Respostas fotossintéticas de macroalgas lóticas do filo Chlorophyta submetidas à herbicidas à base de glifosato
Carregando...
Data
2018-01-23
Autores
Oliveira, Régis de Campos [UNESP]
Título da Revista
ISSN da Revista
Título de Volume
Editor
Universidade Estadual Paulista (Unesp)
Resumo
Herbicidas podem atingir ambientes aquáticos em regiões agrícolas, afetando os produtores primários e, consequentemente, a teia trófica e a ciclagem de nutrientes. Neste contexto, macroalgas lóticas do filo Chlorophyta foram coletadas, cultivadas, e submetidas a três concentrações diferentes (0,28; 3,5; e 6 mg L-1) de glifosato grau técnico e da formulação comercial Roundup®, e uma concentração (0,03 mg L-1) de ácido aminometilfosfônico (AMPA), além do grupo controle (0 mg L-1), para a avalição da resposta fotossintética através da evolução do oxigênio dissolvido, da fluorescência da clorofila a, e da concentração de clorofila a, realizados após um e sete dias de exposição ao herbicida. Os resultados mostram que, no geral, o Roundup® foi o herbicida que mais afetou negativamente as respostas fotossintéticas das macroalgas testadas, gerando danos ao aparato fotossintético, provocando reduções na taxa de fotossíntese líquida, e na concentração de clorofila a. O glifosato grau técnico e o AMPA também causaram efeitos inibitórios significativos para a resposta fotossintética, ainda que em uma escala menor. Em relação às concentrações utilizadas, a concentração de 0,28 mg L-1, que corresponde ao limite permitido pela legislação brasileira para a água destinada a irrigação e consumo animal, gerou reduções efetivas na resposta fotossintética de Nitella microcarpa var. wrightii (Roundup®) Nitella subglomerata (glifosato grau técnico e Roundup®) e Desmidium grevillei (Roundup®). A concentração de 0,03 mg L- 1 utilizada no tratamento com AMPA também inibiu a resposta fotossintética de Oedogonium sp. e Spirogyra sp. Em um segundo experimento, as mesmas análises foram utilizadas para avaliar a mistura de herbicidas glifosato (Roundup®) e ácido 2,4-Diclorofenoxiacético (2,4-D) (Bratt®) nas concentrações recomendadas pelos fabricantes (3,5 mg L-1 e 2,0 mg L-1, respectivamente). Neste experimento, a mistura destes herbicidas gerou poucos efeitos significativos na resposta fotossintética quando comparado aos resultados do tratamento com Roundup®, sugerindo haver um efeito antagônico para a maioria das macroalgas estudadas. De modo geral, os resultados de ambos os experimentos indicam que a forma como o herbicida glifosato se apresenta para as macroalgas testadas no ambiente aquático (e.g. na presença do surfactante, degradado em AMPA, combinado com o 2,4-D), pode gerar flutuações na produtividade (inibição ou estímulo) ao longo do tempo de modo táxon-específico, ressaltando a necessidade de mais estudos sobre os efeitos de possíveis contaminantes ambientais em produtores primários de ambientes aquáticos.
Herbicides can contaminate aquatic environments in agricultural regions, affecting primary producers and, consequently, the food web and nutrient cycling. In this context, lotic macroalgae of the phylum Chlorophyta were collected and cultivated in three different concentrations (0.28; 3.5; and 6 mg L-1) of technical grade glyphosate and Roundup®, and one concentration (0.03 mg L-1) of aminomethylphosphonic acid (AMPA), in addition to the control group (0 mg L-1). Were evaluated the photosynthetic response through the oxygen evolution, chlorophyll a fluorescence, and the chlorophyll a concentration, performed with one and seven days of exposure to the herbicide. The results show that, in general, Roundup® was the herbicide most negatively affected the photosynthetic responses of macroalgae tested, causing damage to the photosynthetic apparatus, reducing the photosynthetic rates, and chlorophyll a concentration. Technical grade glyphosate and AMPA likewise caused significant inhibitory effects on the photosynthetic response, although on a smaller scale. About the concentrations used, the 0.28 mg L-1, which correspond to the limit for Brazilian law in water for irrigation and animal consumption, led to effective reductions in the photosynthetic response of Nitella microcarpa var. wrightii (Roundup®) Nitella subglomerata (glyphosate technical grade and Roundup®) and Desmidium grevillei (Roundup®). The concentration of 0.03 mg L-1 used in the AMPA treatment also inhibited the photosynthetic response of Oedogonium sp. and Spirogyra sp. In a second experiment, the same analyses were performed for a mixture of herbicides glyphosate (Roundup®) and 2,4-Dichlorophenoxyacetic acid (2,4-D) (Bratt®) at the recommended concentration to control weeds (3.5 mg L -1 and 2.0 mg L-1, respectively). In this experiment, the mixture of these herbicides, when comparing the results with the Roundup® treatment, caused few effects on the photosynthetic response, suggesting an antagonistic effect for most of the macroalgae studied. In general, the results of both experiments, indicate that the form that these herbicides take in the environment (e.g. with surfactant, degraded in AMPA, combined with 2,4-D), can generate fluctuations (inhibition or stimulation) on productivity over time in taxon-specific variation, highlighting the need for further studies on the effects of possible environmental contaminants on primary producers of aquatic environments.
Herbicides can contaminate aquatic environments in agricultural regions, affecting primary producers and, consequently, the food web and nutrient cycling. In this context, lotic macroalgae of the phylum Chlorophyta were collected and cultivated in three different concentrations (0.28; 3.5; and 6 mg L-1) of technical grade glyphosate and Roundup®, and one concentration (0.03 mg L-1) of aminomethylphosphonic acid (AMPA), in addition to the control group (0 mg L-1). Were evaluated the photosynthetic response through the oxygen evolution, chlorophyll a fluorescence, and the chlorophyll a concentration, performed with one and seven days of exposure to the herbicide. The results show that, in general, Roundup® was the herbicide most negatively affected the photosynthetic responses of macroalgae tested, causing damage to the photosynthetic apparatus, reducing the photosynthetic rates, and chlorophyll a concentration. Technical grade glyphosate and AMPA likewise caused significant inhibitory effects on the photosynthetic response, although on a smaller scale. About the concentrations used, the 0.28 mg L-1, which correspond to the limit for Brazilian law in water for irrigation and animal consumption, led to effective reductions in the photosynthetic response of Nitella microcarpa var. wrightii (Roundup®) Nitella subglomerata (glyphosate technical grade and Roundup®) and Desmidium grevillei (Roundup®). The concentration of 0.03 mg L-1 used in the AMPA treatment also inhibited the photosynthetic response of Oedogonium sp. and Spirogyra sp. In a second experiment, the same analyses were performed for a mixture of herbicides glyphosate (Roundup®) and 2,4-Dichlorophenoxyacetic acid (2,4-D) (Bratt®) at the recommended concentration to control weeds (3.5 mg L -1 and 2.0 mg L-1, respectively). In this experiment, the mixture of these herbicides, when comparing the results with the Roundup® treatment, caused few effects on the photosynthetic response, suggesting an antagonistic effect for most of the macroalgae studied. In general, the results of both experiments, indicate that the form that these herbicides take in the environment (e.g. with surfactant, degraded in AMPA, combined with 2,4-D), can generate fluctuations (inhibition or stimulation) on productivity over time in taxon-specific variation, highlighting the need for further studies on the effects of possible environmental contaminants on primary producers of aquatic environments.
Descrição
Palavras-chave
Glifosato, AMPA, 2,4-D, Glyphosate, AMPA, 2,4-D, Fotossíntese, Macroalgas verdes, Photosynthesis, Green macroalgae