Resumo. AIM: The diversity and distribution of microalgae communities in a high-altitude (3,000 to 4,500 m a.s.l) Andean wetland, regionally known as bofedal, were examined to assess seasonal and spatial patterns. METHODS: Samples were taken monthly from June to December, 2008 at 13 stations in the Huaytire wetland (16° 54’ S and 70° 20’ W), covering three areas (impacted by urban land use, impacted by camelid pasture, and non-impacted) and three climatologically induced periods (ice-covered, ice-melt and ice-free). RESULTS: A total of 52 genera of algae were recorded. Diatoms were the predominant group in abundance and richness. We found a significantly higher abundance during the ice-melting period, when light exposure and runoff were intermediate, in comparison to the ice-covered (low light and flushing) and ice-free (high light and low runoff) periods. Microalgae abundance was significantly lower in the non-impacted area compared to the sites close to the urban area and to the camelid pastures. Alpha diversity ranged from 8 to 29 genera per sample. High genera exchange was observed throughout the wetland, showing a similar floristic composition (beta diversity = 4%). CONCLUSIONS: We found that diatoms were dominant and adapted to the extreme conditions of the Andean wetland, showing higher abundance during the ice-melt period and in the livestock area. Also, taxa richness was higher in the ice-melt period and in the most-impacted areas.