How an alien seaweed invasion spawned an Antarctic mystery



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Southern bull kelp can drift huge distances before washing ashore.
Ceridwen Fraser, Author provided

Adele Morrison, Australian National University; Andy Hogg, Australian National University; Ceridwen Fraser, Australian National University, and Erik van Sebille, Utrecht University

Two small pieces of seaweed found by a Chilean scientist on an Antarctic beach set in train research that may transform our understanding of ocean drift and reveal what the future holds for Antarctic ecosystems affected by climate change.

It all started in January 2017, when sharp-eyed marine biologist Erasmo Macaya spotted two clumps of southern bull kelp washed up on the tide line of an Antarctic beach.

Most of us would have walked right on by, but it stopped Macaya in his tracks. To him it was as if an alien had just landed – and in many ways that was exactly what had happened.

The kelp that washed up on Antarctica’s Prince George Island.
Erasmo Macaya, Author provided

Every piece of science he knew said that this species of kelp should never have ended up in Antarctica. Its home was the regions around New Zealand, Chile and the sub-Antarctic islands. Indeed, a genetic test later confirmed that the pieces he found had travelled tens of thousands of kilometres from the Kerguelen and South Georgia islands.

So how did the kelp get to Antarctica?

The ocean barrier

Many scientists considered such a journey impossible, because of the fierce barrier of winds and currents that encircle Antarctica. These winds – known to sailors as the Roaring Forties – combine with the world’s strongest ocean current, the Antarctic Circumpolar Current, and the Coriolis force generated by Earth’s rotation.

Together, these forces push floating objects east and north, away from Antarctica. Before Macaya’s discovery, this barrier was thought to be impenetrable to floating debris.

Ocean currents in the Southern Ocean push floating objects east and north away from Antarctica.
Author provided

But if kelp and other organisms could make it to Antarctica, this would have profound consequences for Antarctic ecosystems. So was there a way for the kelp to drift through that barrier?




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Surfing kelp

We took up the challenge, using our ocean models. The mystery deepened when our first modelling attempts suggested that the Southern Ocean was indeed uncrossable by floating kelp. Even ocean eddies – the “weather” of the ocean – were not able to push floating objects southward away from the main ocean currents.

Yet the kelp had undeniably made the crossing. This led us to think about other influences on ocean drift that could play a role. We decided to add a very small effect known as Stokes drift to our models.

You can think of Stokes drift as deep ocean surfing. Waves can push floating objects in unusual directions. In the kelp’s case, each time a wave passes, the kelp will move a short distance with the wave. This drift is slow when waves are small, but in regions with large waves (such as the Southern Ocean) it can be much faster.

During storms around Antarctica, waves are typically 10-15m high. The largest wave ever recorded in the Southern Hemisphere, more than 23m, was in the Southern Ocean off New Zealand. Stokes drift must be large here.

When we added this factor to our ocean models, the change was instant. The massive waves generated by Antarctic storms pushed a small proportion of floating objects southwards. As we report in Nature Climate Change today, this conceivably explains the kelp’s voyage to Antarctica.

Modelling virtual kelp pathways with surface ocean currents and wave motion.

We calculated that the kelp specimens must have drifted at least 20,000km to reach Antarctica – the longest biological rafting events ever recorded.

Our results will also change the way that drift pathways for floating objects – such as plastics, aeroplane crash debris, pumice from volcanoes, driftwood, seaweeds, and messages in bottles – will be calculated, particularly in stormy oceans.

What this means for Antarctica

The implications don’t stop there. Until now, Antarctica was thought to be an isolated ecosystem, largely insulated from environmental change. This is not in fact true.

Southern bull kelp can carry many other species of plants and animals when it detaches and floats out to sea. The discovery that this kelp can raft to Antarctica means we could see major ecological changes in Antarctic marine ecosystems as the climate warms.

So far there is almost no evidence of natural colonisations of Antarctica from northern regions in the past few tens of thousands of years. Many Antarctic plants and animals are distinct from those found on other continents and sub-Antarctic islands.

In fact, the kelp strands Macaya found are the first recorded foreign organisms to have drifted across the Southern Ocean. But our models suggest these are unlikely to be the only ones to have made the trip.

This means that Antarctica’s ecological differences are not really due to physical isolation. It is more likely that the harsh Antarctic climate prevents new plants and animals from establishing themselves.

But Antarctica is changing. Parts of the frozen continent are among the fastest-warming regions on Earth. As Antarctica and the ocean around it warms, the kelp rafts – and other floating organisms, including invertebrates hanging onto the kelp, seeds, driftwood that could harbour insects, and larvae – may one day be able to colonise.

By the end of this century, when parts of Antarctica are expected to be similar to current sub-Antarctic environments, we might see many new species colonising Antarctica, bringing dramatic ecosystem change.

Other human-caused influences may also be felt. If kelp can break through the barrier, then floating plastic debris from the large garbage patches in the South Atlantic and South Pacific, just north of the Southern Ocean, could conceivably make a similar journey.




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Plastic litter is still very rare in the waters around Antarctica. But with ever-growing amounts of plastic entering our oceans and the new drift pathways we have discovered, more plastic will likely find its way south to pollute one of our last near-pristine environments.

The ConversationAnd all of this has been revealed through the discovery of two small pieces of kelp on a distant beach, and the application of a relatively insignificant piece of ocean physics. From these small beginnings we now know that one of the world’s last great wildernesses might not escape our influence.

Adele Morrison, Research Fellow, Australian National University; Andy Hogg, Associate Professor, Australian National University; Ceridwen Fraser, Senior lecturer, Australian National University, and Erik van Sebille, Associate Professor in Oceanography and Climate Change, Utrecht University

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

You’ve heard of a carbon footprint – now it’s time to take steps to cut your nitrogen footprint



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Transport and livestock are both significant contributors to nitrogen pollution.
Annalucia/Shutterstock.com

Ee Ling Ng, University of Melbourne; Deli Chen, University of Melbourne, and Xia Liang, University of Melbourne

Nitrogen pollution has significant environmental and human health costs. Yet it is often conflated with other environmental problems, such as climate change, which is exacerbated by nitrous oxide (N₂O) and nitrogen oxides (NOₓ), or particulate smog, to which ammonia (NH₃) also contributes.

One way to understand our nitrogen use is to look at our nitrogen footprint. This is the amount of reactive nitrogen, which is all forms of nitrogen other than inert nitrogen gas, released into the environment from our daily activities that consume resources including food and energy.




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Nitrogen pollution: the forgotten element of climate change


Our earlier research showed that Australia has a large nitrogen footprint. At up to 47kg of nitrogen per person each year, Australia is far ahead of the US (28kg per person), the second on the leaderboard of per capita reactive nitrogen emissions. Australians’ large nitrogen footprints are created largely by a diet rich in animal protein and high levels of coal use for energy.

The nitrogen footprint

Our new research, published in the Journal of Cleaner Production, takes this concept further by measuring the nitrogen footprint of an entire institution, in this case the University of Melbourne.

The institutional nitrogen footprint is the sum of individual activities at the workplace and institutional activities, such as powering laboratories and lecture theatres in the case of a university.

We calculated that the university’s annual nitrogen footprint is 139 tonnes of nitrogen. It is mainly attributable to three factors: food (37%), energy use (32%) and transport (28%).

The University of Melbourne’s nitrogen footprint in 2015 and projections for 2020.

At the university, food plays a dominant role through the meat and dairy consumed. Nitrogen emissions from food occur mainly during its production, whereas emissions from energy use come mainly from coal-powered electricity use and from fuel used during business travel.

Cutting nitrogen

We also modelled the steps that the university could take to reduce its nitrogen footprint. We found that it could be reduced by 60% by taking action to cut emissions from the three main contributing factors: food, energy use, and travel.

The good news is if the university implements all the changes to energy use detailed in its Sustainability Plan – which includes strategies such as adopting clean energy (solar and wind), optimising energy use and buying carbon credits – this would also reduce nitrogen pollution by as much as 29%.

Changing habits of air travel and food choices would be a challenge, as this requires altering the behaviour of people from a culture that places tremendous value on travelling and a love for coffee and meat.

Generally, Australians fly a lot compared to the rest of the world, at significant cost to the environment. We could offset the travel, and we do take that possibility into account, but as others have written before us, we should not make the mistake of assuming that emissions offsets make air travel “sustainable”.

The question that perhaps need to be asked, for work travel, is “to travel or not to travel?” Let’s face it, why are so many academic conferences set in idyllic locations, if not to entice us to attend?

Animal products are major contributors to nitrogen emissions, given the inefficiency of conversion from the feed to milk or meat. Would people be willing to change their latte, flat white or cappuccino to a long black, espresso or macchiato? Or a soy latte?




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As 96% of the nitrogen emissions occur outside the university’s boundaries, their detrimental effects are invisible to the person on the ground, while the burden of the pollution is often borne far away, both in time and space.

The ConversationBut, as our study shows for the first time, large institutions with lots of staff are well placed to take steps to cut their large nitrogen footprint.

Ee Ling Ng, Research fellow, University of Melbourne; Deli Chen, Professor, University of Melbourne, and Xia Liang, PhD candidate, University of Melbourne

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

The science and art of reef restoration



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Silent Evolution by Jason deCaires Taylor. Taylor makes sculptures and sinks them beneath the sea to create artificial reefs.
© Jason deCaires Taylor

Adam Smith, James Cook University and Ian McLeod, James Cook University

Coral reefs around the world are in crisis. Under pressure from climate change, overfishing, pollution, introduced species and apathy, coral colonies and fish communities are steadily deteriorating.

Coral cover in the Great Barrier reef has declined by an alarming 50% since the 1980s. Some leading scientists believe that the Great Barrier Reef is at a terminal stage.




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One way to address this is through reef restoration. At its simplest, this involves the addition of coral or habitat to a reef. It’s generally undertaken on existing coral reefs, but can also be done on rocky reefs or bare sand.

We have looked back through the decades to celebrate the history of reef restoration, not just in science but also in art, business and politics.

Gardener, by Jason deCaires Taylor.
© Jason deCaires Taylor

Band-aid or reef revolution?

Just as there is no magic solution in human healthcare, there is likewise no magic solution in caring for corals. You do what you can with the resources you have.




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Some scientists have argued that reef restoration is a Band-Aid for the enormous problems that reefs face. We can agree with this point of view, but there are times when a band aid is very useful – and may prevent much more serious injuries.

Reef restoration makes an important local difference, as seen here at Koh Tao, Thailand.
Author provided

Earlier this year the federal government allotted an unprecedented A$500 million dollars to the Great Barrier Reef. This included A$100 million focused on restoration to improve the health of the reef.

Reef restoration science and projects complement community efforts. There is an increasing focus on addressing local issues such as water quality, overfishing, and outbreaks of crown-of-thorns starfish.




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When scientists, industry and government work with local communities we can accelerate the recovery of local reefs.

To do this, we need people who want to make a difference. Once we recognise a degraded ecosystem, we work to reduce stress (like pollution in the water) and add new habitat or helpful species.

Artist Jason deCaires Taylor builds breathtaking underwater sculptures that double as artificial coral reefs.

The history of reef restoration

People have been restoring ecosystems and degraded land for thousands of years. Reef restoration, on the other hand, is relatively new and rarely documented.

Our research indicates that in the modern era there have been three major waves of reef restoration. The first wave started in the 1970s and ‘80s, as scientists were able to easily SCUBA dive and new protective legislation was introduced around the world. This largely involved the addition of new habitats. These could be coral transplants, or artificial constructs likes shipwrecks, concrete pipes, tyres and a purpose built structure called a reef ball.

The second wave from 2000-2010 was associated with scientists and conservationists responding to local concerns from cyclone damage, overfishing, introduced species and over-crowding at tourism sites, particularly in the Caribbean. Restoration methods at this point expanded to removing items as well as adding them, including algae, crown-of-thorns and lionfish.

Reef restoration has evolved over decades.
Author provided

The third wave, from 2016, has focused on new scientific technology such as micro-fragmentation: breaking coral into small pieces so it grows faster. It also emphasises partnerships between government-business-community to reduce threats and restore reefs.

This era also sees a huge increase in communication. Increasingly, we are influenced by social sciences and marketing rather than science and biology in our search for coral reef solutions. Organisations such as Rare, Citizens of the GBR and Reef Check are using citizen scientists, campaigns and pledges to reduce human impact and improve reefs’ health. As an example, the rapid phase out of plastic bags has been led by social media – not science.

Celebrating the Reef restoration Leaders

Documenting the history of reef restoration is important because it allows us to understand our past and be more informed and inspired to take action in the future.

Sculpture at the Underwater Museum at Lanzarote Rubicon.
© Jason deCaires Taylor

The great men and women in our history were innovators who responded to crisis and went against convention by restoring reefs.

We reviewed academic literature and conducted a global survey to find the pioneers who led reef restoration science, management, business and communication. These include Drs Austin Bowden-Kerby, David Vaughan, Todd Barber, Barach Rinkievich and Kristen Marhaver.




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Coral reefs work as nature’s sea walls – it pays to look after them


An idea without action is just a dream. Similarly, an idea that has not been communicated widely and is not known and adopted by the general community cannot result in changed behaviour. Increasingly we recognise that good science and management is not enough without community support and action.


The authors would like to acknowledge the valuable contribution of Nathan Cook, Senior Marine Scientist at Reef Ecologic, to this article.

A presentation on the history of Reef Restoration will occur at the Great Barrier Reef Restoration Symposium, July 16-19, Cairns.

Thanks to Jason deCaires Taylor for the use of images. See more at underwatersculpture.com.

The ConversationThis article was updated on July 25 to clarify the location of the reef pictured demonstrating the impact of restoration.

Adam Smith, Adjunct Associate Professor, James Cook University and Ian McLeod, Senior Research Scientist – Coastal Restoration, James Cook University

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