AUSTRALIA has two very special marine reef environments – we are all familiar with the Great Barrier Reef but there is a second large reef system which is equally important to our coastal environment – the Great Southern Reef.

Rising sea temperatures which are impacting the Great Barrier Reef are also impacting the Great Southern Reef.

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MarineMARINE biologist Ryan Pereira, of Irukandji Shark Encounters and the charity Seashelter, spoke to News Of The Area about this lesser known reef system.

Ryan told News Of The Area, “When we hear the word ‘reef’ we tend to think tropical coral reefs, however those found in temperate regions with intermediate climate conditions are one of the least explored, most beautiful, and productive reefs on the planet.

“Australia is spoiled by not only having the Great Barrier Reef it is also home to The Great Southern Reef, which is a massive series of reefs that extend around Australia’s southern coastline, covering around 71,000 square kilometres from New South Wales around the southern coastline of Australia to Kalbarri in Western Australia.”

The reef has extensive kelp seaweed forests which while not as colourful as tropical corals they are beautiful in their own right.

“These kelp forests are some of the most productive ecosystems on the planet.

“The major fisheries in the reef are the rock lobster (worth around $375 million/year) and abalone (worth around $134 million/year).”

Tourism is also an important element of the reef – it’s estimated that the reef directly supports activities worth nearly $10 billion per year, while the total tourism from the reef and adjacent coastal areas amounts to around $40 billion/year.

“Sadly, the reefs are undergoing a transformation that is poorly understood and the extent of this change could have considerable unpleasant effects to Australia’s unique ecosystems,” Ryan said.

“A recent study found widespread loss of kelp forests following a marine heatwave in 2011 and another in 2021.

“Surveys of reefs along the NSW coastline have found that the area covered by kelp forests declined significantly up to 50 percent in some regions.

“It was observed that after 2011 the kelp did not fully recover, nearly ten years after the heatwave.

Fishermen, divers and researchers have documented a shift from kelp to turf-forming seaweeds and subtropical and tropical fish species that thrive in warmer waters.

“Shifts in the abundance and diversity of species of sea urchins and gastropods were also noted all along NSW, Victoria and even Tasmania,” Ryan said.

Furthermore there are studies which have shown that, “The Indian Ocean along the coast of Western Australia is a global warming hotspot—it’s high up on the list of places around the world experiencing high rates of ocean warming,” Ryan said.

“This region has seen a temperature increase of 0.65° C over the past 50 years.

“Warmer temperatures are shifting southwards at a rate of 20 to 50 kilometres per decade.

“If this trend continues, we could soon see a complete transformation of this region of the Great Southern Reef—away from temperate kelp forests to more tropical species.

“Although everybody loves tropical fish, the lasting effects of complete transformation of kelp forests will have detrimental effects to fisheries, ecological food webs from land to sea, local climates, and tourism,” he said.

Local fishers are already finding species in New South Wales fisheries that previously were only found further north.

By Marian SAMPSON