Reynaldo Luiz Victoria

Bio: Reynaldo Luiz Victoria is an academic researcher from University of São Paulo. The author has contributed to research in topics: Drainage basin & Soil water. The author has an hindex of 49, co-authored 142 publications receiving 7277 citations. Previous affiliations of Reynaldo Luiz Victoria include Escola Superior de Agricultura Luiz de Queiroz.

Biogeochemistry of carbon in the Amazon River

Abstract: Depth-integrated, discharge-weighted water samples were collected over 1,800km ofthe Amazon River on eight cruises at different stages of the hydrograph, 1982-1984. Fine (FPOC, 163 pm) and coarse (CPOC, > 63 rm) particulate organic carbon as weight percentage of suspended sediment varied between 0.9-1.5% for FPOC and 0.5-3.49/o for CPOC. Concentrations of FPOC ranged from 5 mg liter-’ upriver to 2 mg liter-’ downriver in the mainstem and from 6 mg liter-’ inthe Rio Madeira to i 1 in the Rio Negro. CPOC had similar distribution patterns. but with concentrations 15.-30% those of FPOC. Dissolved organic carbon (DOC) averaged 4-6 mg liter-r in the mainstem and up to 12 ml; liter -I in the Rio Negro. Upriver dissolved inorganic carbon (DIC) concentrations of about 1,200 @LM were diluted by tributaries and floodplain drainage to 600 PM at the most downriver site. Evasion ofCO,, invasion of O,, and in situ oxidation were of comparable magnitude, 3-8 pmol m-2 s-r. The average export of total organic carbon (TOC) was 36.1 Tg yr-i (8.5 g m-2 yr-I), of which 62% was DOC, 34% was FPOC, and 4% was CPOC. TOC inputs were insufficient to support in situ oxidation by a factor of at least two. A relatively small, rapidly cycling pool of labile organic matter may coexist with a much larger pool of more refractory material.

Amazonian deforestation and climate

Abstract: An overview of ABRACOS predicting the hydrological impacts of land cover transformation in the humid tropics: the need for integrated research comparisons of long-term soil water storage behaviour under pasture and forest in three areas of Amazonia temperature and moisture profiles in soil beneath forest and pasture areas in Eastern Amazonia thermal diffusivity of Amazonian soils the conclusions from ABRACOS.

Autotrophic Carbon Sources for Fish of the Central Amazon

Abstract: Effective management of the Amazon's commercial fish populations requires an understanding of the factors controlling their production. A fundamental step in the investigation of fish production is to identify the plant groups that contribute energy to fish foodwebs. Stable isotope data for plants and 35 fish species were used to identify autotrophic carbon sources for the central Amazon fish community. Adult fish, aquatic macrophytes, tree parts, periphyton, and phytoplankton were collected in lakes and other flooded environments along the central Amazon floodplain and analyzed for carbon stable isotope composition (°13C) by mass spetroscopy. °13C values for plants ranged from —39.4 to —11.9% with averages of —33.3, —28.8, —27.6, —26.2, and —12.8% for phytoplankton, flooded forests trees, C3 aquatic macrophytes, periphyton, and C4 macrophytes, respectively. The average for all C3 plants (phytoplankton, trees, C3 macrophytes, and Periphyton) was —29.1%, while the average for C4 plants (mainly C4 macrophytes) was —12.8%. Mean °13C values for adult fish ranged from —37.0 to —19.8% with an average of —28.8%. Fish and plant data were used in an isotope mixing model to estimate the relative contribution of different plant groups to fish carbon. C4 macrophytes, which contributed over half of the primary production on the floodplain, accounted on average for only 2.5—17.6% (minimum to maximum) of the carbon in fish. The C3 plants, as a group, were the primary carbon source for 34 fish species, and accounted for an average of 82.4—97.5% of the carbon in all species. Phytoplankton, a minor C3 producer, accounted for a minimum of 36.6% of fish carbon on average, and was the principal carbon source for the commercially important characiform detritivores. Several alternative hypothese are proposed to explain the apparent selective transfer of C3 carbon through Amazon fish foodchains.

Effects of land use on water chemistry and macroinvertebrates in two streams of the Piracicaba river basin, south-east Brazil.

Abstract: SUMMARY 1. Several studies have shown that land use has a strong influence on river chemistry and its biotic components. Most of these studies focused on nitrogen in temperate American and European catchments. Much less is known about the relationship between stream conditions and land use in tropical areas of developing countries. 2. Besides climate, there are three important differences between attributes of temperate and tropical catchments: non-point sources are the dominant contributor of pollution in USA, whereas point source pollution is the most important in our study; use of fertilizer is much smaller in developing countries, and the type of agriculture and management practices are distinct. 3. We test whether the chemical composition of streams and their macroinvertebrate communities can be related to land use. Accordingly, we compared the variability of chemical composition and macroinvertebrate communities in the streams of two catchments (Pisca and Cabras) belonging to the same ecoregion, but having different types of land use. 4. The main land use in the Pisca catchment in 1993 was sugar cane (62%), followed by pasture (22%) and urban centres (10%). In contrast, the main land use in the Cabras catchment was pasture (60%), followed by annual crops (13%) and forest (10%); urban centres occupied only 2% of the catchment. 5. In the Cabras catchment, most of the parameters correlated with a land use index (LUI) (Fig. 2). However, only conductivity, major cations and major anions (with exception of sulfate) had a statistically significant correlation coefficient. More than 90% of the variance was explained for these parameters. DIC, NO3 and richness of invertebrates (RI) also strongly correlated with LUI (R 2 = 0.75), although these correlation coefficients were not significant. Total suspended solids (TSS) had a significant correlation with LUI (R 2 = 0.98), but, the correlation was inverse. In the Pisca catchment, conductivity, major cations (with exception of potassium), major anions, and DIC, DO, and DOC had a strong and statistically significant correlation with LUI. Correlation coefficients were also high for respiration rate, although the correlation was not statistically significant.

Energy Sources for Detritivorous Fishes in the Amazon

Abstract: Detritivorous fishes form an important part of the ichthyomass in the Amazon basin. Most of these fishes are contained in the orders Characiformes and Siluriformes (catfishes). The Characiformes constitute more than 30% of the total fish yield in the Amazon basin, whereas the catfishes are of minor importance. Stable isotope data indicate that Characiformes species receive most of their carbon through food chains originating with phytoplankton, while the Siluriformes receive a significant part of their energy from other plant sources.

Influence of Diet On the Distribtion of Nitrogen Isotopes in Animals

Abstract: The influence of diet on the distribution of nitrogen isotopes in animals was investigated by analyzing animals grown in the laboratory on diets of constant nitrogen isotopic composition. The isotopic composition of the nitrogen in an animal reflects the nitrogen isotopic composition of its diet. The δ^(15)N values of the whole bodies of animals are usually more positive than those of their diets. Different individuals of a species raised on the same diet can have significantly different δ^(15)N values. The variability of the relationship between the δ^(15)N values of animals and their diets is greater for different species raised on the same diet than for the same species raised on different diets. Different tissues of mice are also enriched in ^(15)N relative to the diet, with the difference between the δ^(15)N values of a tissue and the diet depending on both the kind of tissue and the diet involved. The δ^(15)N values of collagen and chitin, biochemical components that are often preserved in fossil animal remains, are also related to the δ^(15)N value of the diet. The dependence of the δ^(15)N values of whole animals and their tissues and biochemical components on the δ^(15)N value of diet indicates that the isotopic composition of animal nitrogen can be used to obtain information about an animal's diet if its potential food sources had different δ^(15)N values. The nitrogen isotopic method of dietary analysis probably can be used to estimate the relative use of legumes vs non-legumes or of aquatic vs terrestrial organisms as food sources for extant and fossil animals. However, the method probably will not be applicable in those modern ecosystems in which the use of chemical fertilizers has influenced the distribution of nitrogen isotopes in food sources. The isotopic method of dietary analysis was used to reconstruct changes in the diet of the human population that occupied the Tehuacan Valley of Mexico over a 7000 yr span. Variations in the δ^(15)C and δ^(15)N values of bone collagen suggest that C_4 and/or CAM plants (presumably mostly corn) and legumes (presumably mostly beans) were introduced into the diet much earlier than suggested by conventional archaeological analysis.

Transformation of the Nitrogen Cycle: Recent Trends, Questions, and Potential Solutions

Abstract: Humans continue to transform the global nitrogen cycle at a record pace, reflecting an increased combustion of fossil fuels, growing demand for nitrogen in agriculture and industry, and pervasive inefficiencies in its use. Much anthropogenic nitrogen is lost to air, water, and land to cause a cascade of environmental and human health problems. Simultaneously, food production in some parts of the world is nitrogen-deficient, highlighting inequities in the distribution of nitrogen-containing fertilizers. Optimizing the need for a key human resource while minimizing its negative consequences requires an integrated interdisciplinary approach and the development of strategies to decrease nitrogen-containing waste.

Streams in the Urban Landscape

Abstract: The world’s population is concentrated in urban areas. This change in demography has brought landscape transformations that have a number of documented effects on stream ecosystems. The most consistent and pervasive effect is an increase in impervious surface cover within urban catchments, which alters the hydrology and geomorphology of streams. This results in predictable changes in stream habitat. In addition to imperviousness, runoff from urbanized surfaces as well as municipal and industrial discharges result in increased loading of nutrients, metals, pesticides, and other contaminants to streams. These changes result in consistent declines in the richness of algal, invertebrate, and fish communities in urban streams. Although understudied in urban streams, ecosystem processes are also affected by urbanization. Urban streams represent opportunities for ecologists interested in studying disturbance and contributing to more effective landscape management.