Eukaryotic community distribution and its relationship to water physicochemical parameters in an extreme acidic environment, Rio Tinto (southwestern Spain)

Abstract

The correlation between water physicochemical parameters and eukaryotic benthic composition was examined in Río Tinto. Principal component analysis showed a high inverse relationship between pH and most of the heavy metals analyzed as well as Dunaliella sp., while Chlamydomonas sp. abundance was positively related. Zn, Cu, and Ni clustered together and showed a strong inverse correlation with the diversity coefficient and most of the species analyzed. These eukaryotic communities seem to be more influenced by the presence of heavy metals than by the pH.

FIG. 1.

Locations of the 12 investigated sampling points in the Tinto River (southwest Spain).

FIG. 2.

(a) TI values for water collected from each sampling site. (b) Means and standard errors of benthic eukaryotic cell densities at each sampling site and the time point as determined by direct microscopic enumeration. (c) The diversity index at each sampling site.

FIG. 3.

UPGMA similarity cluster analysis of the different sampling locations analyzed in the Tinto River based on physicochemical water parameters (a) and biological data from epiphytic eukaryotic communities (b).

FIG. 4.

Two-dimensional plot of the PCA performed for the whole data set, including physicochemical and biological data. T^a, temperature; Cond, conductivity; D, diversity index; Ti, toxicity index; Cya, Cyanidium; Diato, diatoms; Filam, filamentous algae; Hetero, heterotrophic flagellates; Eugl, Euglena; Duna, Dunaliella; Chlo, Chlorella; Chlamy, Chlamydomonas.