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.




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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.

Environmental activism goes digital in lockdown – but could it change the movement for good?



Greta Thunberg talks with Professor Johan Rockström about the coronavirus and the environment at the Nobel Museum in Stockholm, Sweden, April 21 2020.
EPA-EFE/Jessica Gow

William Finnegan, University of Oxford

The environmental movement’s past recently collided with its future. April 22 marked the 50th anniversary of the first Earth Day, a milestone for environmentalism. A few days later, a global school strike was organised by Fridays for Future, the international coalition of young people inspired by Greta Thunberg’s protests against climate change. But after months of careful planning, both occasions were upended by the COVID-19 pandemic – and went online instead.

So when social distancing measures are eased, will protests return to the streets, or do these events mark a turning point?

In 1970, an estimated 20 million Americans (10% of the US population at the time) participated in the first Earth Day. Back then, US senator Gaylord Nelson conceived of a national “teach-in” to raise environmental awareness and recruited Harvard law student Denis Hayes to organise the event.




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Teach-ins had emerged in the mid-1960s as a hybrid of student sit-ins and informal lectures in opposition to the Vietnam War. Rather than going on strike, teachers and students occupied classrooms instead. According to environmental historian Adam Rome, 1,500 universities and 10,000 schools held Earth Day teach-ins in April 1970, “nurturing a generation of activists.”

A postage stamp issued to commemorate the first Earth Day, April 1970.
Michael Rega/Shutterstock

In the decades that followed, the environmental movement grew into a political and cultural force. Yet subsequent Earth Days failed to capture the urgency and grassroots passion of the original.

The 50th anniversary Earth Day sought to address this by going back to its roots. Teach-ins were planned for classrooms and campuses across the world, but COVID-19 closed schools. The day of action evolved into a 12-hour live-stream during which actors, athletes, musicians, politicians, and even Pope Francis shared messages of environmental stewardship and climate action.

The school climate strikes originated in August 2018, when 15-year-old Greta Thunberg skipped school to protest inaction on climate change outside the Swedish parliament.

Within little more than a year, seven million students and their supporters were joining school strikes around the world and Thunberg was making headlines for her scathing speeches at the UN climate conference in Poland and [World Economic Forum in Davos]. Another global strike was scheduled for April 2020, but COVID-19 again pushed the event online.

The school strikes and annual Earth Day celebrations reflect different generations of environmental activism and different philosophies of protest. Yet both have been guided by the environmental slogan “think globally, act locally”. During the pandemic, environmental activists are now thinking globally and acting digitally.

‘Clicktivism’ and digital natives

I’m researching climate change education and youth climate activism in the UK. Like the protesters, I’ve been forced to adapt my plans and have been exploring the digital side of climate activism.

Online activism has been called “clicktivism”, or, disparagingly, “slacktivism”. It’s been characterised as impulsive, noncommittal and easily replicated, emphasising the lower risks and costs of political expression on social media versus protest and political engagement in the real world. But the relationship between digital technology and social movements is more complicated.

Researchers are split on the precise role of digital activism. From one perspective, campaigners can use social media to “supersize” their public engagement. This helps them to reach more people and bypass traditional media channels. Other researchers emphasise the power of the internet to help activists self-organise. Without the structure or hierarchy of traditional organisations, digital platforms can allow completely new forms of activism to flourish.




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Beyond hashtags: how a new wave of digital activists is changing society


A recent study found that climate advocacy groups that started on the internet, such as 350.org, have different online strategies, tactics and theories of change compared to older environmental groups such as Greenpeace. Founded in 2008, 350.org (which is both a URL and reference to the safe level of 350 parts per million carbon dioxide in the atmosphere) led the first wave of internet-savvy, youth-driven environmental organisations.

Successful digital campaigns at 350.org have been described as a virtuous cycle where online tools spur offline action – the results of which can be documented and shared online to inspire further action.

Modern activists can film demonstrations using smartphones and share them online, reaching a much wider audience.
Rachael Warriner/Shutterstock

It’s too early to say how the school climate strikes of 2019 have influenced the broader movement, but current research is exploring how climate strikers are using Instagram and how collective identities on social media may drive collective action. As “digital natives”, these young climate activists grew up with the internet, smartphones and social media. Their movement uses memes and hashtags across YouTube, Instagram and Twitter, where Thunberg has more than four million followers.

While COVID-19 prevents offline action, thousands of #ClimateStrikeOnline social media posts show solitary protesters around the world armed with handmade signs, a virtual echo of where the movement started. When it comes to climate activism, digital natives are now leading the way. The revolution will be live-streamed.The Conversation

William Finnegan, PhD Candidate in Climate Education and Activism, University of Oxford

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