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Alterações histológicas em Eisenia fetida associadas à exposição a agroquímicos presentes nas pastagens da Ilha de São Miguel
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Abstract(s)
Os solos da ilha de São Miguel são enriquecidos naturalmente em metais, devido à sua herança vulcânica. Nesta ilha, as pastagens são sujeitas a diferentes tipos de manuseio agrícola, nomeadamente no que respeita à aplicação de agroquímicos, afetando a qualidade dos solos e dos organismos residentes, como é o caso dos anelídeos terrestres (minhocas). As minhocas são organismos edáficos e por isso importantes bioindicadores da qualidade dos solos. O principal objetivo deste trabalho foi estudar as alterações histológicas em minhocas da espécie Eisenia fetida (Saying, 1989), expostas a solos de pastagens sujeitas a diferentes tipos de manuseio agrícola, usando dois períodos de exposição, contribuindo assim para a biomonitorização dos efeitos ecotoxicológicos nos organismos do solo. Uma cultura sincronizada de Eisenia fetida foi monitorizada no final de dois períodos de exposição (7 e 56 dias) a solos provenientes de pastagens com diferentes tipos de manuseio agrícola (seminatural, permanente e intensivo). Foram medidas as espessuras do epitélio e cutícula, e analisada a atividade secretora do epitélio tegumentar através da coloração PAS-AB. Os resultados mostraram que na exposição de curta duração, a espessura do epitélio e cutícula aumentaram significativamente nas minhocas expostas ao solo semi-natural. Por sua vez, uma exposição de longa duração resultou num aumento significativo da secreção de mucopolissacáridos (AB-positivo) nas minhocas expostas ao solo semi-natural. A utilização destes biomarcadores permitiu avaliar respostas estruturais e funcionais destes organismos face à exposição ao solo de diferentes tipos de pastagem. O solo proveniente da pastagem com maior manuseio agrícola (maior exposição a agroquímicos) demonstrou ser menos prejudicial para E. fetida do que o solo da pastagem seminatural. Provavelmente isto dever-se-á ao facto de, apesar de existirem PTEs no primeiro, as propriedades físico-químicas do solo da pastagem intensiva contribuíram para a retenção dos elementos, alguns deles metais pesados, diminuindo assim a sua biodisponibilidade. Este trabalho permitiu avaliar o risco da biodisponibilidade de PTEs existentes nos solos de pastagens vulcânicas, contribuindo para o desenvolvimento de medidas mitigadoras de efeitos ecotoxicológicos em níveis biológicos superiores, nomeadamente, eventuais efeitos na saúde humana.
ABSTRACT: The soils of the São Miguel Island are naturally enriched with metals due to their volcanic heritage. In this island, pastures are subjected to different types of agricultural handling, especially to agrochemical applications, which affect the quality of soils and resident organisms, such as earthworms. Earthworms are edaphic organisms and therefore important bio indicators of soil quality. In this study, the main objective was to study the histological alterations in the earthworm Eisenia fetida (Saying, 1989) exposed to soil from pastures with distinct agricultural management, using two exposure periods, contributing to the development of biomarkers to bio monitor the ecotoxicological effects of agricultural management on soil organisms. A synchronized set of individuals of Eisenia fetida was monitored at the end of 7 and 56 days of exposure to soil from different pasture types (semi- natural, permanent and intensive management types). Epidermis and cuticle thicknesses were measured and secretory activity was analyzed by PAS-AB staining. After the short-term exposure (7 days) to the semi-natural soil, results showed that the thickness of the epithelia and cuticle increased significantly. Upon long-term exposure (56 days), the parameter mucopolysaccharide secretion (AB-positive), was statistically different in semi-natural soil. The use of these biomarkers allowed to evaluate the structural and functional responses of earthworms, after exposure to soils from pastures subjected to different agricultural management. This study reveals that, the soil with higher agricultural management (higher exposure to agrochemicals) despite being contaminated with PTEs, is less harmuful than the soil from the semi-natural pasture. The physico-chemical properties of the former favour the retention of these metals, decreasing their bioavailability to soil organisms. This work allowed to evaluate the risk of of the analysed PTEs bioavailability in volcanic pasture soils, contributing to the development of mitigation measures of the potential ecotoxicological effects at higher biological levels, namely those regarding human health.
ABSTRACT: The soils of the São Miguel Island are naturally enriched with metals due to their volcanic heritage. In this island, pastures are subjected to different types of agricultural handling, especially to agrochemical applications, which affect the quality of soils and resident organisms, such as earthworms. Earthworms are edaphic organisms and therefore important bio indicators of soil quality. In this study, the main objective was to study the histological alterations in the earthworm Eisenia fetida (Saying, 1989) exposed to soil from pastures with distinct agricultural management, using two exposure periods, contributing to the development of biomarkers to bio monitor the ecotoxicological effects of agricultural management on soil organisms. A synchronized set of individuals of Eisenia fetida was monitored at the end of 7 and 56 days of exposure to soil from different pasture types (semi- natural, permanent and intensive management types). Epidermis and cuticle thicknesses were measured and secretory activity was analyzed by PAS-AB staining. After the short-term exposure (7 days) to the semi-natural soil, results showed that the thickness of the epithelia and cuticle increased significantly. Upon long-term exposure (56 days), the parameter mucopolysaccharide secretion (AB-positive), was statistically different in semi-natural soil. The use of these biomarkers allowed to evaluate the structural and functional responses of earthworms, after exposure to soils from pastures subjected to different agricultural management. This study reveals that, the soil with higher agricultural management (higher exposure to agrochemicals) despite being contaminated with PTEs, is less harmuful than the soil from the semi-natural pasture. The physico-chemical properties of the former favour the retention of these metals, decreasing their bioavailability to soil organisms. This work allowed to evaluate the risk of of the analysed PTEs bioavailability in volcanic pasture soils, contributing to the development of mitigation measures of the potential ecotoxicological effects at higher biological levels, namely those regarding human health.
Description
Dissertação de Mestrado, Ciências Biomédicas, 6 de março de 2020.
Keywords
Eisenia foetida Biodiversidade Microbiana Biomarcador Ecotoxicologia Histologia Pastagem Saúde Ambiental Solo Agroecosystems Bioavailability Earthworms Histology Soil Organisms
Citation
SILVA, Verónica Rodrigues. "Alterações histológicas em Eisenia fetida associadas à exposição a agroquímicos presentes nas pastagens da Ilha de São Miguel". 2020. 48 p.. (Dissertação de Mestrado em Ciências Biomédicas). Ponta Delgada: Universidade dos Açores, 2019. [Consult. Dia Mês Ano]. Disponível em www:<http://hdl.handle.net/10400.3/5867>.