Work

Seabird-derived nitrogen supply enhances photosynthetic activity in a reef-building coral

Year: 2025

Type: article

Abstract: Nutrient subsidies from seabirds (SDN) significantly impact coral reef ecosystems, but access to remote seabird nesting islands limits our understanding of how corals respond to this nutrient source. This study investigates the in natura effects of SDN on coral metabolism at Surprise Island in the southwestern Pacific. Specifically, we examine how the photobiology of the ubiquitous reef-building coral Pocillopora damicornis responds to SDN availability. On Surprise Island, seabird-derived nitrogen follows a well-defined gradient across the land–ocean continuum and significantly contributes to scleractinian coral nitrogen uptake. At stations exposed to SDN discharge, seawater exhibited an elevated N:P ratio due to high nitrate concentrations as phosphate and ammonium concentrations remained similar to those at the reference station. Corals exposed to SDN-enriched coastal waters displayed a 50 % increase in photosynthetic efficiency and a 40 % increase in photosynthetic rate, coupled with a 115 % increase in both symbiont density and chlorophyll concentrations. These findings demonstrate that nitrogen inputs from seabirds stimulate the photosynthetic activity of coral symbionts, highlighting the sensitivity of coral photophysiology to SDN. This underscores the critical link between seabird ecology and coral reefs functioning and emphasizes the need for integrated conservation efforts on coral islands. • There is a coast-ocean gradient in Seabird Derived Nitrogen (SDN) on Surprise island's reef. • Symbiont and chlorophyll a concentration in Pocillopora damicornis are higher by 115 % under elevated SDN. • SDN availability also correlates with 50 % increase in P. damicornis photosynthesis efficiency.

Source: Marine Environmental Research

DOI: 10.1016/j.marenvres.2025.107147

Authors: Martin Thibault, Anne Lorrain, Nicolas N. Duprey, Alfredo Martínez-García, Fanny Houlbrèque