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Abstract(s)
A constante mudança do planeta devido ao aumento dos gases de efeito estufa tem moldado o clima da Terra, existindo uma alteração, principalmente na temperatura, que tem aumentado drasticamente. Nos últimos 100 anos, a temperatura subiu aproximadamente 1oC e prevê-se que aumente mais 0,5oC até 2040. Um dos grandes afetados por este aumento é o meio marinho, um local de grande importância, quer ao nível socioeconómico, quer ao nível ecológico. A temperatura pode afetar a vida marinha de diferentes maneiras, destacando-se o crescimento dos peixes, que pode ser deduzido a partir de estruturas calcificadas, como os otólitos, devido à acumulação sazonal diferenciada. Esta característica dos otólitos torna-os uma ótima base de estudo para criar biocronologias que podem ser usadas em modelos de efeitos mistos. Desta forma é possível estimar as respostas dos organismos às alterações ambientais. Beryx decadactylus é um forte candidato para desenvolver uma biocronologia devido à sua longevidade e à existência de um considerável arquivo de otólitos, adquiridos durante os cruzeiros anuais de monitorização da abundância de peixes demersais e de águas profundas no arquipélago dos Açores. Esta dissertação tem como objetivo principal a identificação dos fatores ambientais responsáveis pela variabilidade no crescimento dos peixes, com base no crescimento dos otólitos de B. decadactylus durante as últimas décadas. Para isso, mediram-se as larguras dos incrementos do otólito de B. decadactylus, sendo usadas para desenvolver uma biocronologia e descrever a variação do crescimento ao longo de 38 anos. O crescimento estava relacionado com fatores intrínsecos (idade, idade à captura e sexo) e extrínsecos [índice da North Atlantic Oscillation (NAO) e da East Atlantic pattern (EAP), temperatura de fundo e das descargas de B. decadactylus nos Açores]. Os resultados demonstraram que a idade e a idade à captura são os fatores intrínsecos que mais influenciam o crescimento do peixe. Quanto aos fatores extrínsecos temperatura de fundo de Verão e o índice NAO mostraram afetar a variação de crescimento em B. decadactylus. Foram ainda explorados os possíveis mecanismos de como estes fatores influenciam o crescimento de B. decadactylus, principalmente de modo indireto, como mudanças na teia alimentar ou níveis reduzidos de oxigênio. Esta informação é essencial para perceber como as alterações climáticas podem influenciar esta espécie com grande importância comercial na região dos Açores.
The constant changes on the planet due to the accumulation of greenhouse gases have shaped the planet’s climate, the main change being the dramatic increase of the temperature. Over the past 100 years, the temperature has risen by approximately 1°C and is expected to escalate by another 0.5°C by 2040. One of the most affected systems by this phenomenon is the marine environment, which has a tremendous socioeconomic and ecological importance. Temperature can affect marine life in different ways, including fish growth, that can be deduced using calcified structures, such as otoliths, due to differential seasonal accumulation. This characteristic makes otoliths an excellent base for the creation of biochronologies, which, in turn, can be used in mixed effects models. This way, it is possible to estimate the organisms' responses to environmental changes. Beryx decadactylus is a strong candidate for developing a biochronology due to its longevity and to the existence of an extensive collection of otoliths that were acquired during annual monitoring surveys of demersal and deep-water fish abundance in the Azores archipelago. This dissertation has the general objective of identifying the environmental factors responsible for growth variation of B. decadactylus. With this aim, otolith increment widths of B. decadactylus were measured and then used to develop a biochronology describing growth variation over 38 years. The existence of a relation between growth and intrinsic (age, age at capture, sex) and extrinsic factors [North Atlantic Oscillation index (NAO), East Atlantic pattern (EAP), temperature-at-depth and B. decadactylus landings in the Azores] was investigated. The results showed that age and age at capture were the intrinsic factors that most influenced fish growth. Regarding extrinsic factors, summer temperature-at-depth and NAO were shown to affect B. decadactylus growth variation. Possible mechanisms of how these factors can influence the growth of B. decadactylus were explored and the conclusions were that indirect processes, such as changes in the food web or lowered oxygen levels, were likely involved. Such information is essential to understand how climate change can influence this species with great commercial importance in the Azores region.
The constant changes on the planet due to the accumulation of greenhouse gases have shaped the planet’s climate, the main change being the dramatic increase of the temperature. Over the past 100 years, the temperature has risen by approximately 1°C and is expected to escalate by another 0.5°C by 2040. One of the most affected systems by this phenomenon is the marine environment, which has a tremendous socioeconomic and ecological importance. Temperature can affect marine life in different ways, including fish growth, that can be deduced using calcified structures, such as otoliths, due to differential seasonal accumulation. This characteristic makes otoliths an excellent base for the creation of biochronologies, which, in turn, can be used in mixed effects models. This way, it is possible to estimate the organisms' responses to environmental changes. Beryx decadactylus is a strong candidate for developing a biochronology due to its longevity and to the existence of an extensive collection of otoliths that were acquired during annual monitoring surveys of demersal and deep-water fish abundance in the Azores archipelago. This dissertation has the general objective of identifying the environmental factors responsible for growth variation of B. decadactylus. With this aim, otolith increment widths of B. decadactylus were measured and then used to develop a biochronology describing growth variation over 38 years. The existence of a relation between growth and intrinsic (age, age at capture, sex) and extrinsic factors [North Atlantic Oscillation index (NAO), East Atlantic pattern (EAP), temperature-at-depth and B. decadactylus landings in the Azores] was investigated. The results showed that age and age at capture were the intrinsic factors that most influenced fish growth. Regarding extrinsic factors, summer temperature-at-depth and NAO were shown to affect B. decadactylus growth variation. Possible mechanisms of how these factors can influence the growth of B. decadactylus were explored and the conclusions were that indirect processes, such as changes in the food web or lowered oxygen levels, were likely involved. Such information is essential to understand how climate change can influence this species with great commercial importance in the Azores region.
Description
Tese de mestrado, Ecologia Marinha, Universidade de Lisboa, Faculdade de Ciências, 2021
Keywords
Alterações climáticas Beryx decadactylus Biocronologia Modelos de efeitos mistos Otólito Teses de mestrado - 2021