Impact of gold mining activities on Holothuria (Halodeima) atra in North Sulawesi, Indonesia

After the discovery of the “Minamata” disease, a neurological syndrome in humans caused by severe mercury poisoning, many studies on toxic metals in marine food webs were carried out. In the coastal marine environments, trace elements, deriving from both natural processes and human activities, contribute to marine pollution, posing potential risks to marine ecosystems. This study focuses on trace elements contamination from gold mining activities in marine sediments and in two tissues (body wall and gut) on Holothuria atra, by comparing samples collected in affected and not affected sites in North Sulawesi (Indonesia). This region is affected by industrial and artisanal gold mining activities. While industrial mines generally use cyanidation method, artisanal gold mines still employ Hg amalgamation to extract gold from ores. Mean concentrations of As, Au, Co, Cr, Cu, Hg, Ni, Pb, Sb and Zn resulted significantly higher in surface sediments at sites that receive discharge from mines than at control sites. Mean concentrations of As, Au, Cr, Hg and Ni in body walls of H. atra were significantly higher at sites that receive discharge from mines than at control sites. Mean concentrations of As, Au, Co, Cr, Cu, Hg, Pb, Sb, Sn and Zn in guts of the same specimens were significantly higher at impacted sites. Nevertheless, pollution levels varied according to the typology and oldness of mining activities. By comparing the results of this study with the few data available on trace elements contamination in H. atra, we notice that levels of trace elements in specimens of North Sulawesi are generally higher both in body walls and in guts than found previous studies, characterised by different kind of impacts. Hg resulted the most concerning element both in surface sediment and in H. atra specimens. Further studies are needed to better understand the effect of Hg and other toxic elements in marine ecosystems and in food webs of impacted areas of North Sulawesi.