Abstract
The Andean Altiplano is characterized by its isolation, high altitude (>3,600 m a.s.l.), and a unique biodiversity, containing water systems such as lakes, rivers, wetlands, and salt flats. Near the southernmost area of the Andean Altiplano are two salt flats, Carcote and Ascotán, the former almost undisturbed by human intervention and the latter historically intervened with by brine mining. These mining activities deplete, pollute, and alter water flow, suggesting a significant threat to ecosystem functions. With regard to identifying the main factors promoting biotic community differentiation in these salt flats at different levels of human intervention, the aim of this study was to compare diatom community indices by guild (high-profile, low-profile, and motile) between these systems with a functional perspective, their relationship to environmental conditions, and the potential anthropic impact on their community structures. Diatom guilds were compared between salt flats based on their diversity, species richness, and abundance relative to ionic concentrations and granulometry. Beta diversity and the percentages of nestedness and turnover for each guild were also estimated. Results showed significant differences in ecological variables between the two salt flats. The largest values of species abundance, richness, and diatom diversity were measured in Carcote, suggesting greater primary productivity and diversity. The results also showed that the species composition of the motile guild was more differentiated between salt flats than those of other guilds (with the greatest diversity and richness), suggesting that motile diatoms are a key guild in maintaining the diatom community and that species from this guild are more sensitive to local conditions from each salt flat. Additionally, beta diversity in all guilds was mainly explained by turnover rather than nestedness, and the turnover was the highest for the motile and low-profile guilds. A more heterogeneous community was observed in Ascotán, showing that the mechanisms of diversity maintenance, such as dispersion abilities, were salt flat dependent. This suggests that the highest diversity could be related to human use, which challenges us to reexamine the effectiveness of past conservation activities in the area and to develop future strategies including both connected basins.
Highlights
The Andean Altiplano is in the Dry Puna ecoregion, close to the Atacama Desert, one of the driest and oldest worldwide
Considering the differences in hydrology and anthropic disturbance history between the Ascotán and Carcote salt flats in the Dry Puna ecoregion, the aim of this study is to compare the diatom community assembly by guild between the salt flats in order to respond to the following questions: are there local differences in the community structure of benthic diatoms in Andean salt flats or at the level of functional groups?; are facilitation associations between diatom guilds promoted under stress environmental conditions?; could differences in the function or structure of the diatom communities be associated with anthropic perturbations, as those produced by intensive mining?; and which mechanism mainly explains the observed beta diversity?
In the case of richness, statistical differences were observed between the salt flat (p 0.001) and the guild (p < 0.001) as main factors (Figure 2B), with higher values of richness observed in Carcote than in Ascotán
Summary
The Andean Altiplano is in the Dry Puna ecoregion, close to the Atacama Desert, one of the driest and oldest worldwide. The Dry Puna stretches from approximately 17 to 27°S in southwest Bolivia, northeast Argentina, and northern Chile in the eastern Atacama Desert. This area is characterized by low annual precipitation (
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