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Integrative indices for health assessment in reef corals under thermal stress
Publication . Dias, Marta; Madeira, Carolina; Jogee, Nadia; Ferreira, Ana; Gouveia, Raúl; Cabral, Henrique; Diniz, Mário; Vinagre, Catarina; UCIBIO - Applied Molecular Biosciences Unit; DQ - Departamento de Química; Elsevier
Global warming is one of the major causes of reef coral ecosystems’ degradation. Predictions of further rise in sea surface temperatures call for urgent action. In this study, a holistic method for bio-monitoring heat stress in reef ecosystems was tested and optimized. Long-term induction of antioxidant enzymes and oxidative stress by elevated temperatures (30 °C and 32 °C) was assessed on fragments of reef-building corals and compared to control conditions (26 °C). The quantification of both oxidative stress, through lipid peroxidation (LPO) levels, and antioxidant enzyme activities: superoxide dismutase (SOD), catalase (CAT), and glutathione S-transferase (GST) in a long-term experiment (60 days), using seven Indo-Pacific reef-building coral species, provided useful information that was interpreted in combination with the observed partial mortality and growth rate of these organisms. These biomarkers were combined in integrated biomarker response (IBR) indices, either in an antioxidant defense mechanisms and oxidative stress response category (approach A: GST, CAT, LPO, and SOD) or in an integrated stress response category – organism performance (approach B: GST, CAT, LPO, SOD, partial mortality, and growth rate). The results of this study indicate that the IBRs were responsive to temperature treatment and dependent on the coral species. The approach B was the most adequate since it better reflected the stress suffered by the tested species, whereas the set of four biochemical biomarkers (approach A) was not enough to explain the organismal response of most of the tested species to thermal stress conditions.
Does predation exacerbate the risk of endosymbiont loss in heat stressed hermatypic corals?
Publication . Madeira, Carolina; Dias, Marta; Ferreira, Ana; Gouveia, Raúl; Cabral, Henrique N.; Diniz, Mário S.; Vinagre, Catarina; UCIBIO - Applied Molecular Biosciences Unit; Frontiers
Ocean warming has been a major driver of coral reef bleaching and mass mortality. Coupled to other biotic pressures, corals’ ability for acclimatization and adaptation may become compromised. Here, we tested the combined effects of warming scenarios (26, 30, and 32°C) and predation (wound vs. no wound) in coral health condition (paleness, bleaching, and mortality), cellular stress responses (heat shock protein 70 kDa Hsp70, total ubiquitin Ub, and total antioxidant capacity TAC), and physiological state (integrated biomarker response index, IBR) of seven Scleractinian coral species, after being exposed for 60 days. Results show that although temperature was the main factor driving coral health condition, thermotolerant species (Galaxea fascicularis, Psammocora contigua, and Turbinaria reniformis) displayed increased paleness, bleaching, and mortality in predation treatments at high temperature, whereas thermosensitive species (Acropora tenuis, Echinopora lamellosa, and Montipora capricornis brown and green morphotypes) all died at 32°C, regardless of predation condition. At the molecular level, results show that there were significant main and interactive effects of species, temperature, and predation in the biomarkers assessed. Temperature affected Hsp70, Ub, and TAC, evidencing the role of protein folding and turnover, as well as reactive oxygen species scavenging in heat stress management. Predation increased Hsp70 and Ub, suggesting the activation of the pro-phenoloxidase system and cytokine activity, whereas the combination of both stressors mainly affected TAC during moderate stress and Ub under severe stress, suggesting that redox balance and defense of homeostasis are crucial in tissue repair at high temperature. IBR levels showed an increasing trend at 32°C in predated coral fragments (although non-significant). We conclude that coral responses to the combination of high temperature and predation pressure display high inter-species variability, but these stressors may pose a higher risk of endosymbiont loss, depending on species physiology and stress intensity.
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Fundação para a Ciência e a Tecnologia
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3599-PPCDT
Número da atribuição
PTDC/MAR-EST/2141/2012