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Large, well-developed and flourishing reefs dominated by the cold-water coral Desmophyllum pertusum have recently been discovered along the Angola margin in the southeastern Atlantic Ocean living under very low oxygen concentrations (0.6–1.5 mL L−1). This study assessed the respiration rates of this coral in a short-term (10 days) aquarium experiment under naturally low oxygen concentrations (1.4 ± 0.5 mL L−1) as well as under saturated oxygen concentrations (6.1 ± 0.6 mL L−1). We found no significant difference in respiration rates between the two oxygen concentrations. Furthermore, the respiration rates of D. pertusum were in the same order of magnitude as those of the same species living under normoxic conditions in other areas. This work expands the current knowledge on the metabolic activity of cold-water corals under hypoxic conditions, evidencing that low oxygen conditions are not a general limiting factor for the overall distribution of D. pertusum.

Coral reefs are declining worldwide primarily because of bleaching and subsequent mortality resulting from thermal stress. Currently, extensive efforts to engage in more holistic research and restoration endeavors have considerably expanded the techniques applied to examine coral samples. Despite such advances, coral bleaching and restoration studies are often conducted within a specific disciplinary focus, where specimens are collected, preserved, and archived in ways that are not always conducive to further downstream analyses by specialists in other disciplines. This approach may prevent the full utilization of unexpended specimens, leading to siloed research, duplicative efforts, unnecessary loss of additional corals to research endeavors, and overall increased costs. A recent US National Science Foundation-sponsored workshop set out to consolidate our collective knowledge across the disciplines of Omics, Physiology, and Microscopy and Imaging regarding the methods used for coral sample collection, preservation, and archiving. Here, we highlight knowledge gaps and propose some simple steps for collecting, preserving, and archiving coral-bleaching specimens that can increase the impact of individual coral bleaching and restoration studies, as well as foster additional analyses and future discoveries through collaboration. Rapid freezing of samples in liquid nitrogen or placing at -80 °C to -20 °C is optimal for most Omics and Physiology studies with a few exceptions; however, freezing samples removes the potential for many Microscopy and Imaging-based analyses due to the alteration of tissue integrity during freezing. For Microscopy and Imaging, samples are best stored in aldehydes. The use of sterile gloves and receptacles during collection supports the downstream analysis of host-associated bacterial and viral communities which are particularly germane to disease and restoration efforts. Across all disciplines, the use of aseptic techniques during collection, p

Deep-sea reef ecosystems are hotspots of biodiversity but are particularly threatened by seawater warming, because the species that live there have evolved within a narrow thermal range. The degree to which cold-water corals (CWCs), the reef builders, can acclimate to changes in their thermal environment requires more investigation. Our study is one of the very first to assess the thermal performance of Dendrophylliidae CWCs on a 2-year basis. Colonies of Dendrophyllia cornigera and D. ramea, collected in the Mediterranean Sea, were exposed during 2 years to their natural mean temperatures (referred as control temperature, CT) or to temperatures being 4 °C (T+4) and 8 °C (T+8) higher. A 4 °C decrease in temperature (T-4) was also tested for D. ramea. Several physiological parameters, such as rates of growth, calcification, and respiration, as well as total organic carbon release were measured after 2 and 20 months of treatment. The results obtained show that Dendrophylliidae corals are able to survive a +4 °C over a two-year period, and even a +8 °C for D. ramea. The elevation in temperature induced a transient increase in all physiological parameters. However, after 20 months, parameters were significantly decreased compared to the first measurement. At the end of the experiment, growth rates were even significantly lower at T+4 and T+8 compared to the control temperature, suggesting that the coral lifespan is significantly reduced over the long term. Finally, we observed a positive relationship between respiration and calcification rates in these corals, suggesting that the calcification process is dependent on the inorganic carbon provided by respiration. Overall, this study shows that physiological processes in CWC species are slow and that long-term incubations are necessary to predict the impact of climate change on their survival capacities.