The accumulation of lipid reserves was investigated in two common cladoceran species typical of neotropical freshwaters. Experiments were performed in order to measure differential accumulation of lipid reserves in response to two algal diets, S. quadricauda and A. gracilis. The larger D. laevis fed with the Ankistrodesmus diet accumulated a higher amount of total lipids. The average lipid content for both diets was 1.1% and 22.1% dry weight for Scenedesmus and Ankistrodemsus, respectively. This difference was found to be highly significant. The superior nutritional quality of A. gracilis was confirmed by the experiments using the smaller Moina micrura. This cladoceran accumulated 11.4% and 19.9% of the average dry weight of lipids from Scenedesmus and Ankistrodesmus, respectively. The study also found that most lipid reserves are concentrated as triacylglycerols in both cladocerans. The relative contribution of this class of lipids also varied according to the diet. For Daphnia, for instance, the average triacylglycerol levels varied from 6.2 to 11.0 with the Scenedesmus and Ankistrodesnus diets, respectively.
Expansion of aquaculture around the world has heavily impacted the environment. Because fertilizers are needed to raise fish, one of the main impacts is eutrophication, which lowers water quality and increases the frequency of algal blooms, mostly cyanobacteria. To evaluate whether the water quality in 30 fishponds in southeastern Brazilian met the requirements of Brazilian legislation, we analyzed biotic and abiotic water conditions. We expected that the high nutrient levels due to fertilization would cause low water quality. We also analyzed cyanotoxins in seston and fish muscle in some systems where cyanobacteria were dominant. The fishponds ranged from eutrophic and hypereutrophic with high phytoplankton biomass. Although cyanobacteria were dominant in most of the systems, cyanotoxins occurred in low concentrations, possibly because only two of the 12 dominant species were potential producers of microcystins. The high phosphorus concentrations caused the low water quality by increasing cyanobacteria, chlorophyll-a, turbidity, and thermotolerant coliforms, and by depleting dissolved oxygen. We found that all the 30 systems were inappropriate for fish culture, according to Brazilian legislation, based on at least one of the parameters measured. Furthermore, there was not any single system in the water-quality thresholds, according to the Brazilian legislation, to grow fish. Our findings indicate the need for better management to minimize the impacts of eutrophication in fishponds, in addition to a rigorous control to guarantee good food.
ResumoThe study verified sanitary aspects in fish ponds with sequential disposal and the effect of the tanks effluent in parallel in the system. Six fish ponds were studied in the dry and the rainy periods and were analyzed microbiological aspects (thermo tolerant coliforms, total coliforms and heterotrophic bacteria), DBO 5 and DQO. It had contamination in the water of supplying for thermo tolerant coliforms, either of human or animals, compromising all the fish ponds studied with sanitary indices undesirable and representing risk in the cultivation of fish. It was found a great contamination of thermo tolerant coliforms, total coliforms, and heterotrophic bacteria in the period of rains with significant differences for DBO5 and total coliforms variables in relation to the showed periods. The high temperatures and the waters of draining had favored the high level of coliforms and heterotrophic bacteria in the period of rains. Through the results was concluded that the parallel tanks and the rainy period had had greater influence that the proper sequential disposal of the fisheries.
AbstractO estudo verificou aspectos sanitários em viveiros de criação de peixes com disposição seqüencial e o efeito dos efluentes de tanques em paralelo no sistema. Foram estudados seis viveiros de criação de peixes nos períodos de chuva e seca e analisados aspectos microbiológicos (coliformes termotolerantes, totais e bactérias heterotróficas), DBO 5 e DQO. Houve contaminação na água de abastecimento por coliformes termotolerantes, seja de origem humana ou animal, comprometendo todos os viveiros estudados com índices sanitários indesejáveis e representando risco na criação de peixes. Foi encontrado um maior aporte de coliformes totais e bactérias heterotróficas no período de chuvas com diferenças significativas nos períodos amostrados em relação à DBO5 e coliformes totais. As altas temperaturas e as águas de escoamento favoreceram as concentrações elevadas de coliformes e bactérias heterotróficas no período de chuvas. Através dos resultados obtidos concluiu-se que os tanques paralelos e o período chuvoso tiveram maior influência que a própria disposição seqüencial dos viveiros. Palavras-chave: Bactérias Heterotróficas. Coliformes. Viveiros de Peixes.
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