Long-term trace element assessment after a mine spill: Pollution persistence and bioaccumulation in the trophic web.

Trace elements can be toxic when they cannot be easily removed after entering an ecosystem, so a long-term assessment is fundamental to guide ecosystem restoration after catastrophic pollution. In 1998, a pyrite mining accident in Aznalcóllar (south-western Spain) spilled toxic waste over a large area of the Guadiamar river basin, where, after restoration tasks, the Guadiamar Green Corridor was established. Eight years after the mine accident (2005-2006), the ground-dwelling insectivorous lizard Psammodromus algirus registered high trace-element levels within the study area compared to specimens from a nearby unpolluted control site. In 2017, 20 years after the accident, we repeated the sampling for this lizard species and also quantified trace elements in vegetation as well as in arthropod samples in order to identify remnant trace-element accumulation with the aim of assessing the transfer of these elements through the trophic web. We found remnant trace-element contamination in organisms of the polluted site compared to those from the unpolluted site. All trace-element concentrations were higher in arthropods than in plants, suggesting these compounds bioaccumulate through the trophic web. Lizards from the polluted areas had higher As, Cd, and Hg concentrations than did individuals from the unpolluted area. Lizard abundance between sampling periods (2005-06 and 2017) did not vary in unpolluted transects but strongly declined at polluted ones. By contrast, the Normalized Difference Vegetation Index indicated that in the study period, the vegetation was similar at the two sampling sites. These results suggest that, 20 years after the accident, the trace-element pollution could be the cause of a severe demographic decline of the lizard in the polluted area.

Does wintering north or south of the Sahara correlate with timing and breeding performance in black-tailed godwits?

Migrating long distances requires time and energy, and may interact with an individual's performance during breeding. These seasonal interactions in migratory animals are best described in populations with disjunct nonbreeding distributions. The black-tailed godwit (Limosa limosa limosa), which breeds in agricultural grasslands in Western Europe, has such a disjunct nonbreeding distribution: The majority spend the nonbreeding season in West Africa, while a growing number winters north of the Sahara on the Iberian Peninsula. To test whether crossing the Sahara has an effect on breeding season phenology and reproductive parameters, we examined differences in the timing of arrival, breeding habitat quality, lay date, egg volume, and daily nest survival among godwits (154 females and 157 males), individually marked in a breeding area in the Netherlands for which wintering destination was known on the basis of resightings. We also examined whether individual repeatability in arrival date differed between birds wintering north or south of the Sahara. Contrary to expectation, godwits wintering south of the Sahara arrived two days earlier and initiated their clutch six days earlier than godwits wintering north of the Sahara. Arrival date was equally repeatable for both groups, and egg volume larger in birds wintering north of the Sahara. Despite these differences, we found no association between wintering location and the quality of breeding habitat or nest survival. This suggests that the crossing of an important ecological barrier and doubling of the migration distance, twice a year, do not have clear negative reproductive consequences for some long-distance migrants.

Bioaccumulation of heavy metals in the lizard Psammodromus algirus after a tailing-dam collapse in Aznalcóllar (Southwest Spain).

Quantification of heavy metal concentrations in biota is a common technique that helps environmental managers measure the level of pollutants circulating in ecosystems. Despite interest in heavy metals as indicators of localized pollution, few studies have assessed these pollutants in reptiles. In 1998, the tailing pond of a pyrite mine near Aznalcóllar (southwestern Spain), containing mud with high heavy metal concentrations, collapsed, releasing 6 million m(3) of toxic sludge into the Guadiamar Basin. Here we analyze heavy metal concentrations in the most common reptile in the area, the large psammodromus, Psammodromus algirus, a rather small lizard. We quantified levels of several elements (Hg, Sb, Cd, Cr, Tl, Sn, Ba, Cu, Pb, Sr, Mn, Rb, As, and Zn) in lizard tail clips collected in and around the affected area during the springs of 2005 and 2006. Samples were collected from two contaminated localities, one directly affected by the spill, and another adjacent to the tailing pond, but not covered by toxic mud. We also collected samples from a nonpolluted control site in the same basin. We found higher concentrations of As, Tl, Sn, Pb, Cd, and Cu in lizards from the affected area than in lizards from the control site, indicating the continued presence of heavy metal pollutants in the terrestrial food chain 8 years after the mine accident. We did not uncover sexual or annual differences in heavy metal concentrations, although concentrations increased with lizard size. We discuss how heavy metals moved across the food chain to lizards, despite intensive restoration efforts after the accident, and suggest that reptiles to be included in biomonitoring programs of heavy metals pollution in terrestrial habitats.