Rare earth elements in corals from the Isla de Sacrificios Reef, Veracruz, Mexico

Rare earth elements (REE) analysis was carried out in two coral species Diploria strigosa and Copophyllia natans from Isla de Sacrificios Reef (ISR) (19° 10′ 51.6″N; 96° 5′ 45.6″W) Veracruz, Mexico. Both corals were cut at the top, middle and bottom parts to detect possible differences in REE concentrations related to water masses and sediment inputs. An enrichment in heavy rare elements (HREE) compared to light rare elements (LREE) at the top of Diploria strigosa and Copophyllia natans, evidenced by (La/Lu)SN <0.5, (La/Yb)SN <0.5 and (Pr/Yb)SN <0.5 is observed. This HREE enrichment in both corals is probably due to the high pH and CO32− content in the seawater. A negative Ce anomaly is observed throughout Diploria strigosa and Copophyllia natans, probably linked with well oxygenated, highly oxidative modern shallow waters, and high nutrients related to suspended matter. Positive Eu anomalies in both corals are due to development of the ISR in shallow waters. Ce/Ce* vs. (Pr/Yb)SN diagram suggests the input of terrigenous material, as all samples have Ce/Ce* and Pr/Yb values outside the seawater range signature. However, the Nd/Yb and (Nd/Yb)SN suggest that the top of Diploria strigosa and Copophyllia natans are associated with coastal waters at about 50 m depth.