Sharks are one of the most threatened groups of marine animals worldwide, mostly owing to overfishing and habitat degradation/loss. Although these cartilaginous fish have evolved to fill many ecological niches across a wide range of habitats, they have limited capability to rapidly adapt to human-induced changes in their environments. Contrary to global warming, ocean acidification was not considered as a direct climate-related threat to sharks. Here we show, for the first time, that an early ontogenetic acclimation process of a tropical shark (Chiloscyllium punctatum) to the projected scenarios of ocean acidification (DpH ¼ 0.5) and warming (þ48C; 308C) for 2100 elicited significant impairments on juvenile shark condition and survival. The mortality of shark embryos at the present-day thermal scenarios was 0% both at normocapnic and hypercapnic conditions. Yet routine metabolic rates (RMRs) were significantly affected by temperature, pH and embryonic stage. Immediately after hatching, the Fulton condition of juvenile bamboo sharks was significantly different in individuals that experienced future warming and hypercapnia; 30 days after hatching, survival rapidly declined in individuals experiencing both ocean warming and acidification (up to 44%). The RMR of juvenile sharks was also significantly affected by temperature and pH. The impact of low pH on ventilation rates was significant only under the higher thermal scenario. This study highlights the need of experimental-based risk assessments of sharks to climate change. In other words, it is critical to directly assess risk and vulnerability of sharks to ocean acidification and warming, and such effort can ultimately help managers and policy-makers to take proactive measures targeting most endangered species.

The ability to understand and predict the effects of ocean warming (under realistic scenarios) on marine biota is of paramount importance, especially at the most vulnerable early life stages. Here we investigated the impact of predicted environmental warming (+3 °C) on the development, metabolism, heat shock response and antioxidant defense mechanisms of the early stages of the common octopus, Octopus vulgaris. As expected, warming shortened embryonic developmental time by 13 days, from 38 days at 18 °C to 25 days at 21 °C. Concomitantly, survival decreased significantly (~29.9 %). Size at hatching varied inversely with temperature, and the percentage of smaller premature paralarvae increased drastically, from 0 % at 18 °C to 17.8 % at 21 °C. The metabolic costs of the transition from an encapsulated embryo to a free planktonic form increased significantly with warming, and HSP70 concentrations and glutathione S-transferase activity levels were significantly magnified from late embryonic to paralarval stages. Yet, despite the presence of effective antioxidant defense mechanisms, ocean warming led to an augmentation of malondialdehyde levels (an indicative of enhanced ROS action), a process considered to be one of the most frequent cellular injury mechanisms. Thus, the present study provides clues about how the magnitude and rate of ocean warming will challenge the buffering capacities of octopus embryos and hatchlings' physiology. The prediction and understanding of the biochemical and physiological responses to warmer temperatures (under realistic scenarios) is crucial for the management of highly commercial and ecologically important species, such as O. vulgaris.

The combined effects of future ocean acidification and global warming on the hypoxia thresholds of marine biota are, to date, poorly known. Here, we show that the future warming and acidification scenario led to shorter embryonic periods, lower survival rates and the enhancement of premature hatching in the cuttlefish Sepia officinalis. Routine metabolic rates increased during the embryonic period, but environmental hypercapnia significantly depressed pre-hatchling's energy expenditures rates (independently of temperature). During embryogenesis, there was also a significant rise in the carbon dioxide partial pressure in the perivitelline fluid (PVF), bicarbonate levels, as well as a drop in pH and oxygen partial pressure ( pO 2 ). The critical partial pressure (i.e. hypoxic threshold) of the pre-hatchlings was significantly higher than the PVF oxygen partial pressure at the warmer and hypercapnic condition. Thus, the record of oxygen tensions below critical pO 2 in such climate scenario indicates that the already harsh conditions inside the egg capsules are expected to be magnified in the years to come, especially in populations at the border of their thermal envelope. Such a scenario promotes untimely hatching and smaller post-hatching body sizes, thus challenging the survival and fitness of early life stages.

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2012 AgradecimentosSe chego agora a bom porto, foi porque não viajei sozinha.Quero, por isso, agradecer, Aos meus cavalos-marinhos, os protagonistas desta aventura.Aos meus orientadores, por me terem aberto a porta da Guia. Ao Rui, pela confiança nesta jovem aprendiz, pela paciência de guiar quem dá os primeiros passos no mundo da Ciência. Ao Luís, pelos conselhos experientes que fizeram daquele forte uma casa para os cavalos-marinhos.A todos no Laboratório da Guia, pelo companheirismo e disponibilidade. Em especial à Marta e à Filipa, por toda a ajuda, desde o início. E ao Tiago, por ser ele próprio, o cientista desenrascado, com uma solução para tudo, e que tantas vezes me salvou.Aos meus colegas de mestrado, por estarmos todos no mesmo barco, onde não faltou o espírito de entreajuda, à Rita, ao Manel, à Vanessa. E em especial à Kuka. Pela paixão contagiante que tem pela Ciência. Pela mão amiga, sempre por perto, sempre pronta. Por ter estado sempre lá, nos incontáveis cafés no terraço, nas viagens de comboio, nas discussões académicas e nas piadas mais tolas. Por toda a confiança. Obrigada.Aos Amigos, aos "mais fixes", aos biólogos e aos outros, aos que estiveram perto, e aos que estando longe estiveram sempre comigo. Aos da "vila" e aos de fora, de Portugal e arredores.Aos de infância e aos de universidade. Aos Professores. Aos escuteiros, com quem aprendi a tirar o "im" de "impossível". Aos que estiveram pouco tempo, e aos que sem saber vão estar para sempre. Porque cada um me deu algo que me fez chegar aqui.Ao Eduardo, por me ouvir, e por falar. Por ser a constância em dias mais tempestuosos.Por acreditar sempre. À minha Família. Aos meus Pais, por tudo.Por me ensinarem a amar a Natureza, a olhá-la para lá do que se vê, e a querer descobrir os seus mistérios. Às minhas irmãs, pela amizade que nunca acaba, e que cresce connosco.