Bárbara Dunck

Responses of primary production, leaf litter decomposition and associated communities to stream eutrophication

We assessed the eutrophication effects on leaf litter decomposition and primary production, and on periphytic algae, fungi and invertebrates. According to the subsidy-stress model, we expected that when algae and decomposers were nutrient limited, their activity and diversity would increase at moderate levels of nutrient enrichment, but decrease at high levels of nutrients, because eutrophication would lead to the presence of other stressors and overwhelm the subsidy effect. Chestnut leaves (Castanea sativa Mill) were enclosed in mesh bags and immersed in five streams of the Ave River basin (northwest Portugal) to assess leaf decomposition and colonization by invertebrates and fungi. In parallel, polyethylene slides were attached to the mesh bags to allow colonization by algae and to assess primary production. Communities of periphytic algae and decomposers discriminated the streams according to the trophic state. Primary production decomposition and biodiversity were lower in streams at both ends of the trophic gradient.

Functional diversity and adaptative strategies of planktonic and periphytic algae in isolated tropical floodplain lake

Functional diversity and adaptative strategies of planktonic and periphytic algae in isolated tropical floodplain lake. This study aimed to test the hypothesis that after a great magnitude and high duration of flood pulse in floodplain, functional diversity of phytoplankton and phycoperiphyton communities will be higher during high water. The strategies’ dynamics evaluated during high and low water periods consisted of size classes, life forms, and functional groups. For the phytoplankton, the adaptations to floating, and for phycoperiphyton, the intensity and structure for attachment to substrate were also analyzed. Functional diversity was calculated from functional dendrograms of species. Functional diversity, richness, and density of both communities presented the greatest values during the high waters. In the high waters, Cryptomonas marsonii Skuja was dominant in plankton and Pseudoanabaena skujae Claus in periphyton, while in the low water, Merismopedia tenuissima Lemm. was dominant in plankton and Fragilaria capucina Desm. was dominant in periphyton. Thus, the flood pulse promoted the dominance of free-floating species in plankton, during the high water, and of metaphytic species in periphyton. In the low water, we observed the dominance of species with higher surface/volume ratio in plankton, and strongly attached in periphyton. We concluded that, in isolated floodplain lake, possibly the flood pulse directs the functional diversity of phytoplankton and phycoperiphyton.

Patterns in species and functional dissimilarity: insights from periphytic algae in subtropical floodplain lakes

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 non-stochastic 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.

Distribution of periphytic algae in wetlands (Palm swamps, Cerrado), Brazil

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.

Planktonic diatoms in lotic and lentic environments in the Lago dos Tigres hydrologic system (Britânia, Goiás, Brazil): Coscinodiscophyceae and Fragilariophyceae

A floristic study of Coscinodiscophyceae and Fragilariophyceae in the Lago dos Tigres hydrologic system is presented. Phytoplankton samples were collected with a plankton net (25 µm mesh) at 11 sampling stations, three in lotic areas and eight in lacustrine zones. Eleven species of Coscinodiscophyceae and eight of Fragilariophyceae were identified; descriptions, comments, their geographic distributions for the midwestern region of Brazil, type of environment (lentic/lotic), and illustrations are provided. Among the taxa found, 13 were recorded for the first time in midwestern Brazil: Aulacoseira alpigena, A. distans, A. granulata var. angustissima, A. granulata var. valida, A. muzzanensis, Discostella stelligera var. stelligera, Fragilaria capucina var. fragilarioides, F. delicatissima var. delicatissima, F. javanica, Pleurosira laevis, Staurosira acutirostrata, Staurosirella crassa, and Ulnaria ulna.

Functional diversity and functional traits of periphytic algae during a short-term successional process in a Neotropical floodplain lake

Due to the lack of knowledge in periphytic algae functional diversity patterns during successional processes in floodplains, the present study aimed to analyze the dynamics of the functional traits and functional diversity of periphytic species during a short-term successional process in a floodplain lake. The functional traits analyzed were size class, growth form, strength of attachment to the substratum, and functional strategies. We evaluated the dynamics of these traits, considering richness, density and biovolume during an 18-day colonization in two hydrological periods. The functional diversity was assessed using the mean pairwise distance index (MPD). Dominant functional traits during the colonization changed in association with the flood pulse. Under the pulse effect, higher development of C-S strategist, loosely attached, filamentous and nanoperiphytic species occurred. The highest values of functional diversity were associated with the algal biomass peak during the colonization and the high water hydrological period, possibly indicating greater efficiency in the ecosystem functioning. These findings show the importance of the functional traits approach in periphyton studies and that the selection of functional traits must be performed taking into account traits that represent the species niche.

Periphytic algae in a floodplain lake and river under low water conditions

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 Parana 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 (Kutzing) Czarnecki and Nitzschia palea (Kutzing) 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.

The genus Pinnularia (Bacillariophyta, Pinnulariaceae) from Lago dos Tigres, Britânia, Goiás, Brazil

Studies of the genus Pinnularia Ehrenb. are only incipient in central-western Brazil, especially in Goias. Only 20 of the 170 taxa known from Brazil were recorded in this state until now. A taxonomic study of Pinnularia from Lago dos Tigres (Tocantins-Araguaia River Basin) recorded 20 specific and infraspecific taxa, distributed in 17 species, including P. instabilis whose lectotype is designated here. Only P. meridiana var. meridiana was previously recorded in aquatic systems of the state. Eighteen taxa are newly recorded for Goias, and one is the first record in Brazil. The Pinnularia flora from Lago dos Tigres contains nine taxa in common with the Amazon River Basin flora, and seven other taxa that occur elsewhere in the Parana River Basin.

First record of Pithophora oedogonia (Montagne) Wittrock (Pithophoraceae) in the Upper Paraná River floodplain, Brazil

Pithophora is the only genus recorded of the Pithophoraceae family in Brazil. Pithophora specimens were found close to banks of Hydrilla verticillata (L.F.) Royle in the Upper Parana River floodplain. The specimens showed intercalary akinetes isospores in the same individual and morphologic similarities with Pithophora oedogonia reported in previous studies. This species constitutes a new citation for the Upper Parana River floodplain and the third report for Brazil.

First Report of Colacium vesiculosum Ehrenberg 1853 (Euglenophyceae), as Epibiont on Planktonic Copepods (Crustacea, Copepoda), in a Brazilian Floodplain Lake

Epibiosis is a facultative association between two organisms: the epibiont, which colonizes the surface of living substrates, and the basibiont, which hosts the epibionts. Among protists, while numerous accounts exist for ciliates as epibionts of zooplankton, little information is available about the occurrence of this relationship between flagellates and microcrustaceans in the neotropics. During a survey on the epibiotic relationship between ciliated protists and planktonic copepods in a tropical floodplain, we reported for the first time the occurrence of Colacium vesiculosum as an epibiont on Thermocyclops minutus and Notodiaptomus amazonicus from southern Brazil. The mean infestation prevalence was significantly higher on adults 30.53% (± 2.85) in comparison with copepodites 0.87% (± 0.55). When hosts were separated by order (Calanoida and Cyclopoida) copepodites presented a mean infestation prevalence of 0.92% (± 0.85) and 0.83% (± 0.60) respectively, while adults had a mean prevalence of 29.55% (± 6.8) and 30.13% (± 5.83), which could be explained by the fact that adult copepods provide a more stable substrate for epibionts.