Abstract
The ability of corals to modulate their nutrition strategy in response to variable nutrient supply remains poorly understood, limiting our understanding of energy flow in coral reef ecosystems and thus our comprehension of their resilience to global changes. We used a naturally occurring nutrient gradient along the reef flat of two seabird-inhabited islets in the SW Pacific to characterize spatiotemporal fluctuations in coastal nutrient availability, and how it modulates the trophic response of the mixotrophic coral Pocillopora damicornis. The clear gradients in dissolved [NOx] and δ15N values of macroalgae and both P. damicornis tissues and symbionts observed along the reef flat during the dry and the rainy season revealed that seabird-derived-N is supplied year-round to the reef flat. Yet, nitrogen isotope values of macroalgae show that the seabirds’ effect on coral reefs varies with sites and seasons. Metrics derived from the SIBER framework revealed that coral nutrition seasonally favored autotrophy when exposed to higher seabird guano concentrations and at inshore stations, while heterotrophy dominated in corals less exposed to seabird-derived nutrient supply. P. Damicornis is therefore able to cope with large changes in nitrogen supply induced by seabird island communities by switching between autotrophy and heterotrophy. These results shed light on the flexibility of resource sharing within the coral-algae symbiosis and highlight the importance of seabird populations to the functioning of coral reef ecosystems.
Highlights
The global success of shallow-water corals relies heavily on their symbiotic association with photosynthetic intracellular dinoflagellate microalgae (Symbiodiniaceae, LaJeunesse et al, 2018)
The ability of shallow water corals to adjust their nutrition between autotrophy and heterotrophy plays a crucial role in their ability to cope with ongoing global warming (e.g., Grottoli et al, 2006; Conti-Jerpe et al, 2020; Thibault et al, 2021)
We used a naturally occurring nutrient gradient along two seabird islets of the SW Pacific to study the spatiotemporal variability of seabird derived-N supply and its influence on the nutritional response of the mixotrophic coral Pocillopora damicornis using stable nitrogen isotope ratios
Summary
The global success of shallow-water corals relies heavily on their symbiotic association with photosynthetic intracellular dinoflagellate microalgae (Symbiodiniaceae, LaJeunesse et al, 2018). The symbiosis supplies the coral with photosynthetically fixed carbon and inorganic N (autotrophy) (Muscatine and Porter, 1977; Muscatine et al, 1981). The dominance of one trophic strategy over the other relies on environmental factors such as depth, turbidity, or resource availability. Seabirds Modulate Corals Trophic Strategies (Anthony and Fabricius, 2000; Palardy et al, 2005; Fox et al, 2019). Recent findings show for instance, that mixotrophic corals increase heterotrophy when located in shallow waters surrounding islands with elevated nearshore primary production (Fox et al, 2018). Variations in coral nutritional plasticity is considered a robust predictor of corals’ resilience to bleaching, which results from a disruption of the symbiose due to ocean warning (e.g., Grottoli et al, 2006; Conti-Jerpe et al, 2020; Thibault et al, 2021)
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
