Marine ecology

The Great Southern Reef is a vast interconnected network of reef systems that fringe the southern margins of the Australian continent. It stretches for 8000 kilometres from Kalbarri in the mid-west, around the southern coastline and north to New South Wales. In all, it comprises 71 000 square kilometres of reef system. [1]

Figure 1

Extent of the Great Southern Reef

Note. From Who’s heard of the Great Southern Reef? by Australian Academy of Science, 2017

(https://www.science.org.au/curious/earth-environment/whos-heard-great-southern-reef).

Copyright 2017 by Thomas Wenberg.

Biodiversity

The defining species of the Great Southern Reef are the kelp forests, which provide the basis for diverse marine communities. The reef system is home to many iconic species such as the giant cuttlefish, sea lions, leafy sea dragons, and blue groper. But scientists believe there are still thousands of species yet to be identified.

You can read more about marine life on the Great Southern Reef website.

The southern continental margins of Australia have been isolated for over 20 million years, meaning that species have evolved in isolation. Many species are endemic to the reef system, existing nowhere else on Earth. The red seaweeds are the most localised, with 77 per cent of species being endemic. Between 30 and 60 per cent of all plant and animal species are endemic to the reef. [2]

Naming the reef

Australia’s Great Barrier Reef is a household name, yet few people have heard of the temperate reef that circles our southern coastlines. The Reef lies within the coastal zone managed by five State Governments, resulting in it being managed as a multitude of small parts. It has only recently been recognised that the reefs comprise a cohesive biological entity. [3]

In 2016 a team of marine scientists from the University of Western Australia called for the temperate reefs to be named as a single entity in order to aid conservation and preservation. The team, led by Thomas Wenberg, coined the name of the Great Southern Reef:

“We came up with the name to give this ecosystem a proper identity that basically conveys how amazing it is, and how unique it is. The reef system is so immense yet towns and cities that are hundreds of kilometres apart share the same productive kelp forests.” [4]

Scientists hope that both Government funding and community stewardship can be activated by naming and recognising the reef. In their 2016 report, Wenberg’s team found that between 2010 and 2014, $55.3 million were directed to coral reef research, while only 4 million was allocated to research on temperate reefs.

Figure 2

Shoreline in the Ngari Capes Marine Park

Note. Unpublished image, copyright 2020 by Jinni Wilson.

Kelp forests

The kelp forms the basis of the ecosystem, the source of the food chain that supports the Reef’s biodiversity. Kelp forests are the ‘biological engine’ that supports and connects the individual ecosystems across the whole of the reef complex. Each hectare of kelp forest can produce up to 65 tonnes of biomass annually, making it one of the most productive biosystems on earth. [5]

Climate change

Rising water temperatures are a major threat to the reef ecosystems. Not only does warmer water degrade the kelp beds, it also allows tropical species to migrate south, changing the ecological balance of the temperate reef systems. In 2011 a warm water event off the coast of Western Australia caused the death of 100 kilometres of kelp forest at Kalbarri. Ninety-five percent of giant kelp forests in Tasmania have also been lost to the impacts of climate change. [6]

Scientists predict that over the coming decades the geographic range of kelp forests will further contract, with a resulting catastrophic impact on marine communities. [7]

Figure 3

Kelp forests impacted by climate change, Kalbarri.

Note. From Warming seas causing massive die-off of Australia’s reef forests, by Mongabay, 2016.

(https://news.mongabay.com/2016/07/warming-seas-causing-massive-die-off-of-australias-reef-forests/)

Copyright 2016 by Thomas Wenberg.

Fossil fuels

Not only do fossil fuels cause global warming, but their extraction poses hazards to marine environments. Oil and gas exploration in the Great Australian Bight could soon expose populations of marine mammals to disturbance from seismic drilling. Damage from underwater blasting impacts on krill populations, the major food source for whales. [8]

Fisheries

Fisheries are a major industry in all regions of the Great Southern Reef. However, over-fishing can threaten populations of particular species. It can also upset the ecological balance. Rock lobsters are a main predator of sea urchins, and the overfishing of lobsters in some regions has contributed to an over-population of urchins. Urchin feed on the kelp forests and in some cases are responsible for destroying them altogether, resulting in denuded sea floors called ‘urchin barrens.’ [9]

Figure 4

Sea urchin

Note. From Sea creatures, by Earth Sea Star, 2020.

(https://earthseastar.com/2020/05/08/marine-life-of-margaret-river/)

Copyright 2020 by Jinni Wilson.

Sustainable use

It is difficult to quantify the economic value of the Great Southern Reef. It contributes to fisheries, recreation, and tourism. In 2007-2008, tourism alone generated 38 billion dollars in regions bordering the Reef. In 2014, abalone and lobster fisheries were worth 500 million dollars. [10] Recognising the economic importance of the reef highlights the need to ensure its sustainable management.

It is hoped that with greater community awareness of the reef, threats can be managed so the reef can continue to support diverse ecologies and economies for generations to come.


Featured image

Red waratah anemone

From Sea Creatures, by Earth Sea Star, 2020.

(earthseastar.com)

Copyright 2020 by Jinni Wilson.


[1] Bennet et al, (2016)

[2] Martinez et al (2018)

[3] Bennet et al (2016)

[4] University of Western Australia (2019)

[5] Martinez et al (2018)

[6] Bradley, (2017).

[7] Martinez et al (2018)

[8] ABC (2019) Great Australian Bight

[9] Layton et al (2020)

[10] Bennett et al (2016)


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