Algas planctônicas do reservatório da Pampulha (MG): Euglenophyta, Chrysophyta, Pyrrophyta, Cyanobacteria

Neste trabalho foram descritos 28 táxons de algas planctônicas pertencentes às divisões Euglenophyta, Chrysophyta, Pyrrophyta e Cyanobacteria, encontradas no reservatório da Pampulha, estado de Minas Gerais. Foram analisadas amostras no período de maio/1992 a fevereiro/1997. Em número de espécies, Euglenophyta foi a que apresentou maior número (13 espécies em uma família), seguidas de Cyanobacteria (oito espécies), Pyrrophyta (cinco espécies) e Chrysophyta (duas espécies). Vinte e três táxons são primeiras citações para o estado de Minas Gerais.

Cylindrospermopsis raciborskii (Woloszynska) Seenayya & Subba Raju(Cyanobacteria): variação semanal e relações com fatores ambientais em um reservatório eutrófico, São Paulo, SP, Brasil

Florações de Cylindrospermopsis raciborskii têm sido cada vez mais freqüentes em reservatórios brasileiros em virtude da sua alta competitividade em ambientes tropicais eutrofizados. Esta espécie é produtora de toxinas extremamente agressivas, as quais podem causar problemas de saúde pública e danos ao meio ambiente. Nosso objetivo foi acompanhar a variação temporal da densidade desta população relacionando-a com variáveis ambientais e detectando os possíveis fatores que interferem no seu desenvolvimento. O lago estudado localiza-se na zona sul do Município de São Paulo (23º39' S e 46º37' W). É um corpo d'água eutrofizado e vem apresentando florações freqüentes de C. raciborskii. Amostras de água foram coletadas semanalmente, na parte mais profunda do lago, durante o período de setembro/97 a setembro/98. Foram analisados o perfil térmico, zona de mistura, transparência, zona eufótica, turbidez, pH, alcalinidade, condutividade, oxigênio dissolvido, nutrientes, clorofila a, densidade da população e densidade total da comunidade fitoplanctônica. A ordenação dos dados abióticos e bióticos foi feita através da análise de componentes principais (PCA) e análise de correspondência canônica (CCA). Durante os meses de novembro e dezembro/97 foram registrados os mais altos valores de densidade de C. raciborskii. Entre 10/12 e 17/12, a espécie contribuiu com 50% para a densidade total da comunidade. Nesse período foram registradas estratificações térmicas, elevados valores de temperatura da água e de turbidez e baixos valores de transparência da água. Os meses de outono e inverno de 1998 foram caracterizados pela ausência da espécie estudada, desestratificação térmica da coluna d'água, baixas temperaturas da água, altos valores de transparência (os maiores já registrados para o ambiente) e pelo aumento considerável dos bancos da macrófita aquática flutuante Eichhornia crassipes (Mart.) Solms. Tais interrelações são discutidas no presente trabalho.

Planktic Cyanobacteria from São Paulo State, Brazil: Chroococcales

The biodiversity studies of planktic cyanobacteria started in 1997 with intensive collecting in different water bodies of São Paulo State. Due to the problems brougth by eutrophication and cyanobacterial blooms, the samplings were concentrated in reservoirs of Alto Tietê region that supply drinking water to millions of people. The samples were collected with 20 µm plankton net or Van Dorn's bottle. Part of each one was preserved in formaldehyde or lugol solution and part was isolated. The culture strains were kept in BG11 and/or AMS1 media. Based on natural and culture material, 26 species were identified belonging to the families Chroococcaceae (2 taxa), Merismopediaceae (12), Microcystaceae (7) and Synechococcaceae (5). Among these species, six are potentialy toxic: Aphanocapsa incerta (Lemmerm.) Cronberg & Komárek, Microcystis aeruginosa (Kütz.) Kütz., M. botrys Teiling, M. panniformis Komárek et al., M. wesenbergii (Komárek) Komárek, and Radiocystis fernandoi Komárek & Komár.-Legn. Bacularia and Coelosphaeriopsis are genera reported for the first time in Brazil.

Effect of nitrate and ammonium on the growth and protein concentration of Microcystis viridis Lemmermann (Cyanobacteria)

Cyanobacteria are a very important group in aquatic systems, particularly in eutrophic waters. Therefore studies about their success in the environment are essential. Many hypotheses have tried to explain the dominance of Cyanobacteria, and several emphasized the importance of various nitrogen sources for the success of the group. In this study, we measured the effect of ammonium and nitrate on the growth and protein concentration of Microcystis viridis (Cyanobacteria). This species is well-known because bloom formation in eutrophic waters. The study was carried out, in experimental batch cultures, using the WC medium with different nitrogen sources: ammonium, nitrate, ammonium + nitrate (50% ammonium + 50% nitrate) and ammonium at different concentrations (to test for possible NH4+ toxicity). Protein, ammonium and nitrate concentrations were measured at end of each experiment, whereas samples for cell counts were taken daily. Results showed that Microcystis viridis grew faster with ammonium (µ = 0.393 day-1) than with nitrate (µ = 0.263 day-1) and ammonium + nitrate (µ = 0.325 day-1). This pattern is explained by the metabolism of ammonium that presents higher uptake and assimilation rates than nitrate. Maximum cell concentration, however, was higher in the ammonium + nitrate treatment, followed by nitrate treatment. Higher protein concentration were observed in the treatment with nitrate. In the ammonium toxicity test, no difference between the control and NH4+ at 50% was found. Thus, the ammonium concentrations used in these experiments were not toxic. Our results suggest that Cyanobacteria is able to grow on both nitrogen sources even if ammonium may allow faster growth and bloom development.

Occurrence of the rare genus Microcrocis P. Richter (Chroococcales, Cyanobacteria) in a coastal lagoon from southern Brazil

The paper records the first occurrence of the genus Microcrocis P. Richter (Chroococcales, Cyanobacteria), represented by M. pulchella (Buell) Geitler, in Brazil. The species was found in two zones, one with freshwater and the other with brackish water, of a coastal lagoon of Rio Grande do Sul State (31°15’-31°30’ S and 50°54’-51°09’ W). Comparison between M. pulchella and its most closely related species is presented. Up to now this species had occurrence records limited to freshwater systems in temperate regions. Its presence in a subtropical coastal lagoon from southernmost Brazil, either in fresh or in brackish water, broadened the knowledge of the distribution area of M. pulchella.

Planktic Cyanobacteria from upper Tietê basin reservoirs, SP, Brazil

Considering the great ecological and sanitary importance of the cyanobacteria and the need of detailed information about these organisms in Brazilian water bodies, the present study aims at contributing towards the knowledge of the cyanobacterial flora of five reservoirs belonging to the upper Tietê Basin, São Paulo: Billings, Guarapiranga, Jundiaí, Pirapora, Ponte Nova and Taiaçupeba. In the past several years, these reservoirs have been submitted to severe environmental deterioration and have repeatedly presented cyanobacterial blooms, including those of toxic species. The samples were collected between 1997 and 2003 either with plankton net (20 µm mesh) or van Dorn's bottle, and preserved with lugol solution or formaldehyde. Some species were isolated and maintained in culture. Forty-eight species of cyanobacteria were identified, with predominance of the order Chroococcales (58%), followed by the orders Oscillatoriales (21%) and Nostocales (21%). Among the 48 studied species, 17 (35%) were considered potentially toxic. The occurrence and biodiversity of the cyanobacteria in each reservoir depend on the environmental conditions. Among the five water bodies, Billings Reservoir presented the most adequate situation for the development of a greater number of species (34), probably due to its high pH values (around 8). Pirapora Reservoir on the other hand, with highest conductivity (445.0 µS cm-1) and lowest Secchi depth values (0.2 m), presented the lowest cyanobacterial biodiversity (14 species).

Cyanoaggregatum brasiliense gen. et sp. nov., a new chroococcal Cyanobacteria from Southern Brazil

The paper proposed Cyanoaggregatum brasiliense, a new genus and species from the plankton of a subtropical brackish coastal lagoon from Rio Grande do Sul State, South Brazil. It differs from all other members of Chroococcales by its characteristic arrangement of cells in irregular groups distributed in a single, flat or slightly curved layer, on irregular rows, slightly distant from each other, forming a mosaic-like pattern slightly below the surface of the mucilaginous colonial envelope. The cell division in one plane perpendicular to the long axis and the lack of pseudo-filaments indicate its classification in the family Synechococcaceae, sub-family Aphanothecoideae. The general characteristics, the diagnostic criteria and the taxonomic position are discussed, and a comparison between Cyanoaggregatum and its most closely related genera is presented. Physical and chemical data on the studied lagoon and geographical distribution are presented.

Subgeneric diversity of Brasilonema (Cyanobacteria, Scytonemataceae)

The recently described scytonematoid cyanobacterial genus Brasilonema is known mainly from tropical and subtropical rain forests (Mata Atlântica) of southeastern Brazil, where it occurs in aerophytic wooden, stony and iron substrates. This genus was defined according to both molecular and morphological criteria. The type species B. bromeliae was described from the specialized habitat: it grows in phytothelmes, epiphytic on both living and died leaves within the rosettes of large bromeliad plants slightly above or in the zone of the water level. The genus Brasilonema is evidently widely distributed in coastal forests of São Paulo State, where it occurs also in remarkable diversity. According to our results, this genus currently comprises seven taxa, which are distinct by different morphology and ecological characteristics.

Cyanobacteria from coastal lagoons of Southern Brazil: coccoid organisms

Considering the great ecological importance of the cyanobacteria and the need for more detailed information about these organisms in Brazilian waters, this paper provides taxonomic information about the unicellular cyanobacteria flora in lagoon systems along the coastal plains of Rio Grande do Sul State. Sampling was performed in different freshwater bodies along the eastern (Casamento Lake area) and western (near the city of Tapes) banks of the Patos Lagoon (30º40' S-30º10' S and 50º30' W-51º30' W). The samples were collected once in the rainy season and once in the dry season (from May 2003 to December 2003) using a plankton net (25 µm mesh) in pelagic and littoral zones, and by squeezing the submerged parts of aquatic macrophytes. Thirty one species belonging to the families Synechoccocaceae (7 taxa), Merismopediaceae (12 taxa), Chamaesiphonaceae (1 taxon), Microcystaceae (4) and Chroococcaceae (7 taxa) were identified. Among these species, five are reported for the first time in Rio Grande do Sul State: Chamaesiphon amethystinus (Rostafinski) Lemmermann, Chroococcus minimus (Keissler) Lemmermann, Coelomoron pusillum (Van Goor) Komárek, Coelosphaerium kuetzingeanum Naegeli, and Cyanodictyon tubiforme Cronberg.

Corticolous cyanobacteria from tropical forest remnants in northwestern São Paulo State, Brazil

Cyanobacteria are common in aquatic environments but are also well-adapted to terrestrial habitats where they are represented by a diversified flora. The present study aimed to contribute to our taxonomic knowledge of terrestrial cyanobacteria by way of a floristic survey of the main components of corticolous communities found in seasonal semideciduous forest fragments. Samples of visible growths of Cyanobacteria, algae, and bryophytes found on tree bark were randomly collected and their taxonomies examined. Eighteen species of Cyanobacteria were found belonging to the genera Aphanothece, Chroococcus, Lyngbya, Phormidium, Porphyrosiphon, Hapalosiphon, Hassalia, Nostoc, Scytonema, and Stigonema. Many genera and species observed in the present work have been reported in previous surveys of the aerophytic flora in several regions of the world, although six species were described only on the basis of populations found in the forest fragments studied, which highlights the importance of taxonomic studies of cyanobacteria in these habitats.

A new species of Lemmermanniella (Cyanobacteria) from the Atlantic Rainforest, Brazil

The Brazilian Atlantic Rainforest is a highly heterogeneous ecosystem comprising large numbers of tropical and subtropical habitats favorable to the development of cyanobacteria. Studies on cyanobacteria in this ecosystem are still rare, however, especially those involving unicellular and colonial types. The high biodiversity and endemism of this biome has been extremely impacted and fragmented, and less than 10% of its original vegetation cover remains today. We describe here a new species of a colonial cyanobacteria, Lemmermanniella terrestris, found on dry soils in a subtropical region of the Atlantic Rainforest in the municipality of Cananéia in southern São Paulo State, Brazil. This new taxon demonstrated all of the diacritical features of the genus Lemmermanniella but, unlike the other species of the genus, it was growing on the soil surface and not in an aquatic environment. A set of morphological features, including colonies composed of subcolonies, and cell dimensions, shapes and contents distinguish it from other species of the genus. Considering that species of Lemmermanniella are found in very distinct habitats (such as thermal and brackish waters) and that they maintain the same life cycle described for the genus in all of those environments, the morphological structures of the colonies can be used as reliable markers for identifying the genus, and its species differ primarily in relation to the habitats they occupy.

Cyanobacteria from coastal lagoons in southern Brazil: non-heterocytous filamentous organisms

This study describes and illustrates non-heterocytous filamentous cyanobacteria found in lagoon systems on the coastal plains of Rio Grande do Sul State. Collections were carried out in different freshwater bodies along the eastern (Casamento Lake area) and western (Tapes City area) margins of the Patos Lagoon (UTM 461948-6595095 and 542910-6645535) using a plankton net (25 µm mesh) in pelagic and littoral zones as well as by squeezing submerged parts of aquatic macrophytes, during both the rainy and dry seasons, from May to December/2003. Twenty two species belonging to the families Phormidiaceae (eight taxa), Pseudanabaenaceae (seven taxa), Oscillatoriaceae (six taxa), and Spirulinaceae (one taxon) were identified. Among these species, five are reported for the first time from Rio Grande do Sul State: Leptolyngbya cebennensis, Microcoleus subtorulosus, Oscillatoria cf. anguina, O. curviceps and Phormidium formosum.

Cyanobacterial toxins in Portugal: effects on aquatic animals and risk for human health

Toxic cyanobacteria are common in Portuguese freshwaters and the most common toxins are microcystins. The occurrence of microcystin-LR (MCYST-LR) has been reported since 1990 and a significant number of water reservoirs that are used for drinking water attain high levels of this toxin. Aquatic animals that live in eutrophic freshwater ecosystems may be killed by microcystins but in many cases the toxicity is sublethal and so the animals can survive long enough to accumulate the toxins and transfer them along the food chain. Among these, edible mollusks, fish and crayfish are especially important because they are harvested and sold for human consumption. Mussels that live in estuarine waters and rivers where toxic blooms occur may accumulate toxins without many significant acute toxic effects. In this study data are presented in order to understand the dynamics of the accumulation and depuration of MCYST-LR in mussels. The toxin is readily accumulated and persists in the shellfish for several days after contact. In the crayfish the toxin is accumulated mainly in the gut but is also cleared very slowly. In carps, although the levels of the toxins found in naturally caught specimens were not very high, some toxin was found in the muscle and not only in the viscera. This raises the problem of the toxin accumulation by fish and possible transfer through the food chain. The data gathered from these experiments and from naturally caught specimens are analyzed in terms of risk for human consumption. The occurrence of microcystins in tap water and the incidence of toxic cyanobacteria in fresh water beaches in Portugal are reported. The Portuguese National Monitoring Program of cyanobacteria is mentioned and its implications are discussed.

Extended hydrogen photoproduction by nitrogen-fixing cyanobacteria

Cyanobacteria are the only prokaryotic organisms performing oxygenic photosynthesis. They comprise a diverse and versatile group of organisms in aquatic and terrestrial environments. Increasing genomic and proteomic data launches wide possibilities for their employment in various biotechnical applications. For example, cyanobacteria can use solar energy to produce H2. There are three different enzymes that are directly involved in cyanobacterial H2 metabolism: nitrogenase (nif) which produces hydrogen as a byproduct in nitrogen fixation; bidirectional hydrogenase (hox) which functions both in uptake and in production of H2; and uptake hydrogenase (hup) which recycles the H2 produced by nitrogenase back for the utilization of the cell. Cyanobacterial strains from University of Helsinki Cyanobacteria Collection (UHCC), isolated from the Baltic Sea and Finnish lakes were screened for efficient H2 producers. Screening about 400 strains revealed several promising candidates producing similar amounts of H2 (during light) as the ΔhupL mutant of Anabaena PCC 7120, which is specifically engineered to produce higher amounts of H2 by the interruption of uptake hydrogenase. The optimal environmental conditions for H2 photoproduction were significantly different between various cyanobacterial strains. All suitable strains revealed during screening were N2-fixing, filamentous and heterocystous. The top ten H2 producers were characterized for the presence and activity of the enzymes involved in H2 metabolism. They all possess the genes encoding the conventional nitrogenase (nifHDK1). However, the high H2 photoproduction rates of these strains were shown not to be directly associated with the maximum capacities of highly active nitrogenase or bidirectional hydrogenase. Most of the good producers possessed a highly active uptake hydrogenase, which has been considered as an obstacle for efficient H2 production. Among the newly revealed best H2 producing strains, Calothrix 336/3 was chosen for further, detailed characterization. Comparative analysis of the structure of the nif and hup operons encoding the nitrogenase and uptake hydrogenase enzymes respectively showed minor differences between Calothrix 336/3 and other N2-fixing model cyanobacteria. Calothrix 336/3 is a filamentous, N2-fixing cyanobacterium with ellipsoidal, terminal heterocysts. A common feature of Calothrix 336/3 is that the cells readily adhere to substrates. To make use of this feature, and to additionally improve H2 photoproduction capacity of the Calothrix 336/3 strain, an immobilization technique was applied. The effects of immobilization within thin alginate films were evaluated by examining the photoproduction of H2 of immobilized Calothrix 336/3 in comparison to model strains, the Anabaena PCC 7120 and its ΔhupL mutant. In order to achieve optimal H2 photoproduction, cells were kept under nitrogen starved conditions (Ar atmosphere) to ensure the selective function of nitrogenase in reducing protons to H2. For extended H2 photoproduction, cells require CO2 for maintenance of photosynthetic activity and recovery cycles to fix N2. Application of regular H2 production and recovery cycles, Ar or air atmospheres respectively, resulted in prolongation of H2 photoproduction in both Calothrix 336/3 and the ΔhupL mutant of Anabaena PCC 7120. However, recovery cycles, consisting of air supplemented with CO2, induced a strong C/N unbalance in the ΔhupL mutant leading to a decrease in photosynthetic activity, although total H2 yield was still higher compared to the wild-type strain. My findings provide information about the diversity of cyanobacterial H2 capacities and mechanisms and provide knowledge of the possibilities of further enhancing cyanobacterial H2 production.