Vulnerability and resilience of mesophotic coral ecosystems to climate change

Identifying critical areas of biodiversity and sites more vulnerable to climate change due to their location and oceanographic conditions
An image taken by scientists from the University of Plymouth at 60m depth at Egmont Atoll, Indian Ocean, in March 2022 using a drop-camera system. The image shows a healthy colony of the reef-building coral species, Pachyseris speciosa

Vulnerability and resilience of mesophotic coral ecosystems to climate change

Identifying critical areas of biodiversity and sites more vulnerable to climate change due to their location and oceanographic conditions
Title: Vulnerability and resilience of mesophotic coral ecosystems to climate change
Funding amount: £3.7 million
Location: Indian Ocean
Dates: 2 February 2026 – 31 January 2031
Project partners: Plymouth Marine Laboratory, Imperial College London, Horniman Museum and Gardens, ARCMarine, Maldives Environmental Regulatory Authority, Maldives Marine Research Institute, Seychelles Island Foundation, Mauritian Government
University of Plymouth PI: Dr Nicola Foster 
 

Overview

This five-year project will assess the vulnerability and resilience of mesophotic coral ecosystems (MCEs) to climate change. MCEs are light-dependent ecosystems that reside between 30–150 m and provide many of the same social and economic benefits as shallow-water reefs (e.g., ecosystem services such as food provision and climate regulation). 
MCEs were previously thought to be more protected from disturbances than shallow-water reefs due to their depth and it was thought that they may provide a refuge to shallow-water species against ocean warming. However, our recent research in the central Indian Ocean has shown that MCEs are also susceptible to thermal stress and may be just as vulnerable to climate change as shallow reefs. 
This project brings together marine ecologists, oceanographers, modellers and regional partners across the Indian Ocean to build on our previous work in the region and transform our understanding of how mesophotic coral ecosystems respond to rising ocean temperatures. Our overarching aim is to identify critical areas of biodiversity and sites more vulnerable to climate change due to their location and oceanographic conditions.

Objectives

We will be working with our national and international partners at every stage of the project to achieve our seven objectives:  
  1. Describe the diversity, distribution, and health of mesophotic coral ecosystems. 
  2. Investigate environmental (hydrodynamic and biogeochemical) influences on mesophotic coral ecosystems, including temperature changes, and how these impact the diversity and health of MCEs. 
  3. Understand the connectivity of MCE populations among sites at a local and regional scale, and over the depth gradient between shallow and deep populations. 
  4. Characterise the reproductive strategies and thermal tolerance of key mesophotic coral species. 
  5. Assess the thermal performance of early life history and adult stages of key mesophotic coral species.
  6. Assess the acclimation potential of early life history stages of coral species to varying environmental conditions.
  7. Build and strengthen our existing network of researchers and managers across the Indian Ocean region to develop a standardised methodology to monitor long-term changes on MCEs, to inform policy and management.

Coral reefs are vital for the health of our planet, yet shallow water corals are extremely vulnerable to climate change and may be almost entirely lost in the coming decades. Until recently, deeper coral reefs were thought to be protected against similar threats – however, our work in the Indian Ocean has challenged that assumption.

This ambitious project will use state-of-the-art technologies to collect comprehensive, long-term data across multiple locations and during significant climate events. We will deliver a fundamental step-change in our understanding of these deeper coral ecosystems, and directly inform conservation and management plans across the Indian Ocean. 

Nicola FosterDr Nicola Foster
Lecturer in Marine Biology

Context of the issue

Shallow-water coral reefs are among the most biodiverse and functionally important marine ecosystems in the world. However, these systems are highly sensitive to ocean warming, and projections indicate that more than 99% could be lost within the next 50 years under continued climate change. Such declines would lead to substantial losses in biodiversity, ecosystem functioning, and the provision of critical ecosystem services. Mesophotic coral ecosystems (MCEs) are light-dependent ecosystems that occur at depths of approximately 30–150 m. These ecosystems develop under reduced light availability compared with shallow coral reefs, yet they support diverse and structurally complex coral assemblages. MCEs provide many of the same ecosystem services as shallow-water reefs, including the support of marine biodiversity, fisheries productivity, and climate regulation. As shallow-water coral reefs continue to be impacted by climate change, MCEs may play a role in sustaining coral reef biodiversity and ecosystem functioning across depth gradients. However, the effect of climate change on MCEs remains understudied, representing a significant gap in our knowledge despite the potentially pivotal importance of MCEs to the biodiversity and functioning of marine ecosystems.
For many years, it was assumed that MCEs may be protected from warming oceans by cooler, more stable conditions found at these deeper depths. However, recent observations, including our own work in the Indian Ocean, have shown that warming can extend far deeper than expected. During the 2019 Indian Ocean Dipole event, we observed widespread coral bleaching at depths of 60–90 m, linked to warming at depth caused by changes in ocean structure. This raises questions about the resilience of MCEs to future climate change and their ability to support biodiversity, ecosystem function and ecosystem service provision as shallow water reefs decline.

How the project addresses the issue 

Our study aims to significantly advance our understanding of the vulnerability of MCEs to climate change and how these ecosystems respond to the changes in temperature that are predicted to become more widespread and severe with climate change. Using ROV surveys, in situ environmental monitoring, numerical modelling, and laboratory-based experimental work, we will investigate the diversity, distribution, functioning and health of MCEs across multiple sites and depths. We will investigate how these ecosystems recover from stress and how they remain connected to shallow water coral reefs. We will also investigate the ocean processes that influence temperatures at depth, and how key mesophotic coral species cope with warming.
The scale of this study is unprecedented. Mesophotic reefs and the oceanographic environment that surrounds them have never been undertaken on this scale before. Our results will help us to understand how the physical environment of the ocean influences how resilient, or how vulnerable, mesophotic reefs are to climate change. This knowledge will help us identify where mesophotic reefs are most at risk, and where they have the greatest potential to recover, allowing decision makers to focus protection where it can make the biggest difference. Throughout the project, we will be working closely with regional researchers and marine managers to develop shared monitoring approaches, so that what we learn directly supports conservation, management, and policy, and helps us understand the role these mesophotic reefs may play in supporting coral reef biodiversity and resilience as a whole.

Centre for Coastal and Ocean Processes and Engineering (C-COPE)

C-COPE brings together strength areas from across the University's Faculty of Science and Engineering with a research focus on the physical and chemical processes in coastal, ocean and marine environments, and their human impacts.
The Centre's sphere of interest stretches from the head of tidal estuaries to the bottom of the ocean, and includes the disciplines of physical oceanography, marine biogeochemistry, coastal engineering and marine geology.
Tuvalu Tepuka atoll