Presentation Details
| Shifts in Foraging Niches, Condition, and Stress in Response to Ocean Heat Hector D.Douglas. Grambling State University, Grambling, Louisiana, USA |
Abstract
Record ocean heat occurred near Culebra, Puerto Rico in June 2024. Nesting seabirds had lower δ15N in red blood cells (RBC), suggesting a shift towards lower trophic levels. A reduction in sardines may have contributed to reduced body condition in white-tailed tropicbirds (Phaethon lepturus) and brown noddies (Anous stolidus). In 2025, sooty terns (Onychoprion fuscatus) had lower δ13C accompanying a sharp increase in Sargassum. Total antioxidant capacity was higher in 2024 and oxidative stress (TBARS) was lower, while the inverse pattern was manifest in sooty terns in 2025. Baseline corticosterone was relatively high in both years. In breast feathers, which are replaced between breeding seasons, corticosterone was higher in 2025. Sooty terns benefit from facilitated foraging, but this may have occurred less if predatory fish were displaced by ocean heat. We found negative correlations between δ15N and δ13C in RBC, a pattern consistent with consumption of small fish fry, which did occur in diets. We found that heat altered marine food webs and we hypothesize that the foraging niches of seabirds shifted away from optimums.
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No part of this publication may be reproduced, distributed, or transmitted in any form or by any means, including photocopying, recording, or other electronic or mechanical methods, without the prior written permission of the author.
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