Influência do nitrato e fosfato no crescimento de Schizomeris leibleinii Kützing (Chaetophorales, Chlorophyta)

Schizomeris leibleinii Kützing é uma alga filamentosa comumente encontrada em ambientes aquáticos continentais eutrofizados ou poluídos por nutrientes orgânicos e é um potencial organismo indicador de poluição orgânica. Estudos envolvendo o cultivo de S. leibleinii sob concentrações variáveis de nitrato e fosfato foram efetuados durante períodos de 50 dias. A biomassa foi expressa através da quantificação da concentração de clorofila a relativa a diferentes tempos de cultivo. Além da análise das curvas de crescimento, os dados obtidos foram submetidos à Anova (uma via) e teste de Tukey para comparação entre os tratamentos. Os resultados revelaram que S. leibleinii apresentou crescimento rápido sob baixas concentrações de nitrato e fosfato, mas o melhor desempenho ocorreu em concentrações altas de nitrato. Verificou-se nesta espécie que condições de estresse ambiental provocam, inicialmente, crescimento rápido, possivelmente acompanhado de intensa reprodução. Apesar do rápido desenvolvimento, a avaliação das curvas de crescimento de S. leibleinii sugere que esta espécie é um estrategista em k. Além disso, a alga mostrou-se mais dependente da concentração de nitrato do que de fosfato, indicando o nitrogênio como limitante do crescimento em meio de cultura.

Photoacclimation in a tropical population of Cladophora glomerata (L.) Kützing 1843 (Chlorophyta) from southeastern Brazil

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Photosynthetic characteristics of a tropical population of Nitella cernua (Characeae, Chlorophyta)

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Temporal dynamics of two species of Chaetophoraceae (Chlorophyta) in tropical streams of São Paulo State, Southeastern Brazil

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Microhabitat and plant structure of Characeae (Chlorophyta) populations in streams from São Paulo State, southeastern Brazil

Microhabitat distribution was investigated in five populations of Characeae (two of Chara guairensis, two of Nitella subglomerata and one of Nitella sp.) to determine the distributional patterns, the morphometric and reproductive adaptations to varying environmental conditions and niche width on a scale of few centimeters. Variations in physical variables revealed some general trends of microhabitat distribution for the Characeae populations studied, with occurrence under the following conditions: slow and narrow current velocities; substrata predominantly composed of small particle size (sand-clay); variable and generally low depths. In terms of morphological adaptations, we found some general patterns: plants with longer whorl branchlets also had longer internodes in all populations studied, whereas longer plants had also thicker axis. The former were generally associated with higher biomass (percent cover). Few correlations of morphological characters were observed with environmental variables (e.g. plant length with irradiance: negative in two populations and positive in one population). Despite the general patterns of occurrence mentioned above, our results also indicated that each population differed in its responses to environmental variables and had particular morphological and reproductive adaptations. The Characean populations occurred under a narrower range of microhabitat conditions than other macroalgae from lotic habitats, particularly lower current velocity (6.7-9.8 cm s(-1)) and a more specific substratum type (sand-clay). Niche width values (0.60-0.99) of the Characeae populations studied indicate a high degree of habitat specialization and are among the highest yet found in lotic macroalgae. The relatively narrow variations in microhabitat conditions and high niche widths here reported for Characean populations, suggest a lower tolerance to variations in current velocity, depth, irradiance and substratum type. These characteristics probably explain the relatively restricted distribution of Characeae species in streams of S (a) over tildeo Paulo State with low frequency of records in most regions.

Microhabitat and morphometric variation of two chaetophoracean (chaetophorales, chlorophyta) species in tropical streams of southeastern Brazil

Two populations of Chaetophora elegans (Roth) C. Agardh and two of Stigeoclonium helveticum Vischer were investigated for microhabitat characteristics and morphological variation in streams of Sao Paulo State, southeastern Brazil. Different patterns of microhabitat distribution were found between species investigated. Populations of C. elegans were distributed under relatively narrow microhabitat conditions (high irradiance, low depth, moderate to high current velocity, rocky substrata and lower values of niche width) and showing little morphometric variation (colony diameter, main axis cell size, and apical branch number). Stigeoclonium helveticum occurred under more diverse microhabitat conditions, revealed by lack of significant difference between sampling units with and without the alga and wider niche width, but also exhibited relatively narrow morphometric variation (plant length, main axis cell and lateral branch cell sizes). The narrow microhabitat conditions and smaller niche width of C. elegans can explain its low abundance (percentage cover) in streams from the area studied as well as in other regions of Sao Paulo State. In contrast, the wider variation of microhabitat conditions and the higher niche widths of S. helveticum suggest that this green alga is able to grow in a high number of stream ecosystems in the region investigated, ranging from undisturbed to highly disturbed habitats. Thus, the results suggest that S. helveticum is a generalist species.

Lead- and copper-complexing extracellular ligands released by Kirchneriella aperta (Chloroccocales, Chlorophyta)

The freshwater planktonic alga Kirchneriella aperta was grown in batch cultures to stationary growth phase. Copper and lead complexation properties of the exudate from stationary and exponential growth phases were determined by titrations monitored by ion-selective electrodes. Molecular weight fractionation dialysis) and analysis of the titration data (Scatchard Plot) revealed that K. aperta releases metal-complexing ligands. Copper is associated with low and high molecular weight compounds, whereas lead forms complexes with only high molecular weight compounds. Gas-liquid chromatography showed that mannose and rhamnose make up 74% of the total high molecular weight organic material, with uronic acids present at 19%.

Copper complexation by Cyanophyta and Chlorophyta exudates

Several freshwater phytoplanktonic species (eukaryotic and prokaryotic) were grown in batch cultures up to stationary phase and quantified by chlorophyll a analysis. The complexation properties (conditional stability constant and total ligand concentration) of their exudates were investigated by complexometric titrations of the culture media using either copper or lead ion-selective electrodes. For most algae, Scatchard plot analysis of the titration data revealed two classes of copper-complexing ligands, one weaker and the other stronger. Strong copper-complexing agents were produced by Cyanophyta mainly in stationary growth phase. During exponential phase, ligand concentrations and the affinity for copper were similar for both Chlorophyta and Cyanophyta. Complexation parameters for Chlorophyta exudates were similar for both growth phases: exponential and stationary. In contrast, ligand concentrations were similar for Cyanophyta, but the conditional stability constants (the strength of association between ligand and metal) were different. Weak lead-complexing ligands were produced exclusively by two Chlorophyta.

Aspectos taxonômicos e amplitude ecológica de Schizomeris leibleinii (Chaetophorales, chlorophyta)

Pós-graduação em Ciências Biológicas (Biologia Vegetal) - IBRC

Uso de meio a base de esterco suíno no cultivo de Ankistrodesmus gracilis (Chlorophyta) em laboratório

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Trentepohliales (Ulvophyceae, Chlorophyta) de biomas brasileiros: flora, taxonomia e filogenia

Pós-graduação em Ciências Biológicas (Biologia Vegetal) - IBRC

Desempenho de Ankistrodesmus gracilis (Reischi) Korsikov (Chlorophyta) cultivada em três meios de cultura em laboratório

Pós-graduação em Aquicultura - FCAV

Clypeina tibanai, sp. nov. (Polyphysacea, Dasycladales, Chlorophyta), mid-Cretaceous green alga from the Potiguar Basin, Brazilian margin of the young South Atlantic Ocean

The fossil genus Clypeina (Michelin, 1845) comprises some 40 species. We describe Clypeina tibanai, a new species from ? upper Albian-Cenomanian strata of the Potiguar Basin, Brazil, characterised by closely set verticils of tubular, bended laterals. It is compared with Clypeina hanabataensis Yabe & Toyama, 1949, a Late Jurassic species, and with Pseudoactinoporella fragilis (Conrad, 1970), an Early Cretaceous taxon. The new species belongs to a short list of green algae found in the young South Atlantic oceanic corridor, an assemblage defining a phycological paleobioprovince discrete from that of the Tethyan realm.

Phylogenetic analysis of Codium species from Brazil, with the description of the new species C. pernambucensis (Bryopsidales, Chlorophyta)

The genus Codium comprises c. 125 species widely distributed in marine coastal environments throughout the world. Due to morphological plasticity, the taxonomic delimitation of Codium species can be difficult. Sequences of the first exon of the large subunit of RUBISCO (rbcL) have been used in the molecular delimitation of species and for phylogenetic purposes. In the present study, we complement previous morphological work on Brazilian Codium species with molecular systematics. Based on the partial rbcL sequences, seven species are recognized along the Brazilian coast: C. decorticatum, C. intertextum, C. isthmocladum, C. profundum, C. spongiosum, C. taylorii and the new species Codium pernambucensis. Ten unique sequences were obtained among the samples examined, which we used in combination with previously published sequences to infer molecular phylogenies using various methods. The resulting trees showed three principal monophyletic groupings: Clade A with species having a prostrate habit, not branched, and mostly with small, grouped utricles; Clade B primarily consisting of upright species with cylindrical branches and large individual utricles; and Clade C composed of upright species with cylindrical branches that are slightly flattened, and have intermediate-sized individual utricles. The Brazilian species grouped with morphologically similar taxa from other geographic localities, and are present in all three main clades. A new sprawling species, Codium pernambucensis is described based on morphology and molecular analyses.