WITH the biggest waves in the world, the deep waters of the Great Australian Bight can be a forbidding environment for humans. Yet, this is home to more apex predators and iconic species than are found anywhere else in Australian waters, and the regular haunt of a multitude of migratory species who consistently return to feed and breed.
From blue whales to sardines, Australian sea lions to little penguins, long-nosed fur seals to flesh-footed shearwaters, the diversity of species and their sheer numbers are mind-boggling. Many of the species found along Australia’s southern coast occur nowhere else in the world.
Due to its remoteness, relatively little has been known about the Bight—not just the ecology but the interplay of the currents, the weather and the geology. An ambitious four-year social, environmental and economic study of the region by over 100 scientists has changed all that, giving rise to a quantum leap in knowledge, the discovery of at least 277 species new to science, and the first clear evidence of the presence of oil and gas.
Commercial fishing, aquaculture and recreational fishing are important components of the region’s economy, generating 25 per cent of Australia’s seafood by value. The South Australian Sardine Fishery is the nation’s largest commercial fishery by volume.
Southern bluefin tuna are one of Australia’s most valuable fisheries—95 per cent of the catch is from the Bight and almost all of this is exported from Port Lincoln to Japan for the high value sashimi market.
Tourism is important too—you can swim with sea lions, cage-dive with great white sharks, or simply stand on the clifftops at the Head of Bight and watch southern right whales calving.
Oil and gas exploration has been occurring in the Bight for years and, while the presence of commercially viable reserves has not been confirmed, that could quickly change.
The $20 million Great Australian Bight Research Program—a collaboration between BP, CSIRO, the South Australian Research and Development Institute (SARDI), the University of Adelaide and Flinders University—concluded in September.
The program set out to provide a whole-of-system understanding of the environmental, economic and social values to support future management of the region.
“The research was very ambitious in breadth and depth,” says Associate Professor Tim Ward, who leads the Marine Ecosystems Science Program at SARDI. “It has produced a quantum shift in our knowledge of how the ecosystem works, we have the first clear evidence of the presence of oil and gas, and overlaying that we have a social and economic baseline, which is really valuable.”
We have new information on the abundance and movement patterns of iconic species such as pygmy blue whales, great white sharks and Australian sea lions, as well as dolphins, fur seals and seabirds.
In a region of the Bight that had previously not been surveyed for cetaceans, researchers used underwater microphones to detect different toothed whale species such as deep-diving sperm whales who produce loud clicking sounds while they forage.
Aerial surveys of common dolphins provided new data on their abundance, with up to 20,000 dolphins sighted in the eastern Great Australian Bight.
The first comprehensive synthesis of data on seals revealed that the Bight contains more than 90 per cent of Australia’s long-nosed fur seals and Australian sea lions.
Areas where these species spend a lot of time and where multiple species overlap have also been mapped.
What makes the Bight such an attractive feeding and breeding ground for so many species? And what is it that keeps their pantry so well stocked?
In the eastern Bight, the winds and the ocean currents were found to play a part, bringing an upwelling of nutrient-rich water to the surface in summer.
In the central Bight, it appears that biological processes driven by microorganisms, not the upwelling, are enriching the water with nitrogen, which in turn is supporting different types of plankton: “The plankton assemblage is transferring energy quickly through the food web which helps explain the high abundance of pelagic [oceanic] fish in the region,” explains SARDI scientist Dr Paul van Ruth.
At depths of up to 5000 metres, sampling the sea floor of the Bight is expensive and until now virtually nothing was known about the organisms that live there.
The first ever systematic study of sea-floor fauna in the Bight—a shared study with the Great Australian Bight Deepwater Marine Program—shows that biodiversity is high. Amazingly, the combined research found 277 species new to science and almost 1000 species found in the Bight for the first time.
According to CSIRO scientist Dr Alan Williams, in terms of sea-floor ecology, the research has “transformed the Bight from one of Australia’s most poorly known deep-sea regions to the best known”.
The research was not confined to the deep waters of the Bight. Sean Pascoe, a marine resource economist with CSIRO, and colleagues from the University of Adelaide, studied the social and economic aspects of the region to understand how local people feel about the prospect of a petroleum industry and to gather important baseline data.
It’s mainly a farming region, with a small, sparse and ageing population that is shrinking as young people leave to find work in the cities.
Local councillors and business leaders are largely positive about the prospect of a petroleum industry, says Pascoe.
“It’s clear that the region doesn’t have the skills required and that most employment will be fly in/fly out. But having more people in the region is seen as a boost to hotels, accommodation, fish-and-chip shops… it’s more the flow-on effects.”
The team modelled the regional economy, mapping the location and value of fisheries, aquaculture and recreational fishing. Through the modelling and hypothetical scenarios, they explored the impact of one of the community’s concerns—the risk of an oil spill.
“We included market impacts and biophysical impacts to assess which sectors may be affected,” explains Pascoe. “We found that offshore fisheries would be mainly ok but aquaculture would be most at risk.”
A rise in shipping levels is one scenario that might result in a collision and oil spill. Researchers from CSIRO and SARDI have integrated the data from the entire research program into two ecosystem models that can be used to explore such scenarios in complementary ways.
“Companies doing development often rely on expert opinion to assess risk,” says CSIRO research scientist Dr Beth Fulton. “Modelling can help play that out a bit more and give an indicator of the spread of effects, their magnitude and their geography. A model is like a flight simulator; you can learn as you go.”
The ecosystem models are two of many decision-support tools developed over the course of the program to support management of the Bight. Along with the data, these tools are part of the program’s legacy.
“Even if oil and gas production doesn’t eventuate,” says Tim Ward, “the Bight is still a valuable area. In that context, this is a really important study—the knowledge we now have, that didn’t exist before, is a strong base for understanding change over time.”