There are no two ways about it, this is a huge surprise. Deeper corals had always been thought of as being resilient to ocean warming, because the waters they inhabit are cooler than at the surface and were believed to remain relatively stable. However, that is clearly not the case and – as a result – there are likely to be reefs at similar depths all over the world that are at threat from similar climatic changes.
Associate Professor in Physical Oceanography and lead scientist on the project
What we have recorded categorically demonstrates that this bleaching was caused by a deepening of the thermocline. This is down to the regional equivalent of an El Nino, and due to climate change these cycles of variability are becoming amplified. Moving forward, bleaching in the deeper ocean here and elsewhere will likely become more regular.
Lead author on the study, published in Nature Communications
Our results demonstrate the vulnerability of mesophotic coral ecosystems to thermal stress and provide new evidence of the impact that climate change is having on every part of our ocean. Increased bleaching of mesophotic corals will ultimately lead to coral mortality and a reduction in the structural complexity of these reefs. This will likely result in a loss of biodiversity and a reduction in the critical ecosystem services that these reefs provide to our planet.
Lecturer in Marine Biology, and co-author on the study
“The oceanography of a region is impacted by naturally occurring cycles that are becoming amplified by climate change. Currently, the region is suffering similar, if not worse, impacts due to the combined influence of El Nino and the Indian Ocean Dipole. While there is no way we can stop the thermocline from deepening, what we can do is expand our understanding of the impacts that these changes will have throughout these environments of which we have so little knowledge. In the face of fast-paced global change, that has never been more urgent.”
Bleached corals observed on the seafloor of the Central Indian Ocean in November 2019
Corals in the same region had recovered by the time of a later research cruise in early 2022
Miss Clara Diaz
Dr Nicola Foster
Lecturer in Marine Biology
Dr Philip Hosegood
Associate Professor in Physical Oceanography
Professor Martin Attrill
Professor of Marine Ecology
Mr Adam Bolton
Technical Specialist in Hydrography
Mr Peter Ganderton
Technical Specialist (Marine Science)
Professor Kerry Howell
Professor of Deep-Sea Ecology