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de Carvalho Godinho Macedo Pegado, Maria Rita
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- Effects of climate change in the early ontogeny of temperate and tropical sharksPublication . Pegado, Maria; Rosa, Rui Afonso Bairrão daA atividade antropogénica está a libertar dióxido de carbono para a atmosfera, que se traduz em alterações físicas e químicas dos nossos oceanos outrora pristinos. Os níveis de dióxido de carbono estão a aumentar a uma velocidade sem precedentes o que resulta no aumento de temperatura (incluindo um aumento de ondas de calor marinhas) e acidificação dos oceanos. Simultaneamente as populações de tubarões estão a diminuir e, como elementos essenciais dos ecossistemas marinhos, é imperativo determinar a sua vulnerabilidade aos potenciais riscos que um oceano em mudança acarreta. Assim, o objetivo da presente dissertação foi investigar os impactos que uma onda de calor marinha e a acidificação dos oceanos poderão ter na ecofisiologia de tubarões temperados (Scyliorhinus canicula) e tropicais (Chiloscyllium plagiosum) juvenis bentónicos, incluindo respostas de stress oxidativo, parâmetros hematológicos, crescimento e performance natatória. Os resultados sugerem que a espécie temperada estudada é mais sensível ao aquecimento que à acidificação, uma vez que a exposição a uma onda de calor marinha alterou a contagem de células sanguíneas e aumentou a taxa de ventilação enquanto a acidificação não surtiu efeitos significativos. Além disso, a acidificação só afetou a espécie tropical estudada, uma vez que uma curta exposição foi suficiente para reduzir a taxa de crescimento, o tempo de natação e a atividade da acetilcolinesterase no cérebro. Os impactos observados parecem indicar alguma resiliência às alterações climáticas. Contudo, até estes efeitos subletais podem reduzir o estado físico e a sustentabilidade destes tubarões a longo curso, com potenciais efeitos cascata ao longo do ecossistema.
- Absence of cellular damage in tropical newly hatched sharks (Chiloscyllium plagiosum) under ocean acidification conditionsPublication . Lopes, Ana Rita; Sampaio, Eduardo; Santos, Catarina; Couto, Ana; Pegado, Maria Rita; Diniz, Mário S.; Munday, Philip L.; Rummer, Jodie L.; Rosa, RuiSharks have maintained a key role in marine food webs for 400 million years and across varying physicochemical contexts, suggesting plasticity to environmental change. In this study, we investigated the biochemical effects of ocean acidification (OA) levels predicted for 2100 (pCO2 ~ 900 μatm) on newly hatched tropical whitespotted bamboo sharks (Chiloscyllium plagiosum). Specifically, we measured lipid, protein, and DNA damage levels, as well as changes in the activity of antioxidant enzymes and non-enzymatic ROS scavengers in juvenile sharks exposed to elevated CO2 for 50 days following hatching. Moreover, we also assessed the secondary oxidative stress response, i.e., heat shock response and ubiquitin levels. Newly hatched sharks appear to cope with OA-related stress through a range of tissue-specific biochemical strategies, specifically through the action of antioxidant enzymatic compounds. Our findings suggest that ROS-scavenging molecules, rather than complex enzymatic proteins, provide an effective defense mechanism in dealing with OA-elicited ROS formation. We argue that sharks' ancient antioxidant system, strongly based on non-enzymatic antioxidants (e.g., urea), may provide them with resilience towards OA, potentially beyond the tolerance of more recently evolved species, i.e., teleosts. Nevertheless, previous research has provided evidence of detrimental effects of OA (interacting with other climate-related stressors) on some aspects of shark biology. Moreover, given that long-term acclimation and adaptive potential to rapid environmental changes are yet experimentally unaccounted for, future research is warranted to accurately predict shark physiological performance under future ocean conditions.
- Seahorses under a changing ocean: the impact of warming and acidification on the behaviour and physiology of a poor-swimming bony-armoured fishPublication . Faleiro, Filipa; Baptista, Miguel; Santos, Catarina; Aurelio, Maria; Pimentel, Marta; Pegado, Maria Rita; Paula, José Ricardo; Calado, Ricardo; Repolho, Tiago; Rosa, RuiSeahorses are currently facing great challenges in the wild, including habitat degradation and overexploitation, and how they will endure additional stress from rapid climate change has yet to be determined. Unlike most fishes, the poor swimming skills of seahorses, along with the ecological and biological constraints of their unique lifestyle, place great weight on their physiological ability to cope with climate changes. In the present study, we evaluate the effects of ocean warming (+4°C) and acidification (ΔpH = -0.5 units) on the physiological and behavioural ecology of adult temperate seahorses, Hippocampus guttulatus. Adult seahorses were found to be relatively well prepared to face future changes in ocean temperature, but not the combined effect of warming and acidification. Seahorse metabolism increased normally with warming, and behavioural and feeding responses were not significantly affected. However, during hypercapnia the seahorses exhibited signs of lethargy (i.e. reduced activity levels) combined with a reduction of feeding and ventilation rates. Nonetheless, metabolic rates were not significantly affected. Future ocean changes, particularly ocean acidification, may further threaten seahorse conservation, turning these charismatic fishes into important flagship species for global climate change issues.