Photos from the field: why losing these tiny, loyal fish to climate change spells disaster for coral


Catheline Froehlich, Author provided

Catheline Y.M. Froehlich, University of Wollongong; Marian Wong, University of Wollongong, and O. Selma Klanten, University of Technology SydneyEnvironmental scientists see flora, fauna and phenomena the rest of us rarely do. In this series, we’ve invited them to share their unique photos from the field.


If you’ve ever dived on a coral reef, you may have peeked into a staghorn coral and seen small fish whizzing through its branches. But few realise that these small fish, such as tiny goby fish, play a crucial role in helping corals weather the storm of climate change.

But alarmingly, our new research found gobies decline far more than corals do after multiple cyclones and heatwaves. This is concerning because such small fish — less than 5 centimetres in length — are critical to coral and reef health.

Unfortunately, the number of cyclones and heatwaves is on the rise. These disasters have begun to occur back-to-back, leaving no time for marine life to recover.

With the recent push by UNESCO to list the Great Barrier Reef as “in danger”, the world is currently on edge about the status of coral reefs. We’re at a critical stage to take all the necessary measures to save coral reefs worldwide, and we must broaden our focus to understand how the important relationships between corals and fish are affected.

This five-lined coral goby (Gobiodon quinquestrigatus) is taking a break on a coral branch.
Catheline Froehlich, Author provided

Goby fish: the snack-sized friends of coral

In all environments, organisms can form relationships where they work together to improve each other’s health. This is called a mutual symbiosis, like a you-scratch-my-back principle.

In coral reefs, other examples of mutual symbioses include invisible zooxanthellae algae living within coral tissue, small cleaner fish removing parasites from big fish, and eels and groupers hunting together.

While this shark is taking a nap, small yellow fish are hiding under its fin, and it is also getting cleaned by a cleaner wrasse (slender black fish with neon blue outline).
Catheline Froehlich, Author provided
Living on the edge: some fish live inside branched corals, while others live around the perimeter of coral bommies like this.
Catheline Froehlich, Author provided

Gobies that live in corals are small, snack-sized fish that rarely venture beyond the prickly borders of their protective coral homes. The Great Barrier Reef is home to more than 20 species of coral gobies, which live in more than 30 species of staghorn corals.

In return for the coral’s protection, the gobies pluck off harmful algae growing on coral branches, produce a toxin to deter potential coral-eating fish, and reduce heat stress by swimming around the coral and stopping stagnant water build up.

The blue-spotted coral goby (Gobiodon erythrospilus) is holding its position by pushing its front pectoral fins against coral branches.
Catheline Froehlich, Author provided
Paired romance: these lemon coral gobies (Gobiodon citrinus) live in monogamous pairs while also sharing their coral with a humbug damselfish (Dascyllus aruanus).
Catheline Froehlich, Author provided

Even if their corals become stressed and bleached, they remain steadfast within the coral, helping it to survive. Without their full-time cleaning staff, corals would be more susceptible when threatened with climate change.

Unfortunately, just like Nemos (clownfish) living inside anemones, climate change threatens the mutual symbioses between gobies and corals.

Coral gobies in decline

While SCUBA diving, we surveyed corals and their goby friends over a four-year period (2014-17) of near-continuous devastation at Lizard Island, on the Great Barrier Reef. Over this time, two category 4 cyclones and two prolonged heatwaves wreaked havoc on this world-renowned reef.

Coral gobies are often hard to spot, so we use underwater flashlights to identify them correctly.
Catheline Froehlich, Author provided

What we saw was alarming. After the two cyclones, the 13 goby species (genus Gobiodon) and 28 coral species (genus Acropora) we surveyed declined substantially.

But after the two heatwaves, gobies suddenly fared even worse than corals. While some coral species persisted better than others, 78% no longer housed gobies.

Importantly, every single goby species either declined, or worse, completely disappeared. The few gobies we found were living alone, which is especially concerning because gobies breed in monogamous pairs, much like most humans do.

After cyclones and heatwaves, we found a lot of dead corals surrounding pockets of living corals and reef life at Lizard Island.
Catheline Froehlich, Author provided
We surveyed coral and goby survival and often found a lot of coral debris after heatwaves.
Catheline Froehlich, Author provided

Without urgent action, the outlook is bleak

More and more studies are showing reef fish behave differently in warmer and more acidic water.

Warmer water is even changing reef fish on a genetic level. Fish are struggling to reproduce, to recognise what is essential habitat, and to detect predators. Research has shown clownfish, for example, could not tell predatory fish (rockcods and dottybacks) from non-predators (surgeonfishes and rabbitfishes) when exposed to more acidic seawater.

Finding Nemo swimming in anemone in Lizard Island. The bright pink surrounding it is the column of the anemone. Picture the column as your neck and the tentacles as your hair.
Abigail Shaughnessy, Author provided

The bigger picture looks bleak. Corals are likely to become increasingly vulnerable if their symbiotic gobies and other inhabitants continue to decline. This could lead to further disruptions in the reef ecosystem because mutual symbioses are important for ecosystem stability.

We need to broaden our focus to understand how animal interactions like these are being affected in these trying times. This is an emerging field of study that needs more research in the face of climate change.

Here, one of my assistants, Al Alder, is measuring the coral so that we can tell what happens to the size of corals after each climatic disaster.
Catheline Froehlich, Author provided
Several fish that are not coral gobies are still found swimming about even after four years of climatic disasters at Lizard Island.
Catheline Froehlich, Author provided

On a global scale, multiple disturbances from cyclones and heatwaves are becoming the norm. We need to tackle the problem from multiple angles. For example, we must meet net zero carbon emissions by 2050 and stop soil erosion and agricultural runoff from flowing into the sea.

If we do not act now, gobies and their coral hosts may become a distant memory in this warming climate.The Conversation

Catheline Y.M. Froehlich, PhD Fellow, University of Wollongong; Marian Wong, Senior Lecturer, University of Wollongong, and O. Selma Klanten, Research Scientist, University of Technology Sydney

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

Pacific Island bats are utterly fascinating, yet under threat and overlooked. Meet 4 species


Artwork by Arison Kul from Lae Papua New Guinea.

John Martin, University of Sydney; David L. Waldien, Christopher Newport University; Junior Novera, The University of Queensland; Justin A. Welbergen, Western Sydney University; Malik OEDIN, Université de Nouvelle Calédonie; Nicola Hanrahan, Charles Darwin University; Tigga Kingston, Texas Tech University, and Tyrone Lavery, Australian National UniversityAm I not pretty enough? This article is part of The Conversation’s new series introducing you to unloved animals that need our help.


A whopping 191 different bat species live in the Pacific Islands across Micronesia, Melanesia, and Polynesia — but these are, collectively, the most imperilled in the world. In fact, five of the nine bat species that have gone extinct in the last 160 years have come from this region.

For too long, the conservation of Pacific Island bats has been largely overlooked in science. Of the 191 existing species, 25% are threatened with extinction, and we lack information to assess the status of a further 15%.

Just as these bats are rare and far-flung across the Pacific islands, so is the expertise and research needed to conserve them along with the vital ecosystem services they provide, such as pollination, seed dispersal, and insect control.

The first-ever Pacific Islands Bat Forum, held earlier this month, sought to change this, bringing together a new network of researchers, conservationists, and community members — 380 people from 40 countries and territories — dedicated to their survival.

So, why should we care about these bats anyway?

Conserving Pacific Island bats is paramount for preserving the region’s diverse human cultures and for safeguarding the healthy functioning of island ecosystems.

In many Pacific Island nations, bats have great cultural significance as totems, food, and traditional currency.

Bats are the largest land animals on many of the Pacific islands, and are vital “keystone species”, maintaining the structure of ecological communities.

Yet, Pacific Island bats are increasingly under threat, including from intensifying land use (farming, housing, roads) invasive species (rats, cats, snakes, ants), and human harvesting. They’re also vulnerable to climate change, which heightens sea levels and increases the intensity of cyclones and heatwaves.

So let’s meet four fascinating — but threatened — Pacific Island bats that deserve more attention.

1. Pacific sheath-tailed bat

Conservation status: endangered

Distribution: American Samoa, Federated States of Micronesia, Fiji, Guam, Northern Mariana Islands, Palau, Samoa, Tonga

Pacific Sheath tailed Bat (Emballonura semicaudata)
Ron Leidich

The Pacific sheath-tailed bat (Emballonura semicaudata) weighs just five-grams and has a weak, fluttering flight. Yet somehow, it has colonised some of the smaller and more isolated islands across the Pacific, from Samoa to Palau. That’s across 6,000 kilometres of ocean!

Over the past decade, this insect-eating, cave-roosting bat has disappeared from around 50% of islands where it has been recorded. The reasons for this are unclear. Disturbance of cave roosts, introduced species such as lantana and goats, and increasing use of pesticides, may all have played a part.

Unfortunately, the Pacific sheath-tailed bat is now presumed extinct in many former parts of its range, including American Samoa, Tonga, and several islands of the Northern Mariana Islands. This leaves Palau, the Federated States of Micronesia, and Fiji as remaining strongholds for the species, though data is limited.

2. Montane monkey-faced bat

Conservation status: critically endangered

Distribution: Solomon Islands

New Georgian monkey-faced bat Pteralopex taki — no picture exists of the Montane monkey-faced bat.
Tyrone Lavery

There are six species of monkey-faced bat — all are threatened, and all are limited to islands across the Solomon Islands, Bougainville, and Fiji.

The montane monkey-faced bat (Pteralopex pulchra) is one species, and weighs around 280 grams, eats fruit and nectar, and has incredibly robust teeth. But perhaps most startling is its ruby-red eyes and wing membranes that are marbled with white and black.

The montane monkey-faced bat has been recorded only once by scientists on a single mountain (Mt Makarakomburu) above the altitude of 1,250 metres, on Guadalcanal Island. This tiny range makes it vulnerable to rare, extreme events such as cyclones, which could wipe out a whole population in one swoop. And being limited to mountain-top cloud forests could place it at greater risk from climate change.

It’s an extreme example of both the endemism (species living in a small, defined area) and inadequacies of scientific knowledge that challenge Pacific island bat conservation.

3. Ornate flying-fox

Conservation status: vulnerable

Distribution: New Caledonia

Ornate flying-fox (Pteropus ornatus)‘
Malik Oedin, IAC

Like many fruit bats across the Pacific, New Caledonia’s endemic ornate flying-fox (Pteropus ornatus) is an emblematic species. Flying-foxes are hunted for bush meat, used as part of cultural practices by the Kanaks (Melanesian first settlers), are totems for some clans, and feature as a side dish during the “New Yam celebration” each year. Their bones and hair are also used to make traditional money.

Because they’re so highly prized, flying-foxes can be subject to illegal trafficking. Despite the Northern and Southern Provinces of New Caledonia having regulated hunting, flying-fox populations continue to decline. Recent studies predict 80% of the population will be gone in the next 30 years if hunting continues at current levels.

On a positive note, earlier this year the Northern Province launched a conservation management program to protect flying-fox populations while incorporating cultural values and practices.

4. Fijian free-tailed bat

Conservation status: endangered

Distribution: Fiji, Vanuatu

Fijian free tailed bat (Chaerophon bregullae)
Dave Waldien

In many ways, the Fijian free-tailed bat (Chaerephon bregullae) has become the face of proactive bat conservation in the Pacific Islands. This insect-eating bat requires caves to roost during the day and is threatened when these caves are disturbed by humans as it interrupts their daytime roosting. The loss of foraging habitat is another major threat.

The only known colony of reproducing females lives in Nakanacagi Cave in Fiji, with around 7,000 bats. In 2014, an international consortium with Fijian conservationists and community members came together to protect Nakanacagi Cave. As a result, it became recognised as a protected area in 2018.

But this species shares many characteristics with three of the nine bat species that have gone extinct globally. This includes being a habitat specialist, its unknown cause of decline, and its potential exposure to chemicals through insect foraging. It’s important we continue to pay close attention to its well-being.

Where do we go from here?

The perspectives of local knowledge from individual islands aren’t always captured in global scientific assessments of wildlife.

In many Pacific Islands, bats aren’t protected by national laws. Instead, in many countries, most land is under customary ownership, which means it’s owned by Indigenous peoples. This includes land in Papua New Guinea, Solomon Islands, and Vanuatu. Consequently, community landowners have the power to enact their own conservation actions.

The emerging Pacific Bat Network, inspired by the recent forum, aims to foster collaborative relationships between scientific conservationists and local leaders for species protection, while respecting cultural practices.

As the Baru Conservation Alliance — a locally-led, not-for-profit group from Malaita, Solomon Islands — put it in their talk at the forum:

conservation is not a new thing for Kwaio.

Now the forum has ended, the diverse network of people passionate about bat conservation is primed to work together to strengthen the conservation of these unique and treasured bats of the Pacific.The Conversation

John Martin, Research Scientist, Taronga Conservation Society Australia & Adjunct lecturer, University of Sydney; David L. Waldien, Adjunct assistant professor, Christopher Newport University; Junior Novera, PhD Candidate, School of Biological Sciences, The University of Queensland; Justin A. Welbergen, President of the Australasian Bat Society | Associate Professor of Animal Ecology, Western Sydney University; Malik OEDIN, PhD Population Biology and Ecology, Université de Nouvelle Calédonie; Nicola Hanrahan, Terrestrial Ecologist, Department of Environment, Parks and Water Security, Northern Territory Government & Visiting Fellow, Charles Darwin University; Tigga Kingston, Professor, Department of Biological Sciences, Texas Tech University, and Tyrone Lavery, Postdoctoral Research Fellow, Australian National University

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

Snorkellers discover rare, giant 400-year-old coral – one of the oldest on the Great Barrier Reef


Richard Woodgett

Adam Smith, James Cook University; Nathan Cook, James Cook University, and Vicki Saylor, Indigenous KnowledgeSnorkellers on the Great Barrier Reef have discovered a huge coral more than 400 years old which is thought to have survived 80 major cyclones, numerous coral bleaching events and centuries of exposure to other threats. We describe the discovery in research published today.

Our team surveyed the hemispherical structure, which comprises small marine animals and calcium carbonate, and found it’s the Great Barrier Reef’s widest coral, and one of the oldest.

It was discovered off the coast of Goolboodi (Orpheus Island), part of Queensland’s Palm Island Group. Traditional custodians of the region, the Manbarra people, have called the structure Muga dhambi, meaning “big coral”.

For now, Muga dhambi is in relatively good health. But climate change, declining water quality and other threats are taking a toll on the Great Barrier Reef. Scientists, Traditional Owners and others must keep a close eye on this remarkable, resilient structure to ensure it is preserved for future generations.

coral and snorkellers
Muga dhambi is the widest coral structure recorded on the Great Barrier Reef.
Richard Woodgett

Far older than European settlement

Muga dhambi is located in a relatively remote, rarely visited and highly protected marine area. It was found during citizen science research in March this year, on a reef slope not far from shore.

We conducted a literature review and consulted other scientists to compare the size, age and health of the structure with others in the Great Barrier Reef and internationally.

We measured the structure at 5.3 metres tall and 10.4 metres wide. This makes it 2.4 metres wider than the widest Great Barrier Reef coral previously measured by scientists.

Muga dhambi is of the coral genus Porites and is one of a large group of corals known as “massive Porites”. It’s brown to cream in colour and made of small, stony polyps.

These polyps secrete layers of calcium carbonate beneath their bodies as they grow, forming the foundations upon which reefs are built.

Muga dhambi’s height suggests it is aged between 421 and 438 years old – far pre-dating European exploration and settlement of Australia. We made this calculation based on rock coral growth rates and annual sea surface temperatures.

The Australian Institute of Marine Science has investigated more than 328 colonies of massive Porites corals along the Great Barrier Reef and has aged the oldest at 436 years. The institute has not investigated the age of Muga dhambi, however the structure is probably one of the oldest on the Great Barrier Reef.

Other comparatively large massive Porites have previously been found throughout the Pacific. One exceptionally large colony in American Samoa measured 17m × 12m. Large Porites have also been found near Taiwan and Japan.

Mountainous island and blue sea
Muga dhambi was discovered in waters off Goolboodi (Orpheus Island).
Shutterstock

Resilient, but under threat

We reviewed environmental events over the past 450 years and found Muga dhambi is unusually resilient. It has survived up to 80 major cyclones, numerous coral bleaching events and centuries of exposure to invasive species, low tides and human activity.

About 70% of Muga dhambi consisted of live coral, but the remaining 30% was dead. This section, at the top of the structure, was covered with green boring sponge, turf algae and green algae.

Coral tissue can die from exposure to sun at low tides or warm water. Dead coral can be quickly colonised by opportunistic, fast growing organisms, as is the case with Muga dhambi.

Green boring sponge invades and excavates corals. The sponge’s advances will likely continue to compromise the structure’s size and health.

We found marine debris at the base of Muga dhambi, comprising rope and three concrete blocks. Such debris is a threat to the marine environment and species such as corals.

We found no evidence of disease or coral bleaching.




Read more:
The Great Barrier Reef is in trouble. There are a whopping 45 reasons why


to come
The structure may be compromised by the advance of a sponge species across Muga dhambi (sponge is the darker half in this image).
Richard Woodgett

‘Old man’ of the sea

A Traditional Owner from outside the region took part in our citizen science training which included surveys of corals, invertebrates and fish. We also consulted the Manbarra Traditional Owners about and an appropriate cultural name for the structure.

Before recommending Muga dhambi, the names the Traditional Owners considered included:

  • Muga (big)
  • Wanga (home)
  • Muugar (coral reef)
  • Dhambi (coral)
  • Anki/Gurgu (old)
  • Gulula (old man)
  • Gurgurbu (old person).

Indigenous languages are an integral part of Indigenous culture, spirituality, and connection to country. Traditional Owners suggested calling the structure Muga dhambi would communicate traditional knowledge, language and culture to other Indigenous people, tourists, scientists and students.




Read more:
How Traditional Owners and officials came together to protect a stunning stretch of WA coast


coral rock under water with sky
It’s hoped the name Muga dhambi will encourage recognition of the connection Indigenous people have to the coral structure.
Richard Woodgett

A wonder for all generations

No database exists for significant corals in Australia or globally. Cataloguing the location of massive and long-lived corals can be benefits.

For example from a scientific perspective, it can allow analyses which can help understand century-scale changes in ocean events and can be used to verify climate models. Social and economic benefits can include diving tourism and citizen science, as well as engaging with Indigenous culture and stewardship.

However, cataloguing the location of massive corals could lead to them being damaged by anchoring, research and pollution from visiting boats.

Looking to the future, there is real concern for all corals in the Great Barrier Reef due to threats such as climate change, declining water quality, overfishing and coastal development. We recommend monitoring of Muga dhambi in case restoration is needed in future.

We hope our research will mean current and future generations care for this wonder of nature, and respect the connections of Manbarra Traditional Owners to their Sea Country.




Read more:
Not declaring the Great Barrier Reef as ‘in danger’ only postpones the inevitable


The Conversation


Adam Smith, Adjunct Associate Professor, James Cook University; Nathan Cook, Marine Scientist , James Cook University, and Vicki Saylor, Manbarra Traditional Owner, Indigenous Knowledge

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

Coral, meet coral: how selective breeding may help the world’s reefs survive ocean heating


Anna Scott, Author provided

Emily Howells, Southern Cross University and David Abrego, Southern Cross UniversityA single generation of selective breeding can make corals better able to withstand extreme temperatures, according to our new research. The discovery could offer a lifeline to reefs threatened by the warming of the world’s oceans.

Our research, published in Science Advances, shows corals from some of the world’s hottest seas can transfer beneficial genes associated with heat tolerance to their offspring, even when crossbred with corals that have never experienced such temperatures.

Across the world, corals vary widely, both in the temperatures they experience and their ability to withstand high temperatures without becoming stressed or dying. In the Persian Gulf, corals have genetically adapted to extreme water temperatures, tolerating summer conditions above 34℃ for weeks at a time, and withstanding daily averages up to 36℃.

These water temperatures are 2-4℃ higher than any other region where corals grow, and are on a par with end-of-century projections for reefs outside the Persian Gulf.

This led us to ask whether beneficial gene variants could be transferred to coral populations that are naïve to these temperature extremes. To find out, we collected fragments of Platygyra daedalea corals from the Persian Gulf, and cross-bred them with corals of the same species from the Indian Ocean, where summer temperatures are much cooler.

Platygyra coral colony
Platygyra, a brain-shaped coral found in many parts of the world.
Emily Howells, Author provided

We then heat-stressed the resulting offspring (more than 12,000 individual coral larvae) to see whether they could withstand temperatures of 33°C and 36°C — the summer maximums of their parents’ respective locations.

Immediate gains

We found an immediate transfer of heat tolerance when Indian Ocean mothers were crossed with Persian Gulf fathers. These corals showed an 84% increase in survival at high temperatures relative to purebred Indian Ocean corals, making them similarly resilient to purebred Persian Gulf corals.

Genome sequencing confirmed that gains in heat tolerance were due to the inheritance of beneficial gene variants from the Persian Gulf corals. Most Persian Gulf fathers produced offspring that were better able to withstand heat stress, and these fathers and their offspring had crucial variants associated with better heat tolerance.

Conversely, most Indian Ocean fathers produced offspring that were less able to survive heat stress, and were less likely to have gene variants associated with heat tolerance.




Read more:
Gene editing is revealing how corals respond to warming waters. It could transform how we manage our reefs


Survival of the fittest

Encouragingly, gene variants associated with heat tolerance were not exclusive to Persian Gulf corals. Two fathers from the Indian Ocean produced offspring with unexpectedly high survival under heat stress, and had some of the same tolerance-associated gene variants that are prevalent in Persian Gulf corals.

This suggests that some populations have genetic variation upon which natural selection can act as the world’s oceans grow hotter. Selective breeding might be able to accelerate this process.




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


We are now assessing the genetic basis for heat tolerance in the same species of coral on the Great Barrier Reef and in Western Australia. We want to find out what gene variants are associated with heat tolerance, how these variants are distributed within and among reefs, and whether they are the same as those that allow corals in the Persian Gulf to survive such extreme temperatures.

This knowledge will help us understand the potential for Australian corals to adapt to rapid warming.

Although our study shows selective breeding can significantly improve the resilience of corals to ocean warming, we don’t yet know whether there are any trade-offs between thermal tolerance and other important traits, and whether there are significant genetic risks involved in such breeding.

Platygyra larvae
Platygyra larvae. It remains to be seen whether the genetic benefits of heat-tolerance genes persist throughout life.
Emily Howells, Author provided

Our study was done on coral larvae without the algae that live in close harmony with corals after they settle on reefs. So it will also be important to examine whether the genetic improvements to heat tolerance continue into the corals’ later life stages, when they team up with these algae.

Of course, saving corals from the perils of ocean warming will require action on multiple fronts — there is no silver bullet. Selective breeding might provide some respite to particular coral populations, but it won’t be enough to protect entire ecosystems, and nor is it a substitute for the urgent reduction of greenhouse emissions needed to limit the oceans’ warming.The Conversation

Emily Howells, Senior Research Fellow in Marine Biology, Southern Cross University and David Abrego, Lecturer, National Marine Science Centre, Southern Cross University

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

The ocean is full of tiny plastic particles – we found a way to track them with satellites


Plastic fragments washed onto Schiavonea beach in Calabria, Italy, in a 2019 storm.
Alfonso Di Vincenzo/KONTROLAB /LightRocket via Getty Images

Christopher Ruf, University of MichiganPlastic is the most common type of debris floating in the world’s oceans. Waves and sunlight break much of it down into smaller particles called microplastics – fragments less than 5 millimeters across, roughly the size of a sesame seed.

To understand how microplastic pollution is affecting the ocean, scientists need to know how much is there and where it is accumulating. Most data on microplastic concentrations comes from commercial and research ships that tow plankton nets – long, cone-shaped nets with very fine mesh designed for collecting marine microorganisms.

But net trawling can sample only small areas and may be underestimating true plastic concentrations. Except in the North Atlantic and North Pacific gyres – large zones where ocean currents rotate, collecting floating debris – scientists have done very little sampling for microplastics. And there is scant information about how these particles’ concentrations vary over time.

Two people lower conical nets off a research ship into the water.
Researchers deploy plankton sampling nets in Lake Michigan.
NOAA, CC BY-SA

To address these questions, University of Michigan research assistant Madeline Evans and I developed a new way to detect microplastic concentrations from space using NASA’s Cyclone Global Navigation Satellite System. CYGNSS is a network of eight microsatellites that was launched in 2016 to help scientists predict hurricanes by analyzing tropical wind speeds. They measure how wind roughens the ocean’s surface – an indicator that we realized could also be used to detect and track large quantities of microplastics.

This story is part of Oceans 21

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

Looking for smooth zones

Annual global production of plastic has increased every year since the 1950s, reaching 359 million metric tons in 2018. Much of it ends up in open, uncontrolled landfills, where it can wash into river drainage zones and ultimately into the world’s oceans.

Researchers first documented plastic debris in the oceans in the 1970s. Today, it accounts for an estimated 80% to 85% of marine litter.

The radars on CYGNSS satellites are designed to measure winds over the ocean indirectly by measuring how they roughen the water’s surface. We knew that when there is a lot of material floating in the water, winds don’t roughen it as much. So we tried computing how much smoother measurements indicated the surface was than it should have been if winds of the same speed were blowing across clear water.

This anomaly – the “missing roughness” – turns out to be highly correlated with the concentration of microplastics near the ocean surface. Put another way, areas where surface waters appear to be unusually smooth frequently contain high concentrations of microplastics. The smoothness could be caused by the microplastics themselves, or possibly by something else that’s associated with them.

By combining all the measurements made by CYGNSS satellites as they orbit around the world, we can create global time-lapse images of ocean microplastic concentrations. Our images readily identify the Great Pacific Garbage Patch and secondary regions of high microplastic concentration in the North Atlantic and the southern oceans.

Tracking microplastic flows over time

Since CYGNSS tracks wind speeds constantly, it lets us see how microplastic concentrations change over time. By animating a year’s worth of images, we revealed seasonal variations that were not previously known.

This animation shows how satellite data can be used to track where microplastics enter the water, how they move and where they tend to collect.

We found that global microplastic concentrations tend to peak in the North Atlantic and Pacific during the Northern Hemisphere’s summer months. June and July, for example, are the peak months for the Great Pacific Garbage Patch.

Concentrations in the Southern Hemisphere peak during its summer months of January and February. Lower concentrations during the winter in both hemispheres are likely due to a combination of stronger currents that break up microplastic plumes and increased vertical mixing – the exchange between surface and deeper water – that transports some of the microplastic down below the surface.

This approach can also target smaller regions over shorter periods of time. For example, we examined episodic outflow events from the mouths of the China’s Yangtze and Qiantang rivers where they empty into the East China Sea. These events may have been associated with increases in industrial production activity, or with increases in the rate at which managers allowed the rivers to flow through dams.

Satellite images, color-coded to show density of microplastic particles in the water.
These images show microplastic concentrations (number of particles per square kilometer) at the mouths of the Yangtze and Qiantang rivers where they empty in to the East China Sea. (A) Average density year-round; (B) short-lived burst of particles from the Qiantang River; (C and D) short-lived bursts from the Yangtze River.
Evans and Ruf, 2021., CC BY

Better targeting for cleanups

Our research has several potential uses. Private organizations, such as The Ocean Cleanup, a nonprofit in The Netherlands, and Clewat, a Finnish company specializing in clean technology, use specially outfitted ships to collect, recycle and dispose of marine litter and debris. We have begun conversations with both groups and hope eventually to help them deploy their fleets more effectively.

Our spaceborne imagery may also be used to validate and improve numerical prediction models that attempt to track how microplastics move through the oceans using ocean circulation patterns. Scholars are developing several such models.

Large barge with conveyor belt pulling plastic debris out of river.
A solar-powered barge that filters plastic out of water, designed by Dutch NGO The Ocean Cleanup, deployed in the Rio Ozama, Dominican Republic, in 2020.
The Ocean Cleanup, CC BY

While the ocean roughness anomalies that we observed correlate strongly with microplastic concentrations, our estimates of concentration are based on the correlations that we observed, not on a known physical relationship between floating microplastics and ocean roughness. It could be that the roughness anomalies are caused by something else that is also correlated with the presence of microplastics.

One possibility is surfactants on the ocean surface. These liquid chemical compounds, which are widely used in detergents and other products, move through the oceans in ways similar to microplastics, and they also have a damping effect on wind-driven ocean roughening.

Further study is needed to identify how the smooth areas that we identified occur, and if they are caused indirectly by surfactants, to better understand exactly how their transport mechanisms are related to those of microplastics. But I hope this research can be part of a fundamental change in tracking and managing microplastic pollution.

[The Conversation’s science, health and technology editors pick their favorite stories. Weekly on Wednesdays.]The Conversation

Christopher Ruf, Professor of Climate and Space Sciences and Engineering, University of Michigan

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

You may have heard the ‘moon wobble’ will intensify coastal floods. Well, here’s what that means for Australia


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Mark Gibbs, Australian Institute of Marine ScienceExtreme floods this month have been crippling cities worldwide. This week in China’s Henan province, a year’s worth of rain fell in just three days. Last week, catastrophic floods swept across western Germany and parts of Belgium. And at home, rain fell in Perth for 17 days straight, making it the city’s wettest July in 20 years.

But torrential rain isn’t the only cause of floods. Many coastal towns and cities in Australia would already be familiar with what are known as “nuisance” floods, which occur during some high tides.

A recent study from NASA and the University of Hawaii suggests even nuisance floods are set to get worse in the mid-2030s as the moon’s orbit begins another phase, combined with rising sea levels from climate change.

The study was conducted in the US. But what do its findings mean for the vast lengths of coastlines in Australia and the people who live there?

A triple whammy

We know average sea levels are rising from climate change, and we know small rises in average sea levels amplify flooding during storms. From the perspective of coastal communities, it’s not if a major flood will occur, it’s when the next one will arrive, and the next one after that.

But we know from historical and paleontological records of flooding events that in many, if not most, cases the coastal flooding we’ve directly experienced in our lifetimes are simply the entrée in terms of what will occur in future.

Flooding is especially severe when a storm coincides with a high tide. And this is where NASA and the University of Hawaii’s new research identified a further threat.

Researchers looked at the amplification phase of the natural 18.6-year cycle of the “wobble” in the moon’s orbit, first identified in 1728.

The orbit of the moon around the sun is not quite on a flat plane (planar); the actual orbit oscillates up and down a bit. Think of a spinning plate on a stick — the plate spins, but also wobbles up and down.




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When the moon is at particular parts of its wobbling orbit, it pulls on the water in the oceans a bit more. This means for some years during the 18.6-year cycle, some high tides are higher than they would have otherwise been.

This results in increases to daily tidal rises, and this, in turn, will exacerbate coastal flooding, whether it be nuisance flooding in vulnerable areas, or magnified flooding during a storm.

View of Earth from the Moon
The moon’s orbit isn’t on a flat plane. It oscillates up and down, like a plate would when it spins on a stick.
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A major wobble amplification phase will occur in the mid-2030s, when climate change will make the problem become severe in some cases.

The triple whammy of the wobble in the moon’s orbit, ongoing upwards creep in sea levels from ocean warming, and more intense storms associated with climate change, will bring the impacts of sea-level rise earlier than previously expected — in many locations around the world. This includes in Australia.

So what will happen in Australia?

The locations in Australia where tides have the largest range, and will be most impacted by the wobble, aren’t close to the major population centres. Australia’s largest tides are close to Broad Sound, near Hay Point in central Queensland, and Derby in the Kimberley region of Western Australia.

However, many Australian cities host suburbs that routinely flood during larger high tides. Near my home in Meanjin (Brisbane), the ocean regularly backs up through the storm water drainage system during large high tides. At times, even getting from the front door to the street can be challenging.

Derby, WA, has one of the biggest tidal ranges in Australia.
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Some bayside suburbs in Melbourne are also already exposed to nuisance flooding. But a number of others that are not presently exposed may also become more vulnerable from the combined influence of the moon wobble and climate change — even when the weather is calm. High tide during this lunar phase, occurring during a major rainfall event, will result in even greater risk.




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In high-income nations like Australia, sea-level rise means increasing unaffordability of insurance for coastal homes, followed by an inability to seek insurance cover at all and, ultimately, reductions in asset values for those unable or unwilling to adapt.

The prognosis for lower-income coastal communities that aren’t able to adapt to sea-level rise is clear: increasingly frequent and intense flooding will make many aspects of daily life difficult to sustain. In particular, movement around the community will be challenging, homes will often be inundated, unhealthy and untenable, and the provision of basic services problematic.

What do we do about it?

While our hearts and minds continue to be occupied by the pandemic, threats from climate change to our ongoing standard of living, or even future viability on this planet, haven’t slowed. We can pretend to ignore what is happening and what is increasingly unstoppable, or we can proactively manage the increasing threat.

Some coastal communities, such as in Melbourne’s bayside suburbs, may experience flooding, even if they never have before.
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Thankfully, approaches to adapting the built and natural environment to sea-level rise are increasingly being applied around the world. Many major cities have already embarked on major coastal adaptation programs – think London, New York, Rotterdam, and our own Gold Coast.

However, the uptake continues to lag behind the threat. And one of the big challenges is to incentivise coastal adaptation without overly impacting private property rights.




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For flood-prone cities, seawalls raise as many questions as they answer


Perhaps the best approach to learning to live with water is led by the Netherlands. Rather than relocating entire communities or constructing large barriers like sea walls, this nation is finding ways to reduce the overall impact of flooding. This includes more resilient building design or reducing urban development in specific flood retention basins. This means flooding can occur without damaging infrastructure.

There are lessons here. Australia’s adaptation discussions have often focused on finding the least worst choice between constructing large seawalls or moving entire communities — neither of which are often palatable. This leads to inaction, as both options aren’t often politically acceptable.

The seas are inexorably creeping higher and higher. Once thought to be a problem for our grandchildren, it is becoming increasingly evident this is a challenge for the here and now. The recently released research confirms this conclusion.




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King tides and rising seas are predictable, and we’re not doing enough about it


The Conversation


Mark Gibbs, Principal Engineer: Reef Restoration, Australian Institute of Marine Science

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

When coral dies, tiny invertebrates boom. This could dramatically change the food web on the Great Barrier Reef


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Kate Fraser, University of TasmaniaThis week, international ambassadors will take a snorkelling trip to the Great Barrier Reef as part of the Australian government’s efforts to stop the reef getting on the world heritage “in danger” list.

The World Heritage Centre of UNESCO is set to make its final decision on whether to officially brand the reef as “in danger” later this month.

To many coral reef researchers like myself, who have witnessed firsthand the increasing coral bleaching and cyclone-driven destruction of this global icon, an in-danger listing comes as no surprise.

But the implications of mass coral death are complex — just because coral is dying doesn’t mean marine life there will end. Instead, it will change.

In recent research, my colleagues and I discovered dead coral hosted 100 times more microscopic invertebrates than healthy coral. This means up to 100 times more fish food is available on reefs dominated by dead coral compared with live, healthy coral.

This is a near-invisible consequence of coral death, with dramatic implications for reef food webs.

When coral dies

Tiny, mobile invertebrates — between 0.125 and 4 millimetres in size — are ubiquitous inhabitants of the surfaces of all reef structures and are the main food source for approximately 70% of fish species on the Great Barrier Reef.

These invertebrates, most visible only under a microscope, are commonly known as “epifauna” and include species of crustaceans, molluscs, and polychaete worms.




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When corals die, their skeletons are quickly overgrown by fine, thread-like “turfing algae”. Turf-covered coral skeletons then break down into beds of rubble.

We wanted to find out how the tiny epifaunal invertebrates — upon which many fish depend – might respond to the widespread replacement of live healthy coral with dead, turf-covered coral.

A sample of epifauna under the microscope.
Kate Fraser

I took my SCUBA gear and a box of lab equipment, and dived into a series of reefs across eastern Australia, from the Solitary Islands in New South Wales to Lizard Island on the northern Great Barrier Reef.

Underwater, I carefully gathered into sandwich bags the tiny invertebrates living on various species of live coral and those living on dead, turf-covered coral.

But things really got interesting back in the laboratory under the microscope. I sorted each sandwich bag sample of epifauna into sizes, identified them as best I could (many, if not most, species remain unknown to science), and counted them.

I quickly noticed samples taken from live coral took just minutes to count, whereas samples from dead coral could take hours. There were exponentially more animals in the dead coral samples.

The Great Barrier Reef may soon be listed as ‘in danger’
Rick Stuart-Smith

Why do they prefer dead coral?

Counting individual invertebrates is only so useful when considering their contribution to the food web. So we instead used the much more useful metric of “productivity”, which looks at how much weight (biomass) of organisms is produced daily for a given area of reef.

We found epifaunal productivity was far greater on dead, turf-covered coral. The main contributors were the tiniest epifauna — thousands of harpacticoid copepods (a type of crustacean) an eighth of a millimetre in size.

In contrast, coral crabs and glass shrimp contributed the most productivity to epifaunal communities on live coral. At one millimetre and larger, these animals are relative giants in the epifaunal world, with fewer than ten individuals in most live coral samples.

Dead coral rubble overgrown with turfing algae.
Rick Stuart-Smith

These striking differences may be explained by two things.

First: shelter. Live coral may look complex to the naked eye, but if you zoom in you’ll find turfing algae has more structural complexity that tiny epifauna can hide in, protecting them from predators.

A coral head is actually a community of individual coral polyps, each with a tiny mouth and fine tentacles to trap prey. To smaller epifauna, such as harpacticoid copepods, the surface of live coral is a wall of mouths and a very undesirable habitat.




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Almost 60 coral species around Lizard Island are ‘missing’ – and a Great Barrier Reef extinction crisis could be next


Second: food. Many epifauna, regardless of size, are herbivores (plant-eaters) or detritivores (organic waste-eaters). Turfing algae is a brilliant trap for fine detritus and an excellent substrate for growing films of even smaller microscopic algae.

This means dead coral overgrown by turfing algae represents a smorgasbord of food options for the tiniest epifauna through to the largest.

Meanwhile, many larger epifauna like coral crabs have evolved to live exclusively on live coral, eating the mucus that covers the polyps or particles trapped by the polyps themselves.

Harpacticoid copepod are just an eighth of a millimetre in size.
Naukhan/Wikimedia, CC BY

What this means for life on the reef?

As corals reefs continue to decline, we can expect increased productivity at the base level of reef food webs, with a shift from larger crabs and shrimp to small harpacticoid copepods.

This will affect the flow of food and energy throughout reef food webs, markedly changing the structure of fish and other animal communities. The abundance of animals that eat invertebrates will likely boom with increased coral death.

We might expect higher numbers of fish such as wrasses, cardinalfish, triggerfish, and dragonets, with species preferring the smallest epifauna most likely to flourish.

The dragonet species, mandarinfish, feeds on the smallest harpacticoid copepod prey.
Rick Stuart-Smith

Invertebrate-eating animals are food for a diversity of carnivores on a coral reef, and most fish Australians want to eat are carnivores, such as coral trout, snapper, and Spanish mackerel.

While we didn’t investigate exactly which species are likely to increase following widespread coral death, it’s safe to say populations of fish targeted by recreational and commercial fisheries on Australia’s coral reefs are likely to change as live coral is lost, some for better and some for worse.




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The Great Barrier Reef is undoubtedly in danger, and it’s important that we make every effort to protect and conserve the remaining live, healthy coral. However, if corals continue to die, there will remain an abundance of life in their absence, albeit very different life from that to which we are accustomed.

As long as there is hard structure for algae to grow on, there will be epifauna. And where there is epifauna, there is food for fish, although perhaps not for all the fish we want to eat.The Conversation

Kate Fraser, Marine Ecologist, University of Tasmania

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

Almost 60 coral species around Lizard Island are ‘missing’ – and a Great Barrier Reef extinction crisis could be next


Michael Emslie

Zoe Richards, Curtin UniversityThe federal government has opposed a recommendation by a United Nations body that the Great Barrier Reef be listed as “in danger”. But there’s no doubt the natural wonder is in dire trouble. In new research, my colleagues and I provide fresh insight into the plight of many coral species.

Worsening climate change, and subsequent marine heatwaves, have led to mass coral deaths on tropical reefs. However, there are few estimates of how reduced overall coral cover is linked to declines in particular coral species.

Our research examined 44 years of coral distribution records around Lizard Island, at the northern end of the Great Barrier Reef. We found 16% of coral species have not been seen for many years and are at risk of either local extinction, or disappearing from parts of their local range.

This is alarming, because local extinctions often signal wider regional – and ultimately global – species extinction events.

Healthy coral near Lizard Island in 2011, top, then six years later after two bleaching events, bottom.
Healthy coral near Lizard Island in 2011, top, then six years later after two bleaching events, bottom.
Zoe Richards

Sobering findings

The Lizard Island reef system is 270 kilometres north of Cairns. It has suffered major disturbances over the past four decades: repeated outbreaks of crown-of-thorns seastars, category 4 cyclones in 2014 and 2015, and coral bleaching events in 2016, 2017 and 2020.

Our research focused on “hermatypic” corals around Lizard Island. These corals deposit calcium carbonate and form the hard framework of the reef.

We undertook hard coral biodiversity surveys four times between 2011 and 2020, across 14 sites. We combined the results with published and photographic species records from 1976 to 2020.

red fleshy coral with blue spots
Micromussa lordhowensis is popular in the aquarium trade.
Zoe Richards

Of 368 hard coral species recorded around Lizard Island, 28 (7.6%) have not been reliably recorded since before 2011 and may be at risk of local extinction. A further 31 species (8.4%) have not been recorded since 2015 and may be at risk of range reduction (disappearance from parts of its local range).

The “missing” coral species include:

  • Acropora abrotanoides, a robust branching shallow water coral that lives on the reef crest and reef flat has not been since since 2009
  • Micromussa lordhowensis, a low-growing coral with colourful fleshy polyps. Popular in the aquarium trade, it often grows on reef slopes but has not been seen since 2005
  • Acropora aspera, a branching coral which prefers very shallow water and has been recorded just once, at a single site, since 2011.

The finding that 59 coral species are at risk of local extinction or range reduction is significant. Local range reductions are often precursors to local species extinctions. And local species extinctions are often precursors to regional, and ultimately global, extinction events.

Each coral species on the reef has numerous vital functions. It might provide habitat or food to other reef species, or biochemicals which may benefit human health. One thing is clear: every coral species matters.




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reddish coral underwater
Acropa abrotanoides, one of the corals ‘missing’ from around Lizard Island.
Zoe Richards

A broader extinction crisis?

As human impacts and climate threats mount, there is growing concern about the resilience of coral biodiversity. Our research suggests such concerns are well-founded at Lizard Island.

Coral reef communities are dynamic, and so detecting species loss can be difficult. Our research found around Lizard Island, the diversity of coral species fluctuated over the past decade. Significant declines were recorded from 2011 to 2017, but diversity recovered somewhat in the three following years.

Local extinctions often happen incrementally and can therefore be “invisible”. To detect them, and to account for natural variability in coral communities, long-term biodiversity monitoring across multiple locations and time frames is needed.

Green coral
Acropora aspera has been recorded just once, at a single location, since 2011.
Anne Hoggett

In most locations however, data on the distribution and abundance of all coral species in a community is lacking. This means it can be hard to assess changes, and to understand the damage that climate change and other human-caused stressors are having on each species.

Only with this extra information can scientists conclusively say if the level of local extinction risk at Lizard Island indicates a risk that coral species may become extinct elsewhere – across the Great Barrier Reef and beyond.




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The Conversation


Zoe Richards, Senior Research Fellow, Curtin University

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