are responsible for Cd seasonal variations in surface seawater Coral skeletal Cd/Ca ratios have potential to be a novel proxy for winter monsoon