Ina de Souza Nogueira

Diversidade (alfa, beta e gama) da comunidade fitoplanctônica de quatro lagos artificiais urbanos do município de Goiânia, GO

O objetivo desse estudo foi comparar o numero de especies fitoplanctonicas (alfa diversidade) em periodos de chuva e seca de quatro lagos urbanos do municipio de Goiânia, bem como avaliar a riqueza total de especies de cada lago (gama diversidade) e estimar essa riqueza usando extrapoladores de riqueza, e ainda investigar as mudancas nas composicoes fitoplanctonica entre os lagos (beta diversidade). Por fim, averiguar a influencia das variaveis abioticas sobre os indices biologicos abordados. Durante o periodo de estudo um total de 325 especies foram inventariadas. Os quatro lagos apresentaram caracteristicas limnologicas distintas e apresentaram elevada riqueza de especies: lago do Jardim Botânico (194 taxons), o lago do Parque Vaca Brava (171), Lago das Rosas (211) e o lago do Bosque dos Buritis (179). Observou-se baixa similaridade floristica e elevada beta diversidade (β-1) variando de 42 (fevereiro de 2001) a 64 (outubro de 2001).

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.

Stenopterobia e Surirella (Bacillariophyceae, Surirellaceae) do Sistema Lago dos Tigres, Britânia, Goiás

Lago dos Tigres System is composed of lotic habitats (Agua Limpa and Vermelho rivers) and lentic habitats (Lago dos Tigres). It has great importance for tourism and agriculture in Britania, Goias state. Considering the lack of studies on diatoms from central western Brazil, this work aimed to identify taxa of Stenopterobia Brebisson and Surirella Turpin, Surirellaceae family, occurring in the plankton of Lago dos Tigres System during the low water period. Sampling was done from June to November 2004 at 11 stations, using a 25-µm plankton net. Sixteen taxa were identified: two taxa were recorded for the genus Stenopterobia and 14 for the genus Surirella. Surirella splendida (Ehrenberg) Kutzing was recorded at all stations. Stenopterobia delicatissima (Lewis) Brebisson and Stenopterobia pelagica Hustedt, Surirella biseriata var. constricta (Grunow) Hustedt, Surirella davidsonii Schmidt, Surirella didyma Kutzing, Surirella linearis var. helvetica (Brun.) Meister, Surirella nervosa (A. Schmidt) Mayer, Surirella rorata Frenguelli and Surirella splendida (Ehrenberg) Kutzing were registered for the first time in central western Brazil. A description, illustration and comments are given for each taxon.

Estrutura de populações de fitoflagelados nas lagoas de inundação do rio Araguaia, Brasil

The aim of this work was to evaluate ecological aspects of phytoflagellate populations during the rainy and dry seasons of 2000 and 2001 in floodplain lakes in the Araguaia River. The analyses were based on species richness, composition and biovolume of the phytoflagellates, associated with climatic and limnological variables of the water. The Mantel test showed weak spatial patterns for phytoflagellate populations; moreover the Mantel test confirmed the importance of the local component in the structure of these populations. The results of DCA applied to the biological data showed that high- and low-water periods were not strikingly different in 2000 and 2001. Biovolume data indicated that the phytoplankton was dominated by Chryptophyceae (functional group Y) and Euglenophyceae (functional group W1) in 2000 and 2001. Species richness and biovolume responded to the flood pulse. Both high- and low-water had different dynamics in the two years; this seems to indicate the importance of the flood pulse for phytoflagellates.

Desmídias (Zygnematophyceae) de hábito filamentoso da região do Vale do Paranã (Goiás, Brasil)

Resumo A regiao do Vale do Parana faz parte do bioma Cerrado e da bacia Tocantins-Araguaia, no estado de Goias. O estudo constitui o primeiro trabalho para regiao e visa apresentar o inventario de desmidias de habito filamentoso. Foram coletadas 102 amostras nos periodos de seca e chuva de 2003 atraves de diferentes metodos. As algas foram analisadas, microfotografadas e identificadas. A analise qualitativa resultou em 17 taxons. Hyalotheca dissiliens var. dissiliens f. dissiliens foi mais frequente no periodo chuvoso, enquanto Spondylosium panduriforme var. panduriforme f. panduriforme e Spondylosium panduriforme var. limneticum no periodo seco. Os alagados de varzea foram os ambientes mais propicios ao desenvolvimento de desmidias, sendo 71% dos taxons, exclusivos deste tipo de ambiente. O ambiente mais rico durante todo periodo estudado foi um alagado de Formosa com 94,1% dos taxons de desmidias filamentosas. Oito novas citacoes foram registradas para o estado de Goias. Abstract The region of the Parana Valley is part of the Cerrado biome and Tocantins-Araguaia basin (Goias state, Brazil). The study constitutes the first work for the region and aims to present the inventory of filamentous desmid forms. 102 samples were coleted in the rainy and dry seasons though different methods. The algae had been analyzed and microphotographed and identified. The qualitative analysis resulted in 17 taxa. Hyalotheca dissiliens var. dissiliens f. dissiliens was most frequent in the rainy while in the dry period Spondylosium panduriforme var. panduriforme f. panduriforme and Spondylosium panduriforme var. limneticum. The floodplain environment had been most propitious for filamentous desmid and 71% of taxa were exclusive of this environment. The sampling station of Formosa presented the most specific richness with 94,1% of taxa filamentous desmid. There were registered eight new taxa to the state of Goias.

Ocorrência e autoecologia de Acanthoceras zachariasii (Brun) Simonsen (Chaetocerales, Coscinodiscophyceae) na região centro-norte do Brasil

In this study we presented the structural and ultrastructural characterization ofAcanthoceras zachariasii (Brun) Simonsen, as well as its geographical distribution in the Amazon River Basin and Tocantins-Araguaia River Basin, Brazil, and provided the lectotypification of the taxon. We analyzed 454 phytoplanktonic samples, but the occurrence of A. zachariasiiwas recorded in only 14 of them. Of the total samples collected along the two basins, A. zachariasii was recorded only in 3.08%, which demonstrates the rarity of this taxon. This species was registered in lentic environments, with mesotrophic to eutrophic conditions, and pH varying from slightly acid to alkaline.

Ultrastructure of the type material of Encyonema leibleinii and E. lacustre (Cymbellales, Bacillariophyta)

Encyonema leibleinii and E. lacustre were among the first species of Encyonema to be described, in 1830 and 1824, respectively. Until now, however, only light microscopic features (and SEM of non-type material for E. lacustre) of these species have been documented. Here, we provide ultrastructural (scanning electron micrograph) characterization of their type material. We find that the SEM , as well as LM, features of E. leibleiniiare indistinguishable from those of E. prostratum and E. paradoxum. Consequently, the results support the synonomization of the three taxa, with E. leibleinii having priority as the first name applied to this entity. Encyonema leibleinii and E. lacustre have similar ultrastructural characteristics, mainly concerning the internal stria structure, and the terminal and central raphe fissures. Based on this information and SEM characterizations in the literature, ultrastructural features of the genus Encyonema are discussed.