Aquatic macrophyte distribution in relation to water and sediment conditions in the Itaipu Reservoir, Brazil

Aquatic macrophyte community distribution along the eastern shoreline of the Itaipu Reservoir (one of the South America's largest impoundments) is described in relation to limnological and sedimentological factors. The central body of the reservoir is mesotrophic, while the arms (flooded influent river valleys) along the eastern shore may be oligo-mesotrophic to eutrophic, depending on time of year and sub-catchment characteristics. Macrophyte community composition and species cover were surveyed at 30 sites in four arms, in relation to sediment total P and organic matter; underwater light regime; and water total P and Kjeldahl N concentration, alkalinity, conductivity, depth and pH. Seventeen euhydrophyte and six emergent macrophyte species were recorded. Large stands of Egeria najas dominated the euhydrophyte vegetation, together with free-floating weed species (Pistia stratiotes Linn., Salvinia auriculata Aublet and Eichhornia crassipes (Mart.) Solms.). Canonical Correspondence Analysis of the data showed that two sets of variables were important predictors of aquatic macrophyte community structure. Floating macrophyte assemblage was closely related to concentration of nutrients in both water and sediment, while light penetration was the strongest predictor of submerged species occurrence. Although a large number of potential nuisance species were present, dense growths were restricted to shallower areas of the Itaipu Reservoir, causing localised problems. The possibility of increasing interference by these plants with fisheries, recreational use, transport and hydroelectricity generation suggests a need for continued monitoring of weed distribution and abundance, and investigation of appropriate management measures.

Growth of free-floating aquatic macrophytes in different concentrations of nutrients

The objective of the study was to evaluate the effect of different concentrations of nitrogen and phosphorus on the growth of the free-floating aquatic macrophytes Eichhornia crassipes, Pistia stratiotes, and Salvinia molesta. The plants were cultured in 2,000-l outdoor concrete tanks. Triplicate tanks, with a continuous flow of effluent from culture ponds containing Nile tilapia, were used for each plant type (n = 3). The plant material was collected monthly from 0.25 m(2) floating quadrats, at the two ends of the tanks (higher nutrient concentrations near the inflow and lower nutrient concentrations near the outflow). In low nutrient concentrations, the maximum relative growth rates (RGRs) for E. crassipes (0.016/day) and P. stratiotes (0.016/day) were significantly lower (P <= 0.05) than for S. molesta (0.029/day). There were no significant differences between the RGRs of S. molesta in the different nutrient concentrations. Eichhornia crassipes and P. stratiotes had their growth limited by nitrogen and phosphorus concentrations. The increase in plant density during the experiment probably also affected the growth of these species. In this context, E. crassipes and P. stratiotes can cause problems in nutrient-rich waterbodies, but under these experimental conditions their growth was limited by nitrogen and/or phosphorus concentrations. The growth of S. molesta was not influenced by the different nutrient concentrations.

Composição química de macrófitas aquáticas flutuantes utilizadas no tratamento de efluentes de aqüicultura

Os objetivos deste trabalho foram avaliar a composição química de duas espécies de macrófitas aquáticas flutuantes (Eichhornia crassipes e Pistia stratiotes), utilizadas no tratamento de efluentes de aqüicultura, e inferir as possibilidades de aproveitamento desses vegetais. E. crassipes apresentou os maiores conteúdos de cálcio (1,51%), magnésio (3.916,67 mg kg-1), manganês (1.233,33 mg kg-1), zinco (81,83 mg kg-1), ferro (5.425,00 mg kg¹) e cobre (25,83 mg kg-1). Na biomassa de P. stratiotes foram obtidos os maiores valores de matéria mineral (18,95%), fósforo (0,38%), nitrogênio (2,40%), proteína bruta (15,02%) e aminoácidos, à exceção de ácido aspártico e triptofano.

Droplet deposition during spray and leaf pH in aquatic weed control

A diversidade morfológica da superfície foliar existente entre as espécies de plantas e a presença de estruturas foliares como tricomas, estômatos, cutícula e ceras podem exercer grande influência na aderência e deposição das gotas de pulverização, assim como na absorção do herbicida. Desta forma, o objetivo do presente trabalho foi estudar, em quatro espécies de plantas daninhas aquáticas (Enhydra anagallis, Eichhornia crassipes, Heteranthera reniformis e Typha subulata), a área de molhamento de gotas de pulverização nas superfícies foliares adaxial e abaxial, bem como o pH foliar. O experimento foi realizado em Botucatu-SP. As plantas foram cultivadas em caixas d'água sob condições de campo, e quando atingiram seu pleno desenvolvimento (antes do florescimento), foram realizadas as avaliações de pH foliar e da área de molhamento de gotas de pulverização. As tensões superficiais das gotas aplicadas (0,5 mL), apresentadas pelas soluções de glyphosate aplicado isolado a 5,0% v v-1 (Rodeo 480 g L-1 e.a. produto comercial), glyphosate + Aterbane BR (5,0% + 0,5% v v-1), glyphosate + Silwet L-77 (5,0% + 0,05% v v-1), além das soluções com os adjuvantes isolados, Aterbane BR (0,5% v v-1) e Silwet L-77 (0,05% v v-1) foram respectivamente 72,1; 28,7; 23,3; 37,3 e 22,1 mN m-1. As médias obtidas de pH foliar variaram entre 5,50 e 7,50, destacando-se a espécie E. anagallis com valores de 6,68 e 7,02 para as faces adaxial e abaxial, respectivamente. Dentre as plantas daninhas aquáticas avaliadas T. subulata foi a espécie que apresentou as maiores médias de área de molhamento nas faces adaxial e abaxial da folha, proporcionada pelas as soluções de glyphosate + Aterbane BR, glyphosate + Silwet L-77 e Silwet L-77, com valores de 12,99-7,03; 20,04-17,95 e 31,81-25,91 mm², respectivamente.

Efficiency of aquatic macrophytes to treat Nile tilapia pond effluents

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

Digestibilidade aparente de macrófitas aquáticas pela tilápia-do-nilo (Oreochromis niloticus) e qualidade da água em relação às concentrações de nutrientes

Objetivou-se com este estudo determinar os coeficientes de digestibilidade aparente (CDA) da proteína bruta e dos aminoácidos de duas espécies de macrófitas aquáticas flutuantes (Eichhornia crassipes e Pistia stratiotes) pela tilápia-do-nilo (Oreochromis niloticus) e verificar a qualidade da água dos aquários de digestibilidade em relação às concentrações de nitrogênio e fósforo. Foram elaboradas três rações, marcadas com 0,10% de óxido de cromo-III, sendo uma ração-referência (purificada) e as demais contendo 30% de cada uma das macrófitas aquáticas. As tilápias-do-nilo (58,8 + 18,5 g) foram alimentadas até a saciedade aparente e a coleta de fezes foi feita pelo sistema Guelph modificado. Os CDA médios da proteína e dos aminoácidos foram, respectivamente, 93,17 e 93,32% para a ração-referência; 59,23 e 60,35% para E. crassipes; e 52,24 e 57,40% para P. stratiotes. Não foram constatadas diferenças significativas entre os valores de CDA da proteína e dos aminoácidos dos ingredientes vegetais. Os resultados obtidos demonstraram reduzida eficiência da tilápia-do-nilo em assimilar a maioria dos aminoácidos de E. crassipes e P. stratiotes. As excretas das tilápias-do-nilo contribuíram para o aumento das concentrações de nitrogênio e fósforo na água dos aquários, independentemente da ração fornecida.

Aquatic macrophytes of Itaipu Reservoir, Brazil: Survey of species and ecological considerations

In a survey of the aquatic macrophytes of the Itaipu Reservoir, we identified 62 taxa in 25 families and 42 genera. The highest number taxa was observed for the emergent macrophytes (40 taxa). Reduced fluctuation in water level, increased light penetration, and sediment enrichment by nutrients and organic matter following the formation of the reservoir favored the appearance of a species-rich community of submerged macrophytes (23% of the taxa identified). The aquatic macrophytes were found mainly near the mouths of the main tributaries of the reservoir, in shallow area of depth less than 2 meters. In addition to the shallow depth, the greater nutrient input from the tributaries and relative protection from wind explained this distribution. Among the species found, Egeria najas merits mention for its occurrence in all localities sampled, with biomass values varying between 98 and 186 gDW/m2. Some potential nuisance species such as Eichhornia crassipes, Salvinia auriculata, and Pistia stratiotes also deserve attention, since they were also observed to be covering large areas of Itaipu Reservoir. © 1999, Paraná Institute of Technology Publication.

Tratamento de efluentes de carcinicultura por macrófitas aquáticas flutuantes

The efficiency of systems composed of two species of floating aquatic macrophyte (Eichhornia crassipes and Pistia stratiotes) to treat effluents from shrimp culture was evaluated in this research. The effluent originated from a pond populated with Macrobrachium amazonicum. Treatment systems consisted of 12 experimental tanks with aquatic macrophyte and three tanks without plants (control). Water samples were collected from the fresh water supply and before and after passing through the treatment systems. There are no differences in the removal of nutrients between the two species. The higher nutrient removal was observed for total phosphorus (41.9% by control; 71.6% by E. crassipes; 69.9 by P. stratiotes; 72.5% by E. crassipes + P. stratiotes and 72.1 by P. stratiotes + E. crassipes) and turbidity (30.6% by control; 80.2% by E. crassipes; 75.2 by P. stratiotes; 79.8% by E. crassipes + P. stratiotes and 81.5 by P. stratiotes + E. crassipes). The systems containing aquatic macrophytes were efficient in nitrogen and phosphorus removal from M. amazonicum culture. © 2008 Sociedade Brasileira de Zootecnia.

Constructed wetland in wastewater treatment

Physical and chemical variables of soil and water were measured to determine the effectiveness of a constructed wetland for wastewater treatment. Eight different macrophyte species, namely Eichhornia crassipes, Alternanthera philoxerodos, Heteranthera reniformis, Hydrocotyle umbeliferae, Lidwigia elegan, Ludwigia sericea, Myriophyllum aquaticum and Thypha domingensis, were transplanted. Inlet water and outlet water were the two sampling sites evaluated. There were significant differences (p < 0,05) when limnological characteristics between inlet and outlet water from the constructed wetland were compared. In general, dissolved oxygen was over 4 mg L-1, and conductivity was high, above 80 μS cm-1. Chlorophyll-a levels generally tended to decrease at the wetland outlet and were higher during the rainy period (fish growth period). Results show that ammonia, total phosphorus, BOD5, phosphorus and organic mattel in the sediment removals in the constructed wetland were higher, indicating that macrophytes played an important role in removing these variables. The use of constructed wetland is a viable technology for the biological treatment in aquaculture and swine wastewater.

Efeito da chuva sobre a ação do herbicida imazapyr no controle de plantas daninhas aquáticas

The aim of this study was to evaluate the influence of different periods of rainfall that occurred after the application of the imazapyr herbicide on the control efficiency of Pistia stratiotes and Eichhornia crassipes. We studied 10 mm rainfall, applied for 5' at different time periods (0h, 2h, 4h, 6h, 8h, 12h, 24h, not simulated rainfall) after the application of imazapyr formulation Arsenal NA, 250 g ai ha -1 (1.0 L cp ha -1). The experiment had completely randomized design with four replications. Plants were evaluated at 7, 14, 21, 28 and 35 days after application (DAA), and the results submitted to analysis of variance by F test and treatment means compared by Tukey's test (p <0. 05). The occurrence of rainfall up to 6 hours after herbicide application, plants of P. stratiotes, negatively affected its efficiency and control; rainfall intervals over 8 hours had no effect in control. The occurrence of rainfall at all time intervals did not affect the control of E. crassipes plants.

Vascular plants of oxbow lakes of Turvo River, Upper Paraná River basin, São Paulo State, Brazil

Vascular plants were investigated in oxbow lakes of Turvo River, Upper Paraná River basin, between Icém and Nova Granada municipalities, state of São Paulo, Brazil. In this region, six lagoons were sampled: Ganzella, Mustafá, Braço Morto, 45, Federal, and Parente. The survey showed a total of 54 species, 36 genera and 22 families. The species richest families were Poaceae, Cyperaceae, and Polygonaceae. Eichhornia crassipes (Pontederiaceae) was the single species encountered in all the six lakes. © 2010 Check List and Authors.

Utilização de meios alternativos e diferentes tipos de recipientes no cultivo de Ankistrodesmus gracilis (Reinsch) Korshikov (Chlorophyceae) em laboratório

A laboratory culture of Ankistrodesmus gracilis algae was evaluated by studying the biology of the species and its chemical composition in a traditional medium (CHU 12) and in two alternative culture media, NPK (20-5-20) and macrophyte (Eichhornia crassipes) + NPK, in three different types of recipients (fiberglass, carboy and plastic bag). First peak in the growth curve of Ankistrodesmus gracilis occurred on the ninth day in macrophyte + NPK medium (74.16 x 10 5 cells mL -1) in a fiberglass recipient. However, highest density (p < 0.01) was reported in medium CHU 12 (122.87 x 10 5 cells mL -1) in a plastic bag on the twelfth day. Cell density was over 70 x 10 5 cells mL -1 starting on the twelfth day. Growth rate of A. gracilis was similar (p > 0.05) in culture media in the three recipients. Protein and fiber were similar (p > 0.05) in the treatments, but lipids were higher (p < 0.05) in NPK. Nitrate, ammonia, total phosphorus and orthophosphate contents were over 1 mg L -1 in NPK (p < 0.01). Results show that alternative media, such as NPK and macrophyte + NPK, are possible for large-scale culture of A. gracilis cultured in three types of recipients. Costs are low, occupying less space when cultured in plastic bags and in the laboratory.

Características da anatomia foliar e da deposição de gotas de pulverização em plantas daninhas aquáticas

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Utilização de macrófitas aquáticas flutuantes no tratamento de efluentes de carcinicultura

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Tratamento de efluentes de piscicultura utilizando sistema tipo wetland povoado com espécies de macrófitas aquáticas de três tipos ecológicos diferentes

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)