High aluminum content in bone of marine mammals and its relation with source levels and origin*

Although aluminum is widely distributed in the earth's crust, its environmental availability and wildlife assimilation rates are only partially known. Here we analyze aluminum concentrations in bone from 10 species of marine mammals inhabiting 3 geographic areas subject to different aluminum inputs: the Rio de la Plata estuary (Uruguay), the coastal waters of Mauritania and the Galapagos archipelago (Ecuador). Overall, concentrations were unusually high as compared to those of terrestrial animals, with lowest concentrations in the Galapagos archipelago, then the Rio de la Plata estuary and finally Mauritania. The aluminum source varied between re-gions, prevailing anthropogenic sources in the Rio de la Plata Estuary and natural sources (wind-blown dust) in Mauritanian waters. The type of source determined contamination levels: anthropogenic sources were most significant for coastal species and showed a decline with distance of habitat from shoreline, while natural sources had a higher influence on open waters because of the dearth of biogenic silica that eliminates aluminum from the water column. Since aluminum remains in bone for several decades, marine mammal bone reflects historical levels of aluminum and therefore is a good bioindicator of the aluminum concentration of the marine environment.

Automated summary

This study analyzed the aluminum concentrations in the bone of 10 species of marine mammals inhabiting different geographic areas with varying aluminum inputs. The results showed unusually high concentrations of aluminum in marine mammal bone compared to terrestrial animals, with the lowest concentrations in the Galapagos archipelago, followed by the Rio de la Plata estuary and Mauritania. The source of aluminum varied between regions, with anthropogenic sources dominating in the Rio de la Plata estuary and natural sources (wind-blown dust) in Mauritanian waters. The type of source determined the contamination levels, with anthropogenic sources being more significant for coastal species and declining with distance from the shoreline.