Stephane Roberty

University of Liège | ulg · Lab of Animal Physiology and Ecophysiology

Photosynthetic organisms have developed various photoprotective mechanisms to cope with exposure to high light intensities. In photosynthetic dinoflagellates that live in symbiosis with cnidarians, the nature and relative amplitude of these regulatory mechanisms are a matter of debate. In our study, the amplitude of photosynthetic alternative elect...

The nitrogen environment and nitrogen status of reef-building coral endosymbionts is one of the important factors determining the optimal assimilation of phototrophic carbon and hence the growth of the holobiont. However, the impact of inorganic nutrient availability on the photosynthesis and physiological state of the coral holobiont is partly und...

Acclimation of corals to light is known to rely on multiple strategies working at different timescales. Among them, photosynthetic alternative electron flows (AEFs) could act as photoprotective mechanisms under fluctuating light intensities. In this work, we first compared the use of AEFs in shallow and mesophotic colonies of the coral Stylophora p...

Environmental stress, such as an increase in the sea surface temperature, triggers coral bleaching, a profound dysfunction of the mutualist symbiosis between the host cnidarians and their photosynthetic dinoflagellates of the Family Symbiodiniaceae. Because of climate change, mass coral bleaching events will increase in frequency and severity in th...

In the past 20 years, a new concept has slowly emerged and expanded to various domains of marine biology research: the holobiont. A holobiont describes the consortium formed by a eukaryotic host and its associated microorganisms including bacteria, archaea, protists, microalgae, fungi, and viruses. From coral reefs to the deep-sea, symbiotic relati...

Seagrass meadows are increasingly threatened by anthropogenic activities and climate change, necessitating restoration efforts such as cutting transplantation. Understanding the complex interactions between plant morphology and physiology is crucial for designing robust restoration strategies and assessing the success of transplantation and recover...

Several phytoplankton species produce the metabolites dimethylsulfoniopropionate (DMSP) and dimethylsulfoxide (DMSO) but their intracellular roles need to be better understood. To improve the understanding of the DMSP antioxidant function suggested by Sunda et al. (2002), we exposed the diatom Skeletonema costatum, the Prymnesiophyceae Phaeocystis...

Abstract The mutualistic relationship existing between scleractinian corals and their photosynthetic endosymbionts involves a complex integration of the metabolic pathways within the holobiont. Respiration and photosynthesis are the most important of these processes and although they have been extensively studied, our understanding of their interac...

The breakdown of the symbiosis between cnidarians and Symbiodiniaceae often occurs upon periods of elevated sea surface temperature and gives rise to bleaching events that affect coral reefs worldwide. In this respect, an impairment of photosynthesis would be responsible for light-dependent generation of toxic reactive oxygen species putatively con...

The sea anemone Entacmaea medusivora (Actiniaria, Anthozoa) commonly feeds on the golden jellyfish Mastigias papua (Rhizostomeae, Scyphozoa) which harbours endosymbiotic dinoflagellate of the genus Cladocopium (Symbiodiniaceae). In this study, we monitored the photosynthetic activity of the endosymbiotic microalgae while their host jellyfish were i...

Important biological and geological events occurred during the early to middle Neoproterozoic. Among diversifying eukaryotic assemblages, populations of Cerebrosphaera, a distinctive and robust organic-walled vesicular microfossil (acritarch), show restricted stratigraphic distribution in several late Tonian to early Cryogenian worldwide succession...

In shallow tropical waters, ultraviolet radiation (UVR) occurs at high intensity simultaneously with high water temperatures, and both stressors are predicted to increase in the future and to have a major impact on reef coral survival. The poor knowledge of the interactive effects of those two factors, however, prevents a good estimation of the cor...

High sea surface temperature accompanied by high levels of solar irradiance are responsible for the disruption of the symbiosis between cnidarians and their symbiotic dinoflagellates from the genus Symbiodinium. This phenomenon, known as coral bleaching, is one of the major threats affecting coral reefs around the world. Since an important molecula...

During the last decades, coral reefs have been affected by several large-scale bleaching events, and such phenomena are expected to increase in frequency and severity in the future, thus compromising their survival. High sea surface temperature accompanied by high levels of solar irradiance has been found to be responsible for the induction of oxid...

Corals exposed to environmental stresses need to engage appropriate physiological strategies to survive. Here, we examined tissue modifications following algal dysfunction. Aiptasia pallida was exposed during 1 week to 3-(3,4-dichlorophenyl)-1,1-dimethylurea (DCMU), the herbicide called diuron. DCMU treatment produced a drastic loss in photosynthet...

Isocitrate lyase is one of the key enzymes of the glyoxylate cycle. This cycle plays an essential role in cell growth on acetate and is important for gluconeogenesis as it bypasses the two oxidative steps of the tricarboxylic acid (TCA) cycle in which CO2 is evolved. In this paper, a null icl mutant of the green microalga Chlamydomonas reinhardtii...

This study provides a baseline describing natural small scale variability of Symbiodinium density in the sentinel coral Acropora globiceps during the summer, under non-bleaching conditions. Spatial scales investigated range from the colony scale (1–10 cm, i.e. among branches of the same colony) to the reef scale (1–10 km, i.e. among stations distri...

Recovery of coral after bleaching episodes is a critical period for the health of the reef ecosystem. While events such as symbiont (genus Symbiodinium) shifting/shuffling or tissue apoptosis have been demonstrated to occur following bleaching, little is known concerning tissue recovery or cell proliferation. Here, we studied the sea anemone Aiptas...

The symbiosis between cnidarians and Symbiodinium algae (dinoflagellates) is the keystone responsible for the formation of the huge and important structures that are coral reefs. Today many environmental and/or anthropogenic threats compromise this tight relationship and lead to more frequent events of drastic loss of Symbiodinium pigments and even...

While many studies have investigated histological changes occurring in cnidarians during bleaching, only a few have focused on continuing changes in tissues during the recovery period. Here, we examine the response of the sea anemone Aiptasia pallida to a transient elevation of water temperature combined with high illumination. Following 30h of exp...