Mapping the seafloor of one of the world’s largest marine parks

By Huw Morgan August 8th, 2019

The Coral Sea Marine Park is one of the world’s largest marine parks and vital to surrounding Pacific Island countries. A month-long voyage by Australia's research vessel to gather and share data and insights with international colleagues has begun, in pursuit of a better understanding of the area's geodynamic and climatic history, as well as biotic evolution.

The RV Investigator

IT is often said that we know more about the planets of our solar system than we do about what goes on in the depths of the world’s oceans. This month a scientific voyage in the Coral Sea Marine Park hopes to clear up some of the questions deep below the waves.

Heading out from Cairns into the Coral Sea before turning north toward Papua New Guinea, then across to Solomon Islands and back to Brisbane will be RV Investigator – Australia’s dedicated blue-water research vessel, capable of operating from the Antarctic ice edge to the equator. Owned and operated by the CSIRO but open for use by the entire Australian research community, Investigator is a national research facility that provides a highly flexible platform for multidisciplinary research across Australia’s vast marine estate and beyond

On board for the 30-day voyage will be 35 scientists, researchers and technicians from more than 10 research institutions both in Australia and overseas.

Exploring the vast range of habitats in the Coral Sea

The Coral Sea Marine Park is one of the world’s largest marine parks, covering more the 989,000 square kilometres, lying beyond the Great Barrier Reef off the coast of Queensland. Stretching more than 2200 km, it has wide range of habitats, including coral reefs (more than 15,000 square kilometres), sandy cays, deep sea plains and canyons.

The Coral Sea – about 220km north east from Rockhampton, Queensland. Image: Huw Morgan / CSIRO

The Coral Sea is hugely environmentally important for the all those nations surrounding it, PNG, Solomon Islands, Vanuatu, New Caledonia, Australia, and others. There are significant industries in the Coral Sea, including commercial fishing and shipping that contribute to economic growth, employment and social wellbeing in coastal towns and communities.

The Coral Sea has a high species diversity and globally significant populations of internationally threatened species. A small number of species are found nowhere else. The area is the spawning grounds for black marlin and the migration route for humpback whales going to and from Antarctica. Six of the world’s seven species of marine turtles can be found there.

Simon Williams, Professor of geophysics at Northwest University, Xian, China, who is alternate Chief Scientist on the voyage, with Associate Professor of geophysics Jo Whittaker, University of Tasmania, and Chief Scientist for the voyage, on the bridge looking at the voyage route prior to leaving Cairns.

“Lots of oceans haven’t been looked at very much,” says Chief Scientist for the voyage, Marine Geophysicist, Associate Professor Jo Whittaker from the University of Tasmania.

“There are lots of areas that are poorly mapped and poorly sampled, and this is just one of them.

“We are interested in mapping what the seafloor looks like because, particularly in Australian waters that are marine park, to manage something you need to know what’s there.

“We know the broad shape of the seafloor from satellite data but we don’t have a good mapping of what the different seafloor shapes are.

“We don’t know where there are canyons, we don’t know where there are flat areas, we don’t know what the substrate is – rocky or sand. So, mapping all of that stuff out does play into habitat mapping.

“That is a focus of one of the projects on the voyage; to try and categorize the seafloor into these different types.”

Mysterious formations

Researchers will be looking at the links between marine habits and the region’s seafloor.

“The geomorphology of the seafloor is a key influence on the Coral Sea’s biodiversity, especially deep-water habitats, so our research will include examining how different habitats are distributed and how this relates to seafloor structures,” says Whittaker.

Using a multi-beam echo sounder, the research team swaths the seafloor while the ship is moving, looking for interesting features and suitable sites to dredge for rocks.

The Louisiade Plateau (a giant undersea plateau about the size of Victoria) in the northern Coral Sea is one mysterious formation Whittaker is hoping may become clearer. It may turn out to be a piece of continental Australia that became separated millions of years ago, or it may not.

“There are a couple of options as to what that (the plateau) could be,” says Whittaker.

“We could find that it is a piece of Australia that rifted off and is now out there further out to sea with ocean crust in between, similar to the Lord Howe Rise.

“Although most people tend to think that it is predominately volcanic. So that could be quite fun to find out.

“There is a bunch of fundamental information that is really not known. There is a lot of interest in how the whole area has evolved. It is a tectonically complex area that has evolved over 50 to 60 million years or so.

“What is the nature of the crust out there? Oceanic and continental crusts are very different and we don’t know for sure whether some areas are oceanic or continental – it is still being debated.

“Things like that are really fundamental pieces of information to understand how that whole area has evolved and what we can expect to find out there and that has implications for what nations can expect to find in their territorial waters.”

Probing the seabed

Investigator is equipped with advanced geoscience equipment to map the seafloor and its underlying structure. Attached to the vessel’s hull is a steel housing called a gondola, which is shaped a bit like a giant wing and contains advanced sonar technology. Acoustic signals are emitted in a beam that can be 30km wide in water depths to 11,500m to reveal, in 3D, seafloor features such as deep-sea canyons and mountains. Investigator also has advanced equipment to probe the make-up of the seabed and below.

Marine biologists on board can study ocean life with the latest fish assessment sonar that can reach to depths of 3,000 m and collect passive data on where species live, eat and breed. Combined with the seafloor mapping technology, this will greatly improve our understanding of ocean ecosystems. The vessel has a range of sampling equipment ranging from small fine gauge surface nets to large ocean trawling nets used to capture species down to 5000m, as well as seafloor sampling equipment, and incubation and refrigeration facilities.

Fredrick Seamount about 1000km southeast of Cairns.

Investigator is one of only a few vessels around the world fitted with a weather radar. Atmospheric research data can be collected from 20 km above and 150 km around the vessel to help us understand and predict changes in local, regional and global weather and rainfall patterns.

Investigator’s unique capability was recognised in 2018 by the World Meteorological Organisation when the vessel was accepted as the first Global Atmosphere Watch (GAW) Regional Mobile Station.

GAW is a long-term global program that provides reliable scientific data and information on the chemical composition of the atmosphere, its natural and anthropogenic change, and helps to improve the understanding of interactions between the atmosphere, the oceans and the biosphere.

Above water

Another study will examine the distribution and abundance of seabirds.

From dawn to dusk, a small dedicated team of birdwatchers sits in an observation room above the main bridge of Investigator – spotting, identifying and cataloguing every bird that passes by.

The project will collect data to quantify the variability in the distribution and abundance of seabirds to examine the relationships between physical oceanographic features and their use as seabird feeding areas.

“Gathering data about the seabirds that we observe during the voyage will also play an important role in informing future management plans for Australia’s marine environment,” says Whittaker.

Observations of marine mammals will also be shared with researchers to help understand the role of oceanographic processes in the distribution of marine mammals at sea around Australia.

Understanding biotic evolution

“The Coral Sea is vital to a range of Pacific nations, and we hope to be able to survey within the exclusive economic zones of some of our neighbours so we can gather and share data and insights with our international colleagues,” says Whittaker.

The voyage research has global significance for understanding the planet’s geodynamic and climatic history, as well as biotic evolution.

Bringing up rocks from dredging the floor in the Coral Sea.

The mapping of seamounts, naturally important habitats for open ocean ecosystems, will help in assessing the biodiversity, conservation and ecosystem health and also identify areas of important conservation value.

“The seamounts are about 2000 m high and the ones we have surveyed before (near Tasmania) have been 20 to 50 km in width and breadth – so they are a decent size!”

The Coral Sea is also home to “hotspot trails” which are thought to arise from deep mantle plumes, whose episodic eruptions have caused environmental crises affecting the world’s atmosphere through the release of gas and aerosols. They are also thought responsible for mass extinctions, and alter ocean circulation and chemistry.

The seafloor mapping in the area will also provide an opportunity for countries such as PNG, New Caledonia and Solomon Islands to further develop their offshore mapping program.

Research on Investigator is funded by the Australian Government through grants of sea time awarded through a competitive application process by the CSIRO Marine National Facility. The Marine National Facility is owned and operated by CSIRO on behalf of the nation.

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