A marine heatwave has wiped out a swathe of WA's undersea kelp forest

July 8, 2016 by Scott Bennett, Julia Santana-Garcon, And Thomas Wernberg, The Conversation
The 2011 heatwave hit kelp forests hard along a long stretch of WA coast. Credit: J. Costa, Author provided

Kelp forests along some 100km of Western Australia's coast have been wiped out, and many more areas damaged, by a marine heatwave that struck the area in 2011.

The heatwave, which featured ocean temperatures more than 2℃ above normal and persisted for more than 10 weeks, ushered in an in marine plant life along a section of Australia's Great Southern Reef, with kelp disappearing to be replaced by tropical species.

As we and our international colleagues report in the journal Science, five years on from the heatwave, these kelp forests show no signs of recovery.

Instead, fish, seaweed and invertebrate communities from these formerly temperate kelp forests are being replaced by subtropical and tropical reef communities. Tropical fish species are now intensely grazing the reef, preventing the kelp forests from recovering.

Assessing the damage

We and our team surveyed reefs along 2,000km of coastline from Cape Leeuwin, south of Perth, to Ningaloo Reef between 2001 and 2015.

Up until 2011, temperate reefs were clearly defined by the distribution of kelp forests which formed dense, highly productive forests as far north as Kalbarri in WA's Mid West.

Since 2011, the boundary between these temperate reefs of southern WA and the more (including Ningaloo) to the north has become less clear-cut. Instead, the sharp divide has been replaced by an intermediate region of turf-dominated reefs.

Kelp forest before (left) and after (right) the marine heatwave.

This has implications for the Great Southern Reef (GSR), which extends more than 8,000km around the southern half of Australia from the southern half of WA all the way to southern Queensland – a coastline that is home to around 70% of Australians.

Kelp forests are the GSR's "biological engine", feeding a globally unique collection of temperate marine species, not to mention supporting some of the most valuable fisheries in Australia and underpinning reef tourism worth more than A$10 billion a year.

But our research shows that on the GSR's western side, kelp forests are being pushed towards Australia's southern edge, where continued warming puts them at risk of losses across thousands of kilometres of coastline because there is no more southerly habitat to which they can retreat.

While the 2011 affected some 1,000km of Western Australia's temperate coastline, it was a stretch of roughly 100km extending south of Kalbarri on the state's Mid West coast that was most severely affected.

In this area alone an estimated 385 square km of kelp forest have been completely wiped out.

Further south, from Geraldton to Cape Leeuwin, the extent of kelp loss was less severe, despite an estimated total area of 960 square km having been lost in the region.

Infographic illustrating the impacts of the heatwave, kelp loss and tropicalisation of temperate reefs. Credit: Awaroo

Northern regions towards Kalbarri were more severely affected because these kelp forests were closer to their limit, and also because this area is closer to the tropical regions like Ningaloo Reef, meaning that tropical species could more easily move in.

The problem was exacerbated by the southward-flowing Leeuwin Current, which helps move south while making it harder for temperate species to move north and recolonise the affected areas of the GSR.

The combination of these physical and ecological processes set within a background warming rate roughly twice the global average, compounds the challenges faced by kelp forests in the region.

The plight of WA's kelp forests provides a strong warning of what the future might hold for Australia's temperate marine environment, and the many services it provides to Australians.

Explore further: Beautiful but a threat: Tropical fish invasion destroys kelp forests

More information: T. Wernberg et al. Climate-driven regime shift of a temperate marine ecosystem, Science (2016). DOI: 10.1126/science.aad8745

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12 comments

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Shootist
1.3 / 5 (12) Jul 08, 2016
When it comes to chaotic systems normal generally means highly variable.

Where are the wheat farms in Greenland? Too cold. Where are the vineyards in Scotland and Norway? Too cold. Yet there once were vineyards and wheat farms where there are none today.

Carry on alarmists.
SteveS
4.7 / 5 (15) Jul 08, 2016
When it comes to chaotic systems normal generally means highly variable.

Where are the wheat farms in Greenland? Too cold. Where are the vineyards in Scotland and Norway? Too cold. Yet there once were vineyards and wheat farms where there are none today.

Carry on alarmists.


Where is your evidence for any of this?

The vikings tried to grow wheat in Greenland, but it was too unreliable as a staple crop.

http://www.archiv...djvu.txt

"As to whether any sort of grain can grow there, my belief is that the country draws but little profit from that source. And yet there are men among those who are counted the wealthiest and most prominent who have tried to sow grain as an experiment; but the great majority in that country do not know what bread is, having never seen it."

The Kings Mirror, written 1250.

As for vineyards in Scotland, where is your evidence?
SamB
4.4 / 5 (7) Jul 08, 2016
From what I understand, the government in BC removed large swathes of kelp in the 40's because they were impeding the seine fish boats from efficiently catching salmon. This alone was responsible for much of the decline in salmon stocks in this province.
Maggnus
4.7 / 5 (14) Jul 09, 2016
Where is your evidence for any of this?
As for vineyards in Scotland, where is your evidence?

He has none, of course, Shootist is a sad old man who can only re-spout previously debunked bullshit. He has realized that his capacity to absorb new knowledge has been severely reduced due to his dementia and advanced aphasia, so he just throws out troll bait in a hateful attempt to "stir the pot".

Best to do what the rest of us do, and simply ignore him. He has nothing to say that's worth reading anyways.
Maggnus
4.7 / 5 (12) Jul 09, 2016
From what I understand, the government in BC removed large swathes of kelp in the 40's because they were impeding the seine fish boats from efficiently catching salmon. This alone was responsible for much of the decline in salmon stocks in this province.
Another gem from the apparently demented. The kelp beds were lost due to over hunting of sea-otter, which resulted in an explosion in the urchin population, which then overgrazed the kelp beds, all of which HURTS young salmon that depend on the kelp beds for sustenance and cover.
Christopher C Wilmers, James A Estes, Matthew Edwards, Kristin L Laidre, and Brenda Konar. 2012. Do
trophic cascades affect the storage and flux of atmospheric carbon? An analysis of sea otters and kelp forests.Frontiers in Ecology and the Environment 10: 409–415

Anthony, Robert G., James A. Estes, Mark A. Ricca, A. Keith Miles, and E. D. Forsman. 2008. Bald Eagles
and Sea Otters in the Aleutian Archipelago: Indirect Effects of Trophic Cascades.
SteveS
4.7 / 5 (14) Jul 09, 2016
Where is your evidence for any of this?
As for vineyards in Scotland, where is your evidence?

He has none, of course, Shootist is a sad old man who can only re-spout previously debunked bullshit. He has realized that his capacity to absorb new knowledge has been severely reduced due to his dementia and advanced aphasia, so he just throws out troll bait in a hateful attempt to "stir the pot".

Best to do what the rest of us do, and simply ignore him. He has nothing to say that's worth reading anyways.


At least he's stopped quoting Freeman Dyson since he found out that he's a Democrat.
HeloMenelo
4.1 / 5 (9) Jul 09, 2016
Where is your evidence for any of this?
As for vineyards in Scotland, where is your evidence?

He has none, of course, Shootist is a sad old man who can only re-spout previously debunked bullshit. He has realized that his capacity to absorb new knowledge has been severely reduced due to his dementia and advanced aphasia, so he just throws out troll bait in a hateful attempt to "stir the pot".

Best to do what the rest of us do, and simply ignore him. He has nothing to say that's worth reading anyways.

shootist always shoots the potty miss :D
BiteMe
Jul 10, 2016
This comment has been removed by a moderator.
ColoradoBob
5 / 5 (8) Jul 11, 2016
Australian mangrove die-off blamed on climate change

Thousands of hectares of mangroves in Australia's remote north have died, scientists said Monday, with climate change the likely cause.

Some 7,000 hectares (17,300 acres), or nine percent of the mangroves in the Gulf of Carpentaria, perished in just one month according to researchers from Australia's James Cook University, the first time such an event has been recorded.

http://www.dailym...nge.html
HeloMenelo
4 / 5 (4) Jul 11, 2016
That's why his mama calls him shitlist.

.. :D
antigoracle
1 / 5 (5) Jul 12, 2016
That's why his mama calls him shitlist.

Why would she name him after you?
HeloMenelo
5 / 5 (2) Jul 13, 2016
She didn't, You were named that by your mommy monkey now now i know it's hard for you to read the big words here on the science forum, not to worry i have a banana for youuuu... ;)

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