Diatoms in marine sediments contaminated by potentially toxic elements from mining activities

Santa Rosalía is located to the northeast of the Baja California Sur, were a copper ore mine was exploited. Mining activities were closed in 1984 and returned in 2014. The wastes were discharged into the Gulf of California, however, eventually they back by currents to the beaches of this town. The objective of this study were 1) to determine the contents of potentially toxic elements (PTE) in beaches and harbor sediments of Santa Rosalía in 2016, 2) to compare their contents of PTE with respect to previous studies, 3) to analyze the assemblages of benthic diatoms. Results show average concentrations (mg kg^-1) that exceed the reference values for the earth’s crust for Cu (3193), Zn (2393), Co (307), Pb (191), Cd (42) U (40). Species richness of live benthic diatoms appeared normal, and although they show deformities, these are not signifcant. It cannot be concluded if the mining wastes are unfavorable to the adjacent biota. Sediment obtained (2016) are equally concentrated than in previous studies, despite the reactivation of mining activities. Those contents exceed the mid-range effect (MRE) of sediments toxicity, which would be harmful to organisms in the area.