Taxonomy of common taxa of Chlorophyceae (Chlorophyta) and Zygnematophyceae (Streptophyta) from periphyton of a Neotropical floodplain

Some orders of algal groups such as Chlorophyceae and Zygnematophyceae have been reported as frequent taxa in periphytic communities of wetlands. The present study aimed at submitting these algal members which occurred in high abundance and frequency in the periphyton of 30 environments of the Upper Paraná River floodplain to a taxonomic survey and to present some ecological data concerning their richness. Periphyton were collected from petioles by scraping of Eichhornia azurea (Sw.) Kunth and preserved with Lugol acetic solution in the Upper Paraná River, Brazil, during high water period in March 2010. Taxa were counted in inverted microscope and those higher than 2,500 individuals in density with frequency of occurrence less than 50% simultaneously in the 30 environments sampled were subjected to a detailed taxonomical treatment under optical microscope coupled to a light camera and ocular micrometer under 1000x. Identifications and descriptions were made according to the algal literature. Some abiotic data were shown. Fifteen taxa belonging to the classes Chlorophyceae and Zygnematophyceae were abundant representing 64.6% of the total density. A Procruste analysis within a Detrended Correspondence Analysis showed that distribution pattern of richness of clorophyceans and zygnematophyceans was represented by common species of these communities, highlighting the importance of knowing about these algae taxonomy

Main predictors of periphyton species richness depend on adherence strategy and cell size.

Periphytic algae are important components of aquatic ecosystems. However, the factors driving periphyton species richness variation remain largely unexplored. Here, we used data from a subtropical floodplain (Upper Paraná River floodplain, Brazil) to quantify the influence of environmental variables (total suspended matter, temperature, conductivity, nutrient concentrations, hydrology, phytoplankton biomass, phytoplankton species richness, aquatic macrophyte species richness and zooplankton density) on overall periphytic algal species richness and on the richness of different algal groups defined by morphological traits (cell size and adherence strategy). We expected that the coefficients of determination of the models estimated for different trait-based groups would be higher than the model coefficient of determination of the entire algal community. We also expected that the relative importance of explanatory variables in predicting species richness would differ among algal groups. The coefficient of determination for the model used to predict overall periphytic algal species richness was higher than the ones obtained for models used to predict the species richness of the different groups. Thus, our first prediction was not supported. Species richness of aquatic macrophytes was the main predictor of periphyton species richness of the entire community and a significant predictor of the species richness of small mobile, large mobile and small-loosely attached algae. Abiotic variables, phytoplankton species richness, chlorophyll-a concentration, and hydrology were also significant predictors, depending on the group. These results suggest that habitat heterogeneity (as proxied by aquatic macrophytes richness) is important for maintaining periphyton species richness in floodplain environments. However, other factors played a role, suggesting that the analysis of species richness of different trait-based groups unveils relationships that were not detectable when the entire community was analysed together.

Epiphytic diatoms (Diatomeae) from Piraquara II urban reservoir, Paraná state / Diatomáceas epifíticas (Diatomeae) no reservatório urbano Piraquara II, estado do Paraná

Abstract We conducted a taxonomical study of epiphytic diatoms on the macrophytes Polygonum hydropiperoides, Ludwigia peruviana and Alternanthera philoxeroides collected in the mesotrophic reservoir Piraquara II flooded in 2009, located in the state of Paraná. A total of 135 infrageneric taxa were identified, among them five at generic level and other five are first records to the state. We provided illustration, valve metrics, meristics limits and taxonomic reference for each taxon. Also, life forms and species frequency are given. The most frequent diatoms totalized 15.3% of total identified taxa and sporadic species represented 54.7%. Achnanthidium minutissimum (Kützing) Czarnecki and Brachysira neoexilis Lange-Bertalot occurred in more than 90% of analyzed samples. Among the very frequent diatoms we found other species included in Achnantidium, Fragilaria and Eunotia. The solitary Discotella stelligera (Cleve & Grunow) Houk & Klee and the short chain Aulacoseira tenella (Nygaard) Simonsen are free living species that entangle among diatoms from the biofilm.

Resumo Realizamos um estudo taxonômico das diatomáceas epifíticas nas macrófitas: Polygonum hydropiperoides, Ludwigia peruviana e Alternanthera philoxeroides, coletadas no reservatório Piraquara II, uma represa urbana mesotrófica inundada em 2009, localizado no estado do Paraná. Um total de 135 táxons infragenéricos foi determinado, entre os quais cinco foram citações pioneiras para o Estado. Ilustrações, limites métricos, merísticos e referências taxonômicas para cada táxon foram providenciadas. Também, dados sobre formas de vida e frequência das espécies foram adicionados. As diatomáceas mais frequentes totalizaram 15,3% dos táxons determinados e as espécies esporádicas representaram 54%. Achnanthidium minutissimum (Kützing) Czarnecki and Brachysira neoexilis Lange-Bertalot ocorreram em mais de 90% das amostras analisadas. Dentre as diatomáceas muito frequentes encontram-se outras espécies de Achnanthidium, Fragilaria e Eunotia. Discostella stelligera (Cleve & Grunow) Houk & Klee, uma diatomácea solitária, e Aulacoseira tenella (Nygaard) Simonsen, com cadeias curtas, são espécies livres que se emaranham entre as diatomáceas do biofilme.

Acanthoceras and Urosolenia species (Diatomeae) in subtropical reservoirs from South Brazil: Ultrastructure, distribution and autoecology / Espécies de Acanthoceras e Urosolenia (Diatomeae) em reservatórios subtropicais do sul do Brasil: ultraestrutura, distribuição e autoecologia

Acanthoceras Honigmann and Urosolenia Round & Crawford emend. Rott, Kling & McGregor species were studied based on samples of 19 hydroelectric power plants reservoirs located in the State of Paraná, Southern Brazil. Autoecological informations of Urosolenia species complement the study. One Acanthoceras and four Urosolenia species were identified: A. zachariasii (Brun) Simonsen, U. amazonica Sala, Núãez-Avellaneda & Vouilloud, U. eriensis var. morsa (West & G.S.West) Bukhtiyarova, U. longiseta Zacharias and U. obesa Freire, Tremarin & Ludwig. Morphological variation of frustules was described and illustrated by optical and scanning electron microscopy, and compared with similar species such as U. delicatissima Sala, Núãez-Avellaneda & Vouilloud and U. eriensis var. eriensis (H.L.Smith) Round & Crawford. The pioneer record of U. amazonica to Brazil and unprecedent details of the ultrastructure of A. zachariasii and U. longiseta are included in this study. Cellular densities differed among evaluated reservoirs showing strong correlations with inorganic nitrogen concentrations, N/P ratio and temperature. The results suggested higher densities in periods of warmer temperatures and low availability of the nitrogen compounds and confirmed that species respond strongly to local environmental gradients.

Espécies de Acanthoceras Honigmann e Urosolenia Round & Crawford emend. Rott, Kling & McGregor foram estudadas com base em amostras provenientes de 19 reservatórios de usinas hidrelétricas do estado do Paraná, sul do Brasil. Informações sobre a autoecologia das espécies de Urosolenia complementam o estudo. Uma espécie de Acanthoceras e quatro de Urosolenia foram identificadas: A. zachariasii (Brun) Simonsen, U. amazonica Sala, Núãez-Avellaneda & Vouilloud, U. eriensis var. morsa (West & G.S.West) Bukhtiyarova, U. longiseta Zacharias e U. obesa Freire, Tremarin & Ludwig. A variação morfológica das frústulas foi descrita e ilustrada através de microscopia óptica e eletrônica de varredura e comparada com a de espécies similares, como U. delicatissima Sala, Núãez-Avellaneda & Vouilloud e U. eriensis var. eriensis (H.L.Smith) Round & Crawford. O registro pioneiro de U. amazonica para o Brasil e detalhes inéditos da ultraestrutura de A. zachariasii e U. longiseta estão contemplados neste estudo. As densidades celulares diferiram entre os reservatórios avaliados e mostraram forte correlação com concentrações de nitrogênio inorgânico, relação N/P e temperatura. Os resultados sugeriram densidades mais elevadas em períodos de temperaturas mais quentes e baixa disponibilidade de compostos nitrogenados e confirmaram que as espécies respondem fortemente aos gradientes ambientais locais.

Desiccation and recovery of periphyton biomass and density in a subtropical lentic ecosystem / Dessecamento e recuperação da biomassa e densidade do perifíton em ecossistema lêntico subtropical

This study assessed the desiccation effects on biomass and algal density of periphyton in a subtropical lentic ecosystem. This experiment was conducted with only one in situ experimental desiccation event for 15 hours in a mature periphytic community. The periphyton after desiccation was distinct in density and biomass estimators (dry weight and chlorophyll a ) when compared to the control periphyton. After the tenth day of desiccation, the community presented similar values for biomass estimators when compared to the control periphyton. The density and biomass estimators of the periphyton community was affected by the desiccation event and required about ten days to recover to pre-disturbance conditions.

Este estudo avaliou os efeitos do dessecamento sobre a biomassa e a densidade algal do perifíton em ecossistema lêntico subtropical. Neste experimento foi realizado um evento in situ de 15h de emersão sobre a comunidade perifítica em estágio maduro de desenvolvimento. O perifíton sujeito ao dessecamento foi distinto na densidade e nos estimadores de biomassa (peso seco e clorofila) em relação ao perifíton controle. Após do décimo dia de dessecamento, a comunidade apresentou valores similares dos estimadores de biomassa quando comparado com o perifíton controle. A densidade e os estimadores de biomassa da comunidade perifítica foram afetadas pelo evento de dessecamento e requereu dez dias para retornar as condições de pré-distúrbio.