Tag Archives: Bleaching

Pristine coral reef found in Tahiti is as yet unaffected by bleaching

UNESCO scuba divers have discovered a new coral reef in the depths of Tahiti’s coastline.

Image credits UNESCO / Alexis Rosenfeld / 1 Ocean.

Most of the news regarding coral reefs we’ve heard recently revolves around bleachings — deadly events that take place when waters get too hot for corals to survive. Amid this backdrop, we get a rare piece of good news: divers from the United Nations Educational, Scientific and Cultural Organization (UNESCO) report discovering a new, massive reef off the coast of Tahiti, the largest island in French Polynesia, South Pacific.

The reef is composed of rose-shaped corals, untouched by humans so far, and in surprisingly good health given the global plight of coral reefs.

New reefs

The reef, which remains unnamed so far, measures around 1.9 miles (3 kilometers) in length and between 98 to 213 feet (30 to 65 meters) across. It formed at a depth of between 100 and 180 feet (31 to 55 meters), unusually deep for a coral reef in the tropics; they are usually found in shallow water, less than 82 feet (25 meters) from the surface.

Researchers believe that this depth helped insulate the reef from the brunt of climate-change-induced effects.

An encrusting plate coral species, Pachyseris speciosa, is the main dweller of the reef. It forms rose-like groupings that can reach up to 6.5 feet (2 meters) wide. The reef was discovered by seafloor explorers of the Ocean 1 project in November 2021.

“It was magical to witness giant, beautiful rose corals which stretch for as far as the eye can see,” Alexis Rosenfeld, an underwater photographer and founder of the Ocean project, which is jointly run by UNESCO, said in a statement. “It was like a work of art.”

The new reef lies close to the upper limit of the mesophotic zone. Corals in this zone receive less sunlight than those in shallower reefs and, to make up for this lack of light, corals like P. speciosa grow wide and flat to maximize their surface area and enable them to capture more light.

Reefs at this depth have historically been very hard to study, as unprotected divers cannot operate here for long due to a variety of reasons. At the same time, this zone is too shallow for the use of remotely operated vehicles (ROVs), according to NOAA. Novel developments, however, such as the use of air-helium mixes to prevent hallucinations and decompression sickness, mean that divers were able to explore these regions for longer periods of time. Better underwater camera equipment also allows them to capture more data faster than ever before, the statement adds, making the mesophotic zone fully explorable for the first time in history.

With the help of such advancements, the team carried out around 200 total diving hours on the reef, allowing them to map it out in great detail and even observe the spawning of corals.

This discovery is particularly exciting as coral reefs are one of the most at-risk ecosystems on the planet. Climate change, chemical and plastic pollution, sediment run-off, overfishing, explosive fishing (using dynamite), and tourism are all affecting them. In total, 237 species of coral are listed as threatened with extinction on the International Union for the Conservation of Nature (IUCN) Red List to date.

Climate change is the main driver of extinction among coral reefs, as it raises sea-surface temperatures and increases the acidity levels of the oceans. This combination of factors causes coral bleaching, a process through which heat-stressed corals expel their symbiotic, photosynthetic algae, the same organisms that supply them with energy. This process, often repeated at short intervals due to warmer climates, is very usually fatal for coral colonies. Roughly 75% of the world’s reefs experienced some degree of bleaching between 2014 and 2017.

The newly-found reef seems unaffected by climate change so far.

“The discovery of this reef in such a pristine condition is good news and can inspire future conservation,” Laetitia Hedouin, a coral expert at the French National Center for Scientific Research, who was involved with the project, said in the statement. “We think that deeper reefs may be better protected from global warming”.

The findings could suggest that mesophotic reefs may have a vital role to play as backups for shallow-water reefs, which are struggling to survive due to bleaching events. They can also provide new homes for species that rely on those reefs, such as fish and crustaceans, when shallow-water reefs are destroyed.

Researchers develop a new tool to identify at-risk corals

One of the first signs that climate change is already upon us came from heat-stressed corals. Now, new research aims to help us understand which species need protection the most.

Image via Pixabay.

Corals form sprawling reefs below the ocean’s surface, which provide food and shelter for a myriad of species. They are a very important link in marine ecosystems and a very useful indicator for their health. But they’re also being slowly killed by the heat. When corals experience an environment that is too hot for too long they ‘evict’ bacteria they share their chalky bodies with. They can recover from such bleaching events if they’re not too frequent. Sadly, however, climate change is making multiple bleaching events take place in quick succession, pushing corals way beyond their breaking point.

New research aims to address the issue by allowing us to tell which coral reefs are at risk of bleaching before such events take place — an ounce of prevention is worth a pound of cure, after all.

Deadly hot

“This is similar to a blood test to assess human health,” said senior author Debashish Bhattacharya, a distinguished professor in the Department of Biochemistry and Microbiology in the School of Environmental and Biological Sciences at Rutgers University-New Brunswick. “We can assess coral health by measuring the metabolites (chemical byproducts) they produce and, ultimately, identify the best interventions to ensure reef health.”

“Coral bleaching from warming waters is an ongoing worldwide ecological disaster. Therefore, we need to develop sensitive diagnostic indicators that can be used to monitor reef health before the visible onset of bleaching to allow time for preemptive conservation efforts.”

The new approach could help us tell exactly which species of coral need special care and protection from climate change, the authors explain. Around 500 million people depend on reefs or reef-supported ecosystems around the world, so such a tool would be no mean feat.

Apart from higher average water temperatures (which lead to bleaching but also higher water acidity), corals and coral reefs need to contend with rising sea levels (which threaten their access to sunlight), unsustainable fishing (which can physically damage the reefs and damages the ecosystem’s balance), invasive species, impacts from crafts or marine debris, and natural events such as cyclones.

The study looked at how Hawaiian stony corals respond to heat stress to identify the metabolites that indicate the organisms are under stress. They used the heat-resistant Montipora capitata and heat-sensitive Pocillopora acuta corals, which were placed in seawater tanks at the Hawai’i Institute of Marine Biology for several weeks under warm conditions. The chemicals they produced were then compared to those of other corals not subjected to heat stress.

“Our work, for the first time, identified a variety of novel and known metabolites that may be used as diagnostic indicators for heat stress in wild coral before or in the early stages of bleaching,” Bhattacharya said.

The team is hard at work replicating their findings in a larger-scale experiment — so far, they say, the results are quite promising. Their end goal is to create a “coral hospital” featuring a new lab-on-a-chip device, which can monitor the organisms’ health in real time.

The paper “Metabolomic shifts associated with heat stress in coral holobionts” has been published in the journal Science Advances.

Climate change killed half the corals in the Great Barrier Reef — and it could get worse soon

Australia’s Great Barrier Reef has lost more than half of its coral population in the last three decades, according to a new study, with climate change being the main driver of this loss. The researchers found that all types of coral had suffered a decline here, in the world’s largest reef system.

Flickr American Rugbier

Coral reefs are some of the most vibrant marine ecosystems on the planet. They are called the rainforests of the sea, as between a quarter and one-third of all marine species rely on them at some point in their life cycle. Fishes and other organisms shelter, find food, and reproduce near them.

The Great Barrier Reef covers nearly 133,000 square miles and is home to more than 1,500 species of fish, 411 species of hard corals, and 4,000 types of mollusk. It also holds great scientific value as the habitat of species such as the dugong and the large green turtle, both threatened with extinction.

A group of researchers from the ARC Centre of Excellence for Coral Reef Studies in Australia assessed coral communities and their colony size along the length of the Great Barrier Reef between 1995 and 2017. The found depletion of virtually all coral populations.

“A vibrant coral population has millions of small, baby corals, as well as many large ones” said Andy Dietzel, co-author, in a statement. “Our results show the ability of the Great Barrier Reef to recover is compromised compared to the past, because there are fewer babies, and fewer large breeding adults.”

Population declines were seen in both shallow and deep-water coral species, the researchers found. Branching and tablet-shaped corals, which provide habitats for several types of fish, were the worst affected by mass bleaching events in 2016 and 2017 (caused by record-breaking temperatures).

Bleaching occurs when corals that are under thermal stress drive out the algae, known as zooxanthellae, that give them color. Corals can recover if normal conditions return, but that can take decades. A study from last year found that damaged coral colonies had struggled to regenerate because most of the adult corals had died.

“We used to think the Great Barrier Reef is protected by its sheer size — but our results show that even the world’s largest and relatively well-protected reef system is increasingly compromised and in decline,” Terry Hughes, co-author, said in a statement. “There’s no time to lose, we have to decrease greenhouse gas emissions.”

Global temperatures have already risen by about 1ºC since pre-industrial times. The Paris Agreement on climate change commits countries to limit global warming to 2ºC, or ideally 1.5º. If that threshold is exceeded, 90% of the world’s corals will be gone, according to a report by the Intergovernmental Panel on Climate Change (IPCC).

The study was published in the journal Proceedings of the Royal Society B.

Microalgae could protect coral reefs from climate change

Coral reefs are among the most biodiverse ecosystems of the planet but also among the most threatened, currently dying at record rates across the world due to climate change.

Credit Wikipedia Commons

Reducing carbon emissions is considered the main way to help them, which would prevent waters from getting too hot and acidic. But researchers in Australia are exploring other alternatives as well, such as training the microalgae that keep corals alive.

Higher average temperatures put stress on coral and can lead to them ejecting their symbiotic algae, a process known as coral bleaching. When that happens, it can be a death sentence for coral and the species that rely on healthy reefs. In an effort to help them, scientists created an exposure therapy experiment for the tiny algae that provide them with life.

“Coral reefs are in decline worldwide,” lead-author Patrick Buerger said in a statement. “Climate change has reduced coral cover, and surviving corals are under increasing pressure as water temperatures rise and the frequency and severity of coral bleaching events increase.”

The researchers exposed ten strains of algae to water heated to about 89 degrees Fahrenheit (or 31ºC) for four years, which is roughly the peak temperature the Great Barrier Reef reached in February. That threshold has been registered to trigger mass bleaching.

Then, the team compared those strains to other algae, which they’d exposed to roughly 81 degrees Fahrenheit (or 27ºC) over the same period. It turns out algae can develop higher heat tolerance. All ten of the strains exposed to higher temperatures evolved to withstand them.

The researchers then introduced those strains to coral larvae and exposed them to water warmed to 89-degree Fahrenheit (or 31ºC) to see if they could also help prevent the coral from bleaching. In three out of the ten cases, the coral didn’t eject the algae. This suggests that algae that have adapted to heat could help restore the world’s coral reefs and buffer them against future change.

“While evidence suggests that corals are slowly adapting to a warmer world, it appears they are struggling to keep pace with climate change,” the researchers said in a statement.

If more research confirms these results and labs are able to develop more heat-resistant algae, scientists could introduce them to coral reefs in the wild. The researchers think this could give reefs a big boost in resisting the effects of the climate crisis.

Despite covering less than 0.1% of the ocean floor, reefs host more than one-quarter of all marine fish species, in addition to many other marine animals. Additionally, reefs provide a wide variety of ecosystem services such as subsistence food, protection from flooding, and sustain the fishing and tourism industries.

The study was published in the journal Science Advances.

Researchers look into reviving bleached corals using ‘non-preferred’ algal symbiotes

New research is looking into what makes algae ‘move in’ with their coral hosts — and why the partnership can turn sour, both under normal conditions and when temperatures increase.

Coral polyp.

Coral polyps extending to feed.
Image credits Егор Камелев.

What we know as corals aren’t really alive. They are large exoskeletons built by tiny animals called polyps. Tiny but industrious, these polyps work tirelessly to create the world’s wonderfully colorful coral reefs. A polyp has a sac-like body that ends in a mouth crowned with stinging tentacles called nematocysts (or cnidae). These animals filter calcium and carbonate ions from seawater that they combine to form the limestone (calcium carbonate) they use to build corals that protect their soft, defenseless bodies. If you ever get a chance to visit a coral reef at night, you’ll see these polyps extend their tentacles out to feed.

However, none of this would be possible without the help of various species of single-celled algae we call zooxanthellae, a type of dinoflagellate. These algae live in symbiosis with the polyps, taking up residence inside their cells in a mutually-beneficial relationship: the algae produce nutrients via photosynthesis, while polyps supply the raw materials. The algae are also what gives coral their dazzling colors, which brings us neatly to the subject of:


Warmer mean ocean temperatures (due to anthropic climate change) can apply so much thermal stress on the polyps that they ‘evict’ their symbiotic bacteria in a phenomenon called bleaching. We refer to it this way because, as the algae get expelled, the coral skeletons revert to their natural color: bone-white. If the bleached coral is not recolonized with new algae soon, however, it can die.

“We’re interested in understanding the cellular processes that maintain those preferential relationships,” says Arthur Grossman from the Carnegie Institution for Science, one of the paper’s co-authors.

“We also want to know if it’s possible that more heat tolerant, non-preferred algae could revive bleached coral communities even if the relationship is less efficient.”

The team focused on sea anemones, which are actually closely related to coral (they’re both part of the phylumCnidaria). Sea anemones also host algae, but are easier to work with than corals. The researchers looked at the differences in cellular function that occur when Exaiptasia pallida, a type of anemone, is colonized by two different types of algae — one native strain that is susceptible to thermal bleaching (Breviolum minutum), the other non-native but more resistant to heat (Durusdinium trenchii).

“In this study we hoped to elucidate proteins that function to improve nutrient exchange between the anemone and its native algae and why the anemone’s success is compromised when it hosts the non-native heat resistant algae,” Grossman said.

The anemones colonized by the native algae strain expressed heightened levels of proteins associated with the metabolism of organic nitrogen and lipids. Both are nutrients that get synthesized through the algae’s photosynthetic activity. These anemones also synthesized a protein called NPC2-d, which is believed to underpin the cnidarians’ ability to take in algae and recognize them as a symbiotic partner.

Anemones colonized by non-native algae species expressed proteins associated with stress, the team explains. This is likely indicative of a less-than-ideal integration between the metabolisms of the two organisms, they add.

“Our findings open doors to future studies to identify key proteins and cellular mechanisms involved in maintaining a robust relationship between the alga and its cnidarian host and the ways in which the metabolism of the organisms are integrated,” Grossman concluded.

The results can be used to further our understanding of the biochemical mechanisms that facilitate successful interactions between algae species and the corals that house them. Researchers can explore the metabolic pathways identified in this study to potentially find ways to merge corals with more heat-resistant species — all in a bid to help them both survive in the warmer world we’re creating on Earth.

The paper “Proteomics quantifies protein expression changes in a model cnidarian colonised by a thermally tolerant but suboptimal symbiont” has been published in the journal Nature.


Researchers unveil the most comprehensive atlas of coral reefs to date

A new research effort from the Khaled bin Sultan Living Oceans Foundation and the University of Miami (UM) Rosenstiel School of Marine and Atmospheric Science created an atlas of the world’s coral reef — the body of data contains maps of over 65,000 square kilometers (25,097 square miles) of coral reefs and their surrounding habitats.


Image via Pixabay.

Scientists now have a new tool at their disposal to accurately map large areas of coral reefs — much cheaper and faster than any time before. Traditionally, coral reef surveys are expensive, slow, and limited in scope. The main problem was that they relied on highly-trained divers swimming through the reefs, gathering data. Using the new model, however, researchers can now create detailed coral reef habitat maps at a regional scale without having to survey the entire reef in person.

Mapped reef

“In order to conserve something, it’s imperative to know where it is located and how much of it you have,” said Sam Purkis, professor and chair of the UM Rosenstiel School Department of Marine Geosciences, and the study’s lead author.

“Developing such an understanding for coral reefs is especially challenging because they are submerged underwater and therefore obscured from casual view. With this study, we demonstrate the potential to use satellite images to make coral reef maps at global scale.”

The atlas is the product of the 10-year long Global Reef Expedition by researchers from the Khaled bin Sultan Living Oceans Foundation, who traveled to over 1,000 coral reefs in 15 countries. They surveyed the reefs down to a one-square meter scale in a bid to help us better understand coral health and resilience. Many of the reefs they surveyed had never been studied before, the team notes.

The survey gathered data on shallow marine habitats such as fore and back reefs as well as associated habitats such as seagrass beds and mangrove forests for key reefs. These associated habitats are key components of tropical coastal ecosystems, the authors explain, which filter water, protect coasts from storms, and support fish populations. Coastal development, overfishing, and climate change impact these associated habitats as they do reefs.

Mapping extent.

The location of sites visited by the Khaled bin Sultan Living Oceans Foundation Global Reef Expedition. Red polygons show the extent of mapping activity and encompass a total area of 65,000 sq. km of habitat situated shallower than 25 m water depth. Accompanying site names in red also.
Image credits Sam J. Purkis et al., (2019), Coral Reefs.

Data collected by divers of the Global Reef Expedition was analyzed and — using ultra-high-resolution satellite imagery –extrapolated across entire reef structures. The team used video footage taken with cameras dropped at precise coordinates along the reef to validate the accuracy of their mapping method. The resulting maps are publicly available on the World Reef Map, an interactive coral reef atlas that anyone can use to explore all of the coral reefs and shallow water marine habitats mapped by the Global Reef Expedition.

“Benthic habitat maps are an essential tool in coral reef conservation as they provide a snapshot of where reefs are located and the status of their health,” said Alexandra Dempsey, the director of science management for the Khaled bin Sultan Living Oceans Foundation and a co-author of the paper.

“Scientists will use these habitat maps as baseline data to help track changes in reef composition and structure over time.”

Although the maps do not cover every reef in the world, they do include a meaningful portion of global reefs, the team says. As it was constructed with data recorded over the last 10 years, it also offers a unique baseline of coral reef health prior to the massive 2017 bleaching event. The team hopes that the publicly-available atlas will help governments, as well as conservation organizations, to protect and restore reefs. It is estimated that 50% of the world’s reefs have been lost in the past 40 years due to climate change and human activity, the paper also writes, underscoring the need for conservation and restoration efforts.

The paper “High-resolution habitat and bathymetry maps for 65,000 sq. km of Earth’s remotest coral reefs” has been published in the journal Coral Reefs.

Pocillopora damicornis.

Widespread coral species shows unique adaptations against environmental changes

One coral species is evolving to cope with climate change, a new paper reveals.

Pocillopora damicornis.

Pocillopora damicornis. Dampier Archipelago, western Australia.
Image credits coral.aims.gov.au

Researchers from the University of Miami (UM) found that the cauliflower coral (Pocillopora damicornis) evolved unique tricks against environmental change. Roughly one-third of its genome is unique among all reef-building corals — and many of these unique genes relate to immune functions, the team explains.

Unique adaptations

This wealth of genes, the team adds, may give P. damicornis a unique edge in survival amid today’s changing environments. As warmer temperatures and higher ocean acidity wreak havoc on reefs across the world, this coral — one of the most abundant and widespread reef-building corals in the world — may help us better understand how anthozoans deal with stress.

“This coral is traditionally thought of as a weed, and yet it may be one of the last corals to survive environmental changes such as climate change,” said Nikki Traylor-Knowles, an assistant professor of marine biology and ecology at the UM Rosenstiel School and senior author of the study.

For the study, the team analyzed the genetic sequences of two healthy fragments and two bleached fragments of P. damicornis. The genome was then compared to publicly available genomes of several coral and cnidarian (jellyfish) species. The results suggest that hard corals like P. damicornis rely heavily on their innate immune systems when adapting to changes in the environment.

Pocillopora damicornis purple.

Pocillopora damicornis. Photographed in a deep, very sheltered habitat on Houtman Abrolhos Islands, south-western Australia.
Image credits coral.aims.gov.au

That in itself isn’t very surprising. An animal’s immune system is a vital part of its survival strategy. Those with stronger immune systems are better equipped to deal with environmental changes, giving them an evolutionary edge. However, P. damicornis had way more genes related to immune functions than the team expected to find — suggesting it has a very robust immune system. As such, it would have a better shot at staying alive even under climate change scenarios, the team adds.

“The study shows that [P. damicornis] is an important coral with a very complex and unique immune system, which may explain why it is able to survive in so many different locations,” said the paper’s lead author Ross Cunning.

“This study helps us better understand how corals deal with stress,” said Traylor-Knowles. “Its complex immune system indicates that it may have the tools to deal with environmental change much more easily than other corals.”

The paper “Comparative analysis of the Pocillopora damicornis genome highlights role of immune system in coral evolution” has been published in the journal Scientific Reports.


Thailand’s going crazy over penis whitening, with over 100 customers queuing up every month

A new type of cosmetic surgery has Thailand firmly gripped: penis whitening.


Image credits Kinkate / Pexels.

Ever wished your family jewels were more moonstone and less… smoky quartz? Then you might want to look for the next flight to Bangkok, Thailand, and join the over 100 men who visit the Lelux Hospital every month to get their privates whitened.

Over the years, the clinic has built a solid reputation among its patients for providing quality cosmetic surgery. Its penis-bleaching days, however, started six months ago when a male customer came in complaining of “dark parts” on his groin. It was smooth if somewhat unassuming sailing for Lelux until Thursday, when the hospital released images of a man undergoing the treatment.

The great white hope

After that, fame and renown hit the clinic’s white-washed walls, with the story going viral on social media and eventually getting wide coverage on Thai television broadcasts.

“These days a lot of people are asking about it. We get around 100 clients a month, three to four clients a day,” said Bunthita Wattanasiri, a manager for the Skin and Laser department at Lelux Hospital, in an interview with AFP.

Most of the clients, she adds, are between 22 and 55 years old. Many of them are also part of Thailand’s LGBTI community. The procedure involves laser whitening for which the doctors use a “very small laser“, Wattanasiiri assured AFP.

“We have to be careful because it’s a sensitive part of the body,” she confesses.

According to skin-care product company Skintrium, laser lightening works by concentrating energy in the form of light of a specific wavelength and focusing it on the blemish. The energy delivered to the tissues results in heating of water molecules as well as direct damage to the tissues, which eventually results in the dark spot becoming obliterated.

They detail that laser lightening works on small areas at a time, so if you’re trying to lighten several spots or a larger area, “you might need to either go for more laser sessions or have a much longer single session than usual”. It’s not without risks, either. Some of the possible side-effects include pain, burning sensations, scarring or changes in skin texture, and there’s always a risk of infection developing.

All in all, a new penis-do at Lelux will cost some $650 (roughly 21,000 in the regional currency, the Thai baht) and five trips to the clinic. That being said, similar services are offered pretty widely in other countries as well. They’re increasingly popular, coat-tailing on several high-profile celebrities (think more Kardashians and less Hawking) that have admitted having these procedures done.

The procedure.

Authorities warn the procedure could be quite painful.
Image credits Lelux Hospital.

However, they have become highly sought-after in Thailand. Partly because of a cultural association between darker skin and outdoor labor in Asia, partly because of the procedure’s novelty on the market.

But it has also cleft Thailand‘s social media presence in twain. There seems to be little room for shades in this black-and-white debate, with one side asking “why not” while the other is worried that it’s just another example of imposing unnatural body standards, even going so far as to consider if the procedure is racist or not.

One 30-year old patient, who had undergone the treatment two months before, told BBC’s Thailand service that he did it “to feel more confident in [his] swimming briefs”.

“The obsession […] people nowadays can’t embrace their own skin colour,” one Facebook user commented on the clinic’s post, which raked in over 19,000 shares in two days.

It’s not the first time Lelux takes to hot waters, either. Last year, the clinic stirred controversy for promoting a cosmetic procedure called “3D Vagina”, in which the customer’s body fat was used to make their genitalia plumper.

In the end, we should all remember the color and fluff doesn’t really matter — it’s all about having a good time. My favorite commenter says she’s “not that serious about the color”, being “more concerned about the size and the moves”.

Losing Nemo: Climate change threatens the colorful clownfish

Warming ocean waters are destroying the conditions necessary for clownfish to survive.

Clownfish and sea anemone in the Andaman Coral Reef. Credits: Ritiks / Wikipedia.

When Finding Nemo came out in 2003, it was a big success. To this day, it’s one of the most cherished animated films, making clownfish one of the world’s most popular animals. But new research finds that fame hasn’t really helped them. Rising temperatures are threatening sea anemones, which are vital for their survival.

Clownfish (also called anemonefish) have a symbiotic relationship with sea anemones. The anemones provide them with shelter, food, oxygen, and sometimes even color. In turn, the fish keep the anemones clean from predators and pests, offering extra nutrients through their excrement. The anemone tentacles are armed with stinging cells which harm most creatures, but to the clownfish, they’re completely harmless. The two creatures help each other a lot, but they also depend on each other — for this reason, when anemones are threatened, clownfish are threatened, too.

In a new study published in the journal Nature Communications, a research team monitored 13 pairs of anemones living in the South Pacific. They were monitored during a key period: the 2016 El Niño weather event, which increased water temperatures by 2°C and caused massive bleaching, for both corals and anemones. For the fish living inside these anemones, it was a disaster. They started laying fewer eggs (73% fewer), and even the eggs that got produced were less viable. For fish living with non-bleached anemones, there was no significant change.

Like corals, sea anemones are threatened by bleaching. Credits: TaniaVdB / Pixabay.

Researchers also drew blood from these fish, showing a drop in concentrations of sex hormones (the equivalents of testosterone and oestrogen) and a sharp spike in levels of the stress hormone cortisol. Therefore, the fish were more stressed and less fertile following the event.

It took four months before the health of both the anemones and the fish improved. But this was just a singular, temporary warming event, which came and went. We already know that the seas have warmed up significantly since the start of the Industrial Age, and things aren’t likely to improve soon. What happens when a longer, more pronounced event occurs? It won’t be good, that’s for sure.

“Since anthropogenic stressors and the rate of change in environmental conditions are expected to multiply in the coming decades, with bleaching and habitat degradation becoming more frequent, understanding whether individuals and populations can adjust their physiology and behavior fast enough, either plastically or through evolutionary change, is a priority in conservation physiology,” the study concludes.

Researchers also warn that this isn’t isolated to clownfish — numerous species depend on corals and anemones for food and support, so if these two go away, they’re taking a lot of fish with them.

Journal Reference: Ricardo Beldade, Agathe Blandin, Rory O’Donnell & Suzanne C. Mills. Cascading effects of thermally-induced anemone bleaching on associated anemonefish hormonal stress response and reproduction. doi:10.1038/s41467-017-00565-w

Coral reefs barely survived bleaching, will be gone within the century unless we act

It’s not the best time to be a coral but, at least, it’s not the worst time to be one either. According to the U.S. National Oceanic and Atmospheric Administration (NOAA), the latest (and longest) global coral bleaching event should be over — but the three consecutive years of bleaching has left almost all of the 29 reefs contained in the United Nations Educational, Scientific and Cultural Organization (UNESCO) World Heritage sites extremely damaged. If we don’t cut greenhouse emissions dramatically, and fast, these reefs “will cease to host functioning coral reef ecosystems by the end of the century,” the UNESCO World Heritage Center in Paris reports.

Dying reef in Mariana Islands, Guam.
Image credits David Burdick / NOAA.

We’ve all had one of those days or weeks when the stress just piles and piles up until you can’t take it anymore and break down — ‘bleaching’ is how corals do their breaking down. But instead of bosses, deadlines, and finals, they get stressed over high temperatures. When bathed in too hot water for too long, the corals will expel their symbiotic algae, known as zooxanthellae. These algae supply the coral with food via photosynthesis and lend them color — so when they’re evicted the coral turns white, or bleaches. That’s how this phenomenon gets its name, and this is how it looks.

If the waters cool down soon enough, the algae will return. But if temperatures stay high and the bleaching persists, the corals will starve to death. Which is bad news for the corals and us both, since reefs support over a million marine species underpinning whole ecosystems that humans draw from. An estimated half billion people around the world directly depend on reefs for income from fishing and tourism. The Great Barrer Reef alone is thought to be worth $42 billion. 

That’s why NOAA’s Coral Reef Watch keeps a close eye on sea surface temperatures using satellite data — so they can model and forecast when and where waters grow warm enough to cause bleaching. The latest warming event started in the Atlantic, Pacific, and Indian ocean basins in mid-2014, and by 2015 coral bleaching was going into overdrive: while previous bouts lasted under a year, the 2015 bleach lasted 3 whole years.

Bleached coral colony photographed around Howland Island during the Pacific RAMP expedition, 2010.
Image credits NOAA.

At the root of the issue lie greenhouse gas emissions, which supply the energy needed to heat the oceans. To get an idea of how it will impact reefs in the future, the World Heritage Centre asked experts — including NOAA — to write the first study “that scientifically quantifies the scale of the issue, makes a prediction of where the future lies, and indicates effects up to the level of individual sites,” said Fanny Douvere, marine program coordinator at the center.

“This has never been done before in a World Heritage context,” she added.

Using on-site observations and data supplied by NOAA, the team reports that 21 of the 29 heritage reefs suffered severe and/or repeated exposure to water hot enough to cause heavy bleaching. These include even relatively pristine reefs, such as Papahānamokuākea in Hawaii and the Seychelles’ Aldabra Atoll, that have not experienced human degradation.

“Coral mortality during the third global bleaching event has been among the worst ever observed,” the report reads.

While reefs can recover from bleaching in about 15 to 25 years, 13 of the 26 heritage reefs were bleached more than twice per decade from 1985 to 2013. So most reefs were in a tight spot even before this latest and longest bleaching event hit, and they simply may not be able to take further damage and regenerate. Indeed, the report projects that if emission patterns don’t change (i.e. a business as usual scenario), we’ll see more bleaching events at shorter intervals and by the end of the century, all 29 World Heritage site reefs will be completely destroyed.

Even if emissions are slashed, reefs still face bad odds from climate change. The Paris Agreement aims to keep global temperature increase below 2°C relative to preindustrial levels but even that falls short. The report calls for a 1.5°C goal, stating that anything above that threshold has a very high chance of causing “severe degradation of the great majority of coral reefs.” Ideally, we’d want to keep under the 1.5°C mark as well, but that’s the highest temperature limit that still gives reefs a fighting chance.

To get some context, this is what a healthy reef looks like.
Image credits Jim E Maragos, U.S. Fish and Wildlife Service.

The report was penned in anticipation of the July 2nd World Heritage Committee meeting in Kraków, Poland. The World Heritage Centre and the International Union for Conservation of Nature have prepared draft decisions based on the findings to be presented to the committee.


Coral bleaching has been captured on video for the first time

Scientists have filmed coral bleaching in action for the first time. The good news is that it looks kinda funny. The bad news is that it’s faster and more severe than we imagined — and with most of the world’s coral colonies critically damaged, destroyed, or soon to be so, we’ve got a huge problem on our hands.

“Who smelt it dealt it” doesn’t apply to climate change, though.
Image via giphy.

The term “coral bleaching” describes a behaviour seen in environmentally-stressed bodies of coral. It’s so called because the organisms lose their colour when the waters they live in become too hot or polluted.

Corals are usually white-ish or cream coloured. The dazzling colours of a coral reef are produced by tiny, pigmented algae that live within the corals and trade nutrients for the safety of the colony. This symbiotic relationship benefits both parties, but in an emergency, the coral aren’t shy to kick their algae buddies to the curb — they expel the algae and lose their pigment, becoming bone-white.

While this last-ditch effort allows the coral to survive in the short run, it will die if conditions don’t improve fast enough so new algae can move in.

“What’s really interesting is just how quickly and violently the coral forcefully evicted its resident symbionts,” says Brett Lewis from the Queensland University of Technology in Australia.

Lewis’s team wanted to understand what causes corals to evict their simbiotic bacteria, and has been observing bleaching in the coral species Heliofungia actiniformis. They placed a number of H. actiniformis corals and Symbiodinium algae in a controlled environment, heated them up, then observed and recorded their response to rising temperatures.

The team raised water temperature from 26 to 32 degrees Celsius (78 to 89 degrees Fahrenheit) over the first 12 hours of the experiment, then kept it constant over the next eight days. The corals weren’t pleased at all by this turn of events, and they basically farted the color out of themselves.

“The H. actiniformis began ejecting the symbionts within the first 2 hours of us raising the water temperature of the system,” says Lewis.

“Our H. actiniformis used a pulsed inflation to expel Symbiodinium over time – inflating their bodies to as much as 340 percent of their normal size before suddenly and violently contracting and ejecting Symbiodinium through their oral openings over the four to eight-day duration of the experiments,” explains co-author Luke Nothdurft.

Even more unsettling is the fact that the researchers chose H. actiniformis because it’s one of the most resilient species of coral found in the Great Barrier Reef. This solitary species of mushroom coral can grow to about 20 cm in diameter and 7 cm in height (7.8 by 2.7 inches,) on a diet of sugars synthesized by Symbiodinium and zooplankton that it catches with its tentacles. Previous studies have found that H. actiniformis is very resilient to thermal stress, and Lewis and his team now think this could be because of its incredibly quick response.

“Our observations suggest this resilience could be due to the rapid expulsion of the coral’s algal symbionts during thermal stress, and could very well increase H. actiniformis’s chance of survival during abnormally high sea temperatures,” he says.

But the findings have some pretty grim implications. Basically, we found out that one of the hardiest species of coral in the Great Barrier Reed owes its survival ability to the fact that it’s willing to sacrifice its nutrient source earlier than other species — and that’s not good news at all. Hopefully, the findings will help mobilize governing bodies to create policies to give out remaining coral reefs a fighting chance.

The full paper, “Expulsion of Symbiodinium by pulsed inflation under hyperthermal stress in Heliofungia actiniformis” has been published in Coral Reefs.