Tag Archives: coral

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.

Table corals have an important role to play in reef recovery, but they’re also quite vulnerable

Table corals could hold the key to saving the Earth’s coral reefs, according to new research.

By now, you probably all know that coral reefs around the world are struggling. Waters that are too warm and too acidic are causing corals to bleach — to eject their symbiotic algae under stress. If this happens enough times in rapid succession, reefs can see massive damage and coral death.

 Acropora coral near the Maldives. Image credits Mal B / Flickr.

We’ve been trying to find a solution to this problem for quite a while. New research may have found something that will help us, in the form of the table coral Acropora. These can regenerate habitats in reefs such as the Great Barrier Reef faster than any other coral type.

Reef Relief

“Table corals are incredibly fast-growing. Habitats in exposed reef slopes recover from disturbances at a rate 14 times higher — that’s more than two decades faster — when table corals are abundant,” says Dr. Juan Carlos Ortiz at the Australian Institute of Marine Science (AIMS), lead author of the paper.

“Their large, flat, plate-like shape provides vital protection for large fish in shallow reef areas and serves as a shelter for small fishes, with some species almost entirely dependent on table corals. Even after death, these corals provide value, as their skeletons are the preferred place for young corals of all types to settle.”

Table corals, also known as plate corals, are generally found in the upper slopes of reefs (where their shape is adapted to withstand wave motions). They’re also sometimes encountered in the mid-shelf area and offshore reefs in the Great Barrier Reef. According to the study, these corals have a unique combination of characteristics. Table corals provide valuable ecological functions, are among the most sensitive coral types, and their role is threatened by a low diversity of species, the authors report.

Overall, however, the paper explains, the Great Barrier Reef would recover significantly slower if table corals declined or disappeared from the area.

Because of this, the authors suggest that protecting these corals should become an additional point of focus for ecosystem management. Selecting particular coral types based on what ecosystem function they perform, rather than (just) how endangered a particular species is, would help promote the health of ecosystems in the Great Barrier Reef, they add.

“Table corals are still frequently seen on outer reefs, but their presence shouldn’t be taken for granted as they are vulnerable to combined impacts,” said Dr. Rachel Pears, Great Barrier Reef Marine Park Authority’s Assistant Director, and study co-author. “These corals do not handle intensifying thermal stress well, are easily killed by anchor damage, highly susceptible to diseases, and are the preferred meal for crown-of-thorns starfish.

“The good news is there are tangible actions we can take to protect these corals such as targeted crown-of-thorns starfish control and anchoring restrictions.”

Still, while they can help, table corals can’t save reefs by themselves. This is because while they do perform important ecosystem functions, they don’t necessarily improve the reef’s biodiversity levels significantly, due to the low number of species in this class.

All of this being said, the real threat facing coral reefs is climate change. While fostering biodiversity and making sure table corals get to do their job will help, the root of the issue is the level of emissions we’re outputting into the ocean and the atmosphere. In order to fix it, we’ll all have to work together to significantly reduce these.

The paper “Important ecosystem function, low redundancy and high vulnerability: The trifecta argument for protecting the Great Barrier Reef’s tabular Acropora” has been published in the journal Conservation Letters.

Fossil Friday: a 6-year-old UK boy finds ancient fossil in his backyard with a toy archeology kit

A six-year-old boy in Walsall, England, is probably the youngest individual to ever make it into a Fossil Friday story. His discovery: a fossilized horn coral, several hundred million years old, that he uncovered in his family’s back yard with a fossil-hunting kit he received for Christmas.

The fossil. Image via standard.co.uk.

Sid, or Siddak Singh Jhamat in full, said he was “excited” to make the discovery, and that he was just looking for worms. His father helped him identify what the fossil actually was through a fossils’ enthusiasts group on Facebook. Estimates place the specimen’s age between 251 and 488 million years old according to Vish Singh, said the boy’s father, and it is most likely a Rugosa coral.

Beginner’s luck

“I was just digging for worms and things like pottery and bricks and I just came across this rock which looked a bit like a horn and thought it could be a tooth or a claw or a horn, but it was actually a piece of coral which is called horn coral,” the schoolboy said.

“I was really excited about what it really was.”

Mr. Singh explains that his son found the “odd-shaped” horn coral in the soil in their back yard, next to “some smaller pieces”. Encouraged by his success, Sid went digging again the next day, finding a congealed block of sand. Locked inside this block were several little molluscs, seashells, and even a partial crinoid specimen.

During the time this coral fossil was still a living coral, the area that is the UK today was just one tiny part of the supercontinent Pangea, and it was also virtually all underwater — an inland lake.

Sid and his coral fossil. Image via standard.co.uk.

The finding is quite surprising because Walsall, the area where the Singh family lives, isn’t really known for its fossils. Other areas of the UK, such as its suggestively named Jurassic Coast, are hotbeds for fossil hunters. Still, Mr. Singh says their garden has lots of natural clay outcroppings, and his son found the coral in one of these.

If anything, this unlikely event showcases that it’s never too early to start looking for fossils. It’s also a good reminder that fossils can, really, be anywhere. That being said, a large specimen such as the one unearthed by Sid and his trusty toy kit is quite a rare discovery even for hardened paleontologists.

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.

Ocean warming is a wrecking ball for coral reef systems. This researcher wants to understand it all

Year in and year out, scientist Thomas DeCarlo saw the writing on the wall — the wall of coral reefs, that is — and his findings are sounding the alarm: ocean warming and acidification could spell doom for coral reef ecosystems.

Coral reefs are vital for the health of the oceans. Image credits: Olga Tsai.

Billion-dollar buffers

“Ocean temperatures are now approaching one degree above what they were in industrial times, with a projected increase of two to four degrees, which could have terrible consequences for corals,” DeCarlo says.

DeCarlo has studied the history of monsoon upwelling, wind patterns, and other weather factors affecting coral reef ecosystems in the Red Sea. His research shows that reefs are essential not just to the corals themselves, but to the entire surrounding ecosystems, and human society as well.

If reefs collapse, so too do biodiverse life systems that rely on them to survive — and the damage will continue to cascade. Coral reefs are a nursery to different marine species, they provide fish for humans, and they buffer shores from storms.

That storm-buffer feature is apparently quite significant in dollars. In a US Geological Survey report, coral reef barriers as a force in flood protection protect $1.8 billion worth of coastal infrastructure and economic activity in the US and trust territories alone. Reefs reduce the energy of the waves as they wash ashore, which prevents or limits coastal erosion, flooding, and water surges.

DeCarlo’s detailed explorations use microsope, climate models, coral cores, and computerized tomography (CT) analysis, to study the relationship between climate stressors, bleaching, and calcification. He’s not the first scientist to study the environmental impact of coral reefs but he has taken a special look at instances where the upwelling of nutrient levels can be toxic to corals.

Composite photo shows samples of coral cores alongside CT scans of coral skeletal cores showing annual pairs of light and dark bands of high and low density. Photo: Thomas DeCarlo.

His plan, he says, is to build a global database of the history of coral bleaching events, helping to fill the gaps in our knowledge of coral resilience and vulnerability. But to do that, we first need to understand how the climate is affecting corals.

High, hot, and deadly

Winds blowing across the ocean surface push water away. Water then rises up from beneath the surface to replace the water that was pushed away, a process known as “upwelling,” explains the National Ocean Service (NOS). The water that rises to the surface is typically colder and is rich in nutrients, which “fertilize” surface waters, and have high biological productivity.

For corals, upwelling can be a blessing or a curse. According to DeCarlo knows, nutrient-dense waters can spell good news or bad news. It depends.

“Summer monsoons circulate nutrient-dense waters from the Gulf of Aden to the Red Sea. The symbiotic algae that live in corals thrive on these nutrients. In return, they provide food and energy for the corals to grow,” said DeCarlo. “But warmer waters create more nutrients, which create more algae, which create more oxygen and waste build-up in corals. When high waste conditions combine with high heat, this situation causes bleaching, which could turn deadly.”

According to the NOS, bleaching events might or might not be a dire threat for coral. If stress caused bleaching is not severe, the coral may recover. But if (1) there is prolonged algae loss and (2) continued stress, coral eventually dies.

There’s much work to be done, and DeCarlo has no intentions of stopping anytime soon. From King Abdullah University of Science and Technology (KAUST) and now on to Hawaii, at Hawaii Pacific University, his work offered valuable insight into the life of corals, but there’s much more research to be done, especially in regards to global warming. DeCarlo’s website states that “global warming is driving an increase in the frequency of mass coral bleaching events worldwide.”

Healthy coral reef and marine life in the central Red Sea of Saudi Arabia. Photo: KAUST.

It took the researcher 4 years to finish his PhD studying corals, an accomplishment he says he is “especially proud of,” since it was a first of its kind comprehensive study.

One important takeaway from this research is that coral reef environments are not a cookie-cutter affair. One-sized conclusions and conservation measures cannot address and fix everything. One must recognize the complexities due to what are the oceanographic settings of any individual coral reef.

Disentangling these oceanographic processes will help us predict when and where we may find coral reefs that are relatively resistant to rising temperatures, and this information will be critical to informing local management decisions.”

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.

Glowing coral reef despite bleaching offers hope for recovery

Among the victims of climate change, coral reefs are clearly some of the most visible. The rise in seawater temperatures in the world’s oceans has caused the death of many corals in recent years in diverse places from Panama to Seychelles.

Credit Wikipedia Commons

Warmer waters can cause bleaching in corals, turning the coral’s tissue in a ghostly white color and eventually killing it. But, in some cases, something different can happen, with corals turning a bright array of colors as part of their last effort to survive.

That phenomenon is called colorful bleaching and has been observed since 2010 but without much knowledge about it. Researchers have now taken a closer look, discovering that glowing corals are telling us they are trying to survive.

When healthy, corals rely on a mutually beneficial coexistence with tiny algae. Corals get energy from photosynthesis provided by the algae, while the algae take shelter and nutrients from the corals. The pigments from the photosynthesis given by the algae are the reason why many corals appear to be brown.

But this deal can be easily altered by rising ocean temperatures. The algae disappear and the white skeletons of the corals get exposed, looking like they were bleached. The corals usually starve without the algae and finally die. This leads to the collapse of the reefs and their decline, affecting ocean biodiversity.

A colorful last stand

A group of researchers decided to investigate the occurrence and reasons behind the colorful bleaching phenomenon registered in recent years. To do so, they did experiments at the University of Southampton’s Coral Reef Laboratory, exposing common corals to different types of light and conditions.

The experiments showed that the bright colors act as a protective layer, similar to sunscreen, when the algae are no longer attached to the corals, encouraging their return. For Jörg Wiedenmann, lead study author, the colorful bleaching is a way for corals to self-regulate, entering into a feedback loop with the algae.

The algae absorb the sunlight that the corals receive, creating the already mentioned pigments. But when the algae are gone the coral has to deal with that excess sunlight and their white skeletons can reflect it. This causes more stress, preventing the reunion between the coral and algae.

“However, if the coral cells can still carry out at least some of their normal functions, despite the environmental stress that caused bleaching, the increased internal light levels will boost the production of colorful, photoprotective pigments,” Wiedenmann said in a statement.

Wiedenmann and his team recreated in their experiments the ocean temperatures in which the colorful bleaching events happen. They discovered that the phenomenon might surface in less extreme ocean-warning events that are shorter and milder or linked to a reaction to changes in nutrients of the corals.

While this gives hope that the corals can actually recover, the researchers emphasized that improving the quality of the water in the different regions of the world and reducing greenhouse gas emissions represent the best ways to guarantee the survival and continued presence of coral reefs.

“Bleaching is not always a death sentence for corals, the coral animal can still be alive,” said Cecilia D’Angelo, study coauthor. “If the stress event is mild enough, corals can re-establish the symbiosis with their algal partner.”

The study was published in the journal Current Biology.

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.

Help NASA save the ocean’s corals by playing a new video game

The new game will help NASA find new ways of mapping coral reefs. (Image: NASA)

In an effort to save our coral reefs, and thus helping to save the planet, NASA is calling on video gamers and citizen scientists to assist them in mapping coral reefs around the world.

In the past few years, the Ames Research Center in California’s Silicon Valley has been developing new ways to peer below an ocean’s surface using “fluid-lensing” cameras. Mounted on drones or aircraft, the cameras have assisted the agency on expeditions to Puerto Rico, Guam, American Samoa, and elsewhere to collect 3D images of the ocean floor, including corals, algae, and seagrass. However, the data alone is not enough to help them gather the whole story of what is happening to corals, so they are reaching out to the public for help.

The data from the public’s help will be processed by a neural network called NeMO-Net, or the Neural Multi-Modal Observation and Training Network. The program allows players to identify and classify corals using these 3D images while virtually traveling the ocean on their own research vessel, the Nautilus.

On each “dive,” players interact with real NASA data, learning about the different kinds of corals that lie on the shallow ocean floor while highlighting where they appear in the imagery. Aboard their virtual research vessel, players will be able to track their progress, earn badges, read through the game’s field guide, and access educational videos about life on the seafloor.

“NeMO-Net leverages the most powerful force on this planet: not a fancy camera or a supercomputer, but people,” said principal investigator Ved Chirayath. “Anyone, even a first-grader, can play this game and sort through these data to help us map one of the most beautiful forms of life we know of.”

Coral reefs occupy less than 0.1% of the world’s ocean area, but provide a home for at least 25 percent of all marine species (Image: Pixabay)

As they play the game, players’ actions help train NASA’s Pleiades supercomputer at Ames to recognize corals from any image of the ocean floor, even those taken with less powerful instruments. The supercomputer “learns” from the coral classifications players make by hand, using machine learning techniques to classify on its own.

The hope is that data gathered from the game will help researchers find new ways to preserve coral reefs. A new study from James Cook University’s ARC Centre of Excellence for Coral Reef Studies recorded severe bleaching on the Great Barrier reefs during offshore dives in February and March. The study showed that some reefs had 90 percent of their shallow water corals bleached.

NASA is touting the game as both a learning experience along with being an important research tool. The more people who play NeMO-NET, they say, the more accurate Pleiades’ mapping abilities will become. After it has been able to accurately classify corals from low-resolution data included in the game, the supercomputer will be able to map out the world’s corals at an unprecedented resolution. With that map, NASA says scientists can better understand what is happening to corals and find ways to preserve them.

So while you’re currently stuck in your house under quarantine, why not help save the world while you’re at it?

You can play NeMO-NET on an iPad.

Oceans could be unviable for coral reefs by 2100 due to warmer, more acidic waters

Warmer and more acidic oceans could destroy nearly all of today’s coral reefs by the end of the century.

Image credits Marcelo Kato.

New research presented Monday at the Ocean Sciences Meeting 2020 paints a dire picture for the Earth’s reefs. According to the team, between 70% and 90% of coral reefs will disappear in the next 20 years due to a combination of climate change and pollution. By 2100, they add, very few habitats suitable for corals will remain on Earth — if any.

Reefless

“Trying to clean up the beaches is great and trying to combat pollution is fantastic. We need to continue those efforts,” said Renee Setter, a biogeographer at the University of Hawaii Manoa who presented the findings.

“But at the end of the day, fighting climate change is really what we need to be advocating for in order to protect corals and avoid compounded stressors.”

The issues identified by the team will likely pose major challenges for ongoing reef conservation programs. For example, the researchers cite efforts to grow corals in laboratories and later transplant them back into wild reefs in an attempt to boost their health and resilience. While there is value to such an approach, Setter cautions that few to no habitats will remain suitable for reefs by 2100, rendering the lab-grown corals powerless.

What we need to do, she argues, is to focus on the issues of rising sea surface temperatures and acidity, as these are the two most pressing environmental factors plaguing reefs today. While pollution also poses a very real threat to marine life in general, the team adds, corals in particular are most at risk from environmental changes associated with human CO2 emissions.

Corals are very sensitive to increased temperatures. They can bear them for a short while but will expel their symbiotic algae if exposure continues for longer periods of time in a process known as ‘bleaching’ (these algae live inside the mineralized structures of the coral, giving them their color, and helping feed the polyps). Bleached corals aren’t necessarily dead, but they’re far less resilient to further shocks and stressors. Bleaching events have greatly increased in frequency in the last few years due to climate change.

A bleached coral reef.
Image via Wikimedia.

Setter and co-author Camilo Mora, also at the University of Hawaii Manoa, mapped the areas of the world that would be suitable for coral reefs over the coming decades. They based this on modeling of future environmental conditions that accounted for factors such as sea surface temperature, wave energy, water acidity levels, pollution, and overfishing in areas currently inhabited by corals. They also factored in human population densities and land cover use as proxies for how much pollution and waste would be present at different sites.

They found that most areas that harbor coral reefs today wouldn’t be able to sustain them by 2045; the situation would only worsen by 2100. Small portions of Baja California and the Red Sea would still be viable, but they’re not ideal locations for coral reefs because of their proximity to rivers, the team explains.

“By 2100, it’s looking quite grim,” said Setter. “Honestly, most sites are out [by this time].”

One of the more encouraging findings is that projected increases in human populations (and an associated increase in pollution) pose a limited threat to reef habitats in the future. On the flip side, the team explains that this is because human activity has already caused significant damage to coral reefs — meaning that there are only so many locations left to impact. Still, the authors underline that CO2 emissions and their associated effect on the climate and water acidity need to be addressed if the corals are to stand a chance in the future.

The poster “Impacts of climate change on site selection for coral restoration” has been presented on Monday, February 17 at the Ocean Sciences Meeting 2020 in San Diego (poster number PC14A-1691).

Tropical forests and coral reefs are buckling under interacting threats

Climate change, extreme weather, and human pressure are causing ecosystems across the tropics to collapse, a new study reports.

Image via Stokpic

The authors analyzed over 100 locations where tropical forests and coral reefs have been affected by hurricanes, floods, heatwaves, droughts, fires, and other types of extreme climate. The findings expand our understanding of the health of these ecosystems, especially in the wider context of climate change and damage caused by human activity.

The findings weren’t encouraging. The team echoes previous research and warns that only decreasing CO2 emissions can help reverse the damaging trend of climate change on ecosystems.

Compounding issues

“Tropical forests and coral reefs are very important for global biodiversity, so it is extremely worrying that they are increasingly affected by both climate disturbances and human activities,” says lead researcher Dr. Filipe França from the Embrapa Amazônia Oriental in Brazil and Lancaster University. “Many local threats to tropical forests and coral reefs, such as deforestation, overfishing, and pollution, reduce the diversity and functioning of these ecosystems. This in turn can make them less able to withstand or recover from extreme weather.”

“Our research highlights the extent of the damage which is being done to ecosystems and wildlife in the tropics by these interacting threats.”

Climate change is causing an increase in the frequency and strength of storms and marine heatwaves, which are very damaging to coral reefs; they both reduce the cover of live coral (i.e. they shrink reefs) and cause long-lasting changes in coral and fish communities, which reduce their ability to reduce further impacts.

On land, tropical forests are also threatened by more frequent and extreme hurricanes, the team explains. Such storms cause the destruction of plants which in turn affects the whole of the ecosystem, as animals, birds, and insects directly rely on the plants for food and shelter. The team explains that in some regions, such as the Caribbean, extreme weather events have decimated wildlife by more than half.

Finally, the interplay between higher average temperatures and shifting precipitation patterns has led to a rise in large-scale wildfires in the tropics, the team explains.

“We are starting to see another wave of global extinctions of tropical birds as forest fragmentation reduces populations to critical levels,” explained Dr Alexander Lees, from Manchester Metropolitan University, co-author of the paper.

The team took the 2015 El Niño as an example. One of the areas that felt its impact the most was Santarém, a city in the Brazilian state of Pará, which experienced “a severe drought and extensive forest fires” that affected local wildlife, the team explains. The drought associated with El Niño impaired the forests’ ability to recover from these fires by affecting dung beetles. The species plays a key role in spreading seeds in the forest, and the dry conditions during the 2015-2016 El Niño caused their activity levels to plummet. Coral reefs were also critically damaged by the same El Niño, explains Professor Nick Graham from Lancaster University.

“The 2015-16 coral bleaching event was the worst ever recorded, with many locations globally losing vast tracts of valuable corals,” he explained.

“Worryingly, these global bleaching events are becoming more frequent due to the rise in ocean temperature from global warming.”

The team underlines that we need new conservation strategies to help ecosystems — especially rainforests and coral reefs — handle multiple, concurrent threats and that we need them fast. However, they also explain that local action may simply not be enough if we don’t tackle global climate change.

The paper “Climatic and local stressor interactions threaten tropical forests and coral reefs” has been published in the journal Philosophical Transactions of the Royal Society B: Biological Sciences.

The Great Barrier Reef sees its greatest spawning event in recent memory

It’s not the best time to be a coral reef — but not all is lost. Over the weekend, corals in the Great Barrier Reef spawned, and it was the biggest spawn event we’ve seen in recent years.

Image via Wikimedia.

Despite extensive damage caused by bleaching events over the last few years, the Great Barrier Reef isn’t ready to throw in the towel just yet. Over the weekend, it engaged in the largest spawning event recorded in recent years. Coral spawning occurs in the Reef in the week after the November full moon, when water temperatures remain around 27 to 28°C. Soft corals being release egg and sperm bundles into the ocean for fertilization, followed by hard corals.

The seed is strong

“The corals are really looking spectacular since the bleaching events of 2016 and 2017,” said Stuart Ireland, a marine biologist from Calypso Productions who filmed the event.

“There was coral spawn everywhere last night. It was like a grey haze with beautiful pink bundles going up; it was a magical night. It’s a testament of how resilient the Great Barrier Reef really is.”

During the spawning period, millions of coral eggs become fertilized and go on to develop into the next generation of coral. The event is vital for the health of the reef. It ensures genetic diversity in individual species and spreads species out throughout the reef. Since corals are immobile, this is their only chance to ‘spread far and wide’ and settle into free spaces.

Typically, these events take place at night. However, the unique conditions this year led to a daytime spawning, explained Russel Hore, a Reef Bio Research Manager at Quicksilver Port Douglas, for Newsport. He adds that there’s a very good chance we’ll see a second spawning in December.

“We expect to see more pressures in the future, but the Great Barrier Reef’s size, complexity and huge biodiversity makes it a very strong ecosystem,” Ireland explains. “The reef has shown us that she is not lying down, she is doing extremely well and fighting for the future.”

The strong spawning event is particularly encouraging as the Great Barrier Reef, despite being the largest coral reef system in the world, is hard-pressed by rising sea temperatures linked to climate heating. Mashable India reports that researchers plan to use this event to restore dead parts of the reef, via the Coral Larval Restoration Project. The project’s page describes it as a “combination of enhanced techniques, aimed at both repairing the reproductive life cycles of corals and re-establishing breeding populations on damaged reefs by ensuring more naturally-produced larvae survive to adulthood.”

However, project leader Professor Peter Harrison said that the Project is, in effect, a bid to buy extra time for corals in the Great Barrier Reef. Climate action, he told Mashable India, is the only way to ensure that reefs will see the future.

3D-printed coral can help save reefs and the fish that live there

New research is looking into 3D-printed corals as a possible cure for the world’s ailing reefs and the animals that call them home.

Close-up of a brain coral.
Image via Pixabay.

Coral reefs aren’t faring very well anywhere on Earth right now. Environmental shocks such as climate shifts, more acidic waters, and pollution are pushing corals — often beyond their limit. As the reefs wither and die, the animals that live there find themselves essentially homeless.

New research at the University of Delaware (UD) is looking into the use of 3D-printed corals as a potential fix.

Hit print

“If the fish on a reef won’t use the 3D-printed coral models as a habitat in the wild, it could place them at greater risk for predation by other larger species,” said Danielle Dixson, an associate professor in UD’s College of Earth, Ocean and Environment’s School of Marine Science and Policy and the paper’s second author.

“If coral larvae won’t settle on 3D-printed materials, they can’t help to rebuild the reef.”

The team has shown that 3D-printed objects don’t impact the behavior of damselfish (a species closely associated with coral reefs) or the survival of a settling stony coral. Fish showed no preference for any of the materials used to print the corals, which suggests that biodegradable materials (such as cornstarch) could successfully be employed in lieu of plastics. This latter finding is particularly relevant in the context of today’s discussion on the role of plastic pollution in the ocean.

The team worked with damselfish and mustard hill coral larvae, which they presented with a coral skeleton and four 3D-printed corals (made from different materials). These artificial corals were replicas of an actual coral skeleton (that the team took around 50 images of using a smartphone). All four filaments used were low-cost, the researchers explain, and widely available; they included polyester and two biodegradable materials, one made from cornstarch and the other from cornstarch and stainless steel powder.

Blue-green damselfish (Chromis viridis) are a common coral-associated fish found in the Indian and Pacific Oceans, while mustard hill corals (Porites astreoides) are a stony coral found in the Caribbean Sea, the team explains. They placed the fish into a tank alongside the corals in a ‘cafeteria-style’ choice experiment — basically, they sat around to see if the fishes preferred one habitat/coral over another. Behavioral analysis showed that the fishes didn’t have a preference between the native coral skeleton and the 3D-printed ones. The fishes’ activity levels (such as frequency of movement and the total distance they swam in the tank) also stayed constant regardless of the habitat they were provided with.

UD alumnus Emily Ruhl, the study’s first author, says that it was surprising to see the fishes behaving the same near a natural or artificial coral skeleton. Furthermore, mustard hill coral larvae settled more readily on 3D-printed coral surfaces than on no settlement surface (as would be the case in a reef destroyed by a storm, for example).

“I thought the natural skeleton would elicit more docile behavior compared to 3D-printed objects,” said Ruhl, who earned her master’s degree in marine biosciences at UD in 2018. “But then we realized the small reef fish didn’t care if the habitat was artificial or calcium carbonate, they just wanted protection.”

When coral reefs degrade, they often lose structural complexity. Reef-associated fish, which tend to spend all of their lives in the reef, rely on this complexity for food and shelter — simpler reefs just don’t give them enough opportunities. Without the proper habitat, they don’t grow to their full size. This mechanism leaves the reef open to an overgrowth of algae (on which larger fish feed) that can destroy the whole reef.

“Offering 3D-printed habitats is a way to provide reef organisms a structural starter kit that can become part of the landscape as fish and coral build their homes around the artificial coral,” Dixson said. “And since the materials we selected are biodegradable, the artificial coral would naturally degrade over time as the live coral overgrows it.”

In addition, 3D-printed coral models can be useful as a control for fish-related laboratory studies, enabling researchers to provide each fish an identical habitat, something that is currently not possible with the use of coral skeletons.

The paper “3D printed objects do not impact the behavior of a coral-associated damselfish or survival of a settling stony coral” has been published in the journal PLOS ONE.

Heatwaves lead to death and decay of corals, research shows

The rise of ocean temperatures is not the single and worst effect of climate change on corals, according to a new study, which warned over the consequences of heatwaves, leading to their death and decay.

Credit: Flickr

Researchers reporting in the journal Current Biology showed that severe marine heatwaves, as happened in Australia’s Great Barrier Reef (GBR) in 2016, are worse for corals than the phenomenon known as bleaching, in which they corals expel the algae living in their tissues and turn white.

“The water temperatures are so warm that the coral doesn’t bleach, it dies,” says Tracy Ainsworth of The University of New South Wales, Sydney, Australia. “We still see the coral become white as the animal dies and its skeleton is exposed to the water, and then we see it very rapidly become overgrown by colonizing algae from both the inside out and the outside in.”

Ainsworth and her team had shown in a previous study that just a 0.5ºC increase in water temperature changes the extent of mortality in corals during bleaching. In the new one, they examined GBR corals following the 2016 mass bleaching event.

At that time, reefs of the northern GBR were exposed to a rapid and severe rise in sea surface temperatures, with more than 30% experiencing temperatures above the established threshold for coral survival. After the heatwave, the corals showed rapid degradation and mortality as microbial biofilms took over.

Ainsworth and colleagues simulated the severe heatwave conditions seen on the GBR in 2016 with two coral species that showed high mortality that year, seeking to better understand the phenomenon.

Their studies show that marine heatwave events on coral reefs are entirely different from the way coral bleaching has been understood.

The simulated heatwave conditions caused immediate heat-induced mortality of the coral colony, as the coral skeleton rapidly dissolves, and its structure is lost. Within days, a complex microbial biofilm encases the exposed coral skeleton, further accelerating the loss of calcium carbonate from the reef to weaken it even further.

Researchers argued that the findings suggest that severe heatwave- induced mortality events should be considered as a distinct biological phenomenon from coral bleaching. They said that such heatwave mortality events and the rapid reef decay that results, likely will become more frequent as the intensity of marine heatwaves increases in the coming years.

“This work provides very clear evidence that the intense heatwave conditions, which are now becoming a feature of bleaching events, are far more severe and are changing how we understand the impact of climate change on coral reefs and the consequences of severe heat-wave events,” said says William Leggat, first author of the study from the University of Newcastle, Australia.

Coral reef.

Corals are moving away from the sweltering tropics — and establishing new reefs

Climate warming is driving corals farther from their traditional neighborhood, the tropics, in favor of more temperate regions.

Coral reef.

Image credits Katrin Knogler.

The number of young corals in equatorial reefs has declined by roughly 85% over the last four decades, new research shows. At the same time, their prevalence in subtropical reefs has doubled. While this undoubtedly poses a great risk to the survival of equatorial reefs, the good news is that the shift could help conserve both corals and other species that live in reefs — all of which are being threatened by climatic shifts.

Re-reefing

“Climate change seems to be redistributing coral reefs, the same way it is shifting many other marine species,” said Nichole Price, lead author of the study and a senior research scientist at the Bigelow Laboratory for Ocean Sciences. “The clarity in this trend is stunning, but we don’t yet know whether the new reefs can support the incredible diversity of tropical systems.”

In the warmer oceans of today, subtropical areas are more comfortable for corals than equatorial ones. Drifting coral larvae are thus starting to settle in areas that never housed corals before. New coral reefs begin developing when larvae find a suitable bit of seafloor away from the reef where they originated.

However, the team believes that only certain types of coral are able to reach these new, comfortable areas, depending on how long their larvae can swim or drift on currents before running out of fat (of which they have quite a limited amount). As such, the exact makeup of these subtropical reefs is still unknown (because it’s hard, slow, and expensive to collect genetic and species diversity data).

“So many questions remain about which species are and are not making it to these new locations, and we don’t yet know the fate of these young corals over longer time frames,” Price said. “The changes we are seeing in coral reef ecosystems are mind-boggling, and we need to work hard to document how these systems work and learn what we can do to save them before it’s too late.”

The team started by compiling a global database of studies all the way back to 1974, when record-keeping first began. Then, they examined tropical and subtropical reefs at altitudes up to 35 degrees north and south of the equator. The shift from older to newer reefs is perfectly mirrored on either side of the equator, they report. Based on these results, the team also mapped areas where “refugee corals” are likely to settle in the future. This is particularly interesting as coral reefs bring immense resources and opportunities to the communities that can access them.

However, the team also notes that it’s not just corals that make a reef — they are highly complex ecosystems of interconnected species, and can only function properly when these species live and mingle together. For example, coralline (symbiotic) algae are needed for the coral larvae to survive once they settle in a new area, but it’s yet unclear whether these algae are also making an appearance into these new areas. At the same time, it’s unclear how the new reefs will fare in the absence of these algae.

The team plans to expand their research to understand the diversity of and relationships between the species in these new reefs.

“We are seeing ecosystems transition to new blends of species that have never coexisted, and it’s not yet clear how long it takes for these systems to reach equilibrium,” said Satoshi Mitarai, an associate professor at Okinawa Institute of Science and Technology Graduate University and an author of the study. “The lines are really starting to blur about what a native species is, and when ecosystems are functioning or falling apart.”

“This report addresses the important question of whether warming waters have resulted in increases in coral populations,” says David Garrison, a program director in the National Science Foundation’s Division of Ocean Sciences, which funded the research. “Whether this offers hope for the sustainability of coral reefs requires more research and monitoring.”

The paper “Global biogeography of coral recruitment: tropical decline and subtropical increase” has been published in the journal Marine Ecology Progress Series.

Staghorn coral.

Miami dredging caused “extensive coral mortality and critical habitat loss” for the US’ only continental reef

Researchers at the University of Miami (UM) Rosenstiel School of Marine and Atmospheric Science say that local reefs have suffered extensive damage from sediment plumes stirred up by the 16-month dredging operation at the Port of Miami.

Sediment plume.

Natural sediment plumes from the Mississippi River (right) and the Atchafalaya River (left).
Image credits NASA.

The team estimates that over half a million corals were killed — those that lived within 550 yards (500 meters) of the dredged channel. Dredging operations, which involve clearing the seabed by scooping out mud, weeds, and rubbish with a dredge, seem to have impacted more than 15 miles (25 kilometers) of Florida’s reef tract, resulting in widespread coral death.

Deadly dredging

“Coral reefs worldwide are facing severe declines from climate change,” said Andrew Baker, associate professor of marine biology and ecology at the UM Rosenstiel School and senior author of the study. “If we want to conserve these ecosystems for the generations that come after us, it’s essential that we do all we can to conserve the corals we still have left.”

“These climate survivors may hold the key to understanding how some corals can survive global changes. We have to start locally by doing all we can to protect our remaining corals from impacts, like dredging, that we have the ability to control or prevent.”

Dredging operations at the Port of Miami began in 2013 as part of a larger construction effort in the area. The team analyzed data that was originally collected by consultants as part of the dredge’s environmental monitoring program. This program did note the loss of coral in the area but wrote it off as the consequence of a coral disease that was making a region-wide outbreak at the same time.

The present research ruled out disease by controlling for its impacts: the team looked at losses in coral species that were known to be immune to the outbreak. They tested whether corals closer to the dredge site were more likely to die during the dredging period than those further away. Most of the documented coral losses near the Port of Miami were the result of dredging, the team found.

Staghorn coral.

Staghorn coral, a species of coral in the Florida Reef.
Image via Wikimedia.

“It was important to differentiate these multiple impacts occurring on the reefs to understand the direct effects of dredging specifically,” said lead author Ross Cunning, who began the project while a postdoctoral scientist at the UM Rosenstiel School and is now a research biologist at the Shedd Aquarium in Chicago.

“We brought together all the available data from satellites, sediment traps, and hundreds of underwater surveys. Together, the multiple, independent datasets clearly show that dredging caused the major damages observed on these reefs.”

The team also looked at sediment plumes, which are clouds of suspended sediment stirred up by the dredges — the team reports they’re big enough to be seen from space — and whether they could predict the damage observed on the reefs below. It turns out that they could; the team says that the satellite-tracked plumes had a very high correlation with coral death on the seafloor. This is the first study to show that satellite data can be reliably used to predict dredging impacts on corals and their habitats.

“This connection allowed us to predict impacts beyond where ship-based monitoring was taking place, and showed that dredging likely damaged this reef several kilometers away,” said study co-author Brian Barnes of the University of South Florida.

“While this same relationship may not apply in all projects, this is a remarkable finding that further establishes Earth-observing satellites as independent monitoring tools to fill in gaps where data are otherwise not available.”

Rachel Silverstein, executive director and waterkeeper of Miami Waterkeeper and a co-author of the study says the study uncovered a “devastating story of loss that we cannot afford to ignore any longer.” She hopes that the team’s findings can be used to guide restoration efforts and to prevent similar tragedies in the future.

Florida can boast the only nearshore reef in the continental United States, but its coral cover has declined by at least 70% since the 1970s, the team explains. Some species in this reef — Staghorn corals (Acropora cervicornis), which were once common in shallow water and have declined by an estimated 98% — are now listed as threatened under the Endangered Species Act. The sites directly adjacent to the dredge site have been designated as “critical habitat” for the staghorn corals.

The paper “Extensive coral mortality and critical habitat loss following dredging and their association with remotely-sensed sediment plumes,” has been published in the journal Marine Pollution Bulletin.

Laura Weber collects a syringe sample from seawater surrounding an Orbicella faveolata coral colony in Jardines de la Reina, Cuba. Credit: Amy Apprill, Woods Hole Oceanographic Institution.

Study finds distinct microbes living near corals

Laura Weber collects a syringe sample from seawater surrounding an Orbicella faveolata coral colony in Jardines de la Reina, Cuba. Credit: Amy Apprill, Woods Hole Oceanographic Institution.

Laura Weber collects a syringe sample from seawater surrounding an Orbicella faveolata coral colony in Jardines de la Reina, Cuba. Credit: Amy Apprill, Woods Hole Oceanographic Institution.

Coral reefs have been called the “rainforests of the sea.” They are some of the most productive and biodiverse ecosystems on Earth. Although they occupy less than one percent of the ocean floor, they are home to more than a quarter of all marine species.

While the algae, which provide the coral with their vibrant color, and the microbial communities, which live within the animals have been extensively studied, the microbes which live just a few centimeters from the surface, have not. However, a new study from scientists at the Woods Hole Oceanographic Institution (WHOI) published in the journal Limnology and Oceanography has begun to describe and catalog these organisms.

“Microbes are everywhere on reefs,” says Laura Weber, lead author of the study and a Ph.D. student in the joint WHOI-MIT program. “There’s roughly a million of them in a single milliliter, which is about 20 drops, of seawater. But we don’t yet have a good sense of the microbial population that exists right next to corals. There’s some evidence from previous studies that corals may be surrounded by unique microbial cells, but many questions are still unanswered. Do these cells differ with coral species or reef site? How might they function?”

Along with her Ph.D. advisor, Amy Apprill, Weber traveled to a protected coral reef system called the “Jardines de la Reina,” located amid a string of remote islands near the southern coast of Cuba. Once there, Weber teamed with local Cuban scientists Patricia Gonzalez-Díaz and Maickel Armenteros to dive on the reefs and collect dozens of small samples from the water near five different species of coral.

A close up view of the surface of an Orbicella faveolata coral. Credit: Amy Apprill, Woods Hole Oceanographic Institution.

A close up view of the surface of an Orbicella faveolata coral. Credit: Amy Apprill, Woods Hole Oceanographic Institution.

Weber’s team discovered that the microbes contained genes which allowed them to interact with the coral surface. When Weber examined the genetic makeup of the microbes, she found that different types of coral had dissimilar microbial communities which existed near them.

“We started finding cool species-specific trends,” Weber says. “I didn’t think we would see any differences at all–but it turned out that in some areas, the bacterium Endozoicomonas, which lives symbiotically with corals, was actually enriched in the seawater closer to corals compared to the surrounding reef water. That means the region adjacent to corals could be important for attracting symbionts to a coral’s surface, or it could represent a region where corals shed their symbionts.”

Coral are currently in danger of disappearing due to increasing changes to our climate. Earth has lost nearly half of its coral as temperatures continue to rise. And at the current rates, they all could be gone by 2050.

Reef fish hover over a pillar coral colony (Dendrogyra cylindrus). Credit: Amy Apprill, Woods Hole Oceanographic Institution.

Reef fish hover over a pillar coral colony (Dendrogyra cylindrus). Credit: Amy Apprill, Woods Hole Oceanographic Institution.

These temperature changes cause mass bleaching of the animal, with mass disease infections becoming more frequent. Carbon dioxide absorbed into the ocean from the atmosphere has already begun to reduce calcification rates in reef-building and reef-associated organisms by altering seawater chemistry through decreases in pH, a process is called ocean acidification. Additionally, rising ocean acidity of the oceans has been making it harder for coral to build their skeletons upward toward sunlight, making them increasingly more vulnerable. How these issues will affect these microorganisms has yet to be seen.

“Scientists have been working for a while now to understand the role of microorganisms in reef environments and within coral colonies,” says Weber. “But now we have evidence that demonstrates a possible relationship between seawater microbes and coral symbionts. That gives us some clues to how they find and infect coral colonies, and how they might impact the health of the corals. It’s very exciting.”

Bleached Acropora coral (foreground) and normal colony (background), Keppel Islands, Great Barrier Reef. Credit: Wikimedia Commons.

Climate change killed almost 90% of the baby coral in the Great Barrier Reef

Bleached Acropora coral (foreground) and normal colony (background), Keppel Islands, Great Barrier Reef. Credit: Wikimedia Commons.

Bleached Acropora coral (foreground) and normal colony (background), Keppel Islands, Great Barrier Reef. Credit: Wikimedia Commons.

Recent, major bleaching events in the Great Barrier Reef — the largest living structure on the planet — has dramatically compromised the recruitment of new corals. According to researchers, the number of juvenile corals that settled in the reef was 89% lower in 2018 than the historical average.

A bleak future

Australia’s Great Barrier Reef has been hampered by four mass coral bleaching events since 1998, the most recent one lasting from June 2014 to May 2017. This was the longest, most damaging coral bleaching event on record killing 30% of the reef. An estimated half billion people around the world directly depend on reefs for income from fishing and tourism. Economic activity derived from the Great Barrer Reef alone is thought to be worth $4.5 billion annually.

Bleaching occurs when the ocean’s waters become too warm and expel the photosynthetic algae, called zooxanthellae, which live in a symbiotic relationship with the coral. Without the algae, the coral dies and seaweeds take over. The main culprit is man-made climate change, which warms and increases the acidity of the waters. Although some think the effects of climate change are hazy and yet to rear their head, it has actually been affecting the reef for at least 20 years. A 2018 study found that the number of ocean heatwaves has risen by more than 50% since 1925, threatening to collapse marine ecosystems all over the world, coral reefs being no exception.

Scientists believe that under normal conditions, the coral would need 10 years to bounce back. But a new study led by researchers at ARC Centre of Excellence for Coral Reef Studies suggests conditions are anything but normal.

The rate of new coral recruitment is abysmally low. Researchers measured how many adult corals along the reef had survived following the mass bleaching events, as well as the number of new corals that had been produced in 2018. Compared to 1990-levels, a period where there were no bleaching events, there was an average 90% decline in coral recruitment across the whole length of the Great Barrier Reef.

Typically, when one reef is destroyed, it can be replenished by babies from another reef. However, the 2016 an 2017 bleaching was so severe that in many parts of the reef there were no longer any adjacent reefs to provide offspring.

Not only does the Great Barrier Reef’s future hang by a thread, what remains of it is also morphing dramatically. Some corals are more resilient than others, which means that they now breed more, altering the coral composition. For instance, the hardest hit species is Acropora, which saw a 93% decline.

Coral reefs are complex ecosystems, so when a coral species disappears, so does the habitat for countless other species of marine wildlife.

“The collapse in stock–recruitment relationships indicates that the low resistance of adult brood stocks to repeated episodes of coral bleaching is inexorably tied to an impaired capacity for recovery, which highlights the multifaceted processes that underlie the global decline of coral reefs. The extent to which the Great Barrier Reef will be able to recover from the collapse in stock–recruitment relationships remains uncertain, given the projected increased frequency of extreme climate events over the next two decades,” the authors wrote in their study.

If current trends continue unabated, coral bleaching might affect 99% of the world’s reefs within this century, the United Nations warns. Previously, the U.N. Intergovernmental Panel on Climate Change warned that tropical reefs could decline by 70% to 90%, if the planet warms by 1.5ºC compared to preindustrial average temperatures — the upper limit set by the Paris Agreement. At 2ºC of warming, 99% of the world’s reefs could perish.

“Going to 2C and above gets to a point where corals can no longer grow back, or you have annual bleaching events. On the other hand, at 1.5C there’s still significant areas which are not heating up or not exposed to the same levels of stress such that they would lose coral, and so we’re fairly confident that we would have parts of those ecosystems remaining,” said Professor Ove Hoegh-Guldberg, a coral reefs expert with the University of Queensland.

Last year, Australian scientists bred baby corals in an artificial environment and later moved them to some of the most damaged parts of the reef. Eight months later, the juvenile coral had survived and grown, lending hope that coral transplants can restore similarly damaged ecosystems, not just in the Great Barrier Reef, but around the world as well. However, this is just patchwork. The only viable long-term solution is cutting global greenhouse emission. But even if we manage to avert 1.5ºC of warming, the Great Barrier Reef will never be the same.

The findings appeared in the journal Nature.

Great Coral Reef hit by massive surge of muddy water — visible from satellite

As if the corals didn’t have enough going against them, a massive water runoff has now spilled into the sea, straight towards the reef.

Image credits: NASA.

An unusual surge of rainfall in Queensland, Australia, has led to swollen rivers, which in turn have overflown and brought massive amounts of muddy water to the ocean. The plume is so large it can be easily seen from satellite, and has already reached the closest reefs some 60 km from the coast.

“If you look at the remote sensing images, the one that’s standing out at the moment is the Burdekin, which is the biggest river in that area,” Frederieke Kroon from the Australian Institute of Marine Science (AIMS), who is part of a team which is monitoring water quality in the region, told ABC.

“Over the last two weeks, other rivers have produced large flood plumes as well, which have dissipated since then,” but they are still affecting an “extraordinarily large area,” she said.

The muddy water stops sunlight from going through the water, essentially smothering the reef and any other wildlife unfortunate enough to be in the area. The net impact of this damage is not yet clear, but researchers are worried that the longer the plume stays in place, the more damage it will do — and there are currently no strong winds to disperse it.

To make matters even worse, the mud washed into the oceans contains common farming chemicals like nitrogen and phosphorus, which could kill even more corals and seagrass.

We really can’t afford to put even more pressure on the coral reef. Rising temperatures and increasing water acidity have put a tremendous amount of environmental pressure on the coral and caused massive bleaching, putting the entire Great Barrier Reef at extreme risk. In addition to these threats, the reef faces many other threats, including poor water quality, parasites, and increasing touristic pressure. Half of the Great Barrier Reef has already disappeared, and if things carry on as usual, it may very well be gone forever. Saving the reef, if possible at all, will require urgent and massive intervention, and this recent event just adds more salt to the wound.

There may yet be one very thin silver lining to this story: the murky waters might actually work to temporarily reduce water temperatures

“If you want to have a flipside to the story that would be one, yes,” marine scientists Frederieke Kroon told the ABC, “but it’s still a huge disturbance to the reef [after] the bleaching and the cyclones that we’ve had over the last couple of years.”

Maldives.

Rising seas might mean more coral reef islands — if we don’t murder all the corals

There might be a silver lining to sea level rise — emphasis on ‘might’.

Maldives.

Coral reef rim islands, Huvadhoo Atoll, Republic of Maldives.
Image credits Prof. Paul Kench.

New research proposes that rising sea levels may help the long-term formation of coral reef islands, such as the Maldives. However, all the other bits of climate change may destroy any benefits it brings.

Climate change, island change

“Coral reef islands are typically believed to be highly vulnerable to rising sea levels. This is a major concern for coral reef island nations, in which reef islands provide the only habitable land,” says lead author Dr. Holly East of the Department of Geography and Environmental Sciences at Northumbria University, Newcastle.

Coral reef islands aren’t very keen on altitude; typically, they’re less than three meters (about 10 feet) above the water’s surface. This obviously makes them very vulnerable to rising sea levels. However, the same high seas might’ve also created the islands, the team reports.

The researchers studied five islands in the southern Maldives. By drilling out core samples, they were able to reconstruct when and how the islands formed. They report that storms off the coast of South Africa created a series of large waves (‘high-energy wave events’) that led to the formation of the Maldives. These violent waves dislodged large chunks of pre-existent reefs and transported them onto reef platforms. This stacking of reef material created the foundations of the islands we see today.

“We have found evidence that the Maldivian rim reef islands actually formed under higher sea levels than we have at present,” Dr. East adds.

“This gives us some optimism that if climate change causes rising sea levels and increases in the magnitude of high-energy wave events in the region, it may actually create the perfect conditions to reactivate the processes that built the reef islands in the first place, rather than drowning them.”

The seas were around 0.5 meters (1.5 feet) higher than today during the islands’ formations — this allowed the waves to carry more energy. Both the higher sea level and large wave events were critical to the construction of the islands. Now, (man-made) climate change is also pushing up sea levels; the team says that projected increases in both sea level and the magnitude of large wave events could actually lead to the growth of reef islands.

For that to happen, however, you need living, healthy coral in the region’s reef communities, Dr. East stresses. And we’re murdering them pretty fast right now.

“As these islands are mostly made from coral, a healthy coral reef is vital to provide the materials for island building. However, this could be problematic as corals face a range of threats under climate change, including increasing sea surface temperatures and ocean acidity,” she says.

“If the reef is unhealthy, we could end up with the perfect building conditions but not the bricks.”

She also cautioned that “the large wave events required for reef island building may devastate island infrastructure, potentially compromising the habitability of reef islands in their current form.” Factoring in higher sea levels as well, she says that reef island nations need to “develop infrastructure with the capacity to withstand, or be adaptable to, large wave events” — a task she summarizes as being a “challenge”.

Their paper, “Coral Reef Island Initiation and Development Under Higher Than Present Sea Levels,” has been published in the journal Geophysical Research Letters.