Coral photosymbiosis on Mid-Devonian reefs

• 成果类型: Article
• 署名作者: Jung, Jonathan; Zoppe, Simon F.; Soete, Till; Moretti, Simone; Duprey, Nicolas N.; Foreman, Alan D.; Wald, Tanja; Vonhof, Hubert; Haug, Gerald H.; Sigman, Daniel M.; Mulch, Andreas; Schindler, Eberhard; Janussen, Dorte; Martinez-Garcia, Alfredo
• 署名单位: Max Planck Society; Goethe University Frankfurt; University of Munster; Swiss Federal Institutes of Technology Domain; ETH Zurich; Princeton University; Senckenberg Biodiversitat & Klima- Forschungszentrum (BiK-F); Leibniz Association; Senckenberg Gesellschaft fur Naturforschung (SGN); Leibniz Association; Senckenberg Gesellschaft fur Naturforschung (SGN)
• 刊物名称: Nature
• ISSN/ISSBN: 0028-5541
• DOI: 10.1038/s41586-024-08101-9
• 发表日期: 2024-12-19
• 关键词: bound organic nitrogen; conodont color; scleractinian corals; stable-isotopes; alteration patterns; paleozoic corals; diagenesis; ocean; carbon; fractionation

摘要

The ability of stony corals to thrive in the oligotrophic (low-nutrient, low-productivity) surface waters of the tropical ocean is commonly attributed to their symbiotic relationship with photosynthetic dinoflagellates1,2. The evolutionary history of this symbiosis might clarify its organismal and environmental roles3, but its prevalence through time, and across taxa, morphologies and oceanic settings, is currently unclear4-6. Here we report measurements of the nitrogen isotope (15N/14N) ratio of coral-bound organic matter (CB-delta 15N) in samples from Mid-Devonian reefs (Givetian, around 385 million years ago), which represent a constraint on the evolution of coral photosymbiosis. Colonial tabulate and fasciculate (dendroid) rugose corals have low CB-delta 15N values (2.51 +/- 0.97 parts per thousand) in comparison with co-occurring solitary and (pseudo)colonial (cerioid or phaceloid) rugose corals (5.52 +/- 1.63 parts per thousand). The average of the isotopic difference per deposit (3.01 +/- 0.58 parts per thousand) is statistically indistinguishable from that observed between modern symbiont-barren and symbiont-bearing corals (3.38 +/- 1.05 parts per thousand). On the basis of this evidence, we infer that Mid-Devonian tabulate and some fasciculate (dendroid) rugose corals hosted active photosymbionts, while solitary and some (pseudo)colonial (cerioid or phaceloid) rugose corals did not. The low CB-delta 15N values of the Devonian tabulate and fasciculate rugose corals relative to the modern range suggest that Mid-Devonian reefs formed in biogeochemical regimes analogous to the modern oligotrophic subtropical gyres. Widespread oligotrophy during the Devonian may have promoted coral photosymbiosis, the occurrence of which may explain why Devonian reefs were the most productive reef ecosystems of the Phanerozoic. Nitrogen isotope evidence of Mid-Devonian photosymbiotic associations in certain types of corals suggests that autotrophic and heterotrophic corals co-existed on extinct reefs, as today, but in warmer oceans, indicating the current warming rate, not temperature, is causing coral bleaching.