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Microbial diversity and population structure studies in the Río Tinto

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Our study site in southwestern Spain focuses on the Río Tinto, a 100-km long, acidic, heavy metal laden river running through the world largest pyritic belt. More than 5,000 years of mining activity has altered this region’s landscape, the nature of the water, an average pH of 2.0 and heavy metal concentrations several orders of magnitude above normal. Environments like the Río Tinto may provide a good terrestrial model for Mars. The river’s name refers to the color of its waters– “tinto” meaning red in Spanish ’ the result of high levels of dissolved ferric iron (Fe3+) kept in solution by the acidity of the water. In other parts of the river, reduced iron also occurs in high concentrations. Geomicrobiological characterizations show that the Tinto’s Fe cycle is operational under both aerobic and anaerobic conditions.
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In this project we are using an integrated approach to assess the molecular diversity of bacterial, achaeal and eukaryotic components of community diversity in selected regions along the Río Tinto. We use molecular techniques to investigate microbial diversity and population structure in the water column at both spatial and temporal scales, and couple these with physicochemical measurements using water samples taken for the molecular surveys. When possible, determination of as many in situ physico-chemical parameters are made on biofilms as well, using microelectrodes available for field measurements. This allows for the correlation of biological diversity information with physicochemical parameters of the river. The outcome through this study will provide a comprehensive view of the microbial ecology of the system, a first step towards establishing an ecological genomics project for the Río Tinto. As part of this effort we seek to answer the following questions:

     1. What accounts for the remarkable eukaryotic diversity in the extreme Río Tinto       environment?
     2. From a molecular perspective, how homogeneous are the blooms of diatoms, euglenids        and other algae that form dense communities in various parts of the river?
     3. How does phylogenetic diversity compare between the water column and biofilms along       the river’s edge?
     4. Does diversity of a given community correlate in any way with physico-chemical       parameters at a given site?
     5. Are environments with greater turbidity more homogeneous than less disturbed ones?
     6. How are the bacterial, archaeal and eukaryotic microbial communities linked to each other        and to what extent do they interact on the gene level?




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  Origin
  The Origin has several   sources of water with   very distinct properties   and varying iron   concentrations.


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Anabel´s Garden
Anabel´s garden has the most conspicuous
eukaryotic diversity and abundance with
many different types of biofilms.





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Berrocal
Berrocal is just downstream of a bridge
and is characterized by deep red water,
localized anoxia, and dramatic concretions of river boulders cemented together with iron precipitates.



Content contributions by Erik Zettler (SEA) and Carmen Palacios (Universite de Perpignan)
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