‘Bright white skeletons’: some Western Australian reefs have the lowest coral cover on record


Corals at Scott Reef in 2012, and at the same site during the 2016 mass bleaching.
James Gilmour/AIMS

James Paton Gilmour, Australian Institute of Marine Science and Rebecca Green, University of Western Australia

Diving on the remote coral reefs in the north of Western Australia during the world’s worst bleaching event in 2016, the first thing I noticed was the heat. It was like diving into a warm bath, with surface temperatures of 34⁰C.

Then I noticed the expanse of bleached colonies. Their bright white skeletons were visible through the translucent tissue following the loss of the algae with which they share a biological relationship. The coral skeletons had not yet eroded and collapsed, a grim reminder of what it looked like just a few months before.

I spent the past 15 years documenting the recovery of these reefs following the first global coral bleaching event in 1998, only to see them devastated again in the third global bleaching event in 2016.




Read more:
Western Australia’s coral reefs are in trouble: we mustn’t ignore them


The WA coral reefs may not be as well known as the Great Barrier Reef, but they’re just as large and diverse. And they too have been affected by cyclones and coral bleaching. Our recent study found many WA reefs now have the lowest coral cover on record.

When my colleague, Rebecca Green, witnessed that mass bleaching for the first time, she asked me how long it would take the reefs to recover.

“Probably not in my lifetime” was my reply – an abrupt but accurate reply considering the previous rate of recovery, future increases in ocean temperatures … and my age.

The worst mass bleaching on record

A similar scene is playing out around the world as researchers document the decline of ecosystems they have spent a lifetime studying.

Our study, published in the journal Coral Reefs, is the first to establish a long-term history of changes in coral cover across eight reef systems, and to document the effects of the 2016 mass bleaching event at 401 sites across WA.




Read more:
The third global bleaching event took its toll on Western Australia’s super-corals


Given the vast expanse of WA coral reefs, our assessment included data from several monitoring programs and researchers from 19 institutions.

These reefs exist in some of the most remote and inaccessible parts of the
world, so our study also relied on important observations of coral bleaching from regional managers, tourist operators and Bardi Jawi Indigenous Rangers in the Kimberley.

Our aim was to establish the effects of climate change on coral reefs along Western Australia’s vast coastline and their current condition.

The heat stress in 2016 was the worst on record, causing mass bleaching and large reductions in coral cover at Christmas Island, Ashmore Reef and Scott Reef. This was also the first time mass bleaching was recorded in the southern parts of the inshore Kimberley region, including in the long oral history of Indigenous Australians who have managed this sea-country for thousands of years.

The mass bleaching events we documented were triggered by a global increase in temperature of 1⁰C above pre-industrial levels, whereas temperatures are predicted to rise by 1.5⁰C between 2030 and 2052.

In that scenario, the reefs that have bleached badly will unlikely have the capacity to fully recover, and mass bleaching will occur at the reefs that have so far escaped the worst impacts.




Read more:
The world’s coral reefs are in trouble, but don’t give up on them yet


The future of WA’s coral reefs is uncertain, but until carbon emissions can be reduced, coral bleaching will continue to increase.

Surviving coral reef refuges must be protected

The extreme El Niño conditions in 2016 severely affected the northern reefs, and a similar pattern was seen in the long-term records.

The more southern reefs were affected by extreme La Niña conditions – most significantly by a heatwave in 2011 that caused coral bleaching, impacted fisheries and devastated other marine and terrestrial ecosystems.

Since 2010, all of WA’s reefs systems have bleached at least once.

Frequent bleaching and cyclone damage have stalled the recovery of reefs at Shark Bay, Ningaloo and at the Montebello and Barrow Islands. And coral cover at Scott Reef, Ashmore Reef and at Christmas Island is low following the 2016 mass bleaching.

In fact, average coral cover at most (75%) reef systems is at or near the lowest on record. But not all WA reefs have been affected equally.

In 2016 there was little (around 10%) bleaching recorded at the northern inshore Kimberley Reefs, at the Cocos Keeling Islands, and at the Rowley Shoals. Coral cover and diversity at these reefs remain high.

And during mass bleaching there were patches of reef that were less affected by heat stress.

These patches of reef will hopefully escape the worst impacts and retain moderate coral cover and diversity as the world warms, acting as refuges. There are also corals that have adapted to survive in parts of the reef where temperatures are naturally hotter.

Some reefs across WA will persist, thanks to these refuges from heat stress, their ability to adapt and to expand their range. These refuges must be protected from any additional stress, such as poor water quality and overfishing.




Read more:
Even the super-corals of Australia’s Kimberley are not immune to climate change


In any case, the longer it takes to curb carbon emissions and other pressures to coral reefs, the greater the loss will be.

Coral reefs support critical food stocks for fisheries around the world and provide a significant contribution to Australia’s Blue Economy, worth an estimated A$68.1 billion.

We are handing environmental uncertainty to the next generation of scientists, and we must better articulate to everyone that their dependence on nature is the most fundamental of all the scientific concepts we explore.The Conversation

James Paton Gilmour, Research Scientist: Coral Ecology, Australian Institute of Marine Science and Rebecca Green, Postdoctoral research associate, University of Western Australia

This article is republished from The Conversation under a Creative Commons license. Read the original article.

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Bleaching has struck the southernmost coral reef in the world


Tess Moriarty, University of Newcastle; Bill Leggat, University of Newcastle; C. Mark Eakin, National Oceanic and Atmospheric Administration; Rosie Steinberg, UNSW; Scott Heron, James Cook University, and Tracy Ainsworth, UNSW

This month corals in Lord Howe Island Marine Park began showing signs of bleaching. The 145,000 hectare marine park contains the most southerly coral reef in the world, in one of the most isolated ecosystems on the planet.

Following early reports of bleaching in the area, researchers from three Australian universities and two government agencies have worked together throughout March to investigate and document the bleaching.

Sustained heat stress has seen 90% of some reefs bleached, although other parts of the marine park have escaped largely unscathed.

Bleaching is uneven

Lord Howe Island was named a UNESCO World Heritage site in 1982. It is the coral reef closest to a pole, and contains many species found nowhere else in the world.

Coral bleaching observed at Lord Howe in March 2019.
Author provided

Two of us (Tess Moriarty and Rosie Steinberg) have surveyed reefs across Lord Howe Island Marine Park to determine the extent of bleaching in the populations of hard coral, soft coral, and anemones. This research found severe bleaching on the inshore lagoon reefs, where up to 95% of corals are showing signs of extensive bleaching.

However, bleaching is highly variable across Lord Howe Island. Some areas within the Lord Howe Island lagoon coral reef are not showing signs of bleaching and have remained healthy and vibrant throughout the summer. There are also corals on the outer reef and at deeper reef sites that have remained healthy, with minimal or no bleaching.

One surveyed reef location in Lord Howe Island Marine Park is severely impacted, with more than 90% of corals bleached; at the next most affected reef site roughly 50% of corals are bleached, and the remaining sites are less than 30% bleached. At least three sites have less than 5% bleached corals.

Healthy coral photographed at Lord Howe marine park in March 2019.
Author provided

Over the past week heat stress has continued in this area, and return visits to these sites revealed that the coral condition has worsened. There is evidence that some corals are now dying on the most severely affected reefs.

Forecasts for the coming week indicate that water temperatures are likely to cool below the bleaching threshold, which will hopefully provide timely relief for corals in this valuable reef ecosystem. In the coming days, weeks and months we will continue to monitor the affected reefs and determine the impact of this event to the reef system, and investigate coral recovery.

What’s causing the bleaching?

The bleaching was caused by high seawater temperature from a persistent summer marine heatwave off southeastern Australia. Temperature in January was a full degree Celsius warmer than usual, and from the end of January to mid-February temperatures remained above the local bleaching threshold.

Sustained heat stressed the Lord Howe Island reefs, and put them at risk. They had a temporary reprieve with cooler temperatures in late February, but by March another increase put the ocean temperature well above safe levels. This is now the third recorded bleaching event to have occurred on this remote reef system.

Satellite monitoring of sea-surface temperature (SST) revealed three periods in excess of the Bleaching Threshold during which heat stress accumulated (measured as Degree Heating Weeks, DHW). Since January 2019, SST (purple) exceeded expected monthly average values (blue +) by as much as 2°C. The grey line and envelope indicate the predicted range of SST in the near future.
Source: NOAA Coral Reef Watch

However, this heatwave has not equally affected the whole reef system. In parts of the lagoon areas the water can be cooler, due to factors like ocean currents and fresh groundwater intrusion, protecting some areas from bleaching. Some coral varieties are also more heat-resistant, and a particular reef that has been exposed to high temperatures in the past may better cope with the current conditions. For a complex variety of reasons, the bleaching is unevenly affecting the whole marine park.

Coral bleaching is the greatest threat to the sustainability of coral reefs worldwide and is now clearly one of the greatest challenges we face in responding to the impact of global climate change. UNESCO World Heritage regions, such as the Lord Howe Island Group, require urgent action to address the cause and impact of a changing climate, coupled with continued management to ensure these systems remain intact for future generations.


The authors thank ProDive Lord Howe Island and Lord Howe Island Environmental Tours for assistance during fieldwork.The Conversation

Tess Moriarty, Phd candidate, University of Newcastle; Bill Leggat, Associate professor, University of Newcastle; C. Mark Eakin, Coordinator, Coral Reef Watch, National Oceanic and Atmospheric Administration; Rosie Steinberg, PhD Student, UNSW; Scott Heron, Senior Lecturer, James Cook University, and Tracy Ainsworth, Associate professor, UNSW

This article is republished from The Conversation under a Creative Commons license. Read the original article.

Exploring Australia’s ‘other reefs’ south of Tasmania



File 20181217 27779 1tg4cyr.jpg?ixlib=rb 1.1
Solenosmilia coral reef with unidentified solitary yellow corals.
CSIRO

Nic Bax, CSIRO and Alan Williams, CSIRO

Off southern Tasmania, at depths between 700 and 1,500 metres, more than 100 undersea mountains provide rocky pedestals for deep-sea coral reefs.

Unlike shallow tropical corals, deep-sea corals live in a cold environment without sunlight or symbiotic algae. They feed on tiny organisms filtered from passing currents, and protect an assortment of other animals in their intricate structures.

Deep-sea corals are fragile and slow-growing, and vulnerable to human activities such as fishing, mining and climate-related changes in ocean temperatures and acidity.

This week we returned from a month-long research voyage on CSIRO vessel Investigator, part of Australia’s Marine National Facility. We criss-crossed many seamounts in and near the Huon and Tasman Fracture marine parks, which are home to both pristine and previously fished coral reefs. These two parks are part of a larger network of Australian Marine Parks that surround Australia’s coastline and protect our offshore marine environment.

The RV Investigator criss-crossed the Huon and Tasman Fracture marine parks.
CSIRO

The data we collected will answer our two key research questions: what grows where in these environments, and are corals regrowing after more than 20 years of protection?




Read more:
Explainer: the RV Investigator’s role in marine science


Our eyes on the seafloor

Conducting research in rugged, remote deep-sea environments is expensive and technically challenging. It’s been a test of patience and ingenuity for the 40 ecologists, technicians and marine park managers on board, and the crew who provide electronics, computing and mechanical support.

But now, after four weeks of working around-the-clock shifts, we’re back in the port of Hobart. We have completed 147 transects covering more 200 kilometres in length and amassed more than 60,000 stereo images and some 300 hours of video for analysis.

The deep tow camera system weighs 350 kilos and has four cameras, four lights and a control unit encased in high-strength aluminium housings.
CSIRO

A deep-tow camera system designed and built by CSIRO was our eye on the seafloor. This 350 kilogram system has four cameras, four lights and a control unit encased in high-strength aluminium housings.

An operations planner plots “flight-paths” down the seamounts, adding a one-kilometre run up for the vessel skipper to land the camera on each peak. The skipper navigates swell, wind and current to ensure a steady course for each one-hour transect.

An armoured fibre optic tow cable relays high-quality, real-time video back to the ship. This enables the camera “pilot” in the operations room to manoeuvre the camera system using a small joystick, and keep the view in focus, a mere two metres off the seafloor.

This is an often challenging job, as obstacles like large boulders or sheer rock walls loom out of the darkness with little warning. The greatest rapid ascent, a near-vertical cliff 45m in height, resulted in highly elevated blood pressure and one broken camera light!

Reaching into their world

Live imagery from the camera system was compelling. As well as the main reef-building stony coral Solenosmilia variabilis, we saw hundreds of other animals including feathery solitary soft corals, tulip-shaped glass sponges and crinoids. Their colours ranged from delicate creams and pinks to striking purples, bright yellows and golds.

To understand the make-up of coral communities glimpsed by our cameras, we also used a small net to sample the seafloor animals for identification. For several of the museum taxonomists onboard, this was their first contact with coral and mollusc species they had known, and even named, only from preserved specimens.

A deepwater hippolytid shrimp with large hooked claw, which it uses to clean coral and get food.
CSIRO

We found a raft of undescribed species, as expected in such remote environments. In many cases this is likely to be the only time these species are ever collected. We also found animals living among the corals, hinting at their complex interdependencies. This included brittlestars curled around corals, polychaete worms tunnelling inside corals, and corals growing on shells.

We used an oceanographic profiler to sample the chemical properties of the water to 2,000m. Although further analysis is required, our aim here is to see whether long-term climate change is impacting the living conditions at these depths.

A curious feature of one of the southern seamounts is that it hosts the world’s only known aggregation of deep-water eels. We have sampled these eels twice before and were keen to learn more about this rare phenomenon.

Using an electric big-game fishing rig we landed two egg-laden female eels from a depth of 1,100 metres: a possible first for the record books.

Dave Logan of Parks Australia with an eel landed from more than a kilometre under the sea.
Fraser Johnston/CSIRO

In a side-project, a team of observers recorded 42 seabird species and eight whale and dolphin species. They have one more set of data towards completing the first circum-Australia survey of marine birds and mammals.

More coral pedestals than we realise

An important finding was that living S. variabilis reefs extended between the seamounts on raised ridges down to about 1,450m. This means there is more of this important coral matrix in the Huon and Tasman Fracture marine parks than we previously realised.

In areas that were revisited to assess the regrowth of corals after two decades of protection from fishing, we saw no evidence that the coral communities are recovering. But there were signs that some individual species of corals, featherstars and urchins have re-established a foothold.




Read more:
Sludge, snags, and surreal animals: life aboard a voyage to study the abyss


In coming months we will work through a sub-sample of our deep-sea image library to identify the number and type of organisms in certain areas. This will give us a clear, quantitative picture of where and at what depth different species and communities live in these marine parks, and a foundation for predicting their likely occurrence both in Australia and around the world.


The seamount corals survey involved 10 organisations: CSIRO, the National Environmental Science Program Marine Biodiversity Hub, Australian Museum, Museums Victoria, Tasmanian Museum and Art Gallery, NIWA (NZ), three Australian universities and Parks Australia.The Conversation

Nic Bax, Director, NERP Marine Biodiversity Hub, CSIRO and Alan Williams, Researcher, CSIRO

This article is republished from The Conversation under a Creative Commons license. Read the original article.

The third global bleaching event took its toll on Western Australia’s super-corals


Verena Schoepf, University of Western Australia

Australia’s iconic Great Barrier Reef has suffered through the worst bleaching event in its history, part of the world’s third mass bleaching event.

However, coral reefs from the other side of the continent have also experienced unprecedented bleaching and coral death. This is bad news because the unique coral reefs of Western Australia’s northwest are home to some of the toughest coral in the world.

Western Australia’s unique coral reefs

Although much less well-known, coral reefs in Western Australia are highly diverse. They include, for example, Australia’s largest fringing reef, the World Heritage-listed Ningaloo Reef, as well as Australia’s largest inshore reef, Montgomery Reef which covers 380 square kilometres.

WA’s remote Kimberley region also features “super-corals” – corals that have adapted to a naturally extreme environment where tidal swings can be up 10m. These corals can therefore tolerate exposure to the air during low tide as well as extreme daily temperature swings.

My past research has shown that these naturally extreme conditions increase the heat tolerance of Kimberley corals but that they are nevertheless not immune to bleaching when water temperatures are unusually hot for too long.

Previously I had put these super-corals in tanks and subjected them to a three-week heatwave to see how they would respond, but I always wondered how they would cope in the wild where such events typically unfold over longer timescales. Unfortunately, I did not have to wait long to find out.

Kimberley reef exposed at low tide before…
Verena Schoepf, Author provided
….and during the bleaching.
Morane Le Nohaic, Author provided

The hottest years on record

2015 was the hottest year on record and 2016 will likely be hotter still. This has caused an unprecedented global coral reef crisis. Although global coral bleaching events already occurred in 1998 and 2010, this third global bleaching event is the longest on record and still ongoing.

Sadly, in WA the Kimberley region was hit the hardest. As part of Australia’s National Coral Bleaching Taskforce, colleagues and I conducted extensive monitoring before, during and after the predicted bleaching event along the entire WA coastline. In the southern Kimberley, we also carried out aerial surveys to assess the situation on a regional level.

Aerial view of a bleached inshore Kimberley reef in April 2016.
Claire Ross and Steeve Comeau, Author provided

The severity and scale of bleaching that we observed in April was devastating. Almost all inshore Kimberley reefs that we surveyed had about 50% bleaching, including Montgomery Reef. Researchers from the Australian Institute of Marine Science found that offshore Kimberley reefs such as Scott Reef fared even worse, with 60-90% bleaching in shallow lagoon waters.

Many corals had already died from the severe bleaching in April, but the final death toll has only been revealed during visits to the Kimberley last month. Vast areas of coral reef are now dead and overgrown with algae, both at the inshore and offshore Kimberley reefs.

According to local Indigenous Rangers and Traditional Owners who assisted in the research, this appears to be unprecedented. Such events had never previously been described in their rich local history of the coastal environment.

Bleached staghorn coral on inshore Kimberley reefs in April 2016.
Verena Schoepf
Dead staghorn coral on the same reefs in October 2016.
Verena Schoepf

Some good news

There was nevertheless some good news. Corals living in intertidal areas, where they regularly experience exposure to air, stagnant water, and extreme temperature fluctuations, bleached less than corals from below the low-tide mark, where conditions are far more moderate. And importantly, the majority of intertidal corals were able to fully recover within a few months.

Similarly, researchers from the Western Australian Museum and Curtin University confirmed last month that intertidal coral reefs in the central Kimberley (Bonaparte Archipelago) were in great condition.

Overall, these observations confirm the findings from my past research which showed that highly-variable, extreme temperature environments can boost the bleaching resistance of corals.

It is also important to note that the 2016 severe bleaching event in WA was restricted to the Kimberley region. Ningaloo Reef as well as coral reefs in the Pilbara and the Abrolhos Islands all escaped the bleaching. This is great news because some of these locations are still recovering from major bleaching in 2010-11 and 2013.

Healthy coral at Ningaloo Reef in 2016.
Morane Le Nohaic

The future of WA’s coral reefs

Although it is now clear that WA’s coral reefs are at risk of bleaching during both El Niño (as in 2016) and La Niña years (as in 2010-11), they have some advantages over other reefs that may hopefully allow them to recover from bleaching more quickly and stay healthy in the long term.

For example, most of WA’s coral reefs are located far away from major population centres and are thus less affected by environmental threats such as poor water quality (though other threats such as oil and gas exploration do exist). We also know that their isolation, particularly in the case of offshore reefs, helped them recover from previous mass bleaching events.

Finally, it is critical that we identify coral populations worldwide that are already naturally adapted to higher temperatures and have a greater bleaching resistance, such as the Kimberley corals.

These super-corals, while not immune to climate change, should be a priority for research into the limits of coral tolerance, as well as conservation efforts.

The Conversation

Verena Schoepf, Research Associate, University of Western Australia

This article was originally published on The Conversation. Read the original article.

Australia: Threat to the Great Barrier Reef


The link below is to an article reporting on the threats facing Australia’s Great Barrier Reef.

For more visit:
http://www.greenpeace.org/australia/en/news/climate/cooking-the-climate-wrecking-the-reef/