Eleven years after the Aznalcóllar pyrite mine rupture, in the north of the Doñana National Park (Huelva), the contamination caused from the spill seems to have been overcome. Spanish researchers have, however, evaluated the environmental quality of the Park's environment with crayfish as bio-indicators.
This methodology demonstrates that contaminants from intensive agriculture being carried out close to the Park are the main threat in this Biosphere Reserve and are already affecting the Puebla del Río and Matochal rice paddies.
The six million cubic metre acid water and toxic pyrite mud spill in 1998 did not have dramatic effects on the Doñana National Park because it did not enter the park limits. There is, however, still concern in the area due to agricultural activity and the use of pesticides in harvests close to the protected Natural Space which could threaten the Park's environmental quality.
"This type of contamination is more diffuse, difficult to evaluate and less relevant in the media than a mine spill", explains Juan López-Barea to SINC, the study's main author and head of the Department of Biochemistry and Molecular Biology at the University of Cordoba (UCO). And yet, agro-chemical contaminants affect, above all, areas situated between the Guadiamar Stream and the Guadalquivir River, sites of important rice cultivation.
The study, which has been published in Science of the Total Environment, has determined that the upper courses of the Rocina Stream, and especially the Partido Stream, are the most affected by agricultural contaminants, since the most intense fruit cultivation is in these areas. The researchers reached these conclusions upon combining the responses from the conventional biomarkers in crayfish (Procambarus clarkii), used as bio-indicators, with the massive analysis of changes in protein expression.
Crayfish: excellent contamination bio-indicators
In the spring and autumn of 2003 and 2004, scientists evaluated the level of contamination at six sites close to the Park, using two sites inside the Doñana Biological Station (EBD-CSIC) with almost no contaminants as a reference. During the four campaigns, and knowing that crayfish respond effectively to pesticides, organic contaminants and pro-oxidative chemical elements, the experts captured and dissected close to 600 animals.
Crayfish, which tend to live in the studied areas, showed an increase in pesticides and pro-oxidative organic contaminants in the Park and its environment, with changes in 12 conventional biochemical biomarkers and changes in the expression of 35 proteins.
This proteomic approach, based on the application of modern methodologies from the Biology of Systems (Proteomics, Transcriptomics, Metallomics), has made it possible to clarify that there are two "highly contaminated" sites: the Puebla del Río (on the Isla Mayor of the Guadalquivir, between the river and the Doñana National Park) and the Matochal (in the Doñana natural ecosystem marsh) rich paddies.
In the Matochal, rice is extensively cultivated "in which pesticides, algaecides and fungicides are used intensively, which alters the expression of a maximum number of proteins", point out the researchers.
The methods employed in this study, developed in Córdoba, are the most groundbreaking of their kind in the world. López-Barea leads the research group BIO151 of Environmental Proteomics at the UCO and applies cutting-edge methodologies to evaluate land and aquatic ecosystems.
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