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- Neuro-oxidative damage and aerobic potential loss of sharks under elevated CO2 and warmingPublication . Rosa, Rui; Paula, José Ricardo; Sampaio, Eduardo; Pimentel, Marta; Lopes, Ana Rita; Baptista, Miguel; Guerreiro, Miguel; Santos, Catarina; Campos, Derek; Almeida-Val, Vera M.F.; Calado, Ricardo; Diniz, Mário; Repolho, TiagoSharks occupy high trophic levels in marine habitats and play a key role in the structure and function of marine communities. Their populations have been declining worldwide by ≥90 %, and their adaptive potential to future ocean conditions is believed to be limiting. Here we experimentally exposed recently hatched bamboo shark (Chiloscyllium punctatum) to the combined effects of tropical ocean warming (+4; 30 °C) and acidification (ΔpH 0.5) and investigated the respiratory, neuronal and antioxidant enzymatic machinery responses. Thirty days post-hatching, juvenile sharks revealed a significant decrease in brain aerobic potential (citrate synthase activity), in opposition to the anaerobic capacity (lactate dehydrogenase). Also, an array of antioxidant enzymes (glutathione S-transferase, superoxide dismutase activity and catalase) acted in concert to detoxify ROS, but this significant upregulation was not enough to minimize the increase in brain’s peroxidative damage and cholinergic neurotransmission. We argue that the future conditions may elicit deleterious deficiencies in sharks’ critical biological processes which, at the long-term, may have detrimental cascading effects at population and ecosystem levels.
- Deficit in digestive capabilities of bamboo shark early stages under climate changePublication . Rosa, Rui; Pimentel, Marta; Galan, Juan; Baptista, Miguel; Lopes, Vanessa M.; Couto, Ana; Guerreiro, Miguel; Sampaio, Eduardo; Castro, Joana; Santos, Catarina; Calado, Ricardo; Repolho, TiagoLittle empirical information is currently available on the potential effects of acidification and/or warming in sharks, but none exist about digestive capabilities under such future conditions. Here, we investigated the impact of both acidification (ΔpH = 0.5) and warming (+4; 30 °C) on the digestive enzyme levels of recently hatched tropical bamboo shark (Chiloscyllium punctatum). Thirty days post-hatching, juvenile sharks revealed a significant increase in pancreatic trypsin levels under warming, but also a significant decrease under acidification, namely a 42 % drop under present-day temperature and 44 % drop under the warming condition. A similar trend was recorded for the alkaline phosphatase activity in shark’s intestine, i.e. the impact of environmental hypercapnia was also quite notorious—a 50 % drop under present-day temperature and 49 % drop under the warming condition. Thus, our present findings suggest that acidification and warming acted antagonistically, leading to similar enzyme activities under present and future conditions. Future directions on this topic of research should point towards the study of other types of sharks, namely pelagic ones with quite higher energetic demands.
- Seagrass ecophysiological performance under ocean warming and acidificationPublication . Repolho, Tiago; Duarte, Bernardo; Dionísio, Gisela; Paula, José Ricardo; Lopes, Ana Rita; Rosa, Inês; F. Grilo, Tiago; Caçador, Isabel; Calado, Ricardo; Rosa, RuiSeagrasses play an essential ecological role within coastal habitats and their worldwide population decline has been linked to different types of anthropogenic forces. We investigated, for the first time, the combined effects of future ocean warming and acidification on fundamental biological processes of Zostera noltii, including shoot density, leaf coloration, photophysiology (electron transport rate, ETR; maximum PSII quantum yield, Fv/Fm) and photosynthetic pigments. Shoot density was severely affected under warming conditions, with a concomitant increase in the frequency of brownish colored leaves (seagrass die-off). Warming was responsible for a significant decrease in ETR and Fv/Fm (particularly under control pH conditions), while promoting the highest ETR variability (among experimental treatments). Warming also elicited a significant increase in pheophytin and carotenoid levels, alongside an increase in carotenoid/chlorophyll ratio and De-Epoxidation State (DES). Acidification significantly affected photosynthetic pigments content (antheraxanthin, β-carotene, violaxanthin and zeaxanthin), with a significant decrease being recorded under the warming scenario. No significant interaction between ocean acidification and warming was observed. Our findings suggest that future ocean warming will be a foremost determinant stressor influencing Z. noltii survival and physiological performance. Additionally, acidification conditions to occur in the future will be unable to counteract deleterious effects posed by ocean warming.
- 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.
- Distinct Bleaching Resilience of Photosynthetic Plastid-Bearing Mollusks Under Thermal Stress and High CO2 ConditionsPublication . Dionísio, Gisela; Faleiro, Filipa; Bispo, Regina; Lopes, Ana Rita; Cruz, Sónia; Paula, José Ricardo; Repolho, Tiago; Calado, Ricardo; Rosa, RuiThe impact of temperature on photo-symbiotic relationships has been highly studied in the tropical reef-forming corals but overlooked in less charismatic groups such as solar-powered sacoglossan sea slugs. These organisms display one of the most puzzling symbiotic features observed in the animal kingdom, i.e., their mollusk-plastid association, which enables them to retain photosynthetic active chloroplasts (i.e., kleptoplasts) retrieved from their algae feed sources. Here we analyze the impact of thermal stress (+4°C) and high pCO2 conditions (ΔpH = 0.4) in survival, photophysiology (i.e., bleaching, photosynthetic efficiency, and metabolism) and stress defense mechanisms (i.e., heat shock and antioxidant response) of solar-powered sacoglossan sea slugs, from tropical (Elysia crispata) and temperate (E. viridis) environments. High temperature was the main factor affecting the survival of both species, while pH only affected the survival of the temperate model. The photobiology of E. viridis remained stable under the combined scenario, while photoinhibition was observed for E. crispata under high temperature and high pCO2. In fact, bleaching was observed within all tropical specimens exposed to warming (but not in the temperate ones), which constitutes the first report where the incidence of bleaching in tropical animals hosting photosynthetic symbionts, other than corals, occurs. Yet, the expulsion of kleptoplasts by the tropical sea slug, allied with metabolic depression, constituted a physiological response that did not imply signs of vulnerability (i.e., mortality) in the host itself. Although the temperate species revealed greater heat shock and antioxidant enzyme response to environmental stress, we argue that the tropical (stenotherm) sea slug species may display a greater scope for acclimatization than the temperate (eurytherm) sea slug. E. crispata may exhibit increased capacity for phenotypic plasticity by increasing fitness in a much narrower thermal niche (minimizing maintenance costs), which ultimately may allow to face severe environmental conditions more effectively than its temperate generalist counterpart (E. viridis).