Research press release


Nature Communications

Ecology: Stress-resistant corals maintain heat tolerance under cooler temperatures



オーストラリア北西部のキンバリー地域のサンゴ礁は、極端な海水温の変動に耐えているが、今回、Verena Schoepfたちの研究グループは、このサンゴ礁のサンゴ群体を使って熱的実験を行った。このサンゴ群体は、水槽内に移植され、水槽内の海水の温度を本来の生息地の水温、それより摂氏4度低い状態、摂氏1度高い状態にそれぞれ安定させ、あるいは水温を変動させて実験が行われた。このサンゴ群体は、摂氏4度低い状態に9か月以上順応し、摂氏1度高い状態に6か月以上順応したが、最高水温がそれぞれの季節の正常範囲を超えると健康状態が低下し始めた。また、このサンゴ群体で2週間の熱ストレス試験が行われたが、その白化閾値は上昇しなかった。


Heat-resistant corals can maintain their health and resistance to heatwaves at cooler temperatures, a study in Nature Communications reports. However, these corals cannot increase their bleaching threshold after acclimatizing to warmer conditions. The findings suggest that corals from thermally extreme conditions could be used to help restore cooler reefs degraded by bleaching, but they will have limited ability to adapt to a rapidly warming environment.

The presence of reefs thriving in highly variable temperatures has fuelled hope that some corals may be able to adapt to warmer oceans, but whether they can do so fast enough to keep up with climate change is uncertain.

Verena Schoepf and colleagues performed thermal experiments on coral colonies from reefs in the Kimberley region of northwest Australia that can tolerate extreme temperature fluctuations. They transplanted colonies into water tanks with either temperatures similar to their native habitat, 4°C cooler or 1 °C warmer under stable or fluctuating temperatures. The corals acclimatized to both cooler (over 9 months) and warmer (over 6 months) conditions, but their health began to decline once maximum temperatures exceeded the normal seasonal range. When the authors subjected the colonies to two-week heat-stress tests, they were unable to increase their bleaching threshold.

These findings suggest that even coral reefs adapted to extreme environments have a limited ability to acclimatize to ocean warming in the future. However, the ability of the corals to retain their heat tolerance, despite exposure to cooler temperatures, suggests that such colonies could provide natural refuges from which larvae may colonize cooler, bleaching-sensitive regions.

doi: 10.1038/s41467-019-12065-0

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