Transport of Cobalt and Silver From the Ocean to a Reef Island by Seabirds in the South China Sea

Seabirds are typical biovectors, delivering both nutrients and metals across ecosystem boundaries. However, seabird transfer of Ag and Co has not been well documented. Using an ornithogenic sediment core collected from the remote Zhaoshu Island, South China Sea, we investigated potential impacts of seabirds on Ag and Co transportation. These two elements exhibited peak abundance in a guano layer in the sediment profile. Via statistical analyses, Ag, Co, and previously identified avian bio-elements (Cn, Zn, Cd, P, As, and Se) had a common source, that is, guano. Guano input was also partly responsible for the distribution of Y, Ce, La, Sc, and U in the bulk sediments. The concentration-versus-depth profiles of Mn, Mo, Bi, Rb, and W were possibly associated with organic matter.