Were coral reefs more complex 7,000 years ago?
New study reveals major trophic simplification in modern Caribbean reefs
Coral reefs are among the most biodiverse marine ecosystems on Earth. Yet over recent decades, they have faced multiple pressures, including climate change, overfishing, and habitat degradation. Despite well-documented ecological decline, direct evidence of how human activities have altered the structure of reef food webs has remained limited.
In our recently published study, we used nitrogen isotopes (δ¹⁵N) preserved in sedimentary fish otoliths and coral skeletons to reconstruct the trophic structure of Caribbean coral reefs approximately 7,000 years ago (mid-Holocene) and to compare it with that of modern reefs.
Using an “ecosystem nitrogen isotope distribution” framework, we quantified food sources and energy-flow pathways across different trophic levels in both time periods.
Our findings show that:
1. Modern reef food chains are approximately 60–70% shorter than those 7,000 years ago.
2. High-trophic-level fishes now occupy significantly lower trophic positions.
3. Low- to mid-trophic-level fishes exhibit more homogenized diets.
These results indicate that energy-flow pathways in modern reefs have been substantially reduced, and ecological roles have become increasingly simplified. The highly differentiated and specialized trophic structure of prehistoric reefs has been compressed into shorter, more simplified food webs.
In theory, diverse and clearly partitioned energy pathways enhance ecosystem stability and resistance to disturbance. In contrast, trophic compression may reduce system resilience, making reefs more vulnerable to external stressors.
This study not only establishes a novel method for reconstructing prehistoric coral reef food webs but also provides quantitative indicators for assessing the health of modern marine ecosystems.
In this study, Dr. Lin was responsible for otolith taxonomy and fish community reconstruction. The paper was published on February 11, 2026, in Nature.
Full article: https://doi.org/10.1038/s41586-025-10077-z
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