Sparkling dolphins swim off our coast, but humans are threatening these natural light shows



Dean Cropp, Author provided

Dr Vanessa Pirotta, Macquarie University

It was 2 am on a humid summer’s night on Sydney’s coast. Something in the distance caught my eye – a pod of glowing dolphins darted towards the bow of the boat. I had never seen anything like it before. They were electric blue, trailing swaths of light as they rode the bow wave.

It was a stunning example of “bioluminescence”. The phenomenon is the result of a chemical reaction in billions of single-celled organisms called dinoflagellates congregating at the sea surface. These organisms are a type of phytoplankton – tiny microscopic organisms many sea creatures eat.




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Dinoflagellates switch on their bioluminescence as a warning signal to predators, but it can also be triggered when they’re disturbed in the water – in this case, by the dolphins.

You can see marine bioluminescence from land in Australia. Places like Jervis Bay and Tasmania are renowned for such spectacles.

But this dazzling night-time show is under threat. Light pollution creates brighter nights and disrupts ecological rhythms along the coast, such as breeding and feeding patterns. With so much human activity close to the shore and at sea, how much longer can we continue to enjoy this natural light show?

Lighting up the world has an ecological price

Light pollution is a well-known problem for inland ecosystems, particularly for nocturnal species.

In fact, a global study published earlier this year identified light pollution as an extinction threat to land bioluminescent species. The study surveyed firefly experts, who considered artificial light to be the second greatest threat to fireflies after habitat destruction.

Artificial light is one of the biggest threats fireflies face.
Shutterstock

At sea, artificial light pollution enters the marine environment temporarily (lights from ships and fishing activities) and permanently (coastal towns and offshore oil platforms). To make matters worse, light from cities can extend further offshore by scattering into the atmosphere and reflecting off clouds. This is known as artificial sky glow.

For organisms with circadian clocks (day-night sleep cycles), this loss of darkness can have damaging effects.

Bioluminescence in Sydney in the wake of the boat the author was on.
Vanessa Pirotta, Author provided

For example it can disrupt animal metabolism, which can lead to weight gain. Artificial light can also change sea turtle nesting behaviour and can disorientate turtle hatchlings when trying to get to sea, lowering their chances of survival.




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It can also disorientate the foraging of fish communities; alter predatory fish behaviour (such as in Yellowfin Bream and Leatherjacks) leading to increased predation in artificial light at night; cause reproductive failure in clownfish; and change the structural composition of marine invertebrate communities.

What are lights along the coast doing to bioluminescent species?
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For zooplankton – a vital species for a range of bigger animals – artificial light disrupts their “diel vertical migration”. This term refers to the movement of zooplankton from the depths of the ocean where they spend the day to reduce fish predation, rising to the surface at night to feed.

What does this mean for bioluminescent species?

Increased exposure to artificial light due to human activities, such as growing cities and increased global shipping movement, may disrupt when and where bioluminescent species hang out.

In turn, this may influence where predators move, leading to disruptions in the marine food web, potentially changing the dynamics of energy transfer efficiency between marine species.

Bioluminescence draws tourists and photographers in Tasmania.
Shutterstock

Bioluminescence usually serves as a communication function, such as to warn off predators, attract a mate or lure prey. For many species, light pollution in the ocean may compromise this biological communication strategy.

And for light-producing organisms such as dinoflagellates, excess artificial light may reduce the effectiveness of their bioluminescence because they won’t shine as bright, potentially increasing their risk of being eaten.

Have you read Julia Baird’s new book? It’s a great introduction to the science behind the ephemeral bioluminescence at sea.
HarperCollins Australia

A 2016 study in the Arctic revealed the critical depth where atmospheric light dims to darkness, and bioluminescence from organisms becomes dominant, was approximately 30 metres below the sea surface.

This means any change to light in the Arctic influences when marine organisms rise to the surface. If there is too much light, these organisms remain deeper for longer where it’s safe – reducing their potential feeding time.




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What can we do?

Understanding the level at which artificial light penetrates the ocean is tricky, especially so when dealing with mobile sources of light pollution such as ships, which are becoming an almost permanent fixture in some areas of the ocean.

Bioluminescence usually serves as a communication function, such as to warn off predators.
Shutterstock

Pockets of darkness still remain in our oceans. But they are becoming rarer, making light pollution a serious global threat to marine life.




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The spectacle of glowing dolphins should serve as a timely reminder of our need to conserve the darkness we have left.

Simple steps at home such as switching off lights and reducing unnecessary outdoor lighting, especially if you live near the ocean, is a step in the right direction to doing your bit for nocturnal species.The Conversation

Dr Vanessa Pirotta, Marine scientist and science communicator, Macquarie University

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

There are 10 catastrophic threats facing humans right now, and coronavirus is only one of them


Arnagretta Hunter, Australian National University and John Hewson, Crawford School of Public Policy, Australian National University

Four months in, this year has already been a remarkable showcase for existential and catastrophic risk. A severe drought, devastating bushfires, hazardous smoke, towns running dry – these events all demonstrate the consequences of human-induced climate change.

While the above may seem like isolated threats, they are parts of a larger puzzle of which the pieces are all interconnected. A report titled Surviving and Thriving in the 21st Century, published today by the Commission for the Human Future, has isolated ten potentially catastrophic threats to human survival.

Not prioritised over one another, these risks are:

  1. decline of natural resources, particularly water
  2. collapse of ecosystems and loss of biodiversity
  3. human population growth beyond Earth’s carrying capacity
  4. global warming and human-induced climate change
  5. chemical pollution of the Earth system, including the atmosphere and oceans
  6. rising food insecurity and failing nutritional quality
  7. nuclear weapons and other weapons of mass destruction
  8. pandemics of new and untreatable disease
  9. the advent of powerful, uncontrolled new technology
  10. national and global failure to understand and act preventatively on these risks.

The start of ongoing discussions

The Commission for the Human Future formed last year, following earlier discussions within emeritus faculty at the Australian National University about the major risks faced by humanity, how they should be approached and how they might be solved. We hosted our first round-table discussion last month, bringing together more than 40 academics, thinkers and policy leaders.

The commission’s report states our species’ ability to cause mass harm to itself has been accelerating since the mid-20th century. Global trends in demographics, information, politics, warfare, climate, environmental damage and technology have culminated in an entirely new level of risk.

The risks emerging now are varied, global and complex. Each one poses a “significant” risk to human civilisation, a “catastrophic risk”, or could actually extinguish the human species and is therefore an “existential risk”.

The risks are interconnected. They originate from the same basic causes and must be solved in ways that make no individual threat worse. This means many existing systems we take for granted, including our economic, food, energy, production and waste, community life and governance systems – along with our relationship with the Earth’s natural systems – must undergo searching examination and reform.

COVID-19: a lesson in interconnection

It’s tempting to examine these threats individually, and yet with the coronavirus crisis we see their interconnection.

The response to the coronavirus has had implications for climate change with carbon pollution reduction, increased discussion about artificial intelligence and use of data (including facial recognition), and changes to the landscape of global security particularly in the face of massive economic transition.

It’s not possible to “solve” COVID-19 without affecting other risks in some way.

Shared future, shared approach

The commission’s report does not aim to solve each risk, but rather to outline current thinking and identify unifying themes. Understanding science, evidence and analysis will be key to adequately addressing the threats and finding solutions. An evidence-based approach to policy has been needed for many years. Under-appreciating science and evidence leads to unmitigated risks, as we have seen with climate change.

The human future involves us all. Shaping it requires a collaborative, inclusive and diverse discussion. We should heed advice from political and social scientists on how to engage all people in this conversation.




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Imagination, creativity and new narratives will be needed for challenges that test our civil society and humanity. The bushfire smoke over the summer was unprecedented, and COVID-19 is a new virus.

If our policymakers and government had spent more time using the available climate science to understand and then imagine the potential risks of the 2019-20 summer, we would have recognised the potential for a catastrophic season and would likely have been able to prepare better. Unprecedented events are not always unexpected.

Prepare for the long road

The short-termism of our political process needs to be circumvented. We must consider how our actions today will resonate for generations to come.

The commission’s report highlights the failure of governments to address these threats and particularly notes the short-term thinking that has increasingly dominated Australian and global politics. This has seriously undermined our potential to decrease risks such as climate change.




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The shift from short to longer term thinking can began at home and in our daily lives. We should make decisions today that acknowledge the future, and practise this not only in our own lives but also demand it of our policy makers.

We’re living in unprecedented times. The catastrophic and existential risks for humanity are serious and multifaceted. And this conversation is the most important one we have today.The Conversation

Arnagretta Hunter, ANU Human Futures Fellow 2020; Cardiologist and Physician., Australian National University and John Hewson, Professor and Chair, Tax and Transfer Policy Institute, Crawford School of Public Policy, Australian National University

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