Aspectos limnológicos de um sistema artificial receptor de resíduos de aquicultura
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Data
2018-02-15
Autores
Mendonça, Gislaine Costa de
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Editor
Universidade Estadual Paulista (Unesp)
Resumo
Este estudo avaliou e descreveu as condições limnológicas de um sistema artificial receptor de resíduos de aquicultura. O sistema é um antigo viveiro que faz parte da fazenda de aquicultura do Centro de Aquicultura da UNESP Jaboticabal, SP (21°15’S, 48°18’O), o qual recebe aproximadamente 65% dos resíduos da fazenda e deságua diretamente sem tratamento prévio no Córrego Jaboticabal (SP). O objetivo deste estudo foi caracterizar a qualidade da água, a composição do sedimento, o grau de trofia e identificar a comunidade zooplanctônica, assim como possíveis espécies indicadoras da qualidade da água; observando se o sistema pode favorecer a redução dos resíduos de aquicultura, visando a reutilização desta água. Foram realizadas coletas quinzenais durante oito meses em 2014, abrangendo os períodos de chuva e seca em três pontos amostrais: entrada, centro e saída de água. A água foi coletada na superfície, para análise de nutrientes, sólidos totais, clorofila-a, oxigênio dissolvido, pH, alcalinidade, transparência e coliformes termotolerantes. O sedimento foi coletado na camada superior, com tubo de pvc e/ou com draga, foram analisados os teores de matéria orgânica, fósforo, cálcio, potássio, magnésio, alumínio e pH. O zooplâncton foi coletado mensalmente (fevereiro/ setembro) nos mesmos pontos amostrais. As amostras de zooplâncton foram coletadas com auxílio de balde graduado (20 L), concentradas em rede de 58 μm e fixadas em formalina a 4%, para posterior identificação e contagem. As concentrações de nutrientes, clorofila-a, coliformes e sólidos, foram superiores (p<0,05) durante o período chuvoso devido o maior fluxo de efluentes em função da intensificação da produção neste período, contribuindo para a eutrofização da água, sem variação entre os pontos amostrais. Durante a estiagem, apenas uma redução de amônia através, resultando no aumento dos níveis de nitrato e nitrito. O zooplâncton foi representada por 74 taxas; 64 Rotifera, 7 Cladocera, 4 Copepoda e 1 Ostracoda, presente em todos os pontos de coleta. Neste estudo, a densidade e riqueza de Rotifera foi elevada em todos os pontos, com a ocorrência de espécies associadas a poluição orgânica, como Brachionus e Filinia, favorecidas por seu rápido ciclo de vida, tamanho pequeno e resistência. A ocorrência de Thermocyclops decipiens, Bosmina longirostris e a dominância do grupo Rotifera indicam que água do sistema está em processo de eutrofização. No entanto, a presença de A. furcatus pode indicar que o sistema ainda não atingiu seu limite máximo de deterioração. A baixa qualidade na água deste viveiro, assim como acúmulo de nutrientes e matéria orgânica no sedimento ocasionam o aumento no grau de trofia do sistema, sendo necessárias medidas que promovam a recuperação da qualidade da água do sedimento neste sistema.
This study evaluated and described the limnological conditions of an artificial aquaculture waste receiver system. The system is an old nursery that is part of the aquaculture farm of the Aquaculture Center of UNESP Jaboticabal, SP (21 ° 15'S, 48 ° 18'O), which receives approximately 65% of the farm waste and flows directly without previous treatment in the Jaboticabal Stream (SP). The objective of this study was to characterize water quality, sediment composition, trophic degree and zooplankton community identification, as well as possible water quality indicator species; observing if the system can favor the reduction of the aquaculture residues, aiming at the reuse of this water. Biweekly collections were carried out during eight months in 2014, covering the periods of rain and drought in three sampling points: inlet water, fishpond center and water outlet. Water was collected on the surface for analysis of nutrients, total solids, chlorophyll a, dissolved oxygen, pH, alkalinity, transparency and thermotolerant coliforms. The organic matter, phosphorus, calcium, potassium, magnesium, aluminum and pH contents were analyzed in the upper layer, using pvc tube and / or dredge. Zooplankton was collected monthly (February / September) at the same sampling points. The zooplankton samples were collected using a graded bucket (20 L), concentrated in a 58 μm mesh and fixed in 4% formalin for further identification and counting. The concentrations of nutrients, chlorophyll a, coliforms and solids were higher (p <0.05) during the rainy period due to the higher flow of effluents due to the intensification of the production in this period, contributing to the eutrophication of the water, without variation between sampling points. During drought, only a reduction of ammonia through, resulting in increased levels of nitrate and nitrite. Zooplankton was represented by 74 taxa; 64 Rotifera, 7 Cladocera, 4 Copepoda and 1 Ostracoda, present at all points of collection. In this study, the density and richness of Rotifera was high in all points, with the occurrence of species associated with organic pollution, such as Brachionus and Filinia, favored by their rapid life cycle, small size and resistance. The occurrence of Thermocyclops decipiens, Bosmina longirostris and the dominance of the Rotifera group indicate that water from the system is in the process of eutrophication. However, the presence of A. furcatus may indicate that the system has not yet reached its maximum deterioration limit. The low water quality of this nursery, as well as the accumulation of nutrients and organic matter in the sediment, causes an increase in the trophic level of the system, and it is necessary to promote the recovery of sediment water quality in this system.
This study evaluated and described the limnological conditions of an artificial aquaculture waste receiver system. The system is an old nursery that is part of the aquaculture farm of the Aquaculture Center of UNESP Jaboticabal, SP (21 ° 15'S, 48 ° 18'O), which receives approximately 65% of the farm waste and flows directly without previous treatment in the Jaboticabal Stream (SP). The objective of this study was to characterize water quality, sediment composition, trophic degree and zooplankton community identification, as well as possible water quality indicator species; observing if the system can favor the reduction of the aquaculture residues, aiming at the reuse of this water. Biweekly collections were carried out during eight months in 2014, covering the periods of rain and drought in three sampling points: inlet water, fishpond center and water outlet. Water was collected on the surface for analysis of nutrients, total solids, chlorophyll a, dissolved oxygen, pH, alkalinity, transparency and thermotolerant coliforms. The organic matter, phosphorus, calcium, potassium, magnesium, aluminum and pH contents were analyzed in the upper layer, using pvc tube and / or dredge. Zooplankton was collected monthly (February / September) at the same sampling points. The zooplankton samples were collected using a graded bucket (20 L), concentrated in a 58 μm mesh and fixed in 4% formalin for further identification and counting. The concentrations of nutrients, chlorophyll a, coliforms and solids were higher (p <0.05) during the rainy period due to the higher flow of effluents due to the intensification of the production in this period, contributing to the eutrophication of the water, without variation between sampling points. During drought, only a reduction of ammonia through, resulting in increased levels of nitrate and nitrite. Zooplankton was represented by 74 taxa; 64 Rotifera, 7 Cladocera, 4 Copepoda and 1 Ostracoda, present at all points of collection. In this study, the density and richness of Rotifera was high in all points, with the occurrence of species associated with organic pollution, such as Brachionus and Filinia, favored by their rapid life cycle, small size and resistance. The occurrence of Thermocyclops decipiens, Bosmina longirostris and the dominance of the Rotifera group indicate that water from the system is in the process of eutrophication. However, the presence of A. furcatus may indicate that the system has not yet reached its maximum deterioration limit. The low water quality of this nursery, as well as the accumulation of nutrients and organic matter in the sediment, causes an increase in the trophic level of the system, and it is necessary to promote the recovery of sediment water quality in this system.
Descrição
Palavras-chave
Resíduos de aquicultura, sedimento de viveiros de aquicultura, estado trófico, zooplâncton, bioindicadores, Aquaculture, aquaculture waste, sediment in aquaculture fishponds, water quality, trophic state