Research press release


Nature Communications

Ecology: Levels of bleaching in deep coral reefs assessed



今回、Pedro Fradeたちの研究グループは、2016年の大規模なサンゴ白化現象におけるグレートバリアリーフ内の9地点の深海サンゴ礁の白化量を調べた。その結果、深海サンゴ礁への影響は深刻だった(水深40メートルでサンゴの40%が白化、6%が死滅)が、その程度は浅瀬よりも低いことが分かった(水深5~25メートルでサンゴの60~69%が白化、8~12%が死滅)。Fradeたちは、夏の初めには冷たい水の湧昇によってより深海にいるサンゴ礁はある程度保護されるが、夏の終わりには冷水の湧昇が止まり、保護効果が失われたことを明らかにした。


Deep coral reefs on the Great Barrier Reef are shown to have lower levels of bleaching than shallower reefs during the 2016 mass bleaching event, according to a paper in Nature Communications. The study suggests that deep reefs may offer some refuge from thermal stress, but the nature of the protection may be transient and limited in providing broad ecological refuge.

It has been suggested that coral reefs found in deep waters (at depths of 30 to 40 metres and beyond) could act as major ecological refuges from mass coral bleaching. However, assessments have been limited because of the logistical complexity of studying these ecosystems.

Pedro Frade and colleagues studied the amount of bleaching experienced by deep reefs at nine sites within the Great Barrier Reef during the large-scale bleaching event of 2016. Impacts on the deep reefs were severe (40% of coral was bleached and 6% dead at 40 metres) but lower than at shallower depths (60-69% of coral was bleached and 8-12% dead at 5-25 metres). The authors found that upwelling of cold water gave deeper reefs some protection in the early summer, but this was lost by late summer when upwelling stopped.

The study highlights the limitations of deep reefs acting as thermal refuges, and the authors argue that both shallow and deep reefs are under threat from mass bleaching events.

doi: 10.1038/s41467-018-05741-0

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