Alterações de conchas de moluscos como modelos para avaliação da contaminação em zonas costeiras
Data
2022-12-15
Autores
Santos, Nayara Gouveia dos 
Gouveia, Nayara
Orientadores
Castro, Ítalo Braga
Tipo
Tese de doutorado
Título da Revista
ISSN da Revista
Título de Volume
Resumo
Moluscos são amplamente empregados em estudos de biomonitoramento de ambientes marinhos por apresentarem alta sensibilidade aos efeitos de substâncias químicas perigosas, além de possuírem a capacidade de armazenarem o histórico das mudanças ambientais ocorridas em seu habitat, em suas conchas. Alterações morfológicas, estruturais e composicionais em conchas de moluscos têm sido propostas como possíveis biomarcadores de contaminação química em zonas costeiras. Apesar do potencial como ferramenta de avaliação ambiental, essas respostas foram pouco estudadas na perspectiva de espécies tropicais. Portanto objetivo geral do presente estudo foi selecionar e avaliar espacialmente, uma espécie de molusco como modelo biológico adequado para ser usado em avaliações da contaminação costeira com base alterações nas matrizes orgânicas e inorgânicas de conchas. Inicialmente, três espécies de moluscos com diferentes hábitos alimentares e amplamente distribuídas em zonas costeiras foram selecionadas e comparadas, a partir de análises morfométricas. O estudo foi realizado usando Lottia subrugosa (herbívoro), Crassostrea brasiliana (filtrador) e Stramonita brasiliensis (carnívoro) obtidos ao longo de um gradiente de contaminação acentuado no Sistema Estuarino de Santos. Duas das três espécies avaliadas (L. subrugosa e S. brasiliensis) apresentaram resposta proporcionais ao longo do gradiente e consistentes com os níveis de contaminação medidos em seus tecidos. Embora ostras sejam tradicionalmente usadas em avaliações da contaminação ambiental, a influência do substrato sobre suas taxas de crescimento e formato desses organismos levou a respostas inconsistentes com os níveis de contaminação. Adicionalmente, modelos de validação cruzada indicaram maior confiabilidade (75%) nas respostas morfométricas observadas nos gastrópodes carnívoros. Sendo assim, a fase subsequente do estudo avaliou alterações na resistência a compressão, composição da matriz orgânica e mineralógica relacionadas às alterações morfométricas originalmente observadas em S. brasiliensis. Os resultados mostraram valores de resistência à compressão e conteúdo total de matriz orgânica proporcionalmente associados a alterações morfológicas e aos níveis de contaminação nos tecidos do gastrópode. Mais além, foram observadas alterações nas razões e aragonita/calcita associadas a contaminação química, as quais anteriormente eram apenas associadas a acidificação oceânica e costeira. Análises adicionais, realizadas na etapa final do estudo, avaliaram os teores de proteína total assim como a fração de proteínas solúveis, com massas superiores a 10 kDa, nas conchas de S. brasiliensis obtidas ao longo do gradiente de contaminação. Contraditoriamente as observações realizadas nos demais estudos, a concentrações de proteínas totais não mostraram diferenças significativas entre organismos obtidos em áreas sob diferentes níveis de contaminação. Adicionalmente, não foram verificadas diferenças entre as massas moleculares das proteínas de matriz de concha (fração solúvel) nas amostras obtidas nos diferentes pontos. Portanto, o presente estudo demonstrou que gastrópodes carnívoros são mais adequados para serem usados em avaliação de qualidade ambiental em zonas costeiras, com base em alterações de parâmetros de conchas. Mais além, alterações na matriz mineralógica, parecem levar a respostas mais consistentes quando comparadas a matriz orgânica.
Molluscs are widely used in biomonitoring studies of marine environments since they are highly sensitive to effects induced by exposure hazardous chemicals. In addition, they may store the history of environmental changes that have occurred in their habitat, in their shells. Morphological, structural and compositional changes in mollusc shells have been proposed as possible biomarkers of chemical contamination in coastal zones. Despite its potential as an environmental assessment tool, these responses were assessed from the perspective of tropical species. Therefore, the general objective of the present study was to select and spatially evaluate mollusk species as a suitable biological model to be used in coastal contamination assessments based on changes in the organic and inorganic matrices of shells. Initially, three species of molluscs with different feeding habits and widely distributed in coastal areas were selected and compared, based on morphometric analyses. The study was carried out using Lottia subrugosa (herbivore), Crassostrea brasiliana (filter) and Stramonita brasiliensis (carnivore) obtained along a contamination gradient in the Santos Estuarine System. Two of the three evaluated species (L. subrugosa and S. brasiliensis) showed proportional responses along the gradient which were consistent with the levels of contamination measured in their tissues. Although oysters are traditionally used in assessments of environmental contamination, the influence of the substrate on their growth rates and shape has led to inconsistent responses with levels of contamination. Additionally, cross-validation models indicated greater reliability (75%) in the morphometric responses observed in carnivorous gastropods. Therefore, the subsequent phase of the study evaluated changes in compressive strength, composition of the organic and mineralogical matrices related to the morphometric changes originally observed in S. brasiliensis. The results showed values of compressive strength and total organic matrix content proportionally associated with morphological changes and contamination levels in gastropod tissues. Further, changes in aragonite/calcite ratios associated with chemical contamination were observed, which were previously only associated with oceanic and coastal acidification. Additional analyses, carried out in the final stage of the study, evaluated the total protein contents, as well as the fraction of soluble proteins, with masses greater than 10 kDa, in the shells of S. brasiliensis obtained along the contamination gradient. Contradictorily to the observations from previous steps, the concentrations of total proteins did not show significant differences between organisms obtained in areas under different levels of contamination. Additionally, no differences were verified between the molecular masses of shell matrix proteins (soluble fraction) in the samples obtained at different points. Therefore, the present study demonstrated that carnivorous gastropods are more suitable to be used in environmental quality assessment in coastal zones, based on changes in shell parameters. Further, changes in the mineralogical matrix seem to lead to more consistent responses when compared to the organic matrix.
Molluscs are widely used in biomonitoring studies of marine environments since they are highly sensitive to effects induced by exposure hazardous chemicals. In addition, they may store the history of environmental changes that have occurred in their habitat, in their shells. Morphological, structural and compositional changes in mollusc shells have been proposed as possible biomarkers of chemical contamination in coastal zones. Despite its potential as an environmental assessment tool, these responses were assessed from the perspective of tropical species. Therefore, the general objective of the present study was to select and spatially evaluate mollusk species as a suitable biological model to be used in coastal contamination assessments based on changes in the organic and inorganic matrices of shells. Initially, three species of molluscs with different feeding habits and widely distributed in coastal areas were selected and compared, based on morphometric analyses. The study was carried out using Lottia subrugosa (herbivore), Crassostrea brasiliana (filter) and Stramonita brasiliensis (carnivore) obtained along a contamination gradient in the Santos Estuarine System. Two of the three evaluated species (L. subrugosa and S. brasiliensis) showed proportional responses along the gradient which were consistent with the levels of contamination measured in their tissues. Although oysters are traditionally used in assessments of environmental contamination, the influence of the substrate on their growth rates and shape has led to inconsistent responses with levels of contamination. Additionally, cross-validation models indicated greater reliability (75%) in the morphometric responses observed in carnivorous gastropods. Therefore, the subsequent phase of the study evaluated changes in compressive strength, composition of the organic and mineralogical matrices related to the morphometric changes originally observed in S. brasiliensis. The results showed values of compressive strength and total organic matrix content proportionally associated with morphological changes and contamination levels in gastropod tissues. Further, changes in aragonite/calcite ratios associated with chemical contamination were observed, which were previously only associated with oceanic and coastal acidification. Additional analyses, carried out in the final stage of the study, evaluated the total protein contents, as well as the fraction of soluble proteins, with masses greater than 10 kDa, in the shells of S. brasiliensis obtained along the contamination gradient. Contradictorily to the observations from previous steps, the concentrations of total proteins did not show significant differences between organisms obtained in areas under different levels of contamination. Additionally, no differences were verified between the molecular masses of shell matrix proteins (soluble fraction) in the samples obtained at different points. Therefore, the present study demonstrated that carnivorous gastropods are more suitable to be used in environmental quality assessment in coastal zones, based on changes in shell parameters. Further, changes in the mineralogical matrix seem to lead to more consistent responses when compared to the organic matrix.
Descrição
Citação
SANTOS, Nayara Gouveia dos. Alterações de conchas de moluscos como modelos para avaliação da contaminação em zonas costeiras. 2022. 106 f. Tese (Doutorado em Bioprodutos e Bioprocessos) - Instituto de Saúde e Sociedade, Universidade Federal de São Paulo, Santos, 2022.