Environmental Drivers of Coral Restoration Success

North Western Australia, Ningaloo (Nyingaluu) Reef, Bundegi Reef

A collaborative effort in North Western Australia led to the project “Environmental Drivers of Coral Restoration Success” to identify suitable sites for coral survival, understand reef dynamics, and optimize restoration strategies. High-resolution numerical modelling, supported by the Aqualink buoy, provided crucial data on wave and temperature conditions to assist in pinpointing the optimal site.

The overarching goal of the “Environmental Drivers of Coral Restoration Success” project was to understand the environmental drivers of coral reef restoration. While there have been a number of successful coral restoration projects to date, these efforts have still generally been implemented at small-scales and with varying levels of success. Research is needed to optimize the design of restored reefs to enhance their resilience to environmental pressures (both present and future) and developing improved strategies that will enable larger-scale reef restoration projects to be implemented using approaches that are less resource-intensive (e.g., by harnessing natural reef processes to help establish and maintain the reef). Overall, there is also a strong need to establish a firm scientific basis for reef restoration, which can be best achieved by establishing comprehensive multidisciplinary research programs that can learn from practical field trials and include collaboration with a range of stakeholders and end users that will become central to implementing large-scale reef restoration in the future (e.g. marine management and conservation agencies, NGOs, community groups, etc.). 

To accomplish this, the collaborative effort focused on Ningaloo (also called Nyingaluu) Reef, which is a UNESCO World Heritage listed site and, apart from 2011, has mainly been spared from mass coral bleaching. However, all coral reefs worldwide are facing escalating threats due to anthropogenic activities and climate change, no matter how remote. "We focus specifically on a part of the Ningaloo Reef, Bundegi Reef, which is located in the Exmouth Gulf on the eastern side of the North West Cape (Photo 1, satellite image of Ningaloo Reef) and was particularly damaged during the most recent mass bleaching event that impacted Western Australia reefs", says Camille Grimaldi from UWA and AIMS. 

Photo 1: Satellite image of the Ningaloo Coast and Exmouth Gulf, credit: inkl

Photo 2: MARS reef stars (or restoration frame); credit: GBR Biology

The “Environmental Drivers of Coral Restoration Success” was part of a broader collaborative project involving the University of Western Australia (UWA), the Australian Institute of Marine Science (AIMS) and the Minderoo Foundation. The success of coral restoration depends on a range of physical and biological processes that govern how target reef organisms interact with their environment. The AIMS sister project, “Towards Climate Resilience Reefs for Restoration”, aimed at monitoring coral population health and growth at Bundegi Reef. It is proposed that the next phase of this project would involve Minderoo and the MARS Foundation utilizing the findings of this study to implement a restoration trial at Bundegi Reef (Photo 2).

Goals

Camille describes that the primary objective of the “Environmental Drivers of Coral Restoration Success” project was to identify the sites with suitable conditions for coral survival and refuges from disturbances across Bundegi Reef. For that, they established the first oceanographic monitoring program across Bundegi Reef and measured a range of relevant environmental variables (current speed and directions, water levels, wave conditions, temperature, and light variability) at specific points across the reef. Even though the reef has been monitored through ecological surveys for decades, there was little to no information about the local oceanography. They then used this information to characterize the site and validate a hydrodynamic and thermodynamic model to expand the environmental characterization beyond the point measurements. Based on all the available information, they were then able to determine the “optimal location” based on the parameters of some of the following criteria: suitable substrate (e.g., rubble), suitable flow conditions (e.g. well flushed), suitable environmental conditions (e.g., wave exposure, temperature regimes) and favorable location for reef establishment (local retention) and strategically located to be a potential key larval source (export potential) and/or sink for neighboring reef communities.

We have also used our data and time at the site to think about broader questions, like what drives the residence time across the Exmouth Gulf, and what coral connectivity happens around the North West Cape, says Camille.

The hydrodynamic model

The hydrodynamic model used for this study was set up using Delft 3D Flexible Mesh and has a fairly high horizontal resolution (<50 m) to resolve all the relevant reef features (e.g., small channels, rapidly changing bathymetry, etc.) across the study area. The wave buoy plays a pivotal role in feeding the model with the incoming wave conditions that drive some of the current flow. The wave climate in the Exmouth Gulf is quite complex and mainly driven by wind waves created by wind along the long stretch of the Exmouth Gulf. Such conditions are not easy to capture in regional wave models, so we are extremely lucky to have the wave buoy offshore (in 20 m of water depth) from Bundegi Reef to provide us with that crucial insight into the local wave climate, says Camille. The temperature measurements from the wave buoys are also used to force temperature simulations.

Role of Aqualink 

Camille discusses the challenges and methodologies involved in temperature monitoring, stating:

"The Aqualink Bundegi data is also used for temperature monitoring quite regularly. Similarly to the wave climate, the satellite sea surface temperature does not always capture the temperature dynamics of the region accurately. We rely mainly on in situ benthic temperature loggers, but because the area is quite remote (the Exmouth Gulf is quite remote and located about 1, 250 km from the main city of Perth in Western Australia), it is often difficult and costly to collect and maintain benthic loggers. The surface to bottom temperature gradients also provide evidence of when the water column is stratified vs. well mixed (even on diurnal cycles)."

Aqualink dashboard

The team and I regularly use the Aqualink dashboard to check the live conditions at a site. For maximum reach, the data is also displayed on wawaves.org (maintained by Dr Cuttler and regrouping all the Sofar wave buoys deployed across Western Australia) and on the Minderoo Exmouth Research Lab website, says Camille.

Smart Mooring buoy

Camille mentions three areas where the data from the Smart Mooring buoy donated by Aqualink is used:

Insights from Camille: Reflections on the Project

Throughout the course of the project, Camille has provided valuable insights into various aspects of the research. Here, we present Camille's reflections on the outcomes and results, success stories, and the importance and impact of the project.

Outcomes and Results

We have come up with a recommended location for the deployment of the restoration frames, which will likely be trialed by MARS and the Minderoo Foundation.

Our results provide timely and critical insights into the Exmouth Gulf environment, as a new marine park is to be established to preserve the region’s unique environmental and cultural values.

Success stories

This project has been a great story of collaboration, even though challenging, working with various organisations (university, governmental agency, philanthropy, management agencies) and across fields (oceanography, ecology, genetics and management) has been a great learning experience and extremely rewarding. 

We have also been able to pinpoint location for restoration, if need be in the future for Bundegi Reef based on scientific evidences, which is rarely done in the restoration space (more often opportunistic or where corals where were previously found).

Importance and Impact

Even if greenhouse gases emission reductions should be the number one priority for the health of coral reefs ecosystems worldwide, restoration has emerged as a potential solution to restore patches of reef locally. With this study, we provided some new information about the environmental variability across Bundegi Reef, outlined a potential site for restoration and characterizes the baseline environmental conditions, which hopefully can help us understand how the system might respond to future climate conditions. 

Acknowledgement

We acknowledge the Baiyungu, Thalanyji and Yinigurdira people of the Ningaloo area as the Traditional custodians and the first marine scientists of the sea Country where this project took place. We would like to thank the Minderoo Foundation through the Minderoo Exmouth Research Lab for their ongoing fieldwork support and for maintaining and servicing the fleet of smart moorings now deployed across the Exmouth and Ningaloo Reef.

Camille Grimaldi, UWA and AIMS, March 25, 2024