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

Abstract

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.

Keywords: Ammonia; Coastal water; Fish farm; Jeju; Rare earth elements; Trace elements.