Biology subjects

Ferrier-Pages, C.

Publications and source records attributed to Ferrier-Pages, C..

4 recordsLinked to original sources

bioRxiv2026

Novel Evidence for Nitrogen-Dependent Regulation of Nitrate Reductase in Coral Symbiosis

The nutritional symbiosis between corals and their photosynthetic dinoflagellate partners underpins the ecological success of reef-building corals in nutrient-poor environments. Although coral holobionts can assimilate the abundant yet highly variable environmental nitrate, direct insight into how nitrate reductase is regulated in these symbiotic algae has been lacking. Here, we provide the first characterization of nitrate reductase protein and gene expression in cultured Symbiodiniaceae exposed to different nitrogen sources and light regimes, revealing the multifactorial nature of its regulation. We demonstrate that nitrate reductase operates as a substrate-induced enzyme: nitrate stimulates protein synthesis in nitrogen-starved cultures, whereas ammonium actively suppresses its expression in a concentration-dependent manner. Light availability and photosynthetic electron transport further modulate protein abundance, suggesting that while nitrate reductase synthesis depends on nitrate availability, its stability may rely on photosynthesis. We also show that nitrate reductase is synthesized within hours of nitrate exposure by symbionts from nitrogen-starved corals, demonstrating that nitrate reduction can occur within the host environment. However, this response is transient and diminished relative to free-living cells, indicating that nitrate reduction is a facultative pathway activated when preferred nitrogen sources are limited. Finally, gene expression measurements and pharmacological inhibition confirm that nitrate reductase regulation is predominantly post-transcriptional, enabling this rapid and reversible control of nitrate assimilation. Together, these findings reveal a tightly regulated and responsive nitrate reduction system in coral symbionts that provides a flexible mechanism contributing to nitrogen homeostasis under fluctuating nutrient regimes.

Molecular Biology↗

bioRxiv2026

Improved coral thermal tolerance through modulation of antioxidant defenses

Mass coral bleaching events, driven by rising ocean temperatures, are pushing reef ecosystems toward collapse on a global scale. Because oxidative stress is an early driver of coral bleaching, strategies that enhance coral antioxidant defenses may improve coral resilience under thermal stress. Here, we tested a targeted antioxidant supplementation designed to enhance oxidative stress regulation in three representative Red Sea scleractinian coral species subjected to a thermal challenge. While responses varied among species and physiological metrics, supplemented corals consistently maintained higher photophysiological performance under heat stress. In Stylophora pistillata, antioxidant supplementation was associated with enhanced catalase activity, maintenance of glutathione redox homeostasis, and lower intracellular reactive oxygen species levels. In contrast, non-fed corals exhibited oxidative imbalance, increased lipid peroxidation, and impaired photophysiological recovery, while corals receiving a non-enriched heterotrophic diet showed an intermediate response characterized by increased catalase activity but persistent glutathione oxidation and elevated ROS during recovery. Together, the dietary treatments revealed a gradient in oxidative regulation, ranging from insufficient antioxidant protection in autotrophic corals to enhanced oxidative homeostasis in antioxidant-supplemented corals. Our findings demonstrate the potential of targeted nutritional antioxidant supplementation to enhance coral oxidative regulation and physiological performance under elevated temperatures, highlighting a promising complementary approach for coral conservation and restoration efforts.

physiology↗

bioRxiv2018

Bio-optical properties and radiative energy budgets in fed and starved scleractinian corals (Pocillopora damicornis) during thermal bleaching

Corals achieve outstanding photosynthetic quantum efficiencies approaching theoretical limits (i.e. 0.125 O2 photon-1) and it is unknown how such photosynthetic efficiency varies with environmental stress. In this study, we investigated the combined effects of thermal stress and active feeding on the radiative energy budget and photosynthetic efficiency of the symbiont-bearing coral Pocillopora damicornis by using fiber-optic and electrochemical microsensors in combination with variable chlorophyll fluorescence imaging. At normal temperature (25{degrees}C), the percentage of absorbed light energy used for photosynthesis was higher for fed (~5-6% under low light exposure) compared to unfed corals (4%). Corals from both feeding treatments responded equally to stress from high light exposure (2400 mol photons m-2 s-1), exhibiting a decrease in photosynthetic energy efficiency down to 0.5-0.6%. Fed corals showed increased resilience against thermal bleaching compared to unfed corals, as fed corals were able to uphold their high photosynthetic energy efficiency for 5 days longer during thermal stress, as compared to unfed corals, which decreased their photosynthetic energy efficiency almost immediately when exposed to thermal stress. We conclude that active feeding is beneficial to corals by prolonging coral health and resilience during thermal stress as a result of an overall healthier symbiont population.

biophysics↗

bioRxiv2018

Effect of feeding and thermal stress on photosynthesis, respiration and the carbon budget of the scleractinian coral Pocillopora damicornis

Studying carbon dynamics in the coral holobiont provides essential knowledge of nutritional strategies and is thus central to understanding coral ecophysiology. In this study, the first aim was to investigate the effect of daily feeding and thermal stress on oxygen (O2) rates measured at polyp-scale with microsensors and at whole fragment scale using incubation methods. The second aim was to assess the carbon budget of the symbiotic association using H13CO3, under the different conditions. Micro- and macro-scale measurements revealed enhanced O2 evolution rates for fed compared to unfed corals. However, gross O2 production in fed corals was increased at high temperature on a macroscale but not on a microscale basis, likely due to a heterogeneous distribution of photosynthesis over the coral surface. Starved corals always exhibited reduced photosynthetic activity at high temperature, which suggests that the nutritional status of the coral host is a key limiting factor for coral productivity under thermal stress. Quantification of photosynthate translocation and carbon budgets showed very low incorporation rates, for both symbionts and host (0.03 - 0.6 g C cm-2 h-1) equivalent to only 0.008 - 0.6 %, of the photosynthetically fixed carbon for P. damicornis, in all treatments. Carbon loss (via respiration and/or mucus release) was about 41 - 47 % and 52 - 76% of the fixed carbon for starved and fed corals, respectively. Such high loss of translocated carbon suggests that P. damicornis is nitrogen and/or phosphorus limited. Heterotrophy might thus cover a larger portion of the nutritional demand for P. damicornis than previously assumed. Our results suggest that active feeding plays a fundamental role in metabolic dynamics and bleaching susceptibility of corals.

ecology↗