Características hidráulicas da erosão em sulcos em um cambissolo do semiárido do Brasil

A erosão em sulcos é formada a partir da concentração do escoamento superficial nas depressões da superfície do terreno, evoluindo para a formação de canais ou ravinas, o que faz aumentar a degradação dos solos pela erosão hídrica. Os objetivos deste trabalho foram avaliar as condições hidráulicas do escoamento em sulcos pré-formados, caracterizando o regime de escoamento, e avaliar mudanças induzidas na geometria desses sulcos. Para isso, um experimento foi realizado num Cambissolo Háplico do sertão pernambucano, município de Serra Talhada, Brasil. Os tratamentos consistiram na aplicação de vazões de 17,5; 47,0; 60,0; 77,0; e 110,0 L min-1; com duração de 20 min, em sulcos pré-formados em um solo recém-preparado. O aprofundamento dos sulcos foi dominante no início dos testes. A partir do momento em que o sulco atingiu o solo não revolvido, o processo erosivo, ou seja, a ação da tensão cisalhante, caracterizou-se principalmente pelo alargamento do canal, desgastando com maior proporção a base das paredes laterais dos sulcos. A ação da concentração do escoamento superficial nos sulcos experimentais produziu regimes de escoamento na faixa de transição supercrítico, atestando a ocorrência da erosão em sulcos. O cisalhamento na base do sulco, provocado pelo escoamento, facilitou o desmoronamento nas paredes laterais.

Influência de práticas conservacionistas na umidade do solo e no cultivo do milho (Zea mays L.) em semiárido nordestino

O semiárido brasileiro possui capacidade produtiva limitada em razão das suas características intrínsecas em relação à vegetação, ao clima e ao solo. A cobertura do solo, uma prática recomendada para essa região, favorece a infiltração, proporcionando melhor aproveitamento da água da chuva e contribuindo para o desenvolvimento das culturas, ao reduzir a perda de água por escoamento superficial. Nesse contexto, este trabalho teve como objetivo avaliar os efeitos de diferentes tipos de cobertura na manutenção da umidade do solo, sob condição de chuva natural, bem como nas características agronômicas da cultura do milho (Zea mays L.), em regime de sequeiro. Para isso, desenvolveu-se experimento em campo, na encosta representativa da Bacia do Alto Ipanema, no semiárido pernambucano. Para monitorar a umidade do solo e o desempenho do cultivo, cinco parcelas com 4,5 m de largura e 11 m de comprimento foram instaladas, adotando-se os seguintes tratamentos: solo descoberto, cultivo do milho com cordão vegetativo de palma forrageira, solo com cobertura natural, cultivo do milho em nível e com barramento em pedras associado com cobertura morta e cultivo do milho morro abaixo. Em cada parcela, foram instalados oito tubos de acesso de PVC, para fins de monitoramento da umidade do solo nas profundidades de 0,20 e 0,40 m, utilizando sonda de nêutrons. A cultura do milho (AG 1051) foi cultivada no período de abril a julho de 2011, com adubação realizada no dia do plantio e 30 dias após; a colheita foi realizada aos 96 dias após o plantio. A umidade do solo foi monitorada quinzenalmente, durante os meses de janeiro a julho de 2011. Dentre as características agronômicas do milho, foram avaliadas: altura do colmo, altura da inserção da primeira espiga, diâmetro basal do colmo, diâmetro da espiga com e sem palha, número de fileiras de grãos, número de grãos, comprimento da espiga com e sem palha, peso da espiga com e sem palha e peso da matéria fresca e da matéria seca do milho ralado. Os tratamentos conservacionistas (cultivo do milho em nível com barramento em pedras associado com cobertura morta e o cultivo do milho com cordão vegetativo de palma forrageira) promoveram maiores valores de umidade do solo e de matéria seca de grãos de milho, em relação ao cultivo morro abaixo, evidenciando-se a importância da disponibilidade de água no solo para suprir a necessidade hídrica da cultura do milho, em regime de sequeiro. O cultivo do milho em nível com barramento em pedras associado com cobertura morta ou com cordão vegetativo de palma forrageira atua eficientemente na redução das perdas de água, quando comparado ao solo descoberto, contribuindo para melhor aproveitamento da água da chuva e maior produtividade de grãos.

Contribuição da cidade de Botucatu - SP com nutrientes (fósforo e nitrogênio) na eutrofização da represa de Barra Bonita

As concentrações de nutrientes (fósforo e nitrogênio) na nascente, cidade e foz do ribeirão Lavapés/ Botucatu-SP foram avaliadas e comparadas com as do rio Capivara. O rio Capivara como o ribeirão Lavapés, possui nascente no alto da cuesta e desemboca suas águas na represa de Barra Bonita/ rio Tietê (Figura 1). O rio Capivara possui uma das nascentes próxima a uma do ribeirão Lavapés e, ambos possuem a foz próxima uma da outra na represa de Barra Bonita. O uso e tipo de solo nas margens de ambos cursos d´águas são bastante parecidos, o que implica em uma poluição rural semelhante, assim a grande diferença que afeta a qualidade da água, entre os dois cursos d´águas é a poluição urbana, na cidade de Botucatu (ribeirão Lavapés). Deste modo procurou-se avaliar a contribuição de nutrientes (fósforo e nitrogênio) do ribeirão Lavapés e rio Capivara na represa de Barra Bonita , e estimar a carga retida no lodo do ribeirão Lavapés e a despejada na represa em função dos lançamentos de esgotos sanitários no mesmo, na cidade de Botucatu. O trabalho foi realizado em um período de seca, sem alagamentos, o que permitiu medir as vazões próximas da foz e avaliar a carga diária, no período, de nutrientes lançados na represa. Foram avaliados também, oxigênio dissolvido, demanda química do oxigênio e condutividade Elétrica. Embora os resultados sejam estimativos e variáveis no tempo, podemos concluir que a poluição na cidade de Botucatu por esgoto sanitário além de inviabilizar o uso da água no seu percurso, e causar outros prejuízos, contribui para agravar a eutrofização na represa de Barra Bonita.

Eutrofização do reservatório Engenheiro Armando Ribeiro Gonçalves, no Rio Grande do Norte: implicações para o abastecimento público e para a piscicultura intensiva em tanques-rede

This study aimed to describe the spatial and temporal patterns of variation in trophic state and its relation with the structure and dynamics of planktonic community of a large reservoir located in semi-arid tropical region of Northeast Brazil. The reservoir Armando Ribeiro Gonçalves is the biggest reservoir of the Rio Grande do Norte State and is responsible for about 53% of all surface water accumulated in the State. The samples of water and plankton were taken monthly in 10 points distributed throughout the longitudinal axis of the reservoir and over a full hydrological cycle. The samples were collected to determine concentrations of total phosphorus, total nitrogen, chlorophyll a and suspended solids (fixed and volatile) and for determining the composition and abundance of phytoplanktonic and zooplanktonic species. During the study period, the reservoir was characterized as eutrophic and there was no trend of increasing the trophic state of the reservoir in the period of drought. The concentrations of total phosphorus and suspended fixed solids decreased towards the dam while the N:P ratios increased in the same direction due to the reduction in the phosphorus concentrations and relative constancy in the nitrogen concentrations. The N:P ratios observed were indicative of greater limitation by phosphorus than by nitrogen. However, as concentrations of both nutrients were high and the water transparency was very low, with secchi depth usually lower than one meter, it seems likely that the planktonic primary production of the reservoir is more limited by the availability of light than the availability of nutrients. High nutrient concentrations coupled with low availability of light may explain the continuing dominance of filamentous cyanobacteria such as Cylindrospermopsis raciborskii in the plankton of the reservoir.These cyanobacteria are potentially toxic and pose a serious environmental problem because it compromises the water quality for public supply, recreation and fishing when present in high densities as in this study. The mesozooplankton of the reservoir was dominated by the calanoid Notodiaptomus cearensis and the cladoceran Diaphanosoma spinulosum. In general, the structure of zooplankton community seems to be particularly influenced by the spatial variation of cyanobacteria. The results of the regression analyses show that both the chlorophyll a concentrations and the cyanobacteria biovolume were more strongly correlated with the nitrogen than with phosphorus and that the water transparency was more strongly correlated with algal biomass than with other sources of turbidity. The maximum load of phosphorus to attain the maximum permissible concentration of total P in the reservoir was estimated in 63.2 tonnes P/ year. The current external P load to the reservoir is estimated in 324 tonnes P / year and must be severely reduced to improve the water quality for water supply and allow the implementation of aquaculture projects that could contribute to the socio-economic development of the region

Variação temporal da Comunidade de macroinvertebrados bentônicos em um riacho intermitente do semiárido brasileiro

In Brazilian semiarid region, the majority of water bodies are temporary and the biodiversity in these ecosystems is poorly known. The goal of this study was to describe the temporal variation of benthic macroinvertebrates in an intermittent stream in the Brazilian semiarid region. From March to July of 2009, surveys of benthic macroinvertebrates and water physiochemical parameters were done in a first order stream located at Piranhas-Açu River basin. 25 macroinvertebrates families were found, 21 belonging to Insecta class. The chironomids were the most abundant group during all study period and were represented by 19 genus. The largest densities and taxonomic richness were seen in the drying phase of the stream while the smallest values were found in the period with the heaviest rainfalls ( wet phase ). Only the families Chironomidae and Ceratopogonidae were found during all study period, suggesting that these groups have better adaptations to support floods and droughts. Furthermore, these two groups seemed to be pioneering in this stream. Among the chironomids, Paratendipes dominated the period of floods while Tanytarsus were more abundant in the drying phase . This study showed that hydrological fluctuation is the main force influencing the macroinvertebrate community in this stream, therefore, efforts seeking the conservation and management of Brazilian semiarid water bodies should consider this high natural variability in flow regime

Alteração da qualidade do solo em zona ripária sob diferentes usos: potencial de poluição para um manancial tropical

The demographic growth press environments that are more susceptible to perturbations, like riparian areas, without knowing about the effects of replacing these natural environments by different land uses on soil quality and, consequently, on watershed. The study of soil quality has evolved as an important tool for soil sustainable management of this component of the biosphere that affects aquatic and terrestrial ecosystems functions. Thus, physical and chemical soil proprieties were measured to assess soil quality under different land uses (agricultural, pasture, urban, industrial and natural vegetation,) in the riparian zone of Extremoz Lake, an important human water source, evaluating whether the soil offers potential risk to water pollution. Data were subjected to descriptive statistics and Principal Component Analysis (PCA). The results showed negative changes in soil quality such as alkalinization and increase in P, Pb, Mn and Zn contents in most anthropized areas. The sandy texture and low organic matter content in all soils showed the fragility of the soil to erosion and leaching of elements in excess to water bodies, evidencing that this soils has potential to diffuse contaminants. Conservative management of soil is necessary to provide an adequate ecological state in riparian zones of the Extremoz Lake, thus allowing controlling and buffering diffuse sources of pollution to this important water supply source

Eutrofização do Reservatório Cruzeta na bacia representativa do rio Seridó RN

Eutrophication has been listed as one of the main problems of water pollution on a global level. In the Brazilian semi-arid areas this problem takes even greater proportions due to characteristical water scarcity of the region. It is extremely important to the predictive eutrophication models development and to the reservoirs management in the semi-arid region, studies that promotes understanding of the mechanisms responsible for the expansion and control of algae blooms, essential for improving the water quality of these environments. The present study had as its main aims, evaluate the temporal pattern of trophic state, considering the influence of nutrients (N and P) and the light availability in the water column in the development of phytoplankton biomass, and perform the mathematical modelling of changes in phosphorus and chlorophyll a concentrations in the Cruzeta man-made lake located on Seridó, a typical semi-arid region of Rio Grande do Norte. To this, a fortnightly monitoring was performed in the reservoir in 05 stations over the months of March 2007 to May 2008. Were measured the concentrations of total phosphorus, total organic nitrogen, chlorophyll a, total, fixed and volatile suspended solids, as well as the measure of transparency (Secchi) and the profiles of photosynthetic active radiation (PAR), temperature, pH, dissolved oxygen and electrical conductivity in the water column. Measurements of vertical profiles have shown some periods of chemical and thermal stratification, especially in the rainy season, due to increased water column depth, however, the reservoir can be classified as warm polimitic. During the study period the reservoir was characterized as eutrophic considering the concentrations of phosphorus and most of the time as mesotrophic, based on the concentrations of chlorophyll a, according to the Thornton & Rast (1993) classification. The N:P relations suggest N limitation, conversely, significant linear relationship between the algae biomass and nutrients (N and P) were not observed in our study. However, a relevant event was the negative and significant correlation presented by Kt and chlorophyll a (r ² = 0.83) at the end of the drought of 2007 and the rainy season of 2008, and the algal biomass collapse observed at the end of the drought season (Dec/07). The equation used to simulate the change in the total phosphorus was not satisfactory, being necessary inclusion of parameters able to increase the power of the model prediction. The chlorophyll a simulation presented a good adjustment trend, however there is a need to check the calibrated model parameters and subsequent equation validation

Influência do uso e ocupação de solo na qualidade de água de um reservatório mesotrófico na região semiárida tropiocal

In the semiarid region of northeastern of Brazil, the reservoirs are vulnerable to water level seasonal fluctuations, they re related to the hydrological cycle. The rain periods are irregular and there are long periods of drought that increases eutrophication process. That happens because of the water level s reduction and nutrient concentration. The Boqueirao, located in northeastern Brazil , is a mesotrophic reservoir. The reservoir is naturally susceptible to deterioration of water quality. This happens because of the potential diffuse sources arising from the use and occupation of the basin, associated with shallow soil caatinga biome and highly vulnerable to erosion. This study aimed to analyze the influence of the use and occupation of the area around and the water quality of the watershed. A study of the area around the Boqueirão was performed, taking the potentially polluting activities. Limnological variables were monitored monthly in 3 points of the reservoir to assess the water quality. Was evidenced an event of prolonged drought, with rainfall below the historical average for the year of study. By the index of water quality, the watershed was classified as " good " during the whole year of 2012. According to the trophic index adopted the reservoir is characterized as mesotrophic. The main anthropogenic impacts identified in the soil were arboreal selective logging, mining, diffuse contribution of residues from agricultural and livestock activities. The lack of precipitation and the degradation of the surrounding area, affect negatively the water quality, requiring immediate control to prevent degradation of the watershed . Although there wasn t a majority polluting activity in the region. The total of several impacting activities, the high susceptibility of the soil and the selective clearing of caatinga vegetation can accelerate the natural process of eutrophication in the water body

Respostas morfogênicas e estruturais de gramíneas tropicais em regime de corte no nordeste brasileiro

The production of forage grasses is directly related to the morphogenesis. The knowledge of the morphogenetic and structural variables of forage plants is important for determining appropriate conditions of grazing livestock to ensure efficient and sustainable. Thus the objective of this study was to evaluate morphogenetic and structural responses of three genera of grasses, Brachiaria, Panicum and Cenchrus in a cutting regime. The experimental design was randomized blocks with three replications and six treatments. After each section were evaluated for forage production, appearance and elongation rates of leaves and stem, phyllochron, final leaf length, number of living leaves, leaf lifespan, leaf senescence rate, tiller density and tiller dynamics. On forage yield the highest values were obtained in cultivars Xaraes, Piata and Massai. The tiller density was higher for cv Massai. It is concluded that the cultivars of Panicum and Brachiaria had a higher tillering dynamics in increasing the turnover rate of tissues that are indicators of forage production, assuming that the cultivars of these genera are predisposed to use forage in the Northeast

Estratégia de vida do peixe anual Hypsolebias antenori (Cyprinodontiformes: Rivulidae) do semiárido brasileiro

This work deals with the life strategy of an endangered annual fish, Hypsolebias antenori (Cyprinodontiformes: Rivulidae), of the Brazilian semiarid region. The eggs of these fish hatch at the onset of the rainy season, grows rapidly and they reproduce during the rainy season. When the water puddles dry out, the entire population dies. The resistant eggs which are buried in the bottom of the dried pools go through diapause stages, during which time the embryonic development becomes temporarily arrested. With the onset of the next rainy season, the eggs hatch and a new generation is formed. Specimens of H. antenori were captured during 2011 and 2013, in temporary water pools located in the hydrographic basin of river Jaguaribe in Ceará, Brazil. Sex ratio, the length-weight relationship, the growth type, first sexual maturity, anatomy and histology of the digestive tract, development of gonads, reproductive strategy, karyotypic pattern of the species, and the conservation status of H. antenori were investigated. The results of this study are presented in the form of eight articles. The first article is about the fish faunal composition of the hydrographic basins of Rio Grande do Norte, Brazil, wherein the record of H. antenori is included. The second article deals with the sex ratio, secondary sexual characteristics of males, the length-weight relationship and the type of growth. Males show a pattern of intense coloration with well developed fins. The sex ratio showed a significant predominance of females (1M:1.7 F). Males were larger in length and weight. The equation of weight and total length relationship was Wt=0.0271Lt3,8937, showing a positively allometric growth, indicating greater increase in weight than in length. The third article discusses the anatomy and histology of the digestive tract of H. antenori. It is considered as a generalist feeder with characteristics of omnivore, which utilizes different food sources. The fourth article discusses the stages and phases of gonad development and type of spawning of H. antenori. The fifth article is about the r reproductive strategy adopted by H. antenori which helps in successful reproduction over a short period of life. The sixth article deals karyotypic pattern of the species, constituting the first cytogenetic contribution to the genus. The seventh article discusses about the risk of extinction of this species which suffers a series of threats, such as, habitat loss through land use, deforestation, construction of reservoirs, pollution due to domestic and industrial sewage, besides pesticides and agrochemicals. Furthermore, decreasing rainfall and intensification of aridity due to global climate changes, interferes with the reproductive cycle. The eighth article deals with aggressive behavior adopted between males and among females during reproduction. All temporary water pools sampled during this study were in high degree of degradation, mainly due to human action. There is a great need for conservation measures to protect the populations of annual fish, including the creation of protected areas in the semiarid ephemeral aquatic environments of Brazil

Comunidade fitoplanctônica como discriminador ambiental em açude eutrófico tropical semiárido (Barragem Armando Ribeiro Gonçalves, RN) e divulgação científica para reflexão social

The knowledge of the phytoplankton community, as an integral and dynamic processes of eutrophication, provides information essential for proper management and handling. A growing problem of cyanobacteria in reservoirs around the world as a result of artificial eutrophication processes, generating a particular concern, because some species produce cyanotoxins, which can cause adverse effects on human health. The present work aims to characterize the spatial and temporal dynamics of phytoplankton, assessing their potential as ecological indicator of water quality in reservoirs semiarid region. The samples of water were collected monthly between 2009 and 2011, at three points along the dam Armando Ribeiro Gonçalves / RN. In each sample were measured physico - chemical analysis of water and biological components. We conducted a scientific dissemination activity, with distribution and reading primer on eutrophication, informative talk about water quality, questionnaires and performing a play in a public school in the city of Itajá / RN. The reservoir was considered eutrophic in three points, taking into account the values of chlorophyll -a and phosphorus, adopted to characterize eutrophic environments of semi-arid areas. High density of cyanobacteria, with a maximum value of 2.227.862 cél.ml- 1 and minimum of 43.456 cél.ml- 1 was recorded in lentic and semilêntico points throughout the study, exceeding the levels of drinking water (20.000 cél.ml- 1) established in 2.914/2011 Ordinance of the Ministry of Health of Brazil. All samples contained microcystin, and 44 % had values superiores1μg L- 1. The thermal pattern of the water column showed micro stratifications with differences of less than 1 ° C from five feet deep. The distribution pattern was the type profile clinogrado with oxygen deficit in the bottom of the reservoir. Oxiclina from 10 meters depth was observed during the rainy season (May-June) in the two years of study. The phytoplankton community was represented by 10 functional groups: S1, M, H1, Lo, P, F, Sn, P, W2 and R. The assessment of the ecological status of the system by the index Q showed poor water quality. The results of the study show that the vertical variations were less pronounced than the seasonal variations of cyanobacteria and phytoplankton community in general in the reservoir. The presence of cyanotoxins confirms the need for the monitoring of water quality and measures to reduce eutrophication in water supply reservoirs semiarid RN and demonstrates the challenge for water managers and health authorities to ensure water quality and consequently minimize risks to human health. Compared to the lecture, the primer was considered more efficient in sensitizing the participants, featuring a dynamic practice, differentiated learning, create opportunities for students to rethink attitudes of respect and care for the environment, and shall have the opportunity to learn the subject content from your reality and living environment. The knowledge generated from the activity of scientific were seen as essential for raising awareness of some of the region`s environmental problems , such as eutrophication

Avaliação do potencial de toxicidade de florações de cianobactérias como subsídio para ações de gestão ambiental em açudes do semiárido potiguar

Blooms negatively compromise the aquatic environment, plants, animals and human health.Some species are toxin-producing, such as the neurotoxin saxitoxin and the hepatotoxin microcystin, which may contaminate water reservoirs, as those existing in the semiarid region of Rio Grande do Norte (Brazil) which are used to supply the population, fishing, aquiculture and recreational activities, thereby providing the risk of human exposure through water intake, dermal contact and respiratory tract. Thus, it is recommended a constant monitoring of the density of cyanobacteria with the quantification of cyanotoxins. One goal with this work was the monitoring of water in four reservoirs in semiarid of RN through the identification and enumeration of cyanobacteria and through the identification and quantification of cyanotoxins by ELISA. Furthermore, we intended to assess the environmental perception of farmers and artisanal fishers in reservoirs of semiarid of RN through semi-structured interviews with questions mostly related to water and eutrophication. Through these objectives the aim was the development of management strategies for aquaculture and prevention of risks to public health. The results showed that the highest values of microcystins were found in the rainy season. Standards for drinking water, according to the guidelines of Ministry of Health 2914/2011 and CONAMA 357/05, setting the maximum values for raw water density of cyanobacteria: 50,000 cel.mL-1; microcystin: 1 μg. L-1 and saxitoxin: 3 μg. L-1. The values found for microcystin ranged between 0.00227 μg. L-1 and 24.1954 μg. L-1. From 128 samples analyzed, 27% were above the limit. There was no clear seasonal pattern for saxitoxins and their values ranged between 0.003 μg. L-1 and 0.766 μg. L-1 with none of the values above the limit. Furthermore, 76% of the densities of cyanobacteria values were above the limit. About environmental perception, 52 interviews were conducted and the results show that the respondents recognize the main uses of water of the rervoirs, recognize the importance and have a positive view about the reservoirs. They also realize that the water has a poor quality and can cause health problems. The results provide data showing the persistence of cyanobacteria and cyanotoxins, many times over the limit, reinforcing the importance of constant monitoring. The assessment of environmental perception gives foundation for later proposed environmental education linked to public health management into the context of this particular population, making it more effective

Contribuição da cidade de Botucatu - SP com nutrientes (fósforo e nitrogênio) na eutrofização da represa de Barra Bonita

As concentrações de nutrientes (fósforo e nitrogênio) na nascente, cidade e foz do ribeirão Lavapés/ Botucatu-SP foram avaliadas e comparadas com as do rio Capivara. O rio Capivara como o ribeirão Lavapés, possui nascente no alto da cuesta e desemboca suas águas na represa de Barra Bonita/ rio Tietê (Figura 1). O rio Capivara possui uma das nascentes próxima a uma do ribeirão Lavapés e, ambos possuem a foz próxima uma da outra na represa de Barra Bonita. O uso e tipo de solo nas margens de ambos cursos d´águas são bastante parecidos, o que implica em uma poluição rural semelhante, assim a grande diferença que afeta a qualidade da água, entre os dois cursos d´águas é a poluição urbana, na cidade de Botucatu (ribeirão Lavapés). Deste modo procurou-se avaliar a contribuição de nutrientes (fósforo e nitrogênio) do ribeirão Lavapés e rio Capivara na represa de Barra Bonita , e estimar a carga retida no lodo do ribeirão Lavapés e a despejada na represa em função dos lançamentos de esgotos sanitários no mesmo, na cidade de Botucatu. O trabalho foi realizado em um período de seca, sem alagamentos, o que permitiu medir as vazões próximas da foz e avaliar a carga diária, no período, de nutrientes lançados na represa. Foram avaliados também, oxigênio dissolvido, demanda química do oxigênio e condutividade Elétrica. Embora os resultados sejam estimativos e variáveis no tempo, podemos concluir que a poluição na cidade de Botucatu por esgoto sanitário além de inviabilizar o uso da água no seu percurso, e causar outros prejuízos, contribui para agravar a eutrofização na represa de Barra Bonita.

Baixa diversidade de zooplâncton na desembocadura de uma represa eutrófica (SP, Brasil): reflexo da poluição?

The Tiete River (in São Paulo state) receives most of the efuents of the metropolitan region of São Paulo; and the Barra Bonita reservoir, 200 km distant downstream, receives and recycle most of that pollution load. This work studied the ecological features of the zooplankton (Rotifera, Cladocera and Copepoda) sampled in a point of Tiete River's mouth. Monthly samples were collected, from April, 2001 to February, 2008. The hypothesis currently tested was that the composition and availability of zooplankton were similar to the others reservoir regions (middle and lacustrine sensu Thornton) and to other reservoirs of the Upper Parana River basin, supporting the idea that these organisms manage to stand the strong pollution. The reservoir shows a typical variation of accumulation, with wide variation of seasonal altimetric grading and large fow in the rainy pe- riod, infuenced by the rainfall regime, with efects upon zooplankton assemblage. As a whole, 24 species were registered: 12 Rotifera, 8 Cladocera and 4 Copepoda. Data showed that the hypothesis formulated must be rejected, due the variation trends of zooplankton environmental attributes not being regular, with relatively high abundance values for a lotic environment in specifc months, and low organism abundance or absence in other months. Those facts can be attributed to pollution efects conducting to low dissolved oxygen concentration (> 4mg.l-1) in some months, which causes the zooplankton community to be very much afected. [K]

Caracterização do regime alimentar de Oreochromis niloticus (Linnaeus, 1758) e Tilapia rendalli (Boulenger, 1897) na represa de Barra Bonita, Médio Rio Tietê, SP

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)