Influência de herbicidas em macrófitas aquáticas

The effects of the herbicides atrazine, 2,4-D, glyphosate (direct and rodeo) and trifluralin were determined on the growth and death of fronds of the aquatic macrophytes Spirodela punctata (G.F.W. Meyer) Thompson and Salvinia minima Baker, through three series of concentrations of each herbicide in climatic chamber (3000 lux, 12/12 hours photoperiod, temperature 23 ± 1°C). After seven days, the concentrations of series 1 (0.025, 0.125, 0.625 and 3.125 mg.L -1) inhibited the growth of Salvinia minima. In Spirodela punctata, only the herbicides rodeo and trifluralin caused growth inhibition. These concentrations did not caused death of fronds in the species. The concentrations of series 2 (40, 60, 80 and 100 mg.L -1) of the herbicides 2,4-D, direct e trifluralin decreased growth of Salvinia minima; death of fronds was caused by 2,4-D and trifluralin to Salvinia minima, and by direct and trifluralin to Spirodela punctata. For the series 3 (200, 400, 600, 800 and 1000 mg.L -1), the herbicide 2,4-D caused growth decrease of both species. The herbicides rodeo and trifluralin showed to be the most lethal for both species. The herbicide atrazine caused death of fronds in Spirodela punctata.

Performance of constructed wetland system for public water supply

The project is being conducted in the town of Analândia, São Paulo, Brazil. The constructed wetlands system for water supply consists of a channel with floating aquatic macrophytes, HDS system (Water Decontamination with Soil - Patent PI 850.3030), chlorinating system, filtering system and distribution. The project objectives include investigating the process variables to further optimize design and operation factors, evaluating the relation of nutrients and plants development, biomass production, shoot development, nutrient cycling and total and fecal coliforms removal, comparing the treatment efficiency among the seasons of the year; and moreover to compare the average values obtained between February and June 1998 (Salati et al., 1998) with the average obtained for the same parameters between March and June 2000. Studies have been developed in order to verify during one year the drinking quality of the water for the following parameters: turbidity, color, pH, dissolved oxygen, total of dissolved solids, COD, chloride, among others, according to the Ministry of Health's Regulation 36. This system of water supply projected to treat 15 L s-1 has been in continuous operation for 2 years, it was implemented with support of the National Environment Fund (FNMA), administered by the Center of Environmental Studies (CEA-UNESP), while the technical supervision and design were performed by the Institute of Applied Ecology. The actual research project is being supported by FAPESP.

Valor nutritivo de macrófitas aquáticas flutuantes (Eichhornia crassipes, Pistia stratiotes e Salvinia molesta) utilizadas no tratamento de efluentes de aqüicultura

The aim of this study was to evaluate the nutritive value of free-floating aquatic macrophytes, Eichhornia crassipes (Mart.) Solms (Pontederiaceae), Pistia stratiotes (L.) (Araceae) and Salvinia molesta (Mitchell) (Salviniaceae) used in a Nile tilapia (Oreochromis niloticus) waste treatment, and these species biomass potential uses. The vegetal biomass samples were collected from 0.25 m 2 floating squares and divided in aerial and submerse parts, to determine the concentrations of cell wall fraction, soluble carbohydrates, polyphenols, lipids, crude protein and total phosphorus. The higher nutritive value was observed in E. crassipes and S. molesta aerial parts, and in P. stratiotes total biomass, due to their lower cell wall fraction mean rates (60.7; 64.2 and 56.9 % dry mass, respectively) and to the higher rates of: crude protein (10.1; 9.1 and 8.8 % dry mass, respectively), soluble carbohydrates (26.6; 18.7 and 12.4 mg.g -1 dry mass, respectively) and lipids (7.6; 4.5 and 4.4% dry mass, respectively). It may be concluded that P. stratiotes total biomass, and E. crassipes and S. molesta aerial biomass have nutritive values with potential use for ruminant feeding or as ration ingredients.

Effect of floating macrophyte cover on the water quality in fishpond

A study was conducted during 23 days in order to evaluate the impact of floating aquatic macrophyte on the water quality of a fishpond. Water samples were collected in four points, three inside the pond and one in water inlet. Drastic reduction of dissolved oxygen was observed in the pond, down to 0.87 mg/L. No significant differences (P > 0.05) were observed for total CO 2, nitrite and ammonia with respect to inlet water (P1) and inside the pond (P2, P3 e P4). Chlorophyll a displayed an inverse relationship with phosphorus. Among nitrogen compounds, ammonia presented the highest concentrations except in water inlet where nitrate was higher, 513.33 μg/l, as well as the highest conductivity values. The pH was slightly acid. The results obtained showed that the macrophyte cover promoted an adverse effect in the medium. Under control, aquatic plants might impact positively due to its capacity to reduce total phosphorus and nitrate in the water column as observed in this study.

Genetic conservation of Brazilian fishes - Present state and perspectives

Natural environments have been worldwide affected by the growing impact of anthropogenic actions that promote the reduction or the extinction of several vertebrate species. Aquatic ecosystems represent one of the most affected environments and many fish species and/or populations have been increasingly fragmented distributed due to habitat degradation, predatory fishing, introduction of exotic species, river sedimentation, deforestation, pollution, reduction of food resource, and construction of hydroelectric dams. Actually, more than 150 Brazilian fish species, including freshwater, estuary and coastal species, can be considered threatened. Information on the diversity, conservation biology and population analysis on threatened species or populations, with several DNA markers, can be extremely useful for the success of fish species-recovery and maintenance programs. Although DNA analysis in Neotropical fish species are just beginning, they tend to increase with the widespread attention to the use of molecular approaches to minimize problems related to the risk of extinction. The accumulation of information on biology and pattern of genetic variation of fish species, associated with ecological and demographic data, and also education and respect to the nature, constitutes a crucial task to develop efficient conservation strategies in order to preserve the genetic diversity in aquatic environments.