On the edge of the north-west continental shelf, far from the Western Australian mainland, lie a series of remote coral reef systems that rise steeply from deep water to almost touch the ocean’s surface.
AIMS has been studying these oceanic reef systems for over 20 years, providing valuable knowledge about their plants and animals. To improve understanding of the entire region’s health over time, we are taking a coordinated approach to mapping, monitoring and assessing the resilience of these remote reef systems.
Scott Reef presents a rare opportunity
AIMS monitors Australia’s largest oceanic reef system, Scott Reef. Sitting in the Indian Ocean we have monitored fish and coral communities there for nearly three decades. The data helps us to understand Scott Reef’s natural variability, how its remote location has protected it from many of the pressures affecting other reefs around the world and how climate change is now threatening its future.
Over the years, the research at Scott Reef has evolved from a basic knowledge on the abundance of life on the reef, to a comprehensive understanding of the reef’s physical environment and biological communities.
Since it was first formed, Scott Reef and its ecosystem have been altered significantly by changes in global climate and ocean level occurring over millions of years. Over timeframes more relevant to humans, other events have also regularly affected the reef and its communities.
Researchers have documented a range of disturbances at the Scott Reefs, such as mass bleaching events and cyclones, since monitoring began. We now understand how these disturbances – in isolation and in combination – threaten the future of the reefs.
AIMS began a formal monitoring program at Scott Reef in 1996. In 1998, the reef suffered severe bleaching during the first global bleaching event. Over 80% of coral cover was lost during this period. Extensive research and monitoring over the following years provided vital information on how isolated coral reefs respond after catastrophic bleaching events, information that is critical to the management of reefs globally. The reef took about 12 years to recover, but not all coral groups returned to their previous cover.
Despite its isolation and limited supply of new coral larvae from surrounding reefs, the Scott Reefs remain reasonably resilient, because good water quality and fish stocks lead to excellent rates of coral survival and growth. The recovery of Scott Reef illustrates that minimising local pressures can be vital to coral reefs, assisting their recovery from global threats that are so difficult to control. The corals also show some level of adaptation to heat stress, however it is clear that the current rate of adaptation cannot keep pace with the rate of climate change, and future mas bleaching events will reduce coral cover and diversity. The long-term trends, including the reef’s response to the most recent mass bleaching in 2016, also highlight which coral groups are most susceptible to climate change and are now rare at the reefs.
The rate of degradation at the Scott Reefs in coming decades is unknown. However, studying the changes in ecosystem health, and the processes of impact and recovery at these isolated reefs, can provide valuable insights into the consequences of climate change for coral reefs globally, and allow us to explore management interventions to slow degradation until the causes are addressed.
Rowley Shoals marine reserve highlights the benefits
Western Australia’s Rowley Shoals – an isolated chain of coral atolls, located 270km off Broome, has been closed to fishing for more than 20 years and has so far escaped extreme heat stress and mass coral bleaching - providing a unique baseline for scientists and a rare glimpse at how habitats can thrive in a relatively undisturbed state.
Drawing on 14 years of data from baited remote underwater video stations (BRUVS), our research compared fish species at Rowley Shoals with other remote reefs facing ongoing fishing pressure in northern Western Australia. The research shows fish diversity and abundance has remained remarkably stable at the Rowley Shoals, indicating marine reserves are hugely beneficial in maintaining fish communities at isolated reefs.
Rowley Shoals is one of the only places in Western Australia with consistently high coral cover and diversity for more than 20 years. Being far from the coastline it has excellent water quality and has escaped mass bleaching events. However, the levels of heat stress at the reefs has increased significantly in recent years, and with it the frequency and severity of bleaching.
This research supports effective environmental management to ensure sustainable use and protection of marine ecosystems, and highlights the effects of climate change and bleaching on the worlds coral reefs.
- Gilmour, J., et al. Discovering Scott Reef. 2013.
- Underwood, J.N., et al., Ecologically relevant dispersal of corals on isolated reefs: implications for managing resilience. Ecological Applications, 2009. 19(1): p. 18-29.
- Gilmour, J.P., et al., Recovery of an isolated coral reef system following severe disturbance. Science, 2013. 340(6128): p. 69-71.
- Gilmour, J.P., et al., A tale of two reef systems: Local conditions, disturbances, coral life histories, and the climate catastrophe. Ecological Applications, 2022. 32(3): p. e2509.
- Gilmour, J.P., et al., The state of Western Australia’s coral reefs. Coral Reefs, 2019. 38: p. 651-667.
Feature image by Nick Thake