Influence of the riparian zone phytophysiognomies on the longitudinal distribution of fishes: evidence from a Brazilian savanna stream

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

Assessment of chromium contamination in the Monte Alegre stream: a case study

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

Seasonal diet shifts of seven fish species in an Atlantic rainforest stream in Southeastern Brazil

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

Stream fish, water and habitat quality in a pasture dominated basin, southeastern Brazil

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

Fish assemblage structure in a first order stream, southeastern Brazil: longitudinal distribution, seasonality, and microhabitat diversity

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

Tolerância à dessecação de sementes de palmito-vermelho (Euterpe espiritosantensis Fernandes)

Com o objetivo de identificar a tolerância à dessecação de sementes de Euterpe espiritosantensis, dois lotes de frutos foram colhidos na coleção de palmeiras do Instituto Agronômico de Campinas, no município de Ubatuba, estado de São Paulo e transportados em embalagem impermeável até a Faculdade de Ciências Agronômicas/UNESP, município de Botucatu, estado de São Paulo, onde foram despolpados. As sementes foram submetidas à secagem em sílica gel a partir das testemunhas não desidratadas (51,4% e 46,6% de teor de água), retirando-se amostras a cada 12 ou 24 horas. O efeito da desidratação foi avaliado através da porcentagem de germinação, e da velocidade de protrusão de embrião, do botão germinativo, da plúmula, e do comprimento das plântulas. Avaliaram-se ainda a matéria seca e o teor de água das sementes. Concluiu-se que as sementes de E. espiritosantensis são recalcitrantes, apresentando porcentagem alta de germinação (90,0% a 87,5%) quando não desidratadas (teor inicial de água de 51,4% a 46,6%). Abaixo de uma faixa de teor de água situada entre 40,7% e 51,4 % os valores de germinação e vigor foram significativamente reduzidos. A mortalidade total das sementes foi observada, com a redução do teor de água das sementes a uma faixa situada entre 13,4% e 15,8%.

Estimated frequency of B-chromosomes and population density of Astyanax scabripinnis paranae in a small stream

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

Botryoidal platinum, palladium and potarite from the Bom Sucesso stream, Minas Gerais, Brazil: Compositional zoning and origin

Platinum-Pd nuggets from the Born Sucesso stream alluvium Minas Gerais, Brazil. have been investigated by electron-probe microanalysis. The nuggets attain 1 mm in maximum dimension and have a botryoidal habit, with pronounced compositional core-to-margin zoning of internal structures, Although there is a wide variation in internal morphology and individual zones vary markedly in thickness (<1-100 mum), a typical composite arborescent nugget comprises a broad irregular core region of massive auriferous Pd-Hg alloy (potarite delta-PdHg) or cavity space + relict potarite enclosed by a narrow zone of platiniferous, palladium or alloy of near Pt50Pd50 composition, and is progressively oscillatory zoned by palladian platinum, with growth eventually enveloping the whole botryoidal colony, to a narrow rim of palladian platinum or pure platinum. Other nuggets comprise an arborescent to dendritic core of auriferous potarite, a broad internal zone of either pure platinum or palladian platinum, and a narrow rim of platinum, the mineral palladium contains up to about 65 at.% Pd; this is the first detailed modern confirmation of palladium in its type locality. Auriferous potarite ranges in composition from similar toPd(3)Hg(2) to near Pd(Hg,Au). The origin of these nuggets remains unclear, but their mineralogy is broadly equivalent to that of palladian gold. potarite and platinum in alluvial sediments and overburden from Devon, England, which are considered to be detrital, and their platinum-group-clement geochemistry is consistent with precipitation from hydrothermal fluids. We suggest that the Bom Sucesso nuggets resulted from high-level episodic hydrothermal alteration of mafic and ultramafic rocks within the drainage basin, with the remobilized Pt and Pd precipitated in open spaces in the enclosing metaquartzites.

Aquatic humus from an unpolluted Brazilian dark-brown stream: general characterization and size fractionation of bound heavy metals

The main pool of dissolved organic carbon in tropical aquatic environments, notably in dark-coloured streams, is concentrated in humic substances (HS). Aquatic HS are large organic molecules formed by micro-biotic degradation of biopolymers and polymerization of smaller organic molecules. From an environmental point of view, the study of metal-humic interactions is often aimed at predicting the effect of aquatic HS on the bioavailability of heavy metal ions in the environment. In the present work the aquatic humic substances (HS) isolated from a dark-brown stream (located in an environmental protection area near Cubatao city in São Paulo-State, Brazil) by means of the collector XAD-8 were investigated. FTIR studies showed that the carboxylic carbons are probably the most important binding sites for Hg(II) ions within humic molecules. C-13-NMR and H-1-NMR studies of aquatic HS showed the presence of constituents with a high degree of aromaticity (40% of carbons) and small substitution. A special five-stage tangential-flow ultrafiltration device (UF) was used for size fractionation of the aquatic HS under study and for their metal species in the molecular size range 1-100 kDa (six fractions). The fractionation patterns showed that metal traces remaining in aquatic HS after their XAD-8 isolation have different distributions. Generally, the major percentage of traces of Mn, Cd and Ni (determined by ICP-AES) was preferably complexed by molecules with relatively high molecular size. Cu was bound by fractions with low molecular size and Co showed no preferential binding site in the various humic fractions. Moreover, the species formed between aquatic HS and Hg(II), prepared by spiking (determined by CVAAS), appeared to be concentrated in the relatively high molecular size fraction F-1 (> 100 kDa).

Food web structure in a tropical stream ecosystem

This study investigated the structure and properties of a tropical stream food web in a small spatial scale, characterizing its planktonic, epiphytic and benthic compartments. The study was carried out in the Potreirinho Creek, a second-order stream located in the south-east of Brazil. Some attributes of the three subwebs and of the conglomerate food web, composed by the trophic links of the three compartments plus the fish species, were determined. Among compartments, the food webs showed considerable variation in structure. The epiphytic food web was consistently more complex than the planktonic and benthic webs. The values of number of species, number of links and maximum food chain length were significantly higher in the epiphytic compartment than in the other two. Otherwise, the connectance was significantly lower in epiphyton. The significant differences of most food web parameters were determined by the increase in the number of trophic species, represented mainly by basal and intermediate species. High species richness, detritus-based system and high degree of omnivory characterized the stream food web studied. The aquatic macrophytes probably provide a substratum more stable and structurally complex than the sediment. We suggest that the greater species richness and trophic complexity in the epiphytic subweb might be due to the higher degree of habitat complexity supported by macrophyte substrate. Despite differences observed in the structure of the three subwebs, they are highly connected by trophic interactions, mainly by fishes. The high degree of fish omnivory associated with their movements at different spatial scales suggests that these animals have a significant role in the food web dynamic of Potreirinho Creek. This interface between macrophytes and the interconnections resultant from fish foraging, diluted the compartmentalization of the Potreirinho food web.

Yeasts and others parameters of pollution of the Ribeirao Claro stream in Rio Claro, São Paulo

The main water source of the Rio Claro municipal district (DAAE) was analysed for determining the level of organic contamination. Temperature, pH, light penetration, conductivity, dissolved oxygen, total dissolved phosphate, ortophosphate, ammonia, heterotrofic bacteria, total coliforms, fecal coliforms, total yeasts and fermentative yeasts were analysed during one year with samples being collected on a monthly basis. Bathing quality of the water from sites 1, 2 and 3 were classified, respectively, as Satisfactory, Very Good and Improper based on fecal coliform counts. Total yeast counts were appropriate as a complement for the appraisal of fresh water contamination by coliform counts. Seventeen yeast species belonging to genera Candida, Cryptococcus, Kloeckera, Pichia and Rhodotorula were found but none of them could be correlated with a level of contamination. Candida famata, C. robusta-like and C. colliculosa were isolated at all of the sites and between the five species found only at the more polluted site, Rhodotorula mucilaginosa was prevalent.

Anthropogenic influences on annual flux of cations and anions at meio stream basin, São Paulo State, Brazil

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

Distribution of stream macroalgae in the eastern Atlantic Rainforest of São Paulo State, southeastern Brazil

Fifty-two stream segments were sampled from 16 August to 13 September in 1993 in the eastern Atlantic Rainforest of São Paulo State, southeastern Brazil (22°55′-25°00′S, 44°48′-48°03′W). Forty-two macroalgal subgeneric taxa were found and the most widespread species were Audouinella pygmaea (21% of sites), Compsopogon leptoclados and Microcoleus subtorulosus (19%). Macroalgal species number per sampling site ranged from 0 to six (2.6 ± 1.7) and was positively correlated to species abundance, whereas species cover ranged from 0 to 70% of the stream bed (15.5 ± 20.8%). No significant correlation was found among macroalgal species number and abundance with any physical or chemical variable analyzed. Most sites were dominated by one or few macroalgal species, mainly, Audouinella macrospora, C. leptoclados and M. subtorulosus. No significant difference was found between the frequency distribution of variables measured for streams and for total macroalgae but the most widespread species (A. pygmaea) differed significantly for current velocity, specific conductance, turbidity and pH. Overall means for macroalgal occurrence include the following values: temperature (X̄ = 19.9°C), current velocity (X̄ = 45 cm s-1), oxygen saturation (X̄ = 66%), specific conductance (X̄ = 59.6 μS cm-1), turbidity (X̄ = 5 NTU) and pH (X̄ = 7.1). This pattern of patchy distribution and dominance by few species has been suggested as typical of stream macroalgal communities and has been ascribed to the rapid fluctuation of physical and chemical conditions. Total macroalgal species richness as well as mean species number per sampling site were considerably lower than found in similar studies of other regions. The Intermediate Disturbance Hypothesis was applied to explain these results: the same factor (high precipitation) responsible for the maintainance of the high species diversity in the surrounding forest can be, paradoxically, a constraint to the development of a more diverse macroalgal flora in streams. © 1996 Kluwer Academic Publishers.