Data needed on benthic habitats

The Coral Sea Marine Park spans over 980,000 square kilometres and hosts highly diverse habitats that sustains rich species diversity. As one of Australia’s newest Marine Park’s, the region lacks baseline data on its reef lagoons, habitats, and species. This information is critical for effective management, and identifying areas of high benthic habitat diversity will assist managers in prioritising areas for conservation.

Mapping benthic habitats in the Coral Sea Marine Park

Our team is identifying and mapping benthic habitat diversity inside the reef lagoons of the Coral Sea Marine Park. These will be the first benthic habitat maps inside the lagoons based on data collected in the field and will form a crucial baseline dataset for monitoring future changes.

In 2022, the team covered around 3,500 square kilometres on a 15-day voyage.

The following methods were used for benthic mapping:

• In-field assessments using a drop-camera to depths of up to 85 meters, with cameras dropped at 492 locations.

• Data recording and re-analysis in CoralNet to identify to genera when possible, with 2,280 images uploaded to CoralNet.

• Use of ArcGIS to produce benthic habitat area maps.

Our team is also identifying fish community assemblages within the reef lagoons to investigate whether different species are found at different depths, and to understand how species use a range of habitats.

To record fish community assemblages, our researchers:

• Deployed Remote Underwater Video Stations (RUVS) in deep water and shallow water to record fish species presence.

• Analysed this video footage using Event Measures software.

This multi-method approach will deliver several key outcomes:

• Production of the first benthic habitat maps inside the reef lagoons, based on data collected in-field. These maps will provide baseline data to measure changes over time, such as habitat loss or gain.

• Collection of the first-ever seagrass herbarium specimens from the Coral Sea Marine Park, to be kept in the Canberra herbarium. This will provide readily accessible genetic samples for future seagrass connectivity research.

• Insights into the difference in fish community assemblages between deep and shallow water inside the reef lagoon. This will provide baseline data on species presence at different depths and enhance our understanding of habitat use.

A snapshot of reef lagoon habitats

Surveys completed to date have provided valuable insights into a range of species living in varied benthic habitats in these reef lagoons.

Our researchers found that all reef lagoons surveyed had vast, complex macroalgae beds, mostly located in deep water. Percent cover of macroalgae was greatest in deep water. Seagrass was recorded to a maximum depth of 63 metres.

All reef lagoons surveyed had vast coral gardens. Coral coverage was greatest for hard coral species compared to soft corals. Percent cover varied with water depth and between reef lagoons, with some lagoons showing greater coral cover in deeper water and others in shallow water.

Our researchers found more fish to be present in deepwater habitats than shallow waters, but the species of fish were the same regardless of water depth.

The results of this project serve as ground-truthing data for satellite mapping of the Coral Sea Marine Park and provide insights into potential areas of higher diversity within these reef lagoons.

Further research is needed to improve these baseline datasets to assist in conservation and management of the Marine Park. This should include investigating the age, gender and size of fish inside the reef lagoons to identify fish nurseries.

Project details

This project is led by Dr Samantha Tol along with Dr Paul York, Professor Michael Rasheed, Dr Robert Coles, Associate Professor Alana Grech, and Professor Andrew Hoey. The project is funded by the Department of Climate Change, Energy, Environment and Water and Parks Australia.