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Tinto River Iron Cycling Community

Ecological State STABLE
Environment acid mine drainage
ENVO:00002186
Source File Tinto_River_Iron_Cycling_Community.yaml

A natural acidic iron-cycling microbial community from the Rio Tinto River in southwestern Spain, distinguished by exceptional eukaryotic diversity (>65% of total biomass) in an extremely acidic environment (mean pH 2.2). While prokaryotic diversity is low with 80% of bacteria belonging to three iron-cycling genera (Leptospirillum, Acidithiobacillus, Acidiphilium), eukaryotic diversity is remarkably high including algae (diatoms, Chlorophyta, Euglenozoa, Rhodophyta), fungi (Hortaea, Acidomyces), and diverse protists (ciliates, amoebae, heliozoans, cercomonads, stramenopiles). The river has constant acidic pH (mean 2.2, range 1.0-2.5) and high metal concentrations (Fe 2.3 g/L, Cu 0.11 g/L, Zn 0.22 g/L) throughout its 100 km length, driven by natural oxidation of massive sulfide deposits in the Iberian Pyrite Belt. The prokaryotic community drives iron cycling through Fe²⁺ oxidation (Leptospirillum, Acidithiobacillus) and heterotrophic carbon cycling (Acidiphilium), creating stromatolite-like iron oxide precipitates. Eukaryotes contribute primary production (photosynthetic algae), heterotrophic consumption (protists, fungi), and trophic structure (ciliate predators, heliozoan top predators). The ecosystem represents a natural analog for early Earth conditions and extraterrestrial iron-rich acidic environments, supporting astrobiology research. Rio Tinto demonstrates that complex food webs with eukaryotic dominance can thrive in extreme acid-metal conditions, challenging assumptions about habitability limits.

Taxonomy

Taxon Ontology ID Functional Roles Abundance
Leptospirillum ferrooxidans NCBITaxon:180
PRIMARY_DEGRADER
DOMINANT
Acidithiobacillus ferrooxidans NCBITaxon:920
PRIMARY_DEGRADER
ABUNDANT
Acidiphilium NCBITaxon:522
CROSS_FEEDER SECONDARY_FERMENTER
ABUNDANT
Bacillariophyceae NCBITaxon:33849
PRIMARY_PRODUCER
COMMON
Chlorophyta NCBITaxon:3041
PRIMARY_PRODUCER
COMMON
Basidiomycota NCBITaxon:5204
PRIMARY_DEGRADER
RARE

Ecological Interactions

Iron Oxidation and Acid Generation

MUTUALISM

Source Taxon: Leptospirillum ferrooxidans

Metabolites: Fe(II) (CHEBI:29033), Fe(III) (CHEBI:29034)

Biological Processes:

Downstream Effects:
→ Heterotrophic Carbon-Iron Coupling

Evidence

  • "Members of Leptospirillum ferrooxidans , Acidithiobacillus ferrooxidans , and Acidiphilium spp., all related to the iron cycle, accounted for most of the prokaryotic microorganisms detected"

Heterotrophic Carbon-Iron Coupling

MUTUALISM

Source Taxon: Acidiphilium

Biological Processes:

  • organic substance catabolic process (GO:1901575)

Evidence

  • "Members of Leptospirillum ferrooxidans , Acidithiobacillus ferrooxidans , and Acidiphilium spp., all related to the iron cycle, accounted for most of the prokaryotic microorganisms detected"

Eukaryotic Primary Production

CROSS_FEEDING

Biological Processes:

Evidence

  • PMID:25369810 - SUPPORT (IN_VIVO)
    "However, highly acidic environments are usually inhabited by acidophilic and acidotolerant eukaryotic microorganisms such as algae, amoebas, ciliates, heliozoan and rotifers, not to mention filamentous fungi and yeasts"

Environmental Factors

Factor Value Unit
pH 2.2 pH units
Iron Concentration 2.3 g/L
Eukaryotic Biomass Dominance 65 % of total biomass
Prokaryotic Diversity 80% % in 3 genera