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Estudo da taxa de eclosão de ovos de resistência de Dafnídeos sob diferentes estímulos
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A Daphnia spp., vulgarmente conhecida por pulga-de-água é um animal aquático de água doce que se alimenta de partículas suspensas. Tem um papel muito importante nos sistemas aquáticos e é um organismo modelo em pesquisas ecológicas e evolutivas, e também em estudos nas áreas de ecologia e ecotoxicologia. A estratégia de reprodução deste organismo varia consoante as características abióticas. Quando está em condições favoráveis a Daphnia spp. reproduz-se assexuadamente, por partenogénese. Quando isso não acontece há reprodução sexuada, onde há a formação de ovos de repouso, chamados Ephippia.Este organismo pode surgir em ambientes diferentes dos sistemas aquáticos naturais, como por exemplo nas Estações de Tratamento de Água Residual. Foi o que aconteceu na ETAR de Fátima em dezembro de 2020. Este facto causou problemas no tratamento das águas residuais e no cumprimento dos parâmetros de descarga. Este trabalho foi realizado no âmbito de um estágio curricular do Mestrado de Desenvolvimento Sustentável, da Escola Superior Agrária de Coimbra, no laboratório de Valorização de Recursos Endógenos e Naturais (VALOREN). O principal objetivo foi estudar a taxa de eclosão de ovos de resistência de Daphnia spp. sob diferentes estímulos nas condições de operação de ETAR urbana, com o apoio de um reator à escala piloto, instalado na ESAC associado a outro trabalho que estava a ser realizado em paralelo a este. Todo o trabalho foi realizado com condições semelhantes às reais, através das amostras de Daphnia spp., e de efluente recebidas da ETAR, para garantir o funcionamento do reator. Ao longo deste trabalho as Daphnia spp. recebidas foram mantidas em culturas de manutenção, no laboratório, como fonte de alimentação destas foram utilizadas lamas ativadas do reator e do clarificado do decantador da instalação piloto. Através das Daphnia spp. em cultura de manutenção e das amostras de lamas ativadas vindas diretamente da ETAR foram recolhidas Ephippia para a realização do trabalho experimental. Os ensaios experimentais desenvolveram-se em três etapas. A primeira consistiu em determinar o peso e as dimensões das Ephippia. O ensaio da toxicidade envolveu a segunda etapa que usou soluções com diferentes concentrações de hipoclorito de sódio e a terceira etapa que considerou soluções com diferentes valores de pH. O primeiro ensaio com hipoclorito de sódio, utilizando microplacas não teve qualquer resultado. Com o segundo ensaio, substituindo as microplacas por tubos de ensaio foi possível observar que as concentrações mais altas de hipoclorito de sódio e o choque de temperatura provocam mais eclosões. Com o ensaio de diferentes valores de pH conclui-se que valores de pH baixos inibem a eclosão das Ephippia.
Daphnia spp., commonly known as the water flea, is a freshwater aquatic animal that feeds on suspended particles. It plays a very important role in aquatic systems and is a model organism in ecological and evolutionary research, as well as in ecology and ecotoxicology studies. The reproduction strategy of this organism varies depending on the abiotic characteristics. When conditions are favourable, Daphnia spp. reproduces asexually, by parthenogenesis. When this doesn't happen there is sexual reproduction, where resting eggs are formed, called Ephippia.This organism can appear in environments other than natural aquatic systems, such as wastewater treatment plants. This is what happened at the Fátima Wastewater Treatment Plant in December 2020. This caused problems with wastewater treatment and compliance with discharge parameters. This work was carried out as part of a curricular internship for the Master's Degree in Sustainable Development at the Coimbra School of Agriculture, in the laboratory for the Valorisation of Endogenous and Natural Resources (VALOREN). The main objective was to study the hatching rate of Daphnia spp. resistance eggs under different stimuli in the operating conditions of an urban wastewater treatment plant, with the support of a pilot-scale reactor installed at the ESAC associated with other work that was being carried out in parallel. All the work was carried out under conditions similar to the real thing, using samples of Daphnia spp. and effluent received from the wastewater treatment plant to ensure the reactor was working properly. Throughout this work, the Daphnia spp. received were kept in maintenance cultures in the laboratory, using activated sludge from the reactor and clarified sludge from the decanter of the pilot plant as their food source. Ephippia were collected from the Daphnia spp. in maintenance culture and from the activated sludge samples coming directly from the wastewater treatment plant to carry out the experimental work. The experimental tests were carried out in three stages. The first consisted of determining the weight and size of the Ephippia. The toxicity test involved the second stage which used solutions with different concentrations of sodium hypochlorite and the third stage which considered solutions with different pH values. The first test with sodium hypochlorite using microplates yielded no results. With the second test, replacing the microplates with test tubes, it was possible to see that the higher concentrations of sodium hypochlorite and the temperature shock caused more hatchings.
Daphnia spp., commonly known as the water flea, is a freshwater aquatic animal that feeds on suspended particles. It plays a very important role in aquatic systems and is a model organism in ecological and evolutionary research, as well as in ecology and ecotoxicology studies. The reproduction strategy of this organism varies depending on the abiotic characteristics. When conditions are favourable, Daphnia spp. reproduces asexually, by parthenogenesis. When this doesn't happen there is sexual reproduction, where resting eggs are formed, called Ephippia.This organism can appear in environments other than natural aquatic systems, such as wastewater treatment plants. This is what happened at the Fátima Wastewater Treatment Plant in December 2020. This caused problems with wastewater treatment and compliance with discharge parameters. This work was carried out as part of a curricular internship for the Master's Degree in Sustainable Development at the Coimbra School of Agriculture, in the laboratory for the Valorisation of Endogenous and Natural Resources (VALOREN). The main objective was to study the hatching rate of Daphnia spp. resistance eggs under different stimuli in the operating conditions of an urban wastewater treatment plant, with the support of a pilot-scale reactor installed at the ESAC associated with other work that was being carried out in parallel. All the work was carried out under conditions similar to the real thing, using samples of Daphnia spp. and effluent received from the wastewater treatment plant to ensure the reactor was working properly. Throughout this work, the Daphnia spp. received were kept in maintenance cultures in the laboratory, using activated sludge from the reactor and clarified sludge from the decanter of the pilot plant as their food source. Ephippia were collected from the Daphnia spp. in maintenance culture and from the activated sludge samples coming directly from the wastewater treatment plant to carry out the experimental work. The experimental tests were carried out in three stages. The first consisted of determining the weight and size of the Ephippia. The toxicity test involved the second stage which used solutions with different concentrations of sodium hypochlorite and the third stage which considered solutions with different pH values. The first test with sodium hypochlorite using microplates yielded no results. With the second test, replacing the microplates with test tubes, it was possible to see that the higher concentrations of sodium hypochlorite and the temperature shock caused more hatchings.
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Keywords
Hipoclorito de sódio Clarificado Lamas ativadas Ephippia Daphnia spp