South Australian algae bloom and implications for other parts of the world

 

The tiny microalgae behind South Australia’s harmful algal bloom is among the most toxic ever tested

Mark Piovesan/Getty

Shauna Murray, University of Technology Sydney; Cheong Xin Chan, The University of Queensland; Craig Styan, University of Adelaide; Greta Gaiani, University of Technology Sydney, and Gustaaf Hallegraeff, University of Tasmania

Over the past 15 months, one of the country’s worst marine environmental disasters has been unfolding in South Australia.

A harmful algal bloom expanded in many coastal seas, killing thousands of fish, birds, shellfish and marine mammals. Even iconic species such as giant cuttlefish and seadragons have washed up dead on beaches.

These blooms happen when particular species of microscopic algae accumulate in a body of water. Several hundred species of microalgae produce toxins that, in high concentrations, can be harmful to humans and deadly to marine creatures.

Our new research shows Karenia cristata, the rare microalgal species behind this catastrophic bloom, is among the most toxic species to marine life ever studied. It’s capable of killing zooplankton, a type of small marine animal, in concentrations of just five cells per millilitre of seawater.

A marine disaster

In March 2025, dozens of surfers and swimmers fell ill after being exposed to water or seafoam on the Fleurieu Peninsula, south of Adelaide.

Local residents and tourists reported respiratory symptoms such as coughing and shortness of breath, as well as skin and eye irritation.

Reports of dead or dying marine creatures followed. And water testing by authorities found the first signs of an algal bloom.

In the following months, the algal bloom spread across SA’s two main gulfs, the Gulf St Vincent and Spencer Gulf. It has proved devastating for the state’s marine ecosystems, aquaculture industries and coastal communities.

The detection of brevetoxins in shellfish forced local oyster and mussel farmers to stop harvesting for up to eight months. Hundreds of coastal businesses, such as recreational fishing charters and wildlife tour operators, lost significant income.

What is Karenia cristata?

K. cristata is an extremely rare microalgal species. Before this bloom, it has only ever been found in two locations: South Africa and an island off the coast of Newfoundland.

There are many different species of Karenia. But they’re often hard to distinguish as their cells have a similar size and shape. This is a problem because Karenia species that look similar can produce completely different toxins, or no toxins at all.

In our new study, we used a method called scanning electron microscopy to get an extremely close-up view of K. cristata cells. This allowed us to compare them with the cells of other types of Karenia.

We also developed several new molecular genetic methods to measure the number and distribution of Karenia during the SA bloom. These genetic methods allowed us to easily distinguish between different Karenia species.

We found the only other Karenia species known to produce brevetoxins, K. brevis, was not in the SA bloom. We also found both K. cristata and K. brevis produced similar concentrations of brevetoxins, but with a different chemical makeup.

We found K. cristata was the dominant Karenia species. It was in 90% of the samples we tested, and remained in high concentrations over time. We also identified four other Karenia species in our samples.

Why is this algae so lethal?

Our latest research suggests the microalgae that caused SA algal bloom is among the deadliest species of its kind, in terms of impact on marine life.

Our team of 25 scientists took a closer look at laboratory-grown strains of K. cristata. To do this, we hand-picked individual cells of microalgae from seawater using ultrafine glass pipettes. We then grew them in bacteria-free, nutrient-rich seawater and made sure the temperature and amount of light stayed the same.

Using these lab-grown cells, we conducted three different experiments to observe how Karenia toxins affect the cells of fish and invertebrates – tiny marine animals that don’t have a backbone such as rotifers, a type of small zooplankton, and larval crustaceans.

The results were startling. K. cristata killed half the invertebrates we studied, even in extremely low concentrations of only five cells per millilitre – or 5,000 cells per litre – of seawater. This makes it more deadly to invertebrates than any other species of toxin-producing algae tested using this same method. The algae had a similar affect on lab-grown fish gill cells.

Compared with our experiments, K. cristata was present in higher concentrations in the waters around SA during the latest algal bloom. In August and September 2025, we routinely recorded concentrations higher than one million cells per litre of seawater off the coast of Adelaide.

This may explain why this bloom was so catastrophic.

Where to from here?

Until now, we thought an algal bloom of this scale could only develop in the warm waters off the southeastern United States. There, harmful algal blooms caused by the K. brevis microalgae are fairly common.

But our research shows other coastal areas around the world could also be at risk – including those with cooler waters.

We urgently need more research to understand the conditions that allow K. cristata to thrive and produce toxins in such high concentrations.

This will allow us to develop monitoring programs that not only detect harmful algae, but also identify which species may be most deadly. Only then can we protect our coastal ecosystems, industries and communities from another marine disaster.

Shauna Murray, Professor; Faculty of Science, University of Technology Sydney; Cheong Xin Chan, Associate Professor, School of Chemistry and Molecular Biosciences, The University of Queensland; Craig Styan, Associate Professor, School of Physics, Chemistry and Earth Sciences, University of Adelaide; Greta Gaiani, Chancellor's Postdoctoral Research Fellow, School of Life Sciences, University of Technology Sydney, and Gustaaf Hallegraeff, Adjunct Senior Researcher, Ecology and Biodiversity, University of Tasmania

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

Climate change - heating of oceans increasing

 

The world’s oceans are the hottest on record for June – and El Niño is set to turn up the heat even more

Artur Debat/Getty

Matthew England, UNSW Sydney; Alex Sen Gupta, UNSW Sydney, and Alistair Hobday, CSIRO

The world’s oceans are the hottest on record for June, pushing past records set during the 2023–24 El Niño years.

Right now, the average sea surface temperature is just under 21°C across the world’s tropical and temperate oceans. Before widespread industrialisation in 1870, the temperature was about 19.6°C.

That may not sound like a big difference. But heating the world’s oceans this much requires a truly enormous amount of energy. Of all the extra heat trapped by greenhouse gases from burning coal, gas and oil, more than 90% has gone into the world’s oceans.

As a result, the oceans are getting rapidly warmer. In 2025, the heat added was the equivalent of about 12 Hiroshima-scale nuclear bombs exploding every second of every day.

To find a climate analogue comparable to what’s happening now in the oceans, we would have to go back around 120,000 years to before the last ice age. Back then, slow shifts in Earth’s orbit led it to heat up gradually over thousands of years. Humans have accomplished a similar result in a little over a century.

But the heat in the ocean doesn’t just stay there. Hotter oceans fuel stronger cyclones, a more humid atmosphere, more intense rainfall and more heat in air masses over the seas, which can in turn make heatwaves over land more likely and more intense.

The El Niño forming in the tropical Pacific right now is likely to be a big one. As it develops, we can expect to see warmer temperatures and extreme events such as marine heatwaves in the western Indian, tropical Atlantic and eastern Pacific Oceans.

Global ocean sea surface temperatures are at the highest level recorded during June. HadISST, CC BY-NC-ND

Where are the hotspots on land and in the ocean?

Europe is sweltering through a record-breaking heatwave. The oceans surrounding the region and in enclosed seas are also exceptionally hot.

Parts of the Mediterranean are up to 6°C hotter than the long-term average.

Parts of the North Sea are up to 3°C warmer than average.

The seas around Europe have been much warmer than average. This map shows temperature anomalies from June 29 2026. opernicus Marine Service Data/European Union, CC BY-NC-ND

The forming El Niño has led to sea surface temperatures about 1.24°C warmer than average across a large area of the central eastern Pacific.

There’s much more heat below the surface as well. Subsurface conditions in the eastern Pacific are more than 6°C above average.

A typical El Niño lasts about a year. The full effect on atmospheric heat becomes clearest towards the end of the cycle. That means while we can expect 2026 to be very hot – perhaps a new record – next year is very likely to be even hotter, as ocean heat is moved back to the surface. We saw this during El Niño events over 2023–24 and 2015–16.

Steady ocean warming coupled with longer-lasting and more intense marine heatwaves pose huge threats to marine ecosystems such as coral reefs, sea grass meadows and coastal reefs. Research on the 2023–24 El Niño and the warm 2024 year showed widespread impacts.

Regions such as the eastern Pacific and the Mediterranean are unusually hot at present. This map shows temperature anomalies on June 30th 2026. Climate Reanalyzer, CC BY-NC-ND

From oceans to land

What happens in the oceans doesn’t stay there.

In June 2023, a record-breaking marine heatwave broke previous temperature records across the North Atlantic Ocean. Soon afterwards, large areas of Europe were hit by intense heatwaves, while extreme rains triggered deadly floods in Spain and severe bushfires broke out around the Mediterranean.

Rising ocean temperatures have many consequences.

A warmer ocean is less able to cool the land over summer. Warmer oceans also lead to more evaporation, boosting humidity and fuelling more intense and more sudden extreme rain and floods. These can have devastating consequences.

During El Niño events, there’s a clear geographical pattern. The regions we expect to be warmer or cooler during an El Niño roughly reflect where we are more or less likely to get marine heatwaves and more intense tropical cyclones.

Typical cyclone areas such as the western Indian Ocean could see stronger cyclones dumping heavier rainfall when they hit land. El Niño tends to bring extreme rain and floods to the western South America and dry conditions over parts of Australia and Southeast Asia.

Global surface temperatures tend to spike during strong El Nino years (red) and fall back during La Nina years, even as climate change drives the baseline higher. HadCRUT, CC BY-NC-ND

Can we prepare?

We are gaining a better understanding of how big climate drivers like El Niño shape weather and how to use ocean data from around the world to develop better seasonal forecasts authorities can use to prepare.

Over the past two years, we have improved our ability to forecast marine heatwaves three to four months ahead in Australia, the United States and other regions. Forecasts give marine authorities a chance to act early by reducing allowable fishery catches and beginning conservation efforts for vulnerable species.

The world’s oceans have been steadily warming since the 1870s, as this climate stripes visualisation shows. El Niño years (red tag above) tend to boost ocean warming while La Niña years (blue tag below) tend to be cooler. Tag width represents strength of the event. HadISST (before 1982)/NOAA OISST (1982 onward), CC BY-NC-ND

This early success in ocean forecasting may be short-lived. The current US administration last year slashed funding for climate data gathering networks and has worked to dismantle the National Center for Atmospheric Research.

This year, the administration announced it would end funding for a key ocean monitoring network before backing down.

Ongoing collection of ocean data is crucial for ocean and land forecasts. If they are weakened or discontinued, we could face the challenge of dealing with worsening climate impacts blind.

Ending the measuring of climate change won’t stop it happening. The only way to keep climate change from steadily worsening is to reach net zero as soon as humanly possible. Until then, we must use forecasts to prepare for what we can’t avoid.

Matthew England, Director of the ARC Centre of Excellence for Our Future Oceans and Scientia Professor in Oceanography, UNSW Sydney; Alex Sen Gupta, Associate Professor in Climate Science, UNSW Sydney, and Alistair Hobday, Chief Research Scientist - Environment, CSIRO

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

Astronomy - what makes a star ?

 

What makes a star a star? A strange ‘in‑between’ celestial object is testing astronomers’ boundaries

NOIRLab/NSF/AURA/R. Proctor

Md Redyan Ahmed, University of Sydney

Around 1,350 light years away from Earth is a star called TOI-2155. It’s a little bigger, heavier and hotter than the Sun, and it’s not particularly interesting or unusual in itself.

But orbiting around TOI-2155 is something very interesting indeed: a much smaller object called TOI-2155b, which we only know about by observing the tiny changes in light from the host star when the smaller object passes in front of it.

What is TOI-2155b? A mini-star? A giant planet? Or something in between? I’m glad you asked.

As my collaborators and I write in a recent paper in The Astronomical Journal, we’re not yet sure whether TOI-2155b is quite a star. But it seems to live on the fascinating boundary between a celestial beacon blazing through the heavens and a failed star that never quite ignites sustained hydrogen fusion.

Why stars fail

Stars start out as huge blobs of gas in space – but how big and heavy does a blob of gas have to be before it becomes a star? It sounds like a simple question, but astronomers have debated the answer for decades.

The gravitational pressure inside a star has to be great enough to fuse hydrogen atoms together into helium atoms, and to do it consistently for a long period. This is what creates the intense stream of heat and light that is a star’s signature.

If an object isn’t quite big enough to generate that much pressure – or if fusion doesn’t really kick off properly for some other reason – the gas becomes a kind of “failed star” known as a brown dwarf. These objects are hot early in life, but without sustained hydrogen fusion they gradually cool, giving off a dim infrared glow.

To learn more about why some blobs become stars and others become brown dwarfs, astrophysicists look for objects in the intermediate zone – the heaviest brown dwarfs and the lightest of stars.

That’s where TOI-2155b comes in. Weighing in at around 80.6 times the mass of Jupiter, it sits right on the theoretical boundary.

Where do stars end and brown dwarfs begin?

Using observations from NASA’s Transiting Exoplanet Survey Satellite (TESS) together with ground-based telescopes around the world, we determined the size and mass of TOI-2155b precisely. Although it is almost the same size as Jupiter, it is around 80 times more massive.

You might expect there to be a precise mass at which an object suddenly becomes a star. But as so often happens, in real life there is no clean line.

The standard theory suggests the difference between planets, brown dwarfs and stars all comes down to mass – but it’s not quite that simple. NASA/JPL-Caltech

Astronomers have traditionally placed the boundary near 75–80 times the mass of Jupiter. But modern theoretical models show the transition depends on other factors as well as mass.

An object’s age, its chemical composition, and even its atmospheric properties influence whether it can have sustained hydrogen fusion. That is why astronomers still disagree about exactly where the mass boundary between brown dwarfs and stars should be drawn.

A remarkably rare object

TOI-2155b may be one of the most massive brown dwarfs ever discovered – or one of the lightest stars. There are very few known objects in this transition zone of mass, and TOI-2155b will help us better understand the boundary.

Astronomy often learns the most from its rarest objects.

However, one object alone cannot determine the exact location of that boundary. Only once we have discovered and precisely studied more objects in this transition region can we refine our models to understand the conditions that allow a star to ignite and burn for billions of years – the process that has made the universe as we know it.

Md Redyan Ahmed, PhD Candidate in Astrophysics, University of Sydney

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

Climate change destroys underwater forests

 

Heat is destroying Australia’s underwater forests. Seaweed biobanks could help save them

Tom Burd, CC BY-NC-ND

Catalina A. Musrri, University of Sydney and Georgina Wood, Flinders University

Australia’s Great Southern Reef is built not by coral but by seaweed. The seaweed forests on these rocky reefs stretch more than 8,000 kilometres around southern Australia.

Amid the swaying fronds live seadragons, rock lobsters, giant cuttlefish and southern blue devils. The reef is home to more than 1,500 seaweed species and contributes billions to the economy each year.

But these remarkable cold water forests face a worsening threat. The ocean is getting steadily warmer, pushing seaweed species outside their survival zone. Much of this damage is done by sudden marine heatwaves, where temperatures spike and remain high for some time. Heatwaves have driven the decline of seaweed forests across the country.

To protect these underwater forests, we need to preserve their genetic diversity. We led the first attempt to cryopreserve (freezing and storing reproductive material at ultra-low temperatures) a key Australian seaweed, crayweed, and found the idea shows promise, though the techniques need to be perfected.

Why does seaweed matter?

Most of us encounter seaweed as a slightly stinky mass spotted when walking along a beach. But underwater, these large algae (not plants) form beautiful forests swaying in the current – some as tall as 30 metres.

Seaweed forests are among the most productive ecosystems on Earth. Like forests on land, they provide habitat, shelter and food for many creatures. They underpin valuable fisheries such as lobster and abalone.

When local populations are wiped out, they take something important with them – genetic diversity. Species with high genetic diversity can better adapt to change. Some populations will be able to tolerate heat better, for instance. But if these populations disappear, their unique genes go with them.

In 2011, an extreme marine heatwave in Western Australia led to two common seaweed species losing an estimated 30 to 65% of their genetic diversity. These losses may mean poorer outcomes in response to intensifying threats.

Seaweed forests are home to many species, such as this shovelnose ray in Australia’s first named seaweed forest, Yanggaa, at Coogee Beach in New South Wales. Operation Crayweed, CC BY-NC-ND

Consider the crayweed

Golden-brown crayweed (Phyllospora comosa) once formed extensive underwater forests along Sydney’s coastline. Many of these disappeared in the 1980s, likely due to sewage pollution. But crayweed didn’t return even after pollution levels fell.

Over the past 14 years, scientists and divers have replanted this species around Sydney through Operation Crayweed. Their work has led to the return of self-sustaining populations, including Australia’s first named seaweed forest – Yanggaa forest at Coogee Beach.

But restoration may not be enough in a rapidly warming ocean. Our research shows separate crayweed populations harbour unique genetic diversity – and some individuals appear better equipped to tolerate heat. It may make sense to plant germlings (baby seaweed) from these individuals in vulnerable populations to boost their chances of survival.

We tested storing crayweed reproductive material at very low temperatures using cryopreservation in liquid nitrogen. Rachel Venhuizen, CC BY-NC-ND

Of seed banks, biobanks and cryopreservation

For decades, thousands of land-based plant species have had their genetic diversity preserved through seed banks. The seeds stored are sleeping but still alive. If planted in the right conditions, they will grow.

Some kelp species can also be kept alive in biobanks – not as seeds, but in a microscopic form (gametophytes) able to be kept alive in laboratories for years. Current kelp collections support research, aquaculture and restoration programs around the world, including in Australia.

These banks are important. But they won’t be enough. The majority of seaweed species dominating the Great Southern Reef are known as fucoids. Unlike true kelps, fucoids don’t have this microscopic life stage – they release sperm and eggs directly into seawater that fertilise and form germlings. This makes species such as crayweed, bull kelp (Durvillaea potatorum), Cystophora sp. and Scytothalia dorycarpa more challenging to conserve.

It is possible to bank species which rely on sexual reproduction, such as humans, cows, corals and fucoids. Assisted reproduction methods such as IVF rely on cryopreservation: storing reproductive material, tissue or early life stages at ultra-low temperatures (around –196 °C) so it remains viable for future use.

Our recent research tested whether frozen crayweed sperm and germlings were viable after being thawed. We found the sperm did well, but the germlings did not (for now). Our ultimate goal is to develop proven methods able to work across a broader range of Australian seaweed species.

Preserving the genetic diversity of seaweed species would mean these genes can be drawn on to bring them back. This buys valuable time and keeps the door open for new methods such as assisted gene flow, where individuals from better-adapted populations are used to help vulnerable ones cope with warmer conditions.

Time for seaweed biobanks?

Australia already has an impressive algal culture collection and is a global leader in coral cryobanking.

Even so, it will take real work to develop methods of preserving the forest-forming seaweed species that rely on sexual reproduction. We need to learn which populations contain unique or threatened genetic diversity, understand which are most vulnerable to climate change and improve freezing and recovery techniques.

Choosing which species and populations should be done alongside Indigenous custodians, governments, conservation organisations and local communities.

Cryobanking doesn’t solve climate change or replace the need to protect habitat. It’s an insurance policy for biodiversity. Much has already been lost. Preserving the remaining genetic diversity of our seaweed forests may well be critical to the survival of the Great Southern Reef.

Catalina A. Musrri, Postdoctoral Research Fellow in Marine Biology, University of Sydney and Georgina Wood, ARC Research Fellow in Marine Science, Flinders University

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

Mars - terraforming quiz and interactive game

Mars from Space (c) ESA

Astronomers and scientists, not to mention science fiction writers, have often considered whether Mars can be colonised by human beings. The nearest planet to Earth, Mars has a thin atmosphere, desolate landscape and a higher radiation exposure yet still the allure of having a colony persists.

The renowned science journal, Nature, has devised an interactive game to see how terraforming Mars might work. The game is short, easy to do and consists of interactive multi-choice questions. Access to the game can be found at this hyperlink: nature.com -terriform mars game

Sydney Film Festival 2026 - Film Review - The Rays and Shadows

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The Rays and Shadows is set in the immediate period before and during World War II and is based on the true life story of newspaper publisher, Jean Luchaire and his daughter, Corinne, a French film actress. Luchaire supports peace between France and Germany and becomes a collaborator with the German occupying forces and a member of the Vichy Government until 1945.

The plot: Jean Luchaire (Jean Dujardin) is a failing newspaper publisher who co-sponsors a peace movement with Germany. He befriends Francophile German citizen, Otto Abetz who secures additional finance for Luchaire's newpaper from German Government sources. When WWII breaks out, Abetz is appointed as the Nazi German Ambassador to the Vichy Government and continues supporting Luchaire. Luchaire's daugher, Corrine (Nastya Golubeva) is a rising star in French cinema but as the war looms her opportunities decline due to a diagnosis of tuberculosis and she increasingly becomes dependent on German support for her career. Both she and her father benefit not only from the German occupation of France but from a range of black market opportunities, embassy parties and access to the Nazi administration. The film portrays the seduction of collaboration, power and privilege extensively. After the war, Jean Luchaire, was placed on trial by the French and executed. His daughter Corrine was found guilty of collaboration but deemed to have committed a lower level offence and she spent her final years under the sentence of indignite nationale before dying from tuberculosis in 1950. 

Nastya Golubeva in The Rays and Shadows

The film is expertly photographed with capable actors however with a screening time of over three hours, the film is too long and would have benefitted from sharper editing. Too many scenes are ancillary to the story and neither essential nor useful. Described as a 'sweeping drama', film director and screenwriter Xavier Giannoli could have wielded the red pen on the script and editing room 'scissors' before release.

Run time: 199 minutes

Rating [/10]: 6 out of 10

Recommended for cinema viewing: No. Recommended for streaming or subscription service viewing

Sydney Film Festival 2026 - Film Review - Sheep in the box

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Best described as sweet but very slow, this film by Japanese screenwriter and film director Hirokazu Kore-eda falls within the sci-fi genre covering the very topical issue of AI and robotics in a very human context.

Plot: Set in the near future, couple Otone (Haruka Ayase) and her husband Kensuke (Daigo Yamamoto) are mourning their young son who has died in mysterious circumstances. Turning to an AI/Robotics company, REbirth, they are supplied with a state-of-the-art humanoid replicantion of their lost son, Kakeru (Rimu Kuwaki). Although initially the humanoid has limited communication, over time this interaction improves despite Kensuke's dismissive references to a 'Tamagotchi' or a 'Roomba'. The couple are astonished to discover that memories of their past life with their son are surfacing from the humanoid. Memories that it should not have.

Rimu Kuwaki in Sheep in the box

The film is very slow moving with long scenes containing little activity or dialogue. It's non violent film generally and has elements of sentimentality especially when the humanoid Kakeru links up with other humanoid and human orphan children to depart for a special forest to make a home for themselves. Acting and cinematography meets the professional standard in film-making and its a pleasurable viewing experience although the film is too long at 126 minutes.

Run time: 126 minutes

Rating [/10]: 7 out of 10

Recommended for cinema viewing: Yes

Sydney Film Festival 2026 - Film Review - Gentle Monster

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The subject of child abuse and its' impact on a family is the central focus of Gentle Monster. 

Plotline: Famous concert pianist, Lucy (Lea Sedoux), her husband Philip (Laurence Rupp) and their young son move to the countryside as Philip is suffering increasingly from burnout. They settle in a country house outside of Munich into a calmer life and all seems idyllic until one morning the police arrive and seize Philip's electronic equipment and remove him for questioning. As the film progresses, Lucy questions if she knows the man she married and moment by moment comes to the realisation that Philip is guilty of trafficking child pornography for money. Lucy seeks a way forward to protect her son and herself while Philip continues to try and save the marriage. She initially supports her husband but following his confession to her and mounting evidence including that photos of their own son had been used, it becomes clear to her that the only option is to leave.

The film is tastefully photographed and veers away from sensationalism with measured performances from the cast. The film does have some structural problems. The flashbacks used to portray images of the previous happy family life and Lucy's various concert performances are not seamless but rather muddled, distracting and seemingly dropped into the film. There are various substrata tensions with various characters alluding to other personal issues that appear unnecessary for the overall story itself. 

Lea Seydoux superbly portrays a woman experiencing a range of emotions from shock, devastation, anger to optimism. Catherine Deneuve is cast as her emotionally distant mother who makes it plain that she never approved of her daughter's marriage but provides her with limited but useful support. Writer and film director Marie Kreutzer has created a powerful and morally complex film traversing a highly emotive topic.

Gentle Monster - Lea Seydoux (r)

Run time: 112 minutes

Rating [/10]: 8 out of 10

Recommended for cinema viewing: Yes