CONICET | Buscador de Institutos y Recursos Humanos

Temporary wetlands are stressed by droughts and interannual water level variations that affect the development and phenology of aquatic communities and disrupt trophic interactions. Waterbirds are vital components of wetlands with strong effects on aquatic communities through fertilization by feces and consumption. In this study we addressed the effects of water level and nutrient availability on phytoplankton through mesocosm experiments, applying a factorial design consisting of two contrasting levels of water depths (shallow and deep) and nutrients (with and without enrichment with feces of the waterbird Chloephaga picta). Feces addition contributed large amounts of phosphorus, enhancing phytoplankton biomass and Chla, regardless the water level. Phytoplankton composition was similar in all treatments; however, nutrient availability and water level drove the plankton succession. Three periods could be detected in the succession: the first was characterized by nutrient release from sediments and feces, and the emergence of colonizing phytoplankters of the FG X3 (Chromulina, Ochromonas); the second showed decreasing nutrients, an increase of phytoplankton biomass and FG diversity (X1, X2, Y, Lo, including Chlorella, Monoraphidium, Plagioselmis, Chlamydomonas, Peridinium), and the increase of zooplankton abundance; and the third displayed nutrient depletion, a decrease of phytoplankton biomass with a predominance of groups X2 and C (Aulacoseira) and the emergence of large zooplankton. Phytoplankton diversity, richness and evenness were higher in the treatments with feces. Overall, our results showed that changes in water level and nutrient enrichment by waterbirds can deeply impact the diversity and production of planktonic communities, underscoring the potential impact of climate driven changes on wetlands´communities.

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