Qualidade da água e estrutura taxonômica e funcional de macroinvertebrados em áreas úmidas com colônias de nidificação de aves aquáticas no sul do Brasil

Abstract

Waterfowl can impact nutrient concentration in wetlands by producing large amounts of nitrogen and phosphorus-rich feces and can control the structure of the macroinvertebrate community via bottom-up mechanism. The objective of this study was to evaluate the water quality and the taxonomic and functional structure of macroinvertebrates in wetlands with nesting colonies of aquatic birds in southern Brazil. Macroinvertebrate communities were seasonally sampled in eight intermittent wetlands differing according to the occurrence of nesting colonies of waterbirds (four with the presence of rookeries; four without). Sampling was done in each wetland in the spring of 2016 (October) and one in the fall of 2017 (May). Water samples were collected for quantification of nutrients (ammonia, total phosphorus, nitrate, total organic nitrogen, total nitrogen, orthophosphate and organic phosphorus), physical and chemical variables of water (water temperature, pH, electrical conductivity, dissolved oxygen, saturation of dissolved oxygen, total dissolved solids and turbidity) were measured in situ and a sediment sample was collected for quantification of the organic matter. The main results showed that the concentrations of ammonia, total phosphorus, organic orthophosphate, organic nitrogen, total nitrogen and total dissolved solids were higher in the wetlands with waterbird nesting than in the wetlands without nests. We sampled 11,471 individuals distributed in 70 taxa. The rates of functional diversity, abundance, richness and taxonomic composition and functional composition were not influenced by the presence of birds, but abundance and taxonomic composition varied between sampling periods. Functional traits such as the debris food type, cylindrical body shape and active aquatic habit were shown to be associated with wetlands with waterbird nesting, whereas traits referring to grabbing and swimmer habits, macrophyte food type and type of passive air dispersion were associated with wetlands without nesting. Among the nutrients, the total phosphorus influenced the functional composition of aquatic insects and the orthophosphate the taxonomic composition. These results contribute to the ecology of wetlands and to a better understanding of the interactions between wetlands, waterbirds and aquatic macroinvertebrates.