Like the ocean’s ‘gut flora’: we sailed from Antarctica to the equator to learn how bacteria affect ocean health


Shutterstock

Eric Jorden Raes, Dalhousie UniversityAboard an Australian research vessel, the RV Investigator, we sailed for 63 days from Antarctica’s ice edge to the warm equator in the South Pacific and collected 387 water samples.

Our goal? To determine how the genetic code of thousands of different micro-organisms can provide insights into the ocean’s functional diversity — the range of tasks performed by bacteria in the ocean.

Our research was published yesterday in Nature Communications. It showed how bacteria can help us measure shifts in energy production at the base of the food web. These results are important, as they highlight an emerging opportunity to use genetic data for large-scale ecosystem assessments in different marine environments.

In light of our rapidly changing climate, this kind of information is critical, as it will allow us to unpack the complexity of nature step by step. Ultimately, it will help us mitigate human pressures to protect and restore our precious marine ecosystems.

Why should we care about marine bacteria?

The oceans cover 71% of our planet and sustain life on Earth. In the upper 100 meters, the sunlit part of the oceans, microscopic life is abundant. In fact, it’s responsible for producing up to 50% of all the oxygen in the world.

A whale breaches the ocean
Marine bacteria provide the energy and food for the entire marine food web, from tiny crustaceans to whales.
Shutterstock

Much like the link recently established between human health and the human microbiome (“gut flora”), ocean health is largely controlled by its bacterial inhabitants.

But the role of bacteria go beyond oxygen production. Bacteria sustain, inject and control the fluxes of energy, nutrients and organic matter in our oceans. They provide the energy and food for the entire marine food web, from tiny crustaceans to fish larvae, whales and the fish we eat.

These micro-organisms also execute key roles in numerous biogeochemical cycles (the carbon, nitrogen, phosphorus, sulphur and iron cycles, to name a few).

So, it’s important to quantify their various tasks and understand how the different bacterial species and their functions respond to environmental changes.

Fundamental questions

Global ocean research initiatives — such as GO-SHIP and GEOTRACES — have been measuring the state of oceans in expeditions like ours for decades. They survey temperature, salinity, nutrients, trace metals (iron, cobalt and more) and other essential ocean variables.

Only recently, however, have these programs begun measuring biological variables, such as bacterial gene data, in their global sampling expeditions.

The author smiles in front of a blue and white ship, with 'Investigator' written on the side.
On board the RV Investigator, we departed Hobart in 2016, beginning our 63-day journey to sample microbes in the South Pacific.
Eric Raes, Author provided

Including bacterial gene data to measure the state of the ocean means we can try to fill critical knowledge gaps about how the diversity of bacteria impacts their various tasks. One hypothesis is whether a greater diversity of bacteria leads to a better resilience in an ecosystem, allowing it to withstand the effects of climate change.

In our paper, we addressed a fundamental question in this global field of marine microbial ecology: what is the relationship between bacterial identity and function? In other words, who is doing what?

What we found

We showed it’s possible to link the genetic code of marine bacteria to the various functions and tasks they execute, and to quantify how these functions changed from Antarctica to the equator.

The functions that changed include taking in carbon dioxide from the atmosphere, bacterial growth, strategies to cope with limited nutrients, and breaking down organic matter.




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


Another key finding is that “oceanographic fronts” can act as boundaries within a seemingly uniform ocean, resulting in unique assemblages of bacteria with specific tasks. Oceanographic fronts are distinct water masses defined by, for instance, sharp changes in temperature and salinity. Where the waters meet and mix, there’s high turbulence.

The change we recorded in energy production across the subtropical front, which separates the colder waters from the Southern Ocean from the warmer waters in the tropics, was a clear example of how oceanographic fronts influenced bacterial functions in the ocean.

Dark blue water meets light blue water under a cloudy sky.
An oceanographic front, where it looks like two oceans meet.
Shutterstock

Tracking changes in our ecosystems

As a result of our research, scientists may start using the functional diversity of bacteria as an indicator to track changes in our ecosystems, like canaries in a coal mine.




Read more:
Half of global methane emissions come from aquatic ecosystems – much of this is human-made


So the functional diversity of bacteria can be used to measure how human growth and urbanisation impact coastal areas and estuaries.

For example, we can more accurately and holistically measure the environmental footprint of aquaculture pens, which are known to affect water quality by increasing concentrations of nutrients such as carbon, nitrogen and phosphorus – all favourite elements utilised by bacteria.

Likewise, we can track changes in the environmental services rendered by estuaries, such as their important role in removing excessive nitrogen that enters the waterways due to agriculture run-off and urban waste.

With 44% of the world’s population living along coastlines, the input of nitrogen to marine ecosystems, including estuaries, is predicted to increase, putting a strain on the marine life there.

Ultimately, interrogating the bacterial diversity using gene data, along with the opportunity to predict what this microscopic life is or will be doing in future, will help us better understand nature’s complex interactions that sustain life in our oceans.




Read more:
Humans are polluting the environment with antibiotic-resistant bacteria, and I’m finding them everywhere


The Conversation


Eric Jorden Raes, Postdoctoral researcher Ocean Frontier Institute, Dalhousie University

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

Think all your plastic is being recycled? New research shows it can end up in the ocean


Shutterstock

Monique Retamal, University of Technology Sydney; Elsa Dominish, University of Technology Sydney; Nick Florin, University of Technology Sydney, and Rachael Wakefield-Rann, University of Technology Sydney

We all know it’s wrong to toss your rubbish into the ocean or another natural place. But it might surprise you to learn some plastic waste ends up in the environment, even when we thought it was being recycled.

Our study, published today, investigated how the global plastic waste trade contributes to marine pollution.

We found plastic waste most commonly leaks into the environment at the country to which it’s shipped. Plastics which are of low value to recyclers, such as lids and polystyrene foam containers, are most likely to end up polluting the environment.

The export of unsorted plastic waste from Australia is being phased out – and this will help address the problem. But there’s a long way to go before our plastic is recycled in a way that does not harm nature.

Man puts items in bins
Research shows plastic meant for recycling often ends up elsewhere.
Shutterstock

Know your plastics

Plastic waste collected for recycling is often sold for reprocessing in Asia. There, the plastics are sorted, washed, chopped, melted and turned into flakes or pellets. These can be sold to manufacturers to create new products.

The global recycled plastics market is dominated by two major plastic types:

  • polyethylene terephthalate (PET), which in 2017 comprised 55% of the recyclable plastics market. It’s used in beverage bottles and takeaway food containers and features a “1” on the packaging

  • high-density polyethylene (HDPE), which comprises about 33% of the recyclable plastics market. HDPE is used to create pipes and packaging such as milk and shampoo bottles, and is identified by a “2”.

The next two most commonly traded types of plastics, each with 4% of the market, are:

  • polypropylene or “5”, used in containers for yoghurt and spreads

  • low-density polyethylene known as “4”, used in clear plastic films on packaging.

The remaining plastic types comprise polyvinyl chloride (3), polystyrene (6), other mixed plastics (7), unmarked plastics and “composites”. Composite plastic packaging is made from several materials not easily separated, such as long-life milk containers with layers of foil, plastic and paper.

This final group of plastics is not generally sought after as a raw material in manufacturing, so has little value to recyclers.




Read more:
China’s recycling ‘ban’ throws Australia into a very messy waste crisis


Symbols on PET plastic item
Items made from PET plastic resin are marked with a ‘1’.
Shutterstock

Shifting plastic tides

China banned the import of plastic waste in January 2018 to prevent the receipt of low-value plastics and to stimulate the domestic recycling industry.

Following the bans, the global plastic waste trade shifted towards Southeast Asian nations such as Vietnam, Thailand, Malaysia, and Indonesia. The largest exporters of waste plastics in 2019 were Europe, Japan and the US. Australia exported plastics primarily to Malaysia and Indonesia.

Australia’s waste export ban recently became law. From July this year, only plastics sorted into single resin types can be exported; mixed plastic bales cannot. From July next year, plastics must be sorted, cleaned and turned into flakes or pellets to be exported.

This may help address the problem of recyclables becoming marine pollution. But it will require a significant expansion of Australian plastic reprocessing capacity.

Map showing the import and export map of plastic waste globally.
Map showing the import and export map of plastic waste globally.
Authors provided

What we found

Our study was funded by the federal Department of Agriculture, Water and the Environment. It involved interviews with trade experts, consultants, academics, NGOs and recyclers (in Australia, India, Indonesia, Japan, Malaysia, Vietnam and Thailand) and an extensive review of existing research.

We found when it comes to the international plastic trade, plastics most often leak into the environment at the destination country, rather than at the country of origin or in transit. Low-value or “residual” plastics – those left over after more valuable plastic is recovered for recycling – are most likely to end up as pollution. So how does this happen?

In Southeast Asia, often only registered recyclers are allowed to import plastic waste. But due to high volumes, registered recyclers typically on-sell plastic bales to informal processors.

Interviewees said when plastic types were considered low value, informal processors frequently dumped them at uncontrolled landfills or into waterways. Sometimes the waste is burned.

Plastics stockpiled outdoors can be blown into the environment, including the ocean. Burning the plastic releases toxic smoke, causing harm to human health and the environment.

Interviewees also said when informal processing facilities wash plastics, small pieces end up in wastewater, which is discharged directly into waterways, and ultimately, the ocean.

However, interviewees from Southeast Asia said their own domestic waste management was a greater source of ocean pollution.

Birds fly over landfill site
Plastic waste meant for recycling can end up in overseas landfill, before it blows into the ocean.
Anupam Nath/AP

A market failure

The price of many recycled plastics has crashed in recent years due to oversupply, import restrictions and falling oil prices, (amplified by the COVID-19 pandemic). However clean bales of PET and HDPE are still in demand.

In Australia, material recovery facilities currently sort PET and HDPE into separate bales. But small contaminants of other materials (such as caps and plastic labels) remain, making it harder to recycle into high quality new products.

Before the price of many recycled plastics dropped, Australia baled and traded all other resin types together as “mixed plastics”. But the price for mixed plastics has fallen to zero and they’re now largely stockpiled or landfilled in Australia.

Several Australian facilities are, however, investing in technology to sort polypropylene so it can be recovered for recycling.

Shampoo bottles in supermarket
High-density polyethylene items such as shampoo bottles comprise a large share of the plastic waste market.
Shutterstock

Doing plastics differently

Exporting countries can help reduce the flow of plastics to the ocean by better managing trade practices. This might include:

  • improving collection and sorting in export countries

  • checking destination processing and monitoring

  • checking plastic shipments at export and import

  • improving accountability for shipments.

But this won’t be enough. The complexities involved in the global recycling trade mean we must rethink packaging design. That means using fewer low-value plastic and composites, or better yet, replacing single-use plastic packaging with reusable options.


The authors would like to acknowledge research contributions from Asia Pacific Waste Consultants (APWC) – Dr Amardeep Wander, Jack Whelan and Anne Prince, as well as Phil Manners at CIE.




Read more:
Here’s what happens to our plastic recycling when it goes offshore


The Conversation


Monique Retamal, Research Principal, Institute for Sustainable Futures, University of Technology Sydney; Elsa Dominish, Senior Research Consultant, Institute for Sustainable Futures, University of Technology Sydney; Nick Florin, Research Director, Institute for Sustainable Futures, University of Technology Sydney, and Rachael Wakefield-Rann, Research Consultant, Institute for Sustainable Futures, University of Technology Sydney

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

Worried about Earth’s future? Well, the outlook is worse than even scientists can grasp



Daniel Mariuz/AAP

Corey J. A. Bradshaw, Flinders University; Daniel T. Blumstein, University of California, Los Angeles, and Paul Ehrlich, Stanford University

Anyone with even a passing interest in the global environment knows all is not well. But just how bad is the situation? Our new paper shows the outlook for life on Earth is more dire than is generally understood.

The research published today reviews more than 150 studies to produce a stark summary of the state of the natural world. We outline the likely future trends in biodiversity decline, mass extinction, climate disruption and planetary toxification. We clarify the gravity of the human predicament and provide a timely snapshot of the crises that must be addressed now.

The problems, all tied to human consumption and population growth, will almost certainly worsen over coming decades. The damage will be felt for centuries and threatens the survival of all species, including our own.

Our paper was authored by 17 leading scientists, including those from Flinders University, Stanford University and the University of California, Los Angeles. Our message might not be popular, and indeed is frightening. But scientists must be candid and accurate if humanity is to understand the enormity of the challenges we face.

Girl in breathing mask attached ot plant in container
Humanity must come to terms with the future we and future generations face.
Shutterstock

Getting to grips with the problem

First, we reviewed the extent to which experts grasp the scale of the threats to the biosphere and its lifeforms, including humanity. Alarmingly, the research shows future environmental conditions will be far more dangerous than experts currently believe.

This is largely because academics tend to specialise in one discipline, which means they’re in many cases unfamiliar with the complex system in which planetary-scale problems — and their potential solutions — exist.

What’s more, positive change can be impeded by governments rejecting or ignoring scientific advice, and ignorance of human behaviour by both technical experts and policymakers.

More broadly, the human optimism bias – thinking bad things are more likely to befall others than yourself – means many people underestimate the environmental crisis.

Numbers don’t lie

Our research also reviewed the current state of the global environment. While the problems are too numerous to cover in full here, they include:

  • a halving of vegetation biomass since the agricultural revolution around 11,000 years ago. Overall, humans have altered almost two-thirds of Earth’s land surface

  • About 1,300 documented species extinctions over the past 500 years, with many more unrecorded. More broadly, population sizes of animal species have declined by more than two-thirds over the last 50 years, suggesting more extinctions are imminent




Read more:
What is a ‘mass extinction’ and are we in one now?


  • about one million plant and animal species globally threatened with extinction. The combined mass of wild mammals today is less than one-quarter the mass before humans started colonising the planet. Insects are also disappearing rapidly in many regions

  • 85% of the global wetland area lost in 300 years, and more than 65% of the oceans compromised to some extent by humans

  • a halving of live coral cover on reefs in less than 200 years and a decrease in seagrass extent by 10% per decade over the last century. About 40% of kelp forests have declined in abundance, and the number of large predatory fishes is fewer than 30% of that a century ago.

State of the Earth's environment
Major environmental-change categories expressed as a percentage relative to intact baseline. Red indicates percentage of category damaged, lost or otherwise affected; blue indicates percentage intact, remaining or unaffected.
Frontiers in Conservation Science

A bad situation only getting worse

The human population has reached 7.8 billion – double what it was in 1970 – and is set to reach about 10 billion by 2050. More people equals more food insecurity, soil degradation, plastic pollution and biodiversity loss.

High population densities make pandemics more likely. They also drive overcrowding, unemployment, housing shortages and deteriorating infrastructure, and can spark conflicts leading to insurrections, terrorism, and war.




Read more:
Climate explained: why we need to focus on increased consumption as much as population growth


Essentially, humans have created an ecological Ponzi scheme. Consumption, as a percentage of Earth’s capacity to regenerate itself, has grown from 73% in 1960 to more than 170% today.

High-consuming countries like Australia, Canada and the US use multiple units of fossil-fuel energy to produce one energy unit of food. Energy consumption will therefore increase in the near future, especially as the global middle class grows.

Then there’s climate change. Humanity has already exceeded global warming of 1°C this century, and will almost assuredly exceed 1.5 °C between 2030 and 2052. Even if all nations party to the Paris Agreement ratify their commitments, warming would still reach between 2.6°C and 3.1°C by 2100.

people walking on a crowded street
The human population is set to reach 10 billion by 2050.
Shutterstock

The danger of political impotence

Our paper found global policymaking falls far short of addressing these existential threats. Securing Earth’s future requires prudent, long-term decisions. However this is impeded by short-term interests, and an economic system that concentrates wealth among a few individuals.

Right-wing populist leaders with anti-environment agendas are on the rise, and in many countries, environmental protest groups have been labelled “terrorists”. Environmentalism has become weaponised as a political ideology, rather than properly viewed as a universal mode of self-preservation.

Financed disinformation campaigns against climate action and forest protection, for example, protect short-term profits and claim meaningful environmental action is too costly – while ignoring the broader cost of not acting. By and large, it appears unlikely business investments will shift at sufficient scale to avoid environmental catastrophe.

Changing course

Fundamental change is required to avoid this ghastly future. Specifically, we and many others suggest:

  • abolishing the goal of perpetual economic growth

  • revealing the true cost of products and activities by forcing those who damage the environment to pay for its restoration, such as through carbon pricing

  • rapidly eliminating fossil fuels

  • regulating markets by curtailing monopolisation and limiting undue corporate influence on policy

  • reigning in corporate lobbying of political representatives

  • educating and empowering women across the globe, including giving them control over family planning.

A coal plant
The true cost of environmental damage should be borne by those responsible.
Shutterstock

Don’t look away

Many organisations and individuals are devoted to achieving these aims. However their messages have not sufficiently penetrated the policy, economic, political and academic realms to make much difference.

Failing to acknowledge the magnitude and gravity of problems facing humanity is not just naïve, it’s dangerous. And science has a big role to play here.

Scientists must not sugarcoat the overwhelming challenges ahead. Instead, they should tell it like it is. Anything else is at best misleading, and at worst potentially lethal for the human enterprise.




Read more:
Mass extinctions and climate change: why the speed of rising greenhouse gases matters


The Conversation


Corey J. A. Bradshaw, Matthew Flinders Professor of Global Ecology and Models Theme Leader for the ARC Centre of Excellence for Australian Biodiversity and Heritage, Flinders University; Daniel T. Blumstein, Professor in the Department of Ecology and Evolutionary Biology and the Institute of the Environment and Sustainability, University of California, Los Angeles, and Paul Ehrlich, President, Center for Conservation Biology, Bing Professor of Population Studies, Stanford University

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

Japan plans to dump a million tonnes of radioactive water into the Pacific. But Australia has nuclear waste problems, too


Tilman Ruff, University of Melbourne and Margaret Beavis

The Japanese government recently announced plans to release into the sea more than 1 million tonnes of radioactive water from the severely damaged Fukushima Daiichi nuclear plant.

The move has sparked global outrage, including from UN Special Rapporteur Baskut Tuncak who recently wrote,

I urge the Japanese government to think twice about its legacy: as a true champion of human rights and the environment, or not.

Alongside our Nobel Peace Prize-winning work promoting nuclear disarmament, we have worked for decades to minimise the health harms of nuclear technology, including site visits to Fukushima since 2011. We’ve concluded Japan’s plan is unsafe, and not based on evidence.

Japan isn’t the only country with a nuclear waste problem. The Australian government wants to send nuclear waste to a site in regional South Australia — a risky plan that has been widely criticised.

Contaminated water in leaking tanks

In 2011, a massive earthquake and tsunami resulted in the meltdown of four large nuclear reactors, and extensive damage to the reactor containment structures and the buildings which house them.

Water must be poured on top of the damaged reactors to keep them cool, but in the process, it becomes highly contaminated. Every day, 170 tonnes of highly contaminated water are added to storage on site.

As of last month, this totalled 1.23 million tonnes. Currently, this water is stored in more than 1,000 tanks, many hastily and poorly constructed, with a history of leaks.

How does radiation harm marine life?

If radioactive material leaks into the sea, ocean currents can disperse it widely. The radioactivity from Fukushima has already caused widespread contamination of fish caught off the coast, and was even detected in tuna caught off California.




Read more:
Four things you didn’t know about nuclear waste


Ionising radiation harms all organisms, causing genetic damage, developmental abnormalities, tumours and reduced fertility and fitness. For tens of kilometres along the coast from the damaged nuclear plant, the diversity and number of organisms have been depleted.

Of particular concern are long-lived radioisotopes (unstable chemical elements) and those which concentrate up the food chain, such as cesium-137 and strontium-90. This can lead to fish being thousands of times more radioactive than the water they swim in.

Failing attempts to de-contaminate the water

In recent years, a water purification system — known as advanced liquid processing — has been used to treat the contaminated water accumulating in Fukushima to try to reduce the 62 most important contaminating radioisotopes.

But it hasn’t been very effective. To date, 72% of the treated water exceeds the regulatory standards. Some treated water has been shown to be almost 20,000 times higher than what’s allowed.




Read more:
The cherry trees of Fukushima


One important radioisotope not removed in this process is tritium — a radioactive form of hydrogen with a half-life of 12.3 years. This means it takes 12.3 years for half of the radioisotope to decay.

Tritium is a carcinogenic byproduct of nuclear reactors and reprocessing plants, and is routinely released both into the water and air.

The Japanese government and the reactor operator plan to meet regulatory limits for tritium by diluting contaminated water. But this does not reduce the overall amount of radioactivity released into the environment.

How should the water be stored?

The Japanese Citizens Commission for Nuclear Energy is an independent organisation of engineers and researchers. It says once water is treated to reduce all significant isotopes other than tritium, it should be stored in 10,000-tonne tanks on land.

If the water was stored for 120 years, tritium levels would decay to less than 1,000th of the starting amount, and levels of other radioisotopes would also reduce. This is a relatively short and manageable period of time, in terms of nuclear waste.

Then, the water could be safely released into the ocean.

Nuclear waste storage in Australia

Australians currently face our own nuclear waste problems, stemming from our nuclear reactors and rapidly expanding nuclear medicine export business, which produces radioisotopes for medical diagnosis, some treatments, scientific and industrial purposes.




Read more:
Australia should explore nuclear waste before we try domestic nuclear power


This is what happens at our national nuclear facility at Lucas Heights in Sydney. The vast majority of Australia’s nuclear waste is stored on-site in a dedicated facility, managed by those with the best expertise, and monitored 24/7 by the Australian Federal Police.

But the Australian government plans to change this. It wants to transport and temporarily store nuclear waste at a facility at Kimba, in regional South Australia, for an indeterminate period. We believe the Kimba plan involves unnecessary multiple handling, and shifts the nuclear waste problem onto future generations.

The proposed storage facilities in Kimba are less safe than disposal, and this plan is well below world’s best practice.

The infrastructure, staff and expertise to manage and monitor radioactive materials in Lucas Heights were developed over decades, with all the resources and emergency services of Australia’s largest city. These capacities cannot be quickly or easily replicated in the remote rural location of Kimba. What’s more, transporting the waste raises the risk of theft and accident.

And in recent months, the CEO of regulator ARPANSA told a senate inquiry there is capacity to store nuclear waste at Lucas Heights for several more decades. This means there’s ample time to properly plan final disposal of the waste.

The legislation before the Senate will deny interested parties the right to judicial review. The plan also disregards unanimous opposition by Barngarla Traditional Owners.




Read more:
Uranium mines harm Indigenous people – so why have we approved a new one?


The Conversation contacted Resources Minister Keith Pitt who insisted the Kimba site will consolidate waste from more than 100 places into a “safe, purpose-built, state-of-the-art facility”. He said a separate, permanent disposal facility will be established for intermediate level waste in a few decades’ time.

Pitt said the government continues to seek involvement of Traditional Owners. He also said the Kimba community voted in favour of the plan. However, the voting process was criticised on a number of grounds, including that it excluded landowners living relatively close to the site, and entirely excluded Barngarla people.

Kicking the can down the road

Both Australia and Japan should look to nations such as Finland, which deals with nuclear waste more responsibly and has studied potential sites for decades. It plans to spend 3.5 billion euros (A$5.8 billion) on a deep geological disposal site.




Read more:
Risks, ethics and consent: Australia shouldn’t become the world’s nuclear wasteland


Intermediate level nuclear waste like that planned to be moved to Kimba contains extremely hazardous materials that must be strictly isolated from people and the environment for at least 10,000 years.

We should take the time needed for an open, inclusive and evidence-based planning process, rather than a quick fix that avoidably contaminates our shared environment and creates more problems than it solves.

It only kicks the can down the road for future generations, and does not constitute responsible radioactive waste management.


The following are additional comments provided by Resources Minister Keith Pitt in response to issues raised in this article (comments added after publication):

(The Kimba plan) will consolidate waste into a single, safe, purpose-built, state-of-the-art facility. It is international best practice and good common sense to do this.

Key indicators which showed the broad community support in Kimba included 62 per cent support in the local community ballot, and 100 per cent support from direct neighbours to the proposed site.

In assessing community support, the government also considered submissions received from across the country and the results of Barngarla Determination Aboriginal Corporation’s own vote.

The vast majority of Australia’s radioactive waste stream is associated with nuclear medicine production that, on average, two in three Australians will benefit from during their lifetime.

The facility will create a new, safe industry for the Kimba community, including 45 jobs in security, operations, administration and environmental monitoring.The Conversation

Tilman Ruff, Associate Professor, Education and Learning Unit, Nossal Institute for Global Health, School of Population and Global Health, University of Melbourne and Margaret Beavis, Tutor Principles of Clinical Practice Melbourne Medical School

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

Ocean warming threatens coral reefs and soon could make it harder to restore them



Climate-driven ocean warming threatens healthy coral reefs, like this one in Hawaii.
Shawna Foo, CC BY-ND

Shawna Foo, Arizona State University

Graphic stating that at 86.9 degrees Fahrenheit, the chance of transplanted corals surviving falls below 50%

CC BY-ND

Anyone who’s tending a garden right now knows what extreme heat can do to plants. Heat is also a concern for an important form of underwater gardening: growing corals and “outplanting,” or transplanting them to restore damaged reefs.

The goal of outplanting is to aid coral reefs’ natural recovery process by growing new corals and moving them to the damaged areas. It’s the same idea as replanting forests that have been heavily logged, or depleted farm fields that once were prairie grasslands.

I have studied how global stressors such as ocean warming and acidification affect marine invertebrates for more than a decade. In a recently published study, I worked with Gregory Asner to analyze the impacts of temperature on coral reef restoration projects. Our results showed that climate change has raised sea surface temperatures close to a point that will make it very hard for outplanted corals to survive.

Coral gardening

Coral reefs support over 25% of marine life by providing food, shelter and a place for fish and other organisms to reproduce and raise young. Today, ocean warming driven by climate change is stressing reefs worldwide.

Rising ocean temperatures cause bleaching events – episodes in which corals expel the algae that live inside them and provide the corals with most of their food, as well as their vibrant colors. When corals lose their algae, they become less resistant to stressors such as disease and eventually may die.

Hundreds of organizations worldwide are working to restore damaged coral reefs by growing thousands of small coral fragments in nurseries, which may be onshore in laboratories or in the ocean near degraded reefs. Then scuba divers physically plant them at restoration sites.

Outplanting is the process of transplanting nursery-grown corals onto reefs.

Outplanting coral is expensive: According to one recent study, the median cost is about US$160,000 per acre, or $400,000 per hectare. It also is time-consuming, with scuba divers placing each outplanted coral by hand. So it’s important to maximize coral survival by choosing the best locations.

We used data from the National Oceanic and Atmosphere Administration’s Coral Reef Watch program, which collects daily satellite-derived measurements of sea surface temperature. We paired this information with survival rates from hundreds of coral outplanting projects worldwide.

We found that coral survival was likely to drop below 50% if the maximum temperature experienced at the restoration site exceeded 86.9 degrees Fahrenheit (30.5 degrees Celsius). This temperature threshold mirrors the tolerance of natural coral reefs.

Globally, coral reefs experience an annual maximum temperature today of 84.9˚F (29.4˚C). This means they already are living close to their upper thermal limit.

When reefs experience temperatures only a few degrees above long-term averages for a few weeks, the stress can cause coral bleaching and mortality. Increases of just a few degrees above normal caused three mass bleaching events since 2016 that have devastated Australia’s Great Barrier Reef.

Map of global sea surface temperatures, color coded to show bleaching risks.
Sea surface temperatures on Aug. 3, 2020, measured from satellites. Warning = possible bleaching; Alert Level 1 = significant bleaching likely; Alert Level 2 = severe bleaching and significant mortality likely.
NOAA Coral Reef Watch

Warmer oceans

Climate scientists project that the oceans will warm up to 3˚C by the year 2100. Scientists are working to create coral outplants that can better survive increases in temperature, which could help to increase restoration success in the future.

When coral restoration experts choose where to outplant, they typically consider what’s on the seafloor, algae that could smother coral, predators that eat coral and the presence of fish. Our study shows that using temperature data and other information collected remotely from airplanes and satellites could help to optimize this process. Remote sensing, which scientists have used to study coral reefs for almost 40 years, can provide information on much larger scales than water surveys.

Coral reefs face an uncertain future and may not recover naturally from human-caused climate change. Conserving them will require reducing greenhouse gas emissions, protecting key habitats and actively restoring reefs. I hope that our research on temperature will help increase coral outplant survival and restoration success.

[Get our best science, health and technology stories. Sign up for The Conversation’s science newsletter.]The Conversation

Shawna Foo, Postdoctoral Research Scholar, Arizona State University

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

Seafloor currents sweep microplastics into deep-sea hotspots of ocean life



A rockfish hides in a red tree coral in the deep sea.
Geofflos

Ian Kane, University of Manchester and Michael Clare, National Oceanography Centre

What if the “great ocean garbage patches” were just the tip of the iceberg? While more than ten million tonnes of plastic waste enters the sea each year, we actually see just 1% of it – the portion that floats on the ocean surface. What happens to the missing 99% has been unclear for a while.

Plastic debris is gradually broken down into smaller and smaller fragments in the ocean, until it forms particles smaller than 5mm, known as microplastics. Our new research shows that powerful currents sweep these microplastics along the seafloor into large “drifts”, which concentrate them in astounding quantities. We found up to 1.9 million pieces of microplastic in a 5cm-thick layer covering just one square metre – the highest levels of microplastics yet recorded on the ocean floor.

While microplastics have been found on the seafloor worldwide, scientists weren’t sure how they got there and how they spread. We thought that microplastics would separate out according to how big or dense they were, in a similar manner to natural sediment. But plastics are different – some float, but more than half of them sink.




Read more:
Pristine Antarctic fjords contain similar levels of microplastics to open oceans near big civilisations


Plastics which once floated can sink as they become coated in algae, or if bound up with other sticky minerals and organic matter. Recent research has shown that rivers transport microplastics to the ocean too, and laboratory experiments revealed that giant underwater avalanches of sediment can transport these tiny particles along deep-sea canyons to greater depths.

We’ve now discovered how a global network of deep-sea currents transports microplastics, creating plastic hotspots within vast sediment drifts. By catching a ride on these currents, microplastics may be accumulating where deep-sea life is abundant.

Once plastic debris has broken down and sinks to the ocean floor, currents sweep the particles into vast drifts.
Ian Kane, Author provided

From bedroom floors to the seafloor

We surveyed an area of the Mediterranean off the western coast of Italy, known as the Tyrrhenian Sea, and studied the bottom currents that flow near the seafloor. These currents are driven by differences in water salinity and temperature as part of a system of ocean circulation that spans the globe. Seafloor drifts of sediment can be many kilometres across and hundreds of metres high, forming where these currents lose their strength.

We analysed sediment samples from the seafloor taken at depths of several hundred metres. To avoid disturbing the surface layer of sediment, we used samples taken with box-cores, which are like big cookie cutters. In the laboratory, we separated microplastics from the sediment and counted them under microscopes, analysing them using infra-red spectroscopy to find out what kinds of plastic polymer types were there.

A microplastic fibre seen under a microscope.
Ian Kane, Author provided

Most microplastics found on the seafloor are fibres from clothes and textiles. These are particularly insidious, as they can be eaten and absorbed by organisms. Although microplastics on their own are often non-toxic, studies show the build-up of toxins on their surfaces can harm organisms if ingested.

These deep ocean currents also carry oxygenated water and nutrients, meaning that the seafloor hotspots where microplastics accumulate may also be home to important ecosystems such as deep-sea coral reefs that have evolved to depend on these flows, but are now receiving huge quantities of microplastics instead.

What was once a hidden problem has now been uncovered – natural currents and the flow of plastic waste into the ocean are turning parts of the seafloor into repositories for microplastics. The cheap plastic goods we take for granted eventually end up somewhere. The clothes that may only last weeks in your wardrobe linger for decades to centuries on the seafloor, potentially harming the unique and poorly understood creatures that live there.The Conversation

Ian Kane, Reader in Geology, University of Manchester and Michael Clare, Principal Researcher in Marine Geoscience, National Oceanography Centre

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

Ocean warming has fisheries on the move, helping some but hurting more



An Atlantic cod on ice. Cod fisheries in the North Sea and Irish Sea are declining due to overfishing and climate change.
Robert F. Bukaty/AP

Chris Free, University of California, Santa Barbara

Climate change has been steadily warming the ocean, which absorbs most of the heat trapped by greenhouse gases in the atmosphere, for 100 years. This warming is altering marine ecosystems and having a direct impact on fish populations. About half of the world’s population relies on fish as a vital source of protein, and the fishing industry employs more the 56 million people worldwide.

My recent study with colleagues from Rutgers University and the U.S. National Oceanic and Atmospheric Administration found that ocean warming has already impacted global fish populations. We found that some populations benefited from warming, but more of them suffered.

Overall, ocean warming reduced catch potential – the greatest amount of fish that can be caught year after year – by a net 4% over the past 80 years. In some regions, the effects of warming have been much larger. The North Sea, which has large commercial fisheries, and the seas of East Asia, which support some of the fastest-growing human populations, experienced losses of 15% to 35%.

The reddish and brown circles represent fish populations whose maximum sustainable yields have dropped as the ocean has warmed. The darkest tones represent extremes of 35 percent. Blueish colors represent fish yields that increased in warmer waters.
Chris Free, CC BY-ND

Although ocean warming has already challenged the ability of ocean fisheries to provide food and income, swift reductions in greenhouse gas emissions and reforms to fisheries management could lessen many of the negative impacts of continued warming.

How and why does ocean warming affect fish?

My collaborators and I like to say that fish are like Goldilocks: They don’t want their water too hot or too cold, but just right.

Put another way, most fish species have evolved narrow temperature tolerances. Supporting the cellular machinery necessary to tolerate wider temperatures demands a lot of energy. This evolutionary strategy saves energy when temperatures are “just right,” but it becomes a problem when fish find themselves in warming water. As their bodies begin to fail, they must divert energy from searching for food or avoiding predators to maintaining basic bodily functions and searching for cooler waters.

Thus, as the oceans warm, fish move to track their preferred temperatures. Most fish are moving poleward or into deeper waters. For some species, warming expands their ranges. In other cases it contracts their ranges by reducing the amount of ocean they can thermally tolerate. These shifts change where fish go, their abundance and their catch potential.

Warming can also modify the availability of key prey species. For example, if warming causes zooplankton – small invertebrates at the bottom of the ocean food web – to bloom early, they may not be available when juvenile fish need them most. Alternatively, warming can sometimes enhance the strength of zooplankton blooms, thereby increasing the productivity of juvenile fish.

Understanding how the complex impacts of warming on fish populations balance out is crucial for projecting how climate change could affect the ocean’s potential to provide food and income for people.

Warming is affecting virtually all regions of the ocean.

Impacts of historical warming on marine fisheries

Sustainable fisheries are like healthy bank accounts. If people live off the interest and don’t overly deplete the principal, both people and the bank thrive. If a fish population is overfished, the population’s “principal” shrinks too much to generate high long-term yields.

Similarly, stresses on fish populations from environmental change can reduce population growth rates, much as an interest rate reduction reduces the growth rate of savings in a bank account.

In our study we combined maps of historical ocean temperatures with estimates of historical fish abundance and exploitation. This allowed us to assess how warming has affected those interest rates and returns from the global fisheries bank account.

Losers outweigh winners

We found that warming has damaged some fisheries and benefited others. The losers outweighed the winners, resulting in a net 4% decline in sustainable catch potential over the last 80 years. This represents a cumulative loss of 1.4 million metric tons previously available for food and income.

Some regions have been hit especially hard. The North Sea, with large commercial fisheries for species like Atlantic cod, haddock and herring, has experienced a 35% loss in sustainable catch potential since 1930. The waters of East Asia, neighbored by some of the fastest-growing human populations in the world, saw losses of 8% to 35% across three seas.

Other species and regions benefited from warming. Black sea bass, a popular species among recreational anglers on the U.S. East Coast, expanded its range and catch potential as waters previously too cool for it warmed. In the Baltic Sea, juvenile herring and sprat – another small herring-like fish – have more food available to them in warm years than in cool years, and have also benefited from warming. However, these climate winners can tolerate only so much warming, and may see declines as temperatures continue to rise.

Shucking scallops in Maine, where fishery management has kept scallop numbers sustainable.
Robert F. Bukaty/AP

Management boosts fishes’ resilience

Our work suggests three encouraging pieces of news for fish populations.

First, well-managed fisheries, such as Atlantic scallops on the U.S. East Coast, were among the most resilient to warming. Others with a history of overfishing, such as Atlantic cod in the Irish and North seas, were among the most vulnerable. These findings suggest that preventing overfishing and rebuilding overfished populations will enhance resilience and maximize long-term food and income potential.

Second, new research suggests that swift climate-adaptive management reforms can make it possible for fish to feed humans and generate income into the future. This will require scientific agencies to work with the fishing industry on new methods for assessing fish populations’ health, set catch limits that account for the effects of climate change and establish new international institutions to ensure that management remains strong as fish migrate poleward from one nation’s waters into another’s. These agencies would be similar to multinational organizations that manage tuna, swordfish and marlin today.

Finally, nations will have to aggressively curb greenhouse gas emissions. Even the best fishery management reforms will be unable to compensate for the 4 degree Celsius ocean temperature increase that scientists project will occur by the end of this century if greenhouse gas emissions are not reduced.

[ Like what you’ve read? Want more? Sign up for The Conversation’s daily newsletter. ]The Conversation

Chris Free, Postdoctoral Scholar, University of California, Santa Barbara

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

A landmark report confirms Australia is girt by hotter, higher seas. But there’s still time to act



Aerial imagery revealing the extent of storm damage in Dee Why on Sydney’s Northern Beaches in 2016 following wild weather.
NEARMAP/AAP

Jess Melbourne-Thomas, CSIRO; Kathleen McInnes, CSIRO; Nathan Bindoff, University of Tasmania, and Nerilie Abram, Australian National University

A landmark scientific report has confirmed that climate change is altering the world’s seas and ice at an unprecedented rate. Australia depends on the ocean that surrounds us for our health and prosperity. So what does this mean for us, and life on Earth?

The Intergovernmental Panel on Climate Change (IPCC) findings were launched in Monaco on Wednesday night. They provide the most definitive scientific evidence yet of warmer, more acidic and less productive seas. Glaciers and ice sheets are melting, causing sea level to rise at an accelerating rate.

The implications for Australia are serious. Extreme sea level events that used to hit once a century will occur once a year in many of the world’s coastal places by 2050. This situation is inevitable, even if greenhouse gas emissions are dramatically curbed.

The findings, titled the Special Report on the Ocean and Cryosphere in a Changing Climate, strengthen the already compelling case for countries to meet their emission reduction goals under the 2015 Paris agreement.

Beachgoers cool off in the water at Bondi Beach in Sydney, February 2019. Australia’s coast dwellers must adapt to the inevitable effects of climate change.
Joel Carrett/AAP



Read more:
‘This situation brings me to despair’: two reef scientists share their climate grief


A rapid and dramatic cut in greenhouse gas emissions would prevent the most catastrophic damage to the ocean and cryosphere (frozen polar and mountain regions). This would help protect the ecosystems and people that rely on them.

The report entailed two years of work by 104 authors and review editors from 36 countries, who assessed nearly 7,000 scientific papers and responded to more than 30,000 review comments.

The picture is worse than we thought

Mountain glaciers and polar ice sheets are shrinking and, together with expansion of the warming ocean, are contributing to an increasing rate of sea level rise.

During the last century, global sea levels rose about 15cm. Seas are now rising more than twice as fast – 3.6mm per year – and accelerating, the report shows.

The IPCC’s projections are more dire than in its 2014 oceans report. It has revised upwards by 10% the effect of the melting Antarctic ice sheet on sea level rise by 2100. Antarctica appears to be changing more rapidly than was thought possible even five years ago, and further work is needed to understand just how quickly ice will be lost from Antarctica in future.

Key components and changes of the ocean and cryosphere, and their linkages in the Earth system.
IPCC, 2019

If you live near the Australian coast, change is coming

By 2050, more than one billion of the world’s people will live on coastal land less than 10 metres above sea level. They will be exposed to combinations of sea level rise, extreme winds, waves, storm surges and flooding from intensified storms and tropical cyclones.

Many of Australia’s coastal cities and communities can expect to experience what was previously a once-in-a-century extreme coastal flooding event at least once every year by the middle of this century.

Our island neighbours in Indonesia and the Pacific will also be hit hard. The report warns that some island nations are likely to become uninhabitable – although the extent of this is hard to assess accurately.

Some change is inevitable and we will have to adapt. But the report also delivered a strong message about the choices that still remain. In the case of extreme sea level events around Australia, we believe a marked global reduction in greenhouse as emissions would buy us more than 10 years of extra time, in some places, to protect our coastal communities and infrastructure from the rising ocean.

Indonesian residents wade through flood water in Jakarta. The northwestern part of Jakarta is rapidly sinking.
MAST IRHAM/EPA

More frequent extreme events are often occurring at the same time or in quick succession. Tasmania’s summer of 2015-16 is a good example. The state experienced record-breaking drought which worsened the fire threat in the highlands. An unprecedented marine heatwave along the east coast damaged kelp forests and caused disease and death of shellfish, and the state’s northeast suffered severe flooding.

This string of events stretched emergency services, energy supplies and the aquaculture and manufacturing industries. The total economic cost to the state government was an estimated A$445 million. The impacts on the food, energy and manufacturing sectors cut Tasmania’s anticipated economic growth by about half.

Reefs and fish stocks are suffering

The ocean has taken a huge hit from climate change – taking up heat, absorbing carbon dioxide that makes the water more acidic, and losing oxygen. It will bring ocean conditions unlike anything we have seen before.

Marine ecosystems and fisheries around the world are under pressure from this barrage of stressors. Overall, the fisheries potential around Australia’s coasts is expected to decline during this century.

Heat build-up in the surface ocean has already triggered a marked rise in the intensity, frequency and duration of marine heatwaves. Ocean heatwaves are expected to become between four and ten times more common this century, depending on how rapidly global warming continues.

The report said coral reefs, including the Great Barrier Reef, are already at very high risk from climate change and are expected to suffer significant losses and local extinctions. This would occur even if global warming is limited to 1.5℃ – a threshold the world is set to overshoot by a wide margin.




Read more:
Extreme weather caused by climate change has damaged 45% of Australia’s coastal habitat


Our choices now are critical for the future

This report reinforces the findings of earlier reports on the importance of limiting global warming warming to 1.5℃ if we are to avoid major impacts on the land, the ocean and frozen areas.

Even if we act now to drastically reduce greenhouse gas emissions, some damage is already locked in and our ocean and frozen regions will continue to change for decades to centuries to come.

Mertz Glacier in east Antarctica. IPCC scientists say the expected effect of melting Antarctic ice on sea level rise is worse than projected five years ago.
Australian Antarctic Division

In Australia, we will need to adapt our coastal cities and communities to unavoidable sea level rise. There are a range of possible options, from building barriers to planned relocation, to protecting the coral reefs and mangroves that provide natural coastal defences.

But if we want to give adaptation the best chance of working, the clear message of this new report is that we need to reduce greenhouse gas emissions as quickly as possible.The Conversation

Jess Melbourne-Thomas, Transdisciplinary Researcher & Knowledge Broker, CSIRO; Kathleen McInnes, Senior research scientist, CSIRO; Nathan Bindoff, Professor of Physical Oceanography, Institute for Marine and Antarctic Studies, University of Tasmania, and Nerilie Abram, ARC Future Fellow, Research School of Earth Sciences; Chief Investigator for the ARC Centre of Excellence for Climate Extremes, Australian National University

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

Meet the super corals that can handle acid, heat and suffocation


Resilient corals are offering hope for bleached reefs.
Emma Camp

Emma F Camp, University of Technology Sydney and David Suggett, University of Technology Sydney

Climate change is rapidly changing the oceans, driving coral reefs around the world to breaking point. Widely publicised marine heatwaves aren’t the only threat corals are facing: the seas are increasingly acidic, have less oxygen in them, and are gradually warming as a whole.

Each of these problems reduces coral growth and fitness, making it harder for reefs to recover from sudden events such as massive heatwaves.




Read more:
Acid oceans are shrinking plankton, fuelling faster climate change


Our research, published today in Marine Ecology Progress Series, investigates corals on the Great Barrier Reef that are surprisingly good at surviving in increasingly hostile waters. Finding out how these “super corals” can live in extreme environments may help us unlock the secret of coral resilience helping to save our iconic reefs.

Bleached coral in the Seychelles.
Emma Camp, Author provided

Coral conservation under climate change

The central cause of these problems is climate change, so the central solution is reducing carbon emissions. Unfortunately, this is not happening rapidly enough to help coral reefs, so scientists also need to explore more immediate conservation options.

To that end, many researchers have been looking at coral that manages to grow in typically hostile conditions, such as around tide pools and intertidal reef zones, trying to unlock how they become so resilient.

These extreme coral habitats are not only natural laboratories, they house a stockpile of extremely tolerant “super corals”.

What exactly is a super coral?

“Super coral” generally refers to species that can survive both extreme conditions and rapid changes in their environment. But “super” is not a very precise term!

Our previous research quantified these traits so other ecologists can more easily use super coral in conservation. There are a few things that need to be established to determine whether a coral is “super”:

  1. What hazard can the coral survive? For example, can it deal with high temperature, or acidic water?

  2. How long did the hazard last? Was it a short heatwave, or a long-term stressor such as ocean warming?

  3. Did the coral survive because of a quality such as genetic adaption, or was it tucked away in a particularly safe spot?

  4. How much area does the coral cover? Is it a small pocket of resilience, or a whole reef?

  5. Is the coral trading off other important qualities to survive in hazardous conditions?

  6. Is the coral super enough to survive the changes coming down the line? Is it likely to cope with future climate change?

If a coral ticks multiple boxes in this list, it’s a very robust species. Not only will it cope well in our changing oceans, we can also potentially distribute these super corals along vulnerable reefs.

Some corals cope surprisingly well in different conditions.
Emma Camp, Author provided

Mangroves are surprise reservoirs

We discovered mangrove lagoons near coral reefs can often house corals living in very extreme conditions – specifically, warm, more acidic and low oxygen seawater.

Previously we have reported corals living in extreme mangroves of the Seychelles, Indonesia, New Caledonia – and in our current study living on the Great Barrier Reef. We report diverse coral populations surviving in conditions more hostile than is predicted over the next 100 years of climate change.

Importantly, while some of these sites only have isolated populations, other areas have actively building reef frameworks.

Particularly significant were the two mangrove lagoons on the Great Barrier Reef. They housed 34 coral species, living in more acidic water with very little oxygen. Temperatures varied widely, over 7℃ in the period we studied – and included periods of very high temperatures that are known to cause stress in other corals.

Mangrove lagoons can contain coral that survives in extremely hostile environments, while nearby coral reefs bleach in marine heatwaves.
Emma Camp, Author provided

While coral cover was often low and the rate at which they build their skeleton was reduced, there were established coral colonies capable of surviving in these conditions.

The success of these corals reflect their ability to adapt to daily or weekly conditions, and also their flexible relationship with various symbiotic micro-algae that provide the coral with essential resources.

While we are still in the early phases of understanding exactly how these corals can aid conservation, extreme mangrove coral populations hold a reservoir of stress-hardened corals. Notably the geographic size of these mangrove locations are small, but they have a disproportionately high conservation value for reef systems.




Read more:
Heat-tolerant corals can create nurseries that are resistant to bleaching


However, identification of these pockets of extremely tolerant corals also challenge our understanding of coral resilience, and of the rate and extent with which coral species can resist stress.The Conversation

Emma F Camp, DECRA & UTS Chancellor’s Research Fellow, Climate Change Cluster, Future Reefs Research Programe, University of Technology Sydney and David Suggett, Associate Professor in Marine Biology, University of Technology Sydney

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

Sharks: one in four habitats in remote open ocean threatened by longline fishing



Though they’re protected worldwide, great white sharks encounter longline fishing vessels in half of their range.
Wildestanimal/Shutterstock

David Sims, University of Southampton

Unlike the many species which stalk the shallow, coastal waters that fisheries exploit all year round, pelagic sharks roam the vast open oceans. These are the long-distance travellers of the submarine world and include the world’s largest fish, the whale shark, and also one of the fastest fish in the sea, the shortfin mako shark, capable of swimming at 40mph.

Because these species range far from shore, you might expect them to escape most of the lines and nets that fishing vessels cast. But over the last 50 years, industrial scale fisheries have extended their reach across the world’s oceans and tens of millions of pelagic sharks are now caught every year for their valuable fins and meat.

On average, large pelagic sharks account for over half of all shark species identified in catches worldwide. The toll this has taken on species such as the shortfin mako has prompted calls to introduce catch limits in the high seas – areas of the ocean beyond national jurisdiction where there is little or no management for the majority of shark species.

We wanted to know where the ocean’s shark hotspots are – the places where lots of different species gather – and how much these places are worked by fishing boats. We took up the challenge of finding out where pelagic sharks hang out by satellite tracking their movements with electronic tags. This approach by our international team of over 150 scientists from 26 countries has an important advantage over fishery catch records. Rather than showing where a fishing boat found them, it can precisely map all of the places sharks visit.

Nowhere to hide

For a new study published in Nature we tracked nearly 2,000 sharks from 23 different species, including great whites, blue sharks, shortfin mako and tiger sharks. We were able to map their positions in unprecedented detail and discern the most visited hotspots where sharks feed, breed and rest.

Hotspots were often located in frontal zones – boundaries in the sea between different water masses that can have the best conditions of temperature and nutrients for phytoplankton to bloom, which attracts masses of zooplankton, as well as the fish and squid that sharks eat.

Then we calculated how much these hotspots overlapped with global fleets of large, longline fishing vessels, which we also tracked by satellite. This type of fishing gear is used very widely on the high seas and catches more pelagic sharks than trawls and other gear. Each longline vessel is capable of deploying a 100km long line bearing over 1,000 baited hooks.

We found that even the most remote parts of the ocean that are many miles from land offer pelagic sharks little refuge from industrial-scale fishing fleets. One in four of the places sharks visited each month overlapped with the areas longline fishing vessels operated in.

Sharks such as the North Atlantic blue and the shortfin mako – which fishers also target for their fins and meat – were much more likely to encounter these vessels, with as much as 76% of the places these species visited most in each month overlapping with where longline vessels were fishing. Even internationally protected species such as great whites and porbeagle sharks encountered longline vessels in half of their tracked range.

It’s now clear that much of the world’s fishing activity on the high seas is centred on shark hotspots, which longlines rake for much of the year. Many large sharks, which are already endangered, face a future without refuge from industrial fishing in the places they gather.

High seas marine protected areas

The maps of shark hotspots and longline fishing activity that we created can at least provide a blueprint for where large-scale marine protected areas aimed at conserving sharks could be set. Outside of these, strict quotas could reduce catches.

The United Nations is creating a high seas treaty for protecting ocean biodiversity – negotiations are due to continue in August 2019 in New York. They’ll consider large-scale marine protected areas for the high seas and we’ll suggest where these could be located to best protect pelagic sharks.

Satellite monitoring could give real-time signals of where sharks and other threatened creatures such as turtles and whales are gathering. Tracking where these species roam and where fishers interact with them will help patrol vessels monitor these high-risk zones more efficiently.

Such management action is overdue for many shark populations in the high seas. Take North Atlantic shortfin makos – not only are they overfished
and endangered, but now we know they have no respite from longline fishing during many months of the year in the places they gather most often. Some of these shark hotspots may not exist in the near future if action isn’t taken now to conserve these species and the habitats they depend on.The Conversation

David Sims, Professor of Marine Ecology, University of Southampton

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