Does Predation Exacerbate the Risk of Endosymbiont Loss in Heat Stressed Hermatypic Corals? Molecular Cues Provide Insights Into Species-Specific Health Outcomes in a Multi-Stressor Ocean

Abstract

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.

Thermal photo-physiological responses of massive heat-resistant coral Porites lutea under fish predated versus non-predated conditions

“…Additionally, Morikawa and Palumbi (2019) found that Porites cylindrica, a reef-building coral species had the highest tolerance compared to Acropora hyacinthus and Acropora gemmifera. Moreover, previous studies reported a decrease in the health conditions of corals when exposed to high temperatures for a longer time (Fujise et al 2014;Zinke et al 2015;Madeira et al 2022), hence 48 hours of exposure to the different treatments could be insufficient to detect changes in the photo-physiology of the corals.…”

“…Even small injuries on the skeletal or tissue structures can induce disturbances in growth and cause fitness consequences (Rotjan and Lewis 2008). Additionally, recurrent corallivory can become a source of chronic stress (Madeira et al 2022).…”

“…Eco-physiological studies brought about insights into mechanisms used by corals while coping through thermal stress challenges (Madeira et al 2022). Chlorophyll a fluorescence is being employed to a greater extent as a fast, non-intrusive, accurate, and practical measure of photosynthetic activity in marine photosynthetic organisms.…”

Bacterial Communities Vary from Different Scleractinian Coral Species and between Bleached and Non-Bleached Corals

“…Different coral species displayed variant degrees of bleaching and disease susceptibility as reported in several studies ( 45 – 47 ). There is mounting evidence to suggest that Porites and Galaxea were relatively resistant to heat tolerance and undergo lower mortality and bleaching rates compared to Acropora ( 40 , 48 , 49 ). In this study, we observed a higher number of OTUs in P .…”

“…fascicularis exhibit higher bleaching thresholds. The host symbiont can obtain or lose high-species variability, depending on the species’ own capacity to resist stressor intensity, symbiotic partnership, and energy metabolism level ( 48 , 49 ). Differences in the bacteria community structure of coral species are also related to the host’s physiological characteristics of the test species.…”