Going to the beach this Easter? Here are four ways we’re not being properly protected from jellyfish



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Thousands of Queensland beachgoers have been stung by bluebottle jellyfish in recent months.
Shutterstock

Lynda Crowley-Cyr, University of Southern Queensland and Lisa-ann Gershwin, CSIRO

The Easter long weekend marks the last opportunity this year for many Australians to go to the beach as the weather cools down. And for some, particularly in Queensland, it means dodging bluebottle tentacles on the sand.

In just over a month this summer, bluebottles stung more than 22,000 people across Queensland, largely at beaches in the southeast. At least eight of these stings required hospitalisation.

To make matters worse, there were more than twice the number of Irukandji jellyfish stings in Queensland than is typically reported for this time of the season. Irukandjis – relatives of the lethal box jellyfish – cause “Irukandji syndrome”, a life-threatening illness.




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Venomous jellyfish can lurk beneath Australia’s picturesque beaches, including in the Whitsundays. Better public awareness is vital.
alexmgn/Shutterstock

There have also been widespread reports that Irukandjis have been migrating southwards. Many reports have assumed there is a southward migration linked to climate change. But Australia’s jellyfish problem is far more complex. Despite the media hype, there exists no evidence that any tropical Irukandji species has migrated, or is migrating, south.

In addition, many people find it surprising to learn there are Irukandji species native to southern waters. Many cases of Irukandji syndrome have been recorded in Moreton Bay (since 1893), New South Wales (since 1905), and even as far south as Queenscliff, near Geelong (in 1998).

So amid the misinformation, pain and misery, why is this jellyfish problem not more effectively managed?




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What is being done to manage jellyfish risks?

In North Queensland, coastal councils have grappled with jellyfish risk for decades.

At popular beaches in the Cairns, Townsville, and Whitsunday regions, visitors are offered protection in the form of lifeguard patrols and stinger nets. Beaches are also peppered with marine stinger warning signs.

But these strategies are not as effective as intended. Stinger nets, for instance, protect people against the larger, deadlier box jellyfish, but not against the tiny Irukandji.

There’s a lack of public awareness about many aspects of stinger safety. For example, that Irukandji can enter the nets; that Irukandji may be encountered on the reefs and islands as well as in many types of weather conditions; and that both Irukandjis and box jellies are typically very difficult to spot in the water.

To make matters worse, visitors, especially international tourists, are completely unaware of these types of hazards at all. This was confirmed in a recently published study that found marine stinger warning signs are not effectively communicating the true risk.

These signs comply with the requirements established by Standards Australia, but do not fully meet research-based design guidelines for effective warning signage.

The high number of stings that continue to occur at patrolled beaches highlights the need for a redesign.




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Reef operators share a similar problem.

Workplace Health and Safety legislation requires businesses for recreational water activities to do all they reasonably can to protect their staff and customers from health and safety risks.

Jellyfish risk management is only mentioned in the Code of Practice applying to diving and snorkelling businesses. But jellyfish stings continue to be widely reported, raising questions about the effectiveness of this law and its applicability to businesses for other water activities like jet skiing, kayaking, and resort watersports.

Can jellyfish risk management improve?

Absolutely! But only with more data and communication about the risks of jellyfish.

A newly established independent Marine Stinger Authority, based in Cairns, will be well positioned to provide all coastal councils, government and tourism organisations, and the wider public with updated research, information and consultation on jellyfish risks in Australia.




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A warning sign at a Queensland beach.
Shutterstock

It’s a good start, and all current strategies provide a level of protection, but there is room for improvement. We have identified the following points as the highest priority:

1. a national reporting system

A national reporting system to capture real-time data about stings. This would inform coastal councils, tourism operators and other stakeholders so they can better protect the public and meet their duty of care.

Such a system has been partially developed by CSIRO, but this has ceased. We are seeking funding to resume development and implementation of this critical public safety tool.

2. improved warning signage

Modification of jellyfish warning signs should be consistent with research-based design guidelines.

Effective signs should, among other things: be noticeable and include a signal-word panel with “WARNING” in appropriate size and coulours to alert of the hazard; be easy to read, including by international visitors; include a well-designed pictogram indicating scale of hazardous jellyfish; and include hazard information, its consequences and how to avoid it.

Any modifications would also need to be monitored to ensure the signs are properly understood where deployed.

3. an updated Code of Practice

The Work Health and Safety Code of Practice should be amended to include all businesses for recreational water activities and make jellyfish risk management mandatory.

4. safety messaging research

More research is needed to better understand the effectiveness of jellyfish management strategies, taking into account the diverse cultural expectations and
languages of visitors at different destinations.

For this Easter break, here a few safety tips for beachgoers:

  • plan ahead and be aware of local conditions

  • don’t touch bluebottles or other jellyfish (they can still sting out of the water)

  • wear stinger protective clothing like a full body lycra suit (a “rashy”) or neoprene wet suit (especially in tropical areas)

  • pack a bottle of vinegar in your beach bag, boat or boot of the car

  • get local advice on recent stings (from lifeguards or tour operators).The Conversation

Lynda Crowley-Cyr, Associae Professsor of Law, University of Southern Queensland and Lisa-ann Gershwin, Research scientist, CSIRO

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

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There’s no ‘garbage patch’ in the Southern Indian Ocean, so where does all the rubbish go?


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Plastic waste on a remote beach in Sri Lanka.
Author provided

Mirjam van der Mheen, University of Western Australia; Charitha Pattiaratchi, University of Western Australia, and Erik van Sebille, Utrecht University

Great areas of our rubbish are known to form in parts of the Pacific and Atlantic oceans. But no such “garbage patch” has been found in the Southern Indian Ocean.

Our research – published recently in Journal of Geophysical Research: Oceans – looked at why that’s the case, and what happens to the rubbish that gets dumped in this particular area.

Every year, up to 15 million tonnes of plastic waste is estimated to make its way into the ocean through coastlines (about 12.5 million tonnes) and rivers (about 2.5 million tonnes). This amount is expected to double by 2025.




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Some of this waste sinks in the ocean, some is washed up on beaches, and some floats on the ocean surface, transported by currents.

The garbage patches

As plastic materials are extremely durable, floating plastic waste can travel great distances in the ocean. Some floating plastics collect in the centre of subtropical circulating currents known as gyres, between 20 to 40 degrees north and south, to create these garbage patches.

The Great Pacific Garbage Patch.
National Oceanic and Atmospheric Administration

Here, the ocean currents converge at the centre of the gyre and sink. But the floating plastic material remains at the surface, allowing it to concentrate in these regions.

The best known of these garbage patches is the Great Pacific Garbage Patch, which contains about 80,000 tonnes of plastic waste. As the National Oceanic and Atmospheric Administration points out, the “patches” are not actually clumped collections of easy-to-see debris, but concentrations of litter (mostly small pieces of floating plastic).

Similar, but smaller, patches exist in the North and South Atlantic Oceans and the South Pacific Ocean. In total, it is estimated that only 1% of all plastic waste that enters the ocean is trapped in the garbage patches. It is still a mystery what happens to the remaining 99% of plastic waste that has entered the ocean.

Rubbish in the Indian Ocean

Even less is known about what happens to plastic in the Indian Ocean, although it receives the largest input of plastic material globally.

For example, it has been estimated that up to 90% of the global riverine input of plastic waste originates from Asia. The input of plastics to the Southern Indian Ocean is mainly through Indonesia. The Australian contribution is small.

The major sources of riverine input of plastic material into the Indian Ocean.
The Ocean Cleanup, CC BY-NC-ND

The Indian Ocean has many unique characteristics compared with the other ocean basins. The most striking factor is the presence of the Asian continental landmass, which results in the absence of a northern ocean basin and generates monsoon winds.

As a result of the former, there is no gyre in the Northern Indian Ocean, and so there is no garbage patch. The latter results in reversing ocean surface currents.

The Indian and Pacific Oceans are connected through the Indonesian Archipelago, which allows for warmer, less salty water to be transported from the Pacific to the Indian via a phenomenon called the Indonesian Throughflow (see graphic, below).

Schematic currents and location of a leaky garbage patch in the southern Indian Ocean: Indonesian Throughflow (ITF), Leeuwin Current (LC), South Indian Counter Current (SICC), Agulhas Current (AC).
Author provided

This connection also results in the formation of the Leeuwin Current, a poleward (towards the South Pole) current that flows alongside Australia’s west coast.

As a result, the Southern Indian Ocean has poleward currents on both eastern and western margins of the ocean basin.

Also, the South Indian Counter Current flows eastwards across the entire width of the Southern Indian Ocean, through the centre of the subtropical gyre, from the southern tip of Madagascar to Australia.

The African continent ends at around 35 degrees south, which provides a connection between the southern Indian and Atlantic Oceans.

How to follow that rubbish

In contrast to other ocean basins, the Indian Ocean is under-sampled, with only a few measurements of plastic material available. As technology to remotely track plastics does not yet exist, we need to use indirect ways to determine the fate of plastic in the Indian Ocean.

We used information from more than 22,000 satellite-tracked surface drifting buoys that have been released all over the world’s oceans since 1979. This allowed us to simulate pathways of plastic waste globally, with an emphasis on the Indian Ocean.

Global simulated concentration of floating waste after 50 years.
Mirjam van der Mheen, Author provided

We found that unique characteristics of the Southern Indian Ocean transport floating plastics towards the ocean’s western side, where it leaks past South Africa into the South Atlantic Ocean.

Because of the Asian monsoon system, the southeast trade winds in the Southern Indian Ocean are stronger than the trade winds in the Pacific and Atlantic Oceans. These strong winds push floating plastic material further to the west in the Southern Indian Ocean than they do in the other oceans.

So the rubbish goes where?

This allows the floating plastic to leak more readily from the Southern Indian Ocean into the South Atlantic Ocean. All these factors contribute to an ill-defined garbage patch in the Southern Indian Ocean.

Simulated concentration of floating waste over 50 years in the Indian Ocean.

In the Northern Indian Ocean our simulations showed there may be an accumulation of waste in the Bay of Bengal.




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It is also likely that floating plastics will ultimately end up on beaches all around the Indian Ocean, transported by the reversing monsoon winds and currents. Which beaches will be most heavily affected is still unclear, and will probably depend on the monsoon season.

Our study shows that the atmospheric and oceanic attributes of the Indian Ocean are different to other ocean basins and that there may not be a concentrated garbage patch. Therefore the mystery of all the missing plastic is even greater in the Indian Ocean.The Conversation

Mirjam van der Mheen, PhD Candidate in Oceanography, University of Western Australia; Charitha Pattiaratchi, Professor of Coastal Oceanography, University of Western Australia, and Erik van Sebille, Associate Professor in Oceanography and Climate Change, Utrecht University

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

Squid team finds high species diversity off Kermadec Islands, part of stalled marine reserve proposal



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This squid belongs to one of the families (Histioteuthidae) that is highly diverse but was not previously recorded from the Kermadecs.
Richard Young, CC BY-SA

Kat Bolstad, Auckland University of Technology and Heather Braid, Auckland University of Technology

Squids and octopuses could be considered the “parrots of the ocean”. Some are smart, and many have complex behaviours. And, of course, they have strange, bird-like beaks.

They are the subject of ancient myths and legends about sea monsters, but they do not live for decades. In fact, their high intelligence and short lifespan represent an unusual paradox.

In our latest research we have discovered several new species that have never been reported from New Zealand waters. Our study almost doubles the known diversity for the Kermadec region, north of New Zealand, which is part of the proposed, but stalled, Kermadec–Rangitāhua ocean sanctuary.




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More than we bargained for

Collectively, squids and octopuses are known as cephalopods, because their limbs attach directly to their head (cephalus). Our team studies cephalopods in our part of the world – the waters between Antarctica and the most northern reaches of New Zealand, the Kermadec Islands – as well as further afield.

Our first inkling of an impressive regional diversity came as we began to open boxes of frozen cephalopod samples at the National Institute for Water and Atmospheric Research (NIWA). These animals had been collected during a deep-sea survey voyage to the Kermadec Islands to better understand the region’s marine biodiversity. Members of the AUT Lab for Cephalopod Ecology and Systematics (ALCES), also known as the “squid lab”, had come to identify and examine them.

As we gently defrosted each specimen, we marvelled at their perfect suckers, iridescent eyes, and shining light organs. We noticed that many species were rare among New Zealand collections. There were some familiar faces, but also some we had only rarely or never encountered before in our local waters. Some were known from neighbouring regions; others, we suspected, might be entirely new to science.

We examined them, photographed each one, took small samples of muscle tissue for DNA analysis, and preserved them for additional work in the future. Then we set about systematically comparing our observations with what had previously been reported in New Zealand waters. And we were in for a surprise.

Doubling known diversity

Among the 150 cephalopod specimens that were collected, we identified 43 species, including 13 species that had not been previously found anywhere in New Zealand waters. Three entire orders – the taxonomic rank above family, which is the level at which, for example, egg-laying mammals split off from all other living mammals – had not been reported from this region: “Bobtail squids” (sepiolids), “comb-fin squids” (genus Chtenopteryx, order Bathyteuthoidea), and myopsid squids (coastal squids with eyes covered by a cornea).

We extracted DNA and obtained sequences for the species that had been seen for the first time in New Zealand waters. This allows us to compare them with individuals from other regions of the world. These included the strange tubercle-covered “glass” (cranchiid) squid Cranchia scabra, and the little “ram’s horn squid” Spirula spirula.

Examples of squid specimens collected recently from the Kermadec Islands Ridge: A) Histioteuthis miranda, B) Heteroteuthis sp. ‘KER’ (likely new to science), C) Chtenopteryx sp. ‘KER1’ (likely new to science), D) Leachia sp. (likely new to science), E) Pyroteuthis serrata, F) Enoploteuthis semilineata. Scale bars: 5mm.
Images by Rob Stewart/Keren Spong, CC BY-ND

Five species appear likely new to science, across a number of families with colourful common names such as “strawberry” and “fire” squids (Histioteuthidae and Pyroteuthidae, respectively). These individuals were genetically distinct from all other specimens that had been previously identified and sequenced (by us or others). Their physical appearances will now need to be compared in detail with other similar-looking species in order to fully evaluate their taxonomic status.

In total, 28 of the species we encountered had not previously been reported in the Kermadecs. This brings the total number of species in the region to at least 70. Of these, half are not known to occur elsewhere in New Zealand waters.

Kermadec–Rangitāhua Ocean Sanctuary

The Kermadec Islands, north-north-east of New Zealand, represent a diverse and nearly pristine environment. The region includes (among other habitats) a chain of seamounts and the second-deepest ocean trench in the world.

Currently, the Kermadec Islands region is on a tentative list of UNESCO World Heritage Sites. A small proportion of the area is already protected by an existing marine reserve, which extends 12 nautical miles around each of five islands and pinnacles.

This map shows New Zealand’s Exclusive Economic Zone (EEZ) in light grey, the existing Kermadec Islands marine reserve in dark grey, and the proposed Kermadec–Rangitāhua Ocean Sanctuary outlined in black.
Heather Braid, Kat Bolstad, CC BY-ND

The proposed Kermadec–Rangitāhua Ocean Sanctuary would extend the protection to 200 nautical miles and protect 15% of New Zealand’s ocean environment. It would be among the world’s largest marine protected areas.




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We strongly support the establishment of the proposed sanctuary, especially since most of the cephalopod taxa newly reported by this research are deep-sea species whose habitat is not protected by the existing marine reserve.

Although the creation of the sanctuary is supported by most political parties, New Zealand First, which is part of the government coalition, opposes it. So does the fishing industry because fishing would be banned. It is possible that the sanctuary might be created with a lower level of protection than originally proposed (with some fishing still permitted), but the government has reached an impasse.

If the Kermadec–Rangitāhua ocean sanctuary were to be established, it would protect habitats that are used by over half of the known squid and octopus biodiversity in New Zealand waters, including 34 species that have so far only been reported from the Kermadec region.The Conversation

Kat Bolstad, Senior Lecturer, Auckland University of Technology and Heather Braid, Postdoctoral Research Fellow, Auckland University of Technology

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

Coral reproduction on the Great Barrier Reef falls 89% after repeated bleaching


Morgan Pratchett, James Cook University

The severe and repeated bleaching of the Great Barrier Reef has not only damaged corals, it has reduced the reef’s ability to recover.

Our research, published today in Nature, found far fewer baby corals are being produced than are needed to replace the large number of adult corals that have died. The rate at which baby corals are settling on the Great Barrier Reef has fallen by nearly 90% since 2016.

While coral does not always die after bleaching, repeated bleaching has killed large numbers of coral. This new research has negative implications for the Reef’s capacity to recover from high ocean temperatures.

How coral recovers

Most corals reproduce by “spawning”: releasing thousands of tight, buoyant bundles with remarkable synchronisation. The bundles burst when they hit the ocean surface, releasing eggs and/or sperm. Fertilised eggs develop into larvae as they are moved about by ocean currents. The larvae settle in new places, forming entirely new coral colonies. This coral “recruitment” is essential to reef recovery.




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The research team, led by my colleague Terry Hughes from the ARC Centre of Excellence for Coral Reef Studies, measured rates of coral recruitment by attaching small clay tiles to the reef just before the predicted mass spawning each year. These settlement panels represent a standardised habitat that allows for improved detection of the coral recruits, which are just 1-2mm in size.

Almost 1,000 tiles were deployed across 17 widely separated reefs after the recent mass bleaching, in late 2016 and 2017. After eight weeks they were collected and carefully inspected under a microscope to count the number of newly settled coral recruits. Resulting estimates of coral recruitment were compared to recruitment rates recorded over two decades prior to the recent bleaching.

Australian Academy of Science.

Rates of coral recruitment recorded in the aftermath of the recent coral bleaching were just 11% of levels recorded during the preceding decades. Whereas there were more than 40 coral recruits per tile before the bleaching, there was an average of just five coral recruits per tile in the past couple of years.




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Reef resilience

The Great Barrier Reef (GBR) is the world’s largest reef system. The large overall size and high number of distinct reefs provides a buffer against most major disturbances. Even if large tracts of the GBR are disturbed, there is a good chance at least some areas will have healthy stocks of adult corals, representing a source of new larvae to enable replenishment and recovery.

Larvae produced by spawning corals on one reef may settle on other nearby reefs to effectively replace corals lost to localised disturbances.

It is reassuring there is at least some new coral recruitment in the aftermath of severe bleaching and mass mortality of adult corals on the GBR. However, the substantial and widespread reduction of regrowth indicates the magnitude of the disturbance caused by recent heatwaves.

Declines in rates of coral recruitment were greatest in the northern parts of the GBR. This is where bleaching was most pronounced in 2016 and 2017, and there was the greatest loss of adult corals. There were much more moderate declines in coral recruitment in the southern GBR, reflecting generally higher abundance of adults corals in these areas. However, prevailing southerly currents (and the large distances involved) make it very unlikely coral larvae from southern parts of the Reef will drift naturally to the hardest-hit northern areas.

It is hard to say how long it will take for coral assemblages to recover from the recent mass bleaching. What is certain is low levels of coral recruitment will constrain coral recovery and greatly increase the recovery time. Any further large-scale developments with also greatly reduce coral cover and impede recovery.




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Reducing carbon emissions

This study further highlights the vulnerability of coral reefs to sustained and ongoing global warming. Not only do adult corals bleach and die when exposed to elevated temperatures, this prevents new coral recruitment and undermines ecosystem resilience.

The only way to effectively redress global warming is to immediately and substantially reduce global carbon emissions. This requires that all countries, including Australia, renew and strengthen their commitments to the Paris Agreement on climate change.

While further management is required to minimise more direct human pressure on coral reefs – such as sediment run-off and pollution – all these efforts will be futile if we do not address global climate change.The Conversation

Morgan Pratchett, Professor, ARC Centre of Excellence for Coral Reef Studies, James Cook University

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

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.

Suffering in the heat: the rise in marine heatwaves is harming ocean species



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Recent marine heatwaves have devastated crucial coastal habitats, including kelp forests, seagrass meadows and coral reefs.
Dan Smale, Author provided

Dan Smale, Marine Biological Association and Thomas Wernberg, University of Western Australia

In the midst of a raging heatwave, most people think of the ocean as a nice place to cool down. But heatwaves can strike in the ocean as well as on land. And when they do, marine organisms of all kinds – plankton, seaweed, corals, snails, fish, birds and mammals – also feel the wrath of soaring temperatures.

Our new research, published today in Nature Climate Change, makes abundantly clear the destructive force of marine heatwaves. We compared the effects on ecosystems of eight marine heatwaves from around the world, including four El Niño events (1982-83, 1986-87, 1991-92, 1997-98), three extreme heat events in the Mediterranean Sea (1999, 2003, 2006) and one in Western Australia in 2011. We found that these events can significantly damage the health of corals, kelps and seagrasses.

This is concerning, because these species form the foundation of many ecosystems, from the tropics to polar waters. Thousands of other species – not to mention a wealth of human activities – depend on them.

We identified southeastern Australia, southeast Asia, northwestern Africa, Europe and eastern Canada as the places where marine species are most at risk of extreme heat in the future.




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Marine heatwaves are defined as periods of five days or more during which ocean temperatures are unusually high, compared with the long-term average for any given place. Just like their counterparts on land, marine heatwaves have been getting more frequent, hotter and longer in recent decades. Globally, there were 54% more heatwave days per year between 1987 and 2016 than in 1925–54.

Although the heatwaves we studied varied widely in their maximum intensity and duration, we found that all of them had negative impacts on a broad range of different types of marine species.

Marine heatwaves in tropical regions have caused widespread coral bleaching.

Humans also depend on these species, either directly or indirectly, because they underpin a wealth of ecological goods and services. For example, many marine ecosystems support commercial and recreational fisheries, contribute to carbon storage and nutrient cycling, offer venues for tourism and recreation, or are culturally or scientifically significant.




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.

Marine heatwaves have had negative impacts on virtually all these “ecosystem services”. For example, seagrass meadows in the Mediterranean Sea, which store significant amounts of carbon, are harmed by extreme temperatures recorded during marine heatwaves. In the summers of both 2003 and 2006, marine heatwaves led to widespread seagrass deaths.




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The marine heatwaves off the west coast of Australia in 2011 and northeast America in 2012 led to dramatic changes in the regionally important abalone and lobster fisheries, respectively. Several marine heatwaves associated with El Niño events caused widespread coral bleaching with consequences for biodiversity, fisheries, coastal erosion and tourism.

Mass die-offs of finfish and shellfish have been recorded during marine heatwaves, with major consequences for regional fishing industries.

All evidence suggests that marine heatwaves are linked to human mediated climate change and will continue to intensify with ongoing global warming. The impacts can only be minimised by combining rapid, meaningful reductions in greenhouse emissions with a more adaptable and pragmatic approach to the management of marine ecosystems.The Conversation

Dan Smale, Research Fellow in Marine Ecology, Marine Biological Association and Thomas Wernberg, Associate professor, University of Western Australia

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