古代の絶滅の後、サンゴ礁の回復はより広範な生態系よりも遅かった(Reefs recovered slower than broader ecosystem following ancient extinction)

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2023-11-29 ペンシルベニア州立大学(PennState)

◆地球上で最も多様で貴重な生態系であるサンゴ礁が気候変動の影響を受けており、新しい研究では、もしサンゴ礁が完全に消失した場合、環境条件が改善された後でも、それらが回復するには何百万年もの時間がかかる可能性があることが示されました。
◆国際的な研究チームは、現代の中国に位置する古代の浅い海の化石を分析し、約2億5,000万年前のペルム紀末の大量絶滅イベントとその後の様子を捉えました。他の海洋生態系が回復した後も、多様な生態系のサンゴ礁が回復するまでに何百万年もかかったことが明らかになりました。サンゴ礁の破壊が続く場合、その回復には何百万年もかかる可能性があり、現代のサンゴ礁の保全の重要性が強調されています。

<関連情報>

ペルム紀末の大量絶滅後の後生動物と藻類のサンゴ礁の長期的かつ段階的な回復 Prolonged and gradual recovery of metazoan-algal reefs following the end-Permian mass extinction

Brian M. Kelley;Meiyi Yu;Daniel J. Lehrmann;Demir Altıner;Jonathan L. Payne
Geology  Published:August 14, 2023
DOI:https://doi.org/10.1130/G51058.1

Early Mesozoic reef stratigraphic ranges, based on Flügel (2002), Martindale et al. (2019), Baud et al. (2021), Wu et al. (2022), Heuer et al. (2022), and references therein, with δ13C values from Payne et al. (2004). Abbreviations: Pan.—Panthalassa; Longobar.—Longobardian; Aeg.—Aegean; Bith.—Bithynian; VPDB—Vienna Peedee belemnite; GBG—Great Bank of Guizhou.

Abstract

The tempo of biotic recovery following extinction reflects the time scales of evolutionary processes and the long-term consequences of degraded ecosystems, but recovery patterns are poorly resolved. In this study, we investigated the tempo of biotic recovery by evaluating metazoan-algal reef assembly following the end-Permian mass extinction. We combined satellite imagery analysis, field mapping, biostratigraphy, and quantitative petrography to assess recovery in the oldest-known and most stratigraphically extensive Lower to Middle Triassic platform-margin reef. The reef occurs in upper Spathian (upper Lower Triassic) to upper Anisian (lower Middle Triassic) strata of the Great Bank of Guizhou (GBG) isolated carbonate platform in south China. Previous work suggests that metazoan-algal reefs were absent for 8–10 m.y. following extinction but were biologically diverse from their Pelsonian (middle Anisian) initiation. This pattern implies that reefs can reassemble rapidly (<< 1 m.y.) when environmental conditions are favorable. In contrast, our analyses indicate that calcareous sponges, calcareous algae, and early scleractinian corals occurred progressively in the GBG reef and that biotic recovery metrics increased gradually. Unlike nonreef ecosystems, biodiverse metazoan-algal reefs were delayed until the late Pelsonian or early Illyrian, postdating broader marine ecosystem recovery and isotopic evidence for carbon-cycle stabilization by 2–4 m.y. Our findings suggest that reef and nonreef ecosystems differ in their recovery pattern and tempo. Reef recovery from severe environmental perturbation can require several million years, even after hospitable conditions return, highlighting the importance of modern reef conservation.

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