Carbon pathways and trophic attributes are conserved in carnivorous reef fishes across a major human disturbance gradient

Sep 30, 2026

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Human habitat degradation and overexploitation drive global biodiversity loss, yet it remains unclear whether hyperdiverse tropical food webs reorganize their energy pathways under human disturbance. Using molecular isotope techniques and an ecosystem-scale natural experiment on Kiritimati Island, the study integrates bulk and amino-acid-specific stable isotope analyses across a well-characterized disturbance gradient. Essential amino-acid δ13C fingerprints and Bayesian mixing models show stable carbon source contributions and trophic positions among generalist carnivorous reef fishes despite community and habitat complexity shifts.

LanguageEnglish

CategoryResearch & Report

FormatPDF

Pages15

Reading Time38 min

AccessFree to download

Abstract

Introduction

Methods and stable isotope approach

Results: carbon sources and trophic positions

Conclusions and implications

DOI: 10. 1111/1365-2656 .70151 R E S E A RC H A RT I C L E Carbon pathways and trophic attributes are conserved in carnivorous reef fishes across a major human disturbance gradient Matthew D. Ramirez1,2,3,4 | Kelton W. McMahon2 | Neil Rooney5 | Rana W. El-Sabaawi1 | Julia K. Baum1,6 1Department of Biology, University of Victoria, Victoria, British Columbia, Canada; 2Graduate School of Oceanography, University of Rhode Island, Narragansett, Rhode Island, USA; 3 Department of Biology and Marine Biology, University of North Carolina Wilmington, Wilmington, North Carolina, USA; 4Center for Marine Science, University of North Carolina Wilmington, Wilmington, North Carolina, USA; 5School of Environmental Sciences, University of Guelph, Guelph, Ontario, Canada and 6Hawaii Institute of Marine Biology, University of Hawaii, Kaneohe, Hawaii, USA Correspondence Matthew D. Ramirez Email: [ramirezmd@uncw.edu](ramirezmd@uncw.edu) Funding information British Columbia Knowledge Development Fund; David and Lucile Packard Foundation; Centre for Asia-Pacific Initiatives, University of Victoria; Pew Charitable Trusts; National Geographic Society; Rufford Foundation; Division of Ocean Sciences, Grant/Award Number: 1446402; Natural Sciences and Engineering Research Council of Canada; Canada Foundation for Innovation Handling Editor: Jacob Allgeier Abstract 1. Habitat degradation and overexploitation are key drivers of biodiversity loss globally. Negative, human-driven changes in habitat quality, species abundance, and community composition are well-documented across systems. While it is understood that human stressors destabilize consumer-resource interactions, how energy pathways and food webs may reorganize in hyperdiverse tropical systems in response to human disturbance remains poorly understood due to their complexity and past methodological limitations. 2. Leveraging recent advances in molecular isotope techniques, we performed an ecosystem-scale natural experiment to evaluate how human disturbance reorganizes carbon pathways and trophic structure in a hyperdiverse tropical system, Kiritimati Island, the world's largest atoll. We specifically employed novel integrations of bulk tissue and amino acid-specific stable isotope analyses applied to six nominally generalist fish species sampled across Kiritimati's welldocumented human disturbance gradient. Sampled fish species comprised 48% of carnivorous reef fish biomass. 3. Essential amino acid stable carbon isotope (δ13CEAA) fingerprinting and Bayesian stable isotope mixing models indicated that the proportional contribution of the carbon sources supporting five of the six sampled fish species did not vary across the disturbance gradient. Energy disproportionately (>80%) originated from planktonic production and microbially reworked detritus for most species, with only minor contributions of carbon sourced from coral and epilithic algal matrices. Reef fish trophic ecology was also consistent across the atoll, with species maintaining isotopic niches (size and position) and trophic positions across This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited. © 2025 The Author(s) . Journal of Animal Ecology published by John Wiley & Sons Ltd on behalf of British Ecological Society. 40 | RAMIREZ et al. the atoll despite significant human disturbance-mediated changes in community composition and habitat complexity. 4. Our findings suggest that the energy channels connecting basal resources to upper trophic level generalist consumers can be highly conserved following significant human disturbance in hyperdiverse tropical systems. On coral atolls, specifically, robust planktonic or detrital energy channels may buffer nominally generalist carnivorous reef fishes from some negative effects of chronic local human disturba

FAQs

What problem does the study address regarding human disturbance and food webs?

It examines whether energy pathways and trophic structure reorganize in hyperdiverse tropical systems under human disturbance, despite known destabilization from human stressors.

How did the researchers study carbon pathways and trophic attributes?

They used an ecosystem-scale natural experiment on Kiritimati Island, combining bulk tissue with amino-acid-specific stable isotope analyses and applying Bayesian stable isotope mixing models.

What key result was found across the human disturbance gradient?

For five of six fish species, the proportional carbon contributions supporting fish diets did not vary with disturbance, and isotopic niches and trophic positions were conserved across the atoll.

What explanation is proposed for conserved energy channels on coral atolls?

The findings suggest robust planktonic or detrital energy channels can buffer nominally generalist carnivorous reef fishes from negative effects of chronic local disturbance, maintaining dominant energy fluxes.

Sep 30, 2026

Upload by Rowan