Eurasian otter (Lutra lutra) as sentinel species for the long-term biomonitoring of the Guadiamar River after the Aznalcóllar mine spill

Raquel Baos,Sonia Cabezas,María José González,Begoña Jiménez,Miguel Delibes

doi:10.1016/j.scitotenv.2021.149669

Abstract

Accidents at mines involving stored tailings have produced catastrophic environmental damage. In April 1998 the dam of the Aznalcóllar mine tailings pond in the surroundings of the Doñana National Park (southwestern Spain) broke, discharging into the Guadiamar River more than 6 million m3 of toxic mud and acidic water with high concentrations of heavy metals and arsenic. We used the Eurasian otter (Lutra lutra) as sentinel species to assess the potential impact of the toxic spill on the river ecosystems and their recovery with time by studying the spatial and temporal variation (1999-2003, 2006) of selected trace element (Cu, Zn, Cd, Pb and As) concentrations in feces. Throughout the sampling period, the highest heavy metal and As levels were found in the most spill-affected reaches of the Guadiamar River (i.e., the Middle and, to a lesser extent, the Lower reaches), pointing out the mining accident as the main origin of the contamination. Overall, levels of trace elements decreased with the time elapsed since the toxic spill, except for Cd (F1,352 = 0.29, P = 0.59). However, rebounds for some elements (Pb, As, and Cu) were also observed, especially in the Middle and Lower reaches of the river, which might be attributed to the residual contamination in abiotic compartments and/or new inputs from industrial and agricultural activities in the nearby areas. Concentrations were relatively high when compared to those reported for both our reference area (Guadalete River) and other metal-polluted zones. We found that the estimated amounts of Pb and As ingested during the first years after the spill in the Guadiamar Middle reach would be high enough to cause reproductive issues. This could affect the local population recovery, although evidence on distribution range and numbers suggests otherwise, with thriving populations at regional scale. Our results support the role of otters as sentinel species for biomonitoring contaminants and thus to evaluate fluvial ecosystem health.

Highlights

Anthropogenic activities have caused a progressive release of heavy metals and metalloids into the environment (Nriagu and Pacyna, 1988; Facchinelli et al, 2001)
Throughout the sampling period, the highest trace element concentrations in otter spraints were reported in the Middle- and, to a lesser extent, the Lower reaches of the Guadiamar River, pointing out the toxic spill as the main origin of the metal contamination
Using the same conservative approach, our results indicate that this exposure continued to be high during the sampling period, i.e., Winter 2000, at least for Pb, while decreasing afterwards

Summary

Introduction

Anthropogenic activities have caused a progressive release of heavy metals and metalloids into the environment (Nriagu and Pacyna, 1988; Facchinelli et al, 2001). Constructed or heavily charged dams may lead to the rupture of the reservoirs where the huge volume of water-rich sludge produced during the flotation of valuable minerals (sulphides) are stored (Van Niekerk and Viljoen, 2005), resulting in the spill of large amounts of pollutants. This occurred at the Boliden-Apirsa mine in Aznalcóllar (southwestern Spain) in 1998 (Grimalt et al, 1999; Ayala-Carcedo, 2004)

Methods

Results

Discussion

Conclusion