Marine life is fleeing the equator to cooler waters. History tells us this could trigger a mass extinction event

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Anthony Richardson, The University of Queensland; Chhaya Chaudhary, University of Auckland; David Schoeman, University of the Sunshine Coast, and Mark John Costello, University of AucklandThe tropical water at the equator is renowned for having the richest diversity of marine life on Earth, with vibrant coral reefs and large aggregations of tunas, sea turtles, manta rays and whale sharks. The number of marine species naturally tapers off as you head towards the poles.

Ecologists have assumed this global pattern has remained stable over recent centuries — until now. Our recent study found the ocean around the equator has already become too hot for many species to survive, and that global warming is responsible.

In other words, the global pattern is rapidly changing. And as species flee to cooler water towards the poles, it’s likely to have profound implications for marine ecosystems and human livelihoods. When the same thing happened 252 million years ago, 90% of all marine species died.

The bell curve is warping dangerously

This global pattern — where the number of species starts lower at the poles and peaks at the equator — results in a bell-shaped gradient of species richness. We looked at distribution records for nearly 50,000 marine species collected since 1955 and found a growing dip over time in this bell shape.

If you look at each line in this chart, you can see a slight dip in total species richness between 1955 and 1974. This deepens substantially in the following decades.
Anthony Richardson, Author provided

So, as our oceans warm, species have tracked their preferred temperatures by moving towards the poles. Although the warming at the equator of 0.6℃ over the past 50 years is relatively modest compared with warming at higher latitudes, tropical species have to move further to remain in their thermal niche compared with species elsewhere.

As ocean warming has accelerated over recent decades due to climate change, the dip around at the equator has deepened.

We predicted such a change five years ago using a modelling approach, and now we have observational evidence.

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For each of the 10 major groups of species we studied (including pelagic fish, reef fish and molluscs) that live in the water or on the seafloor, their richness either plateaued or declined slightly at latitudes with mean annual sea-surface temperatures above 20℃.

Today, species richness is greatest in the northern hemisphere in latitudes around 30°N (off southern China and Mexico) and in the south around 20°S (off northern Australia and southern Brazil).

The tropical water at the equator is renowned for having the richest diversity of marine life, including large aggregations of tuna fish.
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This has happened before

We shouldn’t be surprised global biodiversity has responded so rapidly to global warming. This has happened before, and with dramatic consequences.

252 million years ago…

At the end of the Permian geological period about 252 million years ago, global temperatures warmed by 10℃ over 30,000-60,000 years as a result of greenhouse gas emissions from volcano eruptions in Siberia.

A 2020 study of the fossils from that time shows the pronounced peak in biodiversity at the equator flattened and spread. During this mammoth rearranging of global biodiversity, 90% of all marine species were killed.

125,000 years ago…

A 2012 study showed that more recently, during the rapid warming around 125,000 years ago, there was a similar swift movement of reef corals away from the tropics, as documented in the fossil record. The result was a pattern similar to the one we describe, although there was no associated mass extinction.

Authors of the study suggested their results might foreshadow the effects of our current global warming, ominously warning there could be mass extinctions in the near future as species move into the subtropics, where they might struggle to compete and adapt.

Today…

During the last ice age, which ended around 15,000 years ago, the richness of forams (a type of hard-shelled, single-celled plankton) peaked at the equator and has been dropping there ever since. This is significant as plankton is a keystone species in the foodweb.

Our study shows that decline has accelerated in recent decades due to human-driven climate change.

The profound implications

Losing species in tropical ecosystems means ecological resilience to environmental changes is reduced, potentially compromising ecosystem persistence.

In subtropical ecosystems, species richness is increasing. This means there’ll be species invaders, novel predator-prey interactions, and new competitive relationships. For example, tropical fish moving into Sydney Harbour compete with temperate species for food and habitat.

This could result in ecosystem collapse — as was seen at the boundary between the Permian and Triassic periods — in which species go extinct and ecosystem services (such as food supplies) are permanently altered.

The changes we describe will also have profound implications for human livelihoods. For example, many tropical island nations depend on the revenue from tuna fishing fleets through the selling of licenses in their territorial waters. Highly mobile tuna species are likely to move rapidly toward the subtropics, potentially beyond sovereign waters of island nations.

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Similarly, many reef species important for artisanal fishers — and highly mobile megafauna such as whale sharks, manta rays and sea turtles that support tourism — are also likely to move toward the subtropics.

The movement of commercial and artisanal fish and marine megafauna could compromise the ability of tropical nations to meet the Sustainable Development Goals concerning zero hunger and marine life.

Is there anything we can do?

One pathway is laid out in the Paris Climate Accords and involves aggressively reducing our emissions. Other opportunities are also emerging that could help safeguard biodiversity and hopefully minimise the worst impacts of it shifting away from the equator.

Currently 2.7% of the ocean is conserved in fully or highly protected reserves. This is well short of the 10% target by 2020 under the UN Convention on Biological Diversity.

Manta rays and other marine megafauna leaving the equator will have a huge impact on tourism.
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But a group of 41 nations is pushing to set a new target of protecting 30% of the ocean by 2030.

This “30 by 30” target could ban seafloor mining and remove fishing in reserves that can destroy habitats and release as much carbon dioxide as global aviation. These measures would remove pressures on biodiversity and promote ecological resilience.

Designing climate-smart reserves could further protect biodiversity from future changes. For example, reserves for marine life could be placed in refugia where the climate will be stable over the foreseeable future.

We now have evidence that climate change is impacting the best-known and strongest global pattern in ecology. We should not delay actions to try to mitigate this.

This story is part of Oceans 21

Our series on the global ocean opened with five in-depth profiles. Look out for new articles on the state of our oceans in the lead-up to the UN’s next climate conference, COP26. The series is brought to you by The Conversation’s international network.

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Australia’s marine (un)protected areas: government zoning bias has left marine life in peril since 2012

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Anthony Richardson, Professor, The University of Queensland; Chhaya Chaudhary, , University of Auckland; David Schoeman, Professor of Global-Change Ecology, University of the Sunshine Coast, and Mark John Costello, Professor, University of Auckland

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

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Climate Change and a New Marine Silk Road

Marine protection falls short of the 2020 target to safeguard 10% of the world’s oceans. A UN treaty and lessons from Antarctica could help

John B. Weller, Author provided

Natasha Blaize Gardiner, University of Canterbury and Cassandra Brooks, University of Colorado Boulder

Two-thirds of the world’s oceans fall outside national jurisdictions – they belong to no one and everyone.

These international waters, known as the high seas, harbour a plethora of natural resources and millions of unique marine species.

But they are being damaged irretrievably. Research shows unsustainable fisheries are one of the greatest threats to marine biodiversity in the high seas.

According to a 2019 global assessment report on biodiversity and ecosystem services, 66% of the world’s oceans are experiencing detrimental and increasing cumulative impacts from human activities.

In the high seas, human activities are regulated by a patchwork of international legal agreements under the 1982 UN Convention on the Law of the Sea (UNCLOS). But this piecemeal approach is failing to safeguard the ecosystems we depend on.

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The world’s ocean is bearing the brunt of a changing climate. Explore its past and future in our new series

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Empty pledges

A decade ago, world leaders updated an earlier pledge to establish a network of marine protected areas (MPAs) with a mandate to protect 10% of the world’s oceans by 2020.

But MPAs cover only 7.66% of the ocean across the globe. Most protected sites are in national waters where it’s easy to implement and manage protection under the provision of a single country.

In the more remote areas of the high seas, only 1.18% of marine ecosystems have been gifted sanctuary.

The Southern Ocean accounts for a large portion of this meagre percentage, hosting two MPAs. The South Orkney Islands southern shelf MPA covers 94,000 square kilometres, while the Ross Sea region MPA stretches across more than 2 million square kilometres, making it the largest in the world.

Currently, the world’s largest marine protected area is in the Ross Sea region off Antarctica.
Natasha Gardiner, CC BY-ND

The Commission for the Conservation of Antarctic Marine Living Resources (CCAMLR) is responsible for this achievement. Unlike other international fisheries management bodies, the commission’s legal convention allows for the closing of marine areas for conservation purposes.

A comparable mandate for MPAs in other areas of the high seas has been nowhere in sight — until now.

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An ocean like no other: the Southern Ocean’s ecological richness and significance for global climate

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A new ocean treaty

In 2017, the UN started negotiations towards a new comprehensive international treaty for the high seas. The treaty aims to improve the conservation and sustainable use of marine organisms in areas beyond national jurisdiction. It would also implement a global legal mechanism to establish MPAs in international waters.

This innovative international agreement provides an opportunity to work across institutional boundaries towards comprehensive high seas governance and protection. It is crucial to use lessons drawn from existing high seas marine protection initiatives, such as those in the Southern Ocean, to inform the treaty’s development.

The final round of treaty negotiations is pending, delayed by the COVID-19 pandemic, and significant detail within the treaty’s draft text remains undeveloped and open for further debate.

Lessons from Southern Ocean management

CCAMLR comprises 26 member states (including the European Union) and meets annually to make conservation-based decisions by unanimous consensus. In 2002, the commission committed to establishing a representative network of MPAs in Antarctica in alignment with globally agreed targets for the world’s oceans.

The two established MPAs in the high seas are far from an ecologically representative network of protection. In October 2020, the commission continued negotiations for three additional MPAs, which would meet the 10% target for the Southern Ocean, if agreed.

But not a single proposal was agreed. For one of the proposals, the East Antarctic MPA, this marks the eighth year of failed negotiations.

Fisheries interests from a select few nations, combined with complex geopolitics, are thwarting progress towards marine protection in the Antarctic.

CCAMLR’s two established MPAs (in grey) are the South Orkney Islands southern shelf MPA and the Ross Sea region MPA. Three proposed MPAs (hashed) include the East Antarctic, Domain 1 and Weddell Sea proposals.
C. Brooks, CC BY-ND

CCAMLR’s progress towards its commitment for a representative MPA network may have ground to a halt, but the commission has gained invaluable knowledge about the challenges in establishing MPAs in international waters. CCAMLR has demonstrated that with an effective convention and legal framework, MPAs in the high seas are possible.

The commission understands the extent to which robust scientific information must inform MPA proposals and how to navigate inevitable trade-offs between conservation and economic interests. Such knowledge is important for the UN treaty process.

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Why are talks over an East Antarctic marine park still deadlocked?

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As the high seas treaty moves closer to adoption, it stands to outpace the commission regarding progress towards improved marine conservation. Already, researchers have identified high-priority areas for protection in the high seas, including in Antarctica.

Many species cross the Southern Ocean boundary into other regions. This makes it even more important for CCAMLR to integrate its management across regional fisheries organisations – and the new treaty could facilitate this engagement.

But the window of time is closing with only one round of negotiation left for the UN treaty. Research tells us Antarctic decision-makers need to use the opportunity to ensure the treaty supports marine protection commitments.

Stronger Antarctic leadership is urgently needed to safeguard the Southern Ocean — and beyond.

Natasha Blaize Gardiner, PhD Candidate, University of Canterbury and Cassandra Brooks, Assistant Professor Environmental Studies, University of Colorado Boulder

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

Study identifies nine research priorities to better understand NZ’s vast marine area

New Zealand’s coastline spans a distance greater than from the south pole to the north pole.
from http://www.shutterstock.com, CC BY-ND

Rebecca Jarvis, Auckland University of Technology and Tim Young, Auckland University of Technology

The islands of New Zealand are only the visible part of a much larger submerged continent, known as Te Riu a Māui or Zealandia. Most of New Zealand’s sovereign territory, around 96%, is under water – and this means that the health of the ocean is of paramount importance.

Most of the Zealandia continent is under water.
CC BY-SA

New Zealand’s marine and coastal environments have significant ecological, economic, cultural and social value, but they face many threats. Disjointed legislation and considerable knowledge gaps limit our ability to effectively manage marine resources.

With the UN decade of ocean science starting in 2021, it is essential that we meet the challenges ahead. To do so, we have asked the New Zealand marine science community to collectively identify the areas of research we should focus on.

Ten important science questions were identified within nine research areas. The full list of 90 questions can be found in the paper and policy brief, but these are the nine priority areas:

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No-take marine areas help fishers (and fish) far more than we thought

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1. Food from the ocean

Fisheries and aquaculture are vital sources of food, income and livelihoods, and it is crucial that we ensure these industries are sustainable. Our study has identified the need for new methods to minimise bycatch, mitigate environmental impacts and better understand the influence of commercial interests in fishers’ ability to adequately conserve and manage marine environments.

2. Biosecurity

The number of marine pests has increased by 10% since 2009, and questions remain around how we can best protect our natural and cultural marine heritage. Future directions include the development of new techniques to improve the early detection of invasive species, and new tools to identify where they came from, and when they arrived in New Zealand waters.

3. Climate change

Climate change already has wide ranging impacts on our coasts and oceans. We need research to better understand how climate change will affect different marine species, how food webs might respond to future change, and how ocean currents around New Zealand might be affected.

Climate change already affects marine species and food webs.
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4. Marine reserves and protected areas

Marine protected areas are widely recognised as important tools for marine conservation and fisheries management. But less than 1% of New Zealand’s waters is protected to date. Future directions include research to identify where and how we should be implementing more protected areas, whether different models (including protection of customary fisheries and temporary fishing closures) could be as effective, and how we might integrate New Zealand’s marine protection into a wider Pacific network.

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5. Ecosystems and biodiversity

While we know about 15,000 marine species, there may be as many as 65,000 in New Zealand. On average, seven new species are identified every two weeks, and there is much we do not know about our oceans. We need research to understand how we can best identify the current baseline of biodiversity across New Zealand’s different marine habitats, predict marine tipping points and restore degraded ocean floor habitats.

6. Policy and decision making

New Zealand’s policy landscape is complicated, at times contradictory, and we need an approach to marine management that better connects science, decision making and action. We also need to understand how to navigate power in decision making across diverse interests to advance an integrated ocean policy.

7. Marine guardianship

Marine guardianship, or kaitiakitanga, means individual and collective stewardship to protect the environment, while safeguarding marine resources for future generations. Our research found that citizen science can help maximise observations of change and connect New Zealanders with their marine heritage. It can also improve our understanding of how we can achieve a partnership between Western and indigenous science, mātauranga Māori.

8. Coastal and ocean processes

New Zealand’s coasts span a distance greater than from the south pole to the north pole. Erosion and deposition of land-based sediments into our seas has many impacts and affects ocean productivity, habitat structure, nutrient cycling and the composition of the seabed.

Future research should focus on how increased sedimentation affects the behaviour and survival of species at offshore sites and on better methods to measure physical, chemical and biological processes with higher accuracy to understand how long-term changes in the ocean might influence New Zealand’s marine ecosystems.

9. Other anthropogenic factors

Our study identified a range of other human threats that need more focused investigation, including agriculture, forestry mining and urban development.
We need more research into the relative effects of different land-use types on coastal water quality to establishing the combined effects of multiple contaminants (pesticides, pharmaceuticals, etc) on marine organisms and ecosystems. Pollution with microplastics and other marine debris is another major issue.

We hope this horizon scan will drive the development of new research areas, complement ongoing science initiatives, encourage collaboration and guide interdisciplinary teams. The questions the New Zealand marine science community identified as most important will help us fill existing knowledge gaps and make greater contributions to marine science, conservation, sustainable use, policy and management.

Rebecca Jarvis, Research Fellow, Auckland University of Technology and Tim Young, Marine Scientist, Auckland University of Technology

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

Drilling for oil in the Great Australian Bight would be disastrous for marine life and the local community

A recent poll showed seven out of ten South Australian voters are against drilling in the Great Australian Bight.
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Sarah Duffy, Western Sydney University and Christopher Wright, University of Sydney

The Great Australian Bight is home to a unique array of marine life. More than 85% of species in this remote stretch of rocky coastline are not found anywhere else in the world. It’s also potentially one of “Australia’s largest untapped oil reserves”, according to Norwegian energy company Equinor.

Equinor has proposed to drill a deepwater oil well 370km offshore to a depth of more than two kilometres in search of oil.

But a recent poll showed seven out of ten South Australian voters are against drilling in the Bight. And hundreds of people recently gathered on an Adelaide beach in protest.

Their main concerns include the lack of economic benefits for local communities, more fossil fuel investment, weak regulation and the potential for an oil spill, devastating our “Great Southern Reef”.

Drilling in the Great Australian Bight has occurred since the 1960s, but never as deep as what Equinor has proposed.

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The Coalition government argues the project will improve energy security and bring money and jobs to the region. Labor announced recently that, if elected, it would commission a study on the consequences of a spill in the region.

So what’s the worst that could happen?

As discussed in a Sydney Environment Institute workshop in April, drilling in the Bight would have disastrous environment and economic implications.

A spill could leak between 4.3 million barrels and 7.9 million barrels – the largest oil spill in history, according to estimates from the 2016 Worst Credible Discharge report, authored by Equinor and its former joint-venture partner, BP.

The Bight is a wild place, with violent storms and strong winds and waves. The geography is remote, unmonitored, largely unpopulated and lacks physical infrastructure to respond effectively to an oil spill.

In such an event, Equinor has said it would take 17 days to respond in a best-case scenario. The worst-case scenario is 39 days, and the goal scenario is 26 days.

In modelling for the worst-case scenario, the company predicts the oil from a spill could even reach from Albany in Western Australia to Port Macquarie in New South Wales.

How likely is an oil spill?

Reports from Norwegian regulators, compiled by Greenpeace, reveal Equinor had more than 50 safety and control breaches, including ten oil leaks, in the last three-and-a-half years. Each incident occurred in regulatory environments with stricter conditions than in Australia.

Our independent regulator, NOPSEMA, does not require inspections of wells during construction to ensure they meet safety standards.

This can be disastrous. For instance, the failure to properly construct the Montara Well in the North West Shelf caused the worst oil spill in Australian history.

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The missing stories from Montara oil spill media coverage

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NOPSEMA does not have a set standard for well control. This is a risky proposition because in recent years three of the four major international oil spills from well blowouts occurred in exploration wells, the kind planned for the Bight.

And Greenpeace has questioned the independence of NOPSEMA after it was revealed the regulator will speak at an event promoting oil exploration in the Great Australian Bight.

Adding billions to the GDP, but there’s a catch

The Great Australian Bight boasts more marine diversity than the Great Barrier Reef and attracts more than 8 million visitors a year.

Equinor’s proposed project risks local fishing and tourism industries that rely on a pristine natural environment and contribute $10 billion a year to our economy, twice as much as the Great Barrier Reef.

The Great Australian Bight is home to at least 14 schools of bottlenose dolphins.
Shutterstock

A 2018 ACIL Allen report on the economic impact of drilling in the Great Australian Bight suggested Australia’s GDP could gain A$5.9 billion a year if the region turns out to be a major oil field.

But the catch is that this would require 101 oil wells to be successfully drilled, and many of the expected benefits wouldn’t be realised until between 2040 and 2060. What’s more, this windfall wouldn’t reach the pockets of locals, but would largely land in federal government coffers via the Petroleum Resource Rent Tax.

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These predictions are based on optimistic estimates of oil prices, and the report assumes our oil demand will remain on an upwards trajectory, which would mean we breach the Paris targets by a significant margin.

Worryingly, Equinor’s former partner in this venture, energy giant BP, even tried to claim an oil spill would benefit the local economy, and said:

In most instances, the increased activity associated with cleanup operations will be a welcome boost to local economies.

There is little evidence to support the argument that this drilling will lead to better energy security.

Given Australia doesn’t have the capacity to refine oil domestically, it’s likely most, if not all, of the oil extracted would be processed overseas.

From a security point of view, far more impact would come from reducing our reliance on oil through better vehicle emission standards and promoting a system-wide shift to electric vehicles.

No real benefit to the community

The Great Australian Bight is home to Australia’s most productive fishery, which directly employs 3,900 locals. An oil spill would threaten 9,000 jobs in South Australia alone.

By comparison, Equinor claim that the construction phase of the project would create 1,361 jobs, most of which require experience that would not be found in local communities. For instance, fly-in fly-out workers from Adelaide would take ongoing jobs on the rigs.

Equinor has had more than 50 safety and control breaches in the last three-and-a-half years, occurring in stricter regulatory environments than in Australia.
Shutterstock

Equinor has already completed seismic testing, which involves firing soundwaves into the ocean floor to detect the presence of oil and gas. The testing alone has pushed schools of tuna further out to sea, increasing costs and risks for local fisherman.

You decide, is it worth it?

Decisions over resource projects with significant environmental impacts need to be based on a thorough cost-benefit analysis and include the precautionary principle.

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The economic advantage to either local communities or the Australian public from this proposal is in doubt. And Australians are entitled to ask their politicians why so little is demanded of these organisations.

In the lead-up to a critical federal election, we are left to ask why our political leaders are doubling down on a fossil fuel bet with no clear advantages and a significant downside risk.

Sarah Duffy, Lecturer, School of Business, Western Sydney University and Christopher Wright, Professor of Organisational Studies, University of Sydney

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

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 getting hotter, lasting longer and doing more damage

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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.

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.

Plastic and Marine Life

The link below is to an article reporting on how plastic is leading to reproductive problems for marine wildlife.

For more visit:
https://www.theguardian.com/environment/2019/feb/27/plastics-leading-to-reproductive-problems-for-wildlife

Shark Bay: A World Heritage Site at catastrophic risk

Shark Bay was hit by a brutal marine heatwave in 2011.
W. Bulach/Wikimedia Commons, CC BY-SA

Matthew Fraser, University of Western Australia; Ana Sequeira, University of Western Australia; Brendan Paul Burns, UNSW; Diana Walker, University of Western Australia; Jon C. Day, James Cook University, and Scott Heron, James Cook University

The devastating bleaching on the Great Barrier Reef in 2016 and 2017 rightly captured the world’s attention. But what’s less widely known is that another World Heritage-listed marine ecosystem in Australia, Shark Bay, was also recently devastated by extreme temperatures, when a brutal marine heatwave struck off Western Australia in 2011.

A 2018 workshop convened by the Shark Bay World Heritage Advisory Committee classified Shark Bay as being in the highest category of vulnerability to future climate change. And yet relatively little media attention and research funding has been paid to this World Heritage Site that is on the precipice.

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Shark Bay stromatolites at risk from climate change

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Shark Bay.
Openstreetmap.org/Wikimedia Commons, CC BY-SA

Shark Bay, in WA’s Gascoyne region, is one of 49 marine World Heritage Sites globally, but one of only four of these sites that meets all four natural criteria for World Heritage listing. The marine ecosystem supports the local economy through tourism and fisheries benefits.

Around 100,000 tourists visit Shark Bay each year to interact with turtles, dugongs and dolphins, or to visit the world’s most extensive population of stromatolites – stump-shaped colonies of microbes that date back billions of years, almost to the dawn of life on Earth.

Commercial and recreational fishing is also extremely important for the local economy. The combined Shark Bay invertebrate fishery (crabs, prawns and scallops) is the second most valuable commercial fishery in Western Australia.

Under threat

However, this iconic and valuable marine ecosystem is under serious threat. Shark Bay is especially vulnerable to future climate change, given that the temperate seagrass that underpins the entire ecosystem is already living at the upper edge of its tolerable temperature range. These seagrasses provide vital habitat for fish and marine mammals, and help the stromatolites survive by regulating the water salinity.

Stromatolites are a living window to the past.
Matthew Fraser

Shark Bay received the highest rating of vulnerability using the recently developed Climate Change Vulnerability Index, created to provide a method for assessing climate change impacts across all World Heritage Sites.

In particular, extreme marine heat events were classified as very likely and predicted to have catastrophic consequences in Shark Bay. By contrast, the capacity to adapt to marine heat events was rated very low, showing the challenges Shark Bay faces in the coming decades.

The region is also threatened by increasingly frequent and intense storms, and warming air temperatures.

To understand the potential impacts of climatic change on Shark Bay, we can look back to the effects of the most recent marine heatwave in the area. In 2011 Shark Bay was hit by a catastrophic marine heatwave that destroyed 900 square kilometres of seagrass – 36% of the total coverage.

This in turn harmed endangered species such as turtles, contributed to the temporary closure of the commercial crab and scallop fisheries, and released between 2 million and 9 million tonnes of carbon dioxide – equivalent to the annual emissions from 800,000 homes.

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Read more:
Climate change threatens Western Australia’s iconic Shark Bay

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Some aspects of Shark Bay’s ecosystem have never been the same since. Many areas previously covered with large, temperate seagrasses are now bare, or have been colonised by small, tropical seagrasses, which do not provide the same habitat for animals. This mirrors the transition seen on bleached coral reefs, which are taken over by turf algae. We may be witnessing the beginning of Shark Bay’s transition from a sub-tropical to a tropical marine ecosystem.

This shift would jeopardise Shark Bay’s World Heritage values. Although stromatolites have survived for almost the entire history of life on Earth, they are still vulnerable to rapid environmental change. Monitoring changes in the microbial makeup of these communities could even serve as a canary in the coalmine for global ecosystem changes.

The neglected bay?

Despite Shark Bay’s significance, and the seriousness of the threats it faces, it has received less media and funding attention than many other high-profile Australian ecosystems. Since 2011, the Australian Research Council has funded 115 research projects on the Great Barrier Reef, and just nine for Shark Bay.

Coral reefs rightly receive a lot of attention, particularly given the growing appreciation that climate change threatens the Great Barrier Reef and other corals around the world.

The World Heritage Committee has recognised that local efforts alone are no longer enough to save coral reefs, but this logic can be extended to other vulnerable marine ecosystems – including the World Heritage values of Shark Bay.

Safeguarding Shark Bay from climate change requires a coordinated research and management effort from government, local industry, academic institutions, not-for-profits and local Indigenous groups – before any irreversible ecosystem tipping points are reached. The need for such a strategic effort was obvious as long ago as the 2011 heatwave, but it hasn’t happened yet.

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Marine heatwaves are getting hotter, lasting longer and doing more damage

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Due to the significant Aboriginal heritage in Shark Bay, including three language groups (Malgana, Nhanda and Yingkarta), it will be vital to incorporate Indigenous knowledge, so as to understand the potential social impacts.

And of course, any on-the-ground actions to protect Shark Bay need to be accompanied by dramatic reductions in greenhouse emissions. Without this, Shark Bay will be one of the many marine ecosystems to fundamentally change within our lifetimes.

Matthew Fraser, Postdoctoral Research Fellow, University of Western Australia; Ana Sequeira, ARC DECRA Fellow, University of Western Australia; Brendan Paul Burns, Senior Lecturer, UNSW; Diana Walker, Emeritus Professor, University of Western Australia; Jon C. Day, PSM, Post-career PhD candidate, ARC Centre of Excellence for Coral Reef Studies, James Cook University, and Scott Heron, Senior Lecturer, James Cook University

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

Coastal seas around New Zealand are heading into a marine heatwave, again

This summer, coastal seas to the north and east of New Zealand are even warmer than during last year’s marine heat wave.
from http://www.shutterstock.com, CC BY-ND

Craig Stevens, National Institute of Water and Atmospheric Research and Ben Noll, National Institute of Water and Atmospheric Research

As New Zealanders are enjoying their days at the beach, unusually warm ocean temperatures look to be a harbinger of another marine heatwave.

Despite the exceptional conditions during last year’s heatwave in the Tasman Sea, this summer’s sea surface temperatures to the north and east of New Zealand are even warmer.

The latest NIWA climate assessment shows that sea surface temperatures in coastal waters around New Zealand are well above average. Marine heatwave conditions are already occurring in parts of the Tasman Sea and the ocean around New Zealand and looking to become the new normal.

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Marine heatwaves are getting hotter, lasting longer and doing more damage

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Changing sea surface temperature anomalies (conditions compared to average) in the oceans around New Zealand during the first two weeks of January – comparing 2009 to 2019. Source: NIWA

What’s in a name

Currently, marine heatwaves are defined as periods that last for five or more days with temperatures warmer than the 90th percentile based on a 30-year historical baseline. Given we are likely to experience many more such events as the oceans continue to warm, it is time to understand and categorise the intensity of marine heat.

The names Hurricane Katrina, tropical cyclone Giselle (which sank the ferry Wahine 50 years ago), tropical cyclone Winston give a malevolent personality to geophysical phenomena. Importantly they get graded into categories, so we can rapidly assess their potential impact.

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Winston strikes Fiji: your guide to cyclone science

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An Australian team has developed a classification scheme for marine heatwaves. The team used an approach similar to that used for hurricanes and cyclones – changing conditions can be slotted into to a sequence of categories. At the moment it looks like we are in marine heat wave category one conditions, but potentially entering category two if it continues to warm.

Turning the heat up on marine life

A marine heatwave is potentially devastating for marine ecosystems. It is also an indication that the hidden buffer in the climate system – the fact that the oceans have absorbed 93% of the excess heat – is starting to change. Individual warm seasons have always occurred, but in future there will be more of them and they will keep getting warmer.

The Great Barrier Reef has already been hit hard by a succession of marine heatwave events, bleaching the iconic corals and changing the structure of the ecosystem it supports.

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The 2016 Great Barrier Reef heatwave caused widespread changes to fish populations

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Further south, off Tasmania’s east coast, a number of species that normally occur in tropical waters have extended their range further south. A number of fish species, lobster and octopus species have also taken up residence along the Tasmanian coast, displacing some of the species that call this coast home. Mobile species can escape the warmer temperatures, but sedentary plants and animals are hardest hit.

In New Zealand, aquaculture industries will find it more difficult to grow fish or mussels as coastal waters continue to warm. If the same trends seen off Tasmania occur here, areas with substantial kelp canopies will struggle and start to be replaced by species normally seen further north. But the impacts will likely be very variable because the warming will be heavily influenced by wind and ocean currents and different locations will feel changes to a greater or lesser extent.

NIWA’s research vessel Kaharoa has deployed Argo floats in the Southern Ocean and in waters around New Zealand.
NIWA, CC BY-ND

Predicting the seasons

As important as it is to identify a marine heatwave at the time, reliable predictions of developing conditions would help fishers, aquaculture companies and local authorities – and in fact anyone living and working around the ocean.

Seasonal forecasting a few months ahead is difficult. It falls between weather and climate predictions. In a collaboration between the National Institute of Water and Atmospheric Research and the Australian Bureau of Meteorology, we are examining how well long-term forecasts of ocean conditions around New Zealand stack up. Early forecasts suggested this summer would not be as warm as last year. But it now looks like this summer will again be very warm in the ocean.

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Read more:
This summer’s sea temperatures were the hottest on record for Australia: here’s why

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One of the important points to keep in mind is that when we are at the beach, we are sampling only the surface temperature. The same is true of satellites – they monitor less than the top millimetre of the ocean.

Sea surface temperatures are several degrees above normal at the moment. But in deeper waters, because of the high heat content of water, even a tenth of a degree is significant. Temperature in the deeper ocean is monitored by a network of moored buoys on and off the continental shelf along the Australian coast. New Zealand has almost nothing that would be comparable.

Measuring temperature in real time

What we can look to, in the absence of moored buoys, is a fleet of ocean robots that monitor temperature in real time. Argo floats drift with ocean currents, sink to two kilometres every ten days and then collect data as they return to the surface.

These data allowed us to identify that the 2017/18 marine heatwave around New Zealand remained shallow. Most of the warmer water was in the upper 30 metres. Looking at the present summer conditions, one Argo robot off New Zealand’s west coast shows it is almost four degrees above normal in the upper 40 metres of the ocean. On the east coast, near the Chatham Islands, another float shows warmed layers to 20 metres deep. To the south, the warming goes deeper, down to almost 80 metres.

Our work using the Australian Bureau of Meteorology forecast model highlights how variable the ocean around New Zealand is. Different issues emerge in different regions, even if they are geographically close.

The research on categories of marine heatwaves shows we will have to keep shifting what we regard as a heat wave as the ocean continues to warm. None of this should come as a surprise. We have known for some time that the world’s oceans are storing most of the additional heat and the impacts of a warming ocean will be serious.

Craig Stevens, Associate Professor in Ocean Physics, National Institute of Water and Atmospheric Research and Ben Noll, Meteorologist/forecaster, National Institute of Water and Atmospheric Research

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

Desal plants might do less damage to marine environments than we thought

Some sea creatures are displaced by the desalination plant, but others actually grow.
Supplied

Graeme Clark, UNSW and Emma Johnston, UNSW

Millions of people all over the world rely on desalinated water. Closer to home, Australia has desalination plants in Melbourne, Adelaide, Perth, the Gold Coast, and many remote and regional locations.

But despite the growing size and number of desalination plants, the environmental impacts are little understood. Our six-year study, published recently in the journal Water Research, looked at the health the marine environment before, during and after the Sydney Desalination Plant was operating.

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Read more:
Fixing cities’ water crises could send our climate targets down the gurgler

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Our research tested the effect of pumping and “diffusing” highly concentrated salt water (a byproduct of desalination) back into the ocean.

Contrary to our expectation that high salt levels would impact sea creatures, we found that ecological changes were largely confined to an area within 100m of the discharge point, and reduced shortly after the plant was turned off. We also found the changes were likely a result of strong currents created by the outfall jets, rather than high salinity.

Desalination is growing

We examined six underwater locations at about 25m depth over a six-year period during which the plant was under construction, then operating, and then idle. This let us rigorously monitor impacts to and recovery of marine life from the effects of pumping large volumes of hypersaline water back into the ocean. We tested for impacts and recovery at two distances (30m and 100m) from the outfall.

This study provides the first before-and-after test of ecological impacts of desalination brine on marine communities, and a rare insight into mechanisms behind the potential impacts of a growing form of human disturbance.

About 1% of the world’s population now depends on desalinated water for daily use, supplied by almost 20,000 desalination plants that produce more than 90 million cubic meters of water per day.

Increasingly frequent and severe water shortages are projected to accelerate the growth in desalination around the world. By 2025, more than 2.8 billion people in 48 countries are likely to experience water scarcity, with desalination expected to become an increasingly crucial water source for many coastal populations.

Effect of the diffusers

The diffusers that pump concentrated salt water into the ocean at a high velocity (to increase dilution) are so effective that salinity was almost at background levels within 100m of the outfall. However, the diffusion process increased the speed of currents close to the outfall.

This strong current affects species differently, depending on how they settle and feed. Marine species with strong swimming larvae, such as barnacles, can easily settle in high flow and then benefit from faster delivery of food particles. These animals increased in number and size near the outfall. In contrast, species with slow swimming larvae, such as tubeworms, lace corals and sponges, prefer settling and feeding in low current and became less abundant near the outfall.

Therefore, the high-pressure diffusers designed to reduce hypersalinity may have inadvertently caused impacts due to flow. However, these ecological changes may be less concerning than those caused by hypersalinity, as the currents were still within the range that marine communities experience naturally.

Our findings are important, because as drought conditions around the nation worsen and domestic water supplies are coming under strain, desalination is starting to ramp up in eastern and southern Australia.

For instance, water levels at Sydney’s primary dam at Warragamba have dropped to around 65% and the desalination plant is contracted to start supplying drinking water back into the system when dam levels fall below 60%. This plant can potentially double in capacity if needed.

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Read more:
Melbourne’s desalination plant is just one part of drought-proofing water supply

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There is a rapid expansion of the use of desalination, with global capacity increasing by 57% between 2008 and 2013. Our results will help designers and researchers in this area ensure desalination plants minimise their effect on local coastal systems.

Graeme Clark, Senior Research Associate in Ecology, UNSW and Emma Johnston, Professor and Dean of Science, UNSW

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