Significant contribution of coastal fish-farm activities to the inventory of trace elements in coastal waters: Traced by ammonia and rare earth elements

In this study, we investigated the influence of fish-farm activities on the inventory of trace elements (Mn, Fe, Co, Ni, and Cu) in the coastal waters off the fish-farm plants on Jeju Island, Korea. NH4+ and rare earth elements (REEs) were used as tracers to examine the production and removal processes. Relatively higher concentrations of trace elements were observed in the coastal waters and significantly correlated with NH4+. Our results suggest that the excess dissolved trace elements in the coastal waters could be mainly produced inside fish farms, together with the production of NH4+ and light-REEs (La to Nd). Although dissolved trace elements were found to be partially scavenged onto particles in the fish-farm rearing waters, indicated by the significant removal of particle-reactive Ce, these particles would be eventually discharged into the coastal ocean and release the dissolved trace elements back into the water columns.

Automated summary

In this study, the impact of fish-farm activities on trace elements in the coastal waters off Jeju Island, Korea was investigated. The concentrations of trace elements were higher in the coastal waters and correlated with NH4+. Excess dissolved trace elements in the coastal waters were mainly produced inside fish farms, along with NH4+ and light-REEs. Although some dissolved trace elements were scavenged onto particles in fish-farm rearing waters, these particles would be eventually discharged into the coastal ocean and release the trace elements back into the water columns.