Seascape configuration determines spatial patterns of seabird‐vectored nutrient enrichment to coral reefs

Stuart, Courtney E.; Pittman, Simon J.; Stamoulis, Kostantinos A.; Benkwitt, Cassandra E.; Epstein, Hannah E.; Graham, Nicholas A. J.; Smith, Andrew C.; Lacey, Jack H.; Bistolas, Kalia S. I.; DeVore, Jayna L.; Ducatez, Simon; Wedding, Lisa M.

Seascape configuration determines spatial patterns of seabird‐vectored nutrient enrichment to coral reefs

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Official URL: https://doi.org/10.1002/ecog.07863

Abstract/Summary

Pelagic‐feeding seabirds deliver nutrient subsidies that enhance the productivity, biodiversity, and resilience of terrestrial and marine ecosystems, particularly in nutrient‐poor tropical environments. However, the biogeophysical variables governing the fluxes of these nutrients within and among interconnected ecosystems remain poorly understood. To address this, we examined the spatial distribution of seabird‐vectored nutrients in the seascape of Tetiaroa, a semi‐enclosed coral atoll in French Polynesia, where seabird populations and associated nutrient cycles are recovering after recent rat eradication. We focus on the nitrogen isotope (δ 15 N) signatures of a dominant marine alga as evidence of seabird‐vectored nutrient uptake. Integrating stable isotope analysis within a seascape ecology framework, we show that breeding seabird biomass, depth, distance to land, geographic location within the atoll, and seafloor curvature drive spatial patterns of nutrient enrichment. Specifically, our models account for up to 88% of the variation in algal δ 15 N signatures and reveal peak enrichment in shallow, nearshore areas where water flow slows and converges due to localised seafloor curvature. These results extend previous research by highlighting seafloor geomorphology, notably curvature, as a modulator of fine‐scale nutrient delivery patterns. Although a complex model incorporating 11 high‐resolution biogeophysical variables enhanced spatial predictions by revealing fine‐scale variations, a simpler model using only five of these variables was comparably effective in capturing overall spatial trends. This study identifies the key seascape configuration and complexity characteristics likely to affect the spatial patterns of recovery potential following the restoration of seabird‐driven nutrient cycles, offering valuable guidance for ongoing restoration efforts in this coupled island‐reef system. Future investigations could assess how the effects of biogeophysical variables on nutrient delivery vary in magnitude and direction across different geographic, geological, and anthropogenic contexts.

Item Type:

Publication - Article

Digital Object Identifier (DOI):

10.1002/ecog.07863

ISSN:

0906-7590

Date made live:

11 Sep 2025 13:58 +0 (UTC)

URI:

https://nora.nerc.ac.uk/id/eprint/540213