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Understanding spatial and temporal changes in species composition has long demanded the attention of ecologists. However, only recently questions related to changes in species functional traits have been investigated. We explored patterns of species and functional dissimilarity of periphytic algae at six lakes sampled over a year across a subtropical floodplain. We evaluated the importance of turnover and nestedness components across space and time; the influence of environmental dissimilarity, spatial distance, and time on species and functional dissimilarity; and whether functional dissimilarity results from nonstochastic assembly processes. We used six functional traits to describe 155 species. Functional dissimilarity was estimated by functional dendrograms, and stochasticity was evaluated using null models. The turnover component was greater than nestedness for species and functional dissimilarity. Environmental dissimilarity, spatial distance, or time did not significantly explain species or functional dissimilarity. However, functional dissimilarity was significantly greater than expected given the observed species dissimilarity. The main finding of this study is that community assembly was deterministic with respect to traits. Further, each lake contributed similarly to the overall species and traits pool. These results highlight the importance of comparing species and functional dissimilarities to reach a better understanding of the organization of periphytic algal communities.

The distribution of periphytic algae communities depends on various factors such as type of substrate, level of disturbance, nutrient availability and light. According to the prediction that impacts of anthropogenic activity provide changes in environmental characteristics, making impacted Palm swamps related to environmental changes such as deforestation and higher loads of nutrients via allochthonous, the hypothesis tested was: impacted Palm swamps have higher richness, density, biomass and biovolume of epiphytic algae. We evaluated the distribution and structure of epiphytic algae communities in 23 Palm swamps of Goiás State under different environmental impacts. The community structure attributes here analyzed were composition, richness, density, biomass and biovolume. This study revealed the importance of the environment on the distribution and structuration of algal communities, relating the higher values of richness, biomass and biovolume with impacted environments. Acidic waters and high concentration of silica were important factors in this study. Altogether 200 taxa were identified, and the zygnemaphycea was the group most representative in richness and biovolume, whereas the diatoms, in density of studied epiphyton. Impacted Palm swamps in agricultural area presented two indicator species, Gomphonema lagenula Kützing and Oedogonium sp, both related to mesotrophic to eutrophic conditions for total nitrogen concentrations of these environments.Keywords: acidic water, anthropogenic activity, ecology, epiphyton. Distribuição de algas perifíticas em áreas úmidas (Veredas, Cerrado), Brasil ResumoA distribuição de comunidades de algas perifíticas depende de vários fatores, como tipo de substrato, nível de distúrbio, disponibilidade de nutrientes e luz. De acordo com a predição de que impactos de ação antrópica proporcionam alterações nas características ambientais -tornando Veredas impactadas relacionadas a alterações ambientais, como desmatamentos e maiores cargas de nutrientes via alóctone -, a hipótese testada foi: Veredas impactadas apresentam maiores riqueza, densidade, biomassa e biovolume de algas epifíticas. Avaliaram-se a distribuição e a estruturação de comunidades de algas epifíticas em 23 Veredas do Estado de Goiás sob diferentes impactos ambientais. Os atributos da estrutura de comunidade avaliados foram composição, riqueza, densidade, biomassa e biovolume. Este estudo revelou a importância das características ambientais na distribuição e na estruturação das comunidades de algas, relacionando os maiores valores de riqueza, biomassa e biovolume dos organismos aos ambientes impactados. Águas ácidas e altas concentrações de sílica foram fatores importantes no estudo. Ao todo, foram identificados 200 táxons, sendo as zignemafíceas o grupo mais representativo em riqueza e biovolume, enquanto as diatomáceas, as mais representativas em densidade do epifíton estudado. Veredas impactadas em área de agropecuária apresentaram duas espécies indicadoras, Gomphonema lagenula e Oedogonium sp., ambas re...

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Drought events will become more frequent due the climate change. In floodplains, periphytic algae are responsible for part of the primary production, are the principal source of organic carbon deposition, play an important role in mineralization and nutrient cycling, and are the base of the food web for many organisms. As algae distribution in aquatic environments is a strong indicator of physical and chemical conditions of the sites, we aimed to determine the structure of periphytic algae in lentic and lotic environments during drought conditions and to uncover the main local abiotic factors in community structuring. We hypothesized diatoms would be more frequent than green algae and desmids at both sites, due to their resistance characteristics, and that higher periphyton algal richness, density and diversity would occur in the lake due to the greater availability of nutrients and the absence of flow. The study was carried out in the Finado Raimundo lake and the Ivinhema river in the Upper Paraná river floodplain during the low water period of 2011. Petioles of the aquatic macrophyte Eichhornia azurea (Sw.) Kunth were used as a substrate for periphytic algae. We found a total of 171 species, 104 species in the lake and 80 in the river. Diatoms were predominant at both sites due to their strategic traits, and between sites, there were different patterns in the periphytic algal community structure, owing to the distinctive physical and chemical characteristics of the lake and the river. Achnanthidium minutissimum (Kützing) Czarnecki and Nitzschia palea (Kützing) W. Smith were the most abundant species in both environments. Our results showed patterns of periphytic algae in a floodplain during drought conditions, which will assist in understanding their structuring during future drought scenarios.