corals

Helping Corals With Beneficial Bacteria | Earth Wise

March 31, 2021 By EarthWise Leave a Comment

A group of researchers at the King Abdullah University of Science and Technology in Saudi Arabia is exploring a novel technology to improve the health of corals. Around the globe, corals are being stressed by pathogens, toxins, and warming waters leading to widespread bleaching events.

The new idea is to introduce beneficial bacteria to the corals, thereby boosting the strength and resilience of their symbiotic partners. The concept is akin to the use of probiotics in plant science. Corals rely on bacterial and algal symbionts to provide nutrients, energy (through photosynthesis), toxin regulation, and protection against pathogens.

The researchers selected bacteria that are naturally symbiotic to specific coral species on reefs in the Red Sea, ensuring that no alien bacteria are accidentally introduced. A probiotic cocktail comprising six bacteria strains was used in a laboratory setting. Results in the lab have been promising so far, as they have observed dynamic and metabolic alterations to the corals that boosted their chances of survival under heat stress.

Success in the lab will need to be translated to success in the open oceans, which is challenging. Scaling up and seeding whole reefs might involve robots and artificial intelligence in order to deliver probiotics either into sediments or directly onto corals.

The use of beneficial microorganisms is not the solution to the global destruction of coral reefs. Only worldwide CO₂ mitigation can ultimately accomplish that. But the probiotic approach might buy corals some time as they deal with shifting environmental pressures and try to adapt to a changing world.

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Microbiome boost may help corals resist bleaching

Photo, posted March 18, 2018, courtesy of Steven dos Remedios via Flickr.

Earth Wise is a production of WAMC Northeast Public Radio.

Caribbean Coral Reefs Under Siege | Earth Wise

January 4, 2021 By EarthWise Leave a Comment

Coral reefs around the world have been suffering from warming seas and increasing acidification, both a result of human activity. In the Caribbean, a new threat has emerged in the form of invasive algae.

New research published in Scientific Reports explains how an aggressive, crust-like alga is overgrowing shallow reefs and taking the place of coral that was damaged by powerful storms that exposed areas of the undersea rock where corals grew.

Researchers from Oxford University, the Carnegie Institution, and California State University Northridge have been studying these peyssonnelid algal crusts, or PACs, for several years in the U.S. Virgin Islands. The PAC has been out-competing coral larvae for surface space and then growing over the existing reef architecture, greatly damaging delicate reef ecosystems.

New corals actually prefer to settle on crusty surfaces created by a different type of algae called crustose algae, or CCA. CCA acts as guideposts for coral larvae by producing biochemical signals as part of a microbial community that entice baby coral to affix itself.

In contrast, the destructive PAC algae exclude coral settlement. The researchers determined that the microbial community associated with PAC algae is deployed to deter grazing from fish and other marine creatures. Unfortunately, it also deters coral.

Fragile coral ecosystems are already under assault by environmental pollution and global warming. Now, in the aftermath of powerful hurricanes like Irma and Maria, algal crusts are taking over reef communities and posing an existential threat to Caribbean corals.

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An unusual microbiome characterises a spatially-aggressive crustose alga rapidly overgrowing shallow Caribbean reefs

Photo, posted January 11, 2015, courtesy of Falco Ermert via Flickr.

Earth Wise is a production of WAMC Northeast Public Radio.

Helping Out Corals With Cool Water | Earth Wise

October 22, 2020 By EarthWise Leave a Comment

Coral bleaching is happening five times more frequently than it did forty years ago. Its increasing occurrence is a result of global warming which leads to marine heat waves – periods of higher ocean water temperatures. Heat stress on living coral animals causes them to expel the algae that live symbiotically within the coral structure. As the algae is expelled, the coral fades in color looking like it is bleached. Without its algae partner, the coral eventually dies.

Given the increasing occurrence of marine heat waves, scientists are seeking novel ways to decrease heat stress in corals. A new study by the Bermuda Institute of Ocean Science is investigating the use of artificial upwelling – the application of cooler, deep water – as a way to mitigate thermal stress on corals.

Upwelling is a natural process in the ocean in which winds push surface water away from a region – for example, a coastline – which then allows the uplift of deeper, colder waters to the surface. Because such deeper waters are typically rich in nutrients, upwelling is important for supporting many of the world’s important commercial fisheries. For this reason, artificial upwelling has sometimes been used to increase fish stocks in certain locations.

The new work placed coral colonies in aquaria in Bermuda and tested the effects of varying amounts and temperatures of deep cold-water pulses upon corals subjected to thermal stress. The results showed that even short intrusions of cooler deep water (less than two hours per day) can mitigate thermal stress in corals. The next steps are to find suitable parameters for artificial upwelling that maximize the benefits while minimizing potential harmful side effects on the corals and the ecosystems they support.

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Can pumping up cold water from deep within the ocean halt coral bleaching?

Photo, posted February 24, 2008, courtesy of Roderick Eime via Flickr.

Earth Wise is a production of WAMC Northeast Public Radio.

Artificial Aquatic Polyps | Earth Wise

September 16, 2020 By EarthWise Leave a Comment

Corals are often mistaken for rocks because of their hardened surfaces. And, since they attach or “take root” to the sea floor, they are often mistaken for plants. But unlike rocks, corals are alive. And unlike plants, corals do not make their own food. Corals are actually animals.

Most of these structures that we call “coral” are made up of hundreds to thousands of tiny coral creatures called polyps. A coral polyp, which is often no thicker than a nickel, has a saclike body and mouth that is encircled by stinging tentacles. Polyps are responsible for a host of ecosystem services, including nourishing corals, and aiding coral survival by generating self-made currents through the motion of their soft bodies.

Inspired by these marine organisms, researchers from the University of Warwick in the UK and Eindhoven University of Technology in the Netherlands have collaborated to develop an artificial aquatic polyp capable of removing contaminants from water. The 1 square centimeter wireless robot polyp can attract, grasp, and release objects, moving under the influence of a magnetic field and whose “tentacles” are triggered by light.

The next step for the researchers is to see if the technology can be successfully scaled up from laboratory to pilot scale. In order for that to happen, the team has to design an array of artificial polyps capable of working harmoniously together.

Corals are an incredibly important part of ocean ecosystems. And while it remains to be seen how much value artificial polyps can achieve in future applications, it serves as another example of scientists emulating nature to create more sustainable designs.

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Aquatic robots can remove contaminant particles from water

An artificial aquatic polyp that wirelessly attracts, grasps, and releases objects

Photo, posted April 14, 2011, courtesy of Derek Keats via Flickr.

Earth Wise is a production of WAMC Northeast Public Radio.

A Devastating Threat To Coral Reef Habitats | Earth Wise

March 25, 2020 By EarthWise 2 Comments

According to new research from scientists at the University of Hawaii Manoa, the warming and acidifying oceans could wipe out nearly all existing coral reef habitats by 2100. In fact, the researchers predict that 70-90% of coral reefs will disappear over the next 20 years alone as a consequence of climate change and pollution.

Some organizations are attempting to save coral habitats by transplanting live corals from labs to reefs. The idea is that the new young corals will help revive the reefs. But after mapping where such restoration efforts would be most successful, the research indicates that there will be little to no suitable habitat remaining for corals by 2100. Small portions of Baja California and the Red Sea are two of the sites that could remain viable by 2100, although neither are ideal due to their proximity to rivers. Sea surfaces temperature and acidity are two of the most important factors in determining the viability of a site for restoration.

Warming ocean waters stress corals, which cause them to expel the symbiotic algae living inside them. This turns the often colorful corals white – an event known as coral bleaching. Bleached corals are not dead corals, but they are at a higher risk of dying. These coral bleaching events are becoming more frequent as a result of the changing climate.

The projected increases in human pollution will only play a minor role in the future elimination of coral reef habitats. Ironically, that’s because humans have already caused such extensive damage to coral reefs that there aren’t many locations left to impact.

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Warming, acidic oceans may nearly eliminate coral reef habitats by 2100

Photo, posted September 28, 2009, courtesy of Matt Kieffer via Flickr.

Earth Wise is a production of WAMC Northeast Public Radio.

Community Action And Coral Reefs

January 1, 2020 By EarthWise Leave a Comment

Coral reef habitats are some of the densest and most varied ecosystems on earth. While coral reefs cover just 0.2% of the ocean floor, scientists estimate that nearly one million different species of fish, invertebrates, and algae can be found in or around coral reefs.

However, climate change is wreaking havoc on the health of coral reefs. Warming and acidifying oceans are resulting in enormous coral losses. Overfishing, development, and pollution are also threatening coral reef health.

According to new research, positive community action can help boost fish populations in coral reefs and safeguard future fish numbers. The paper, which was recently published in the journal Proceedings of the National Academy of Sciences, details the social and ecological outcomes of work being done in Papua New Guinea since 2001.

These communities have established a traditional system of rotational fishing closures in order to manage their fisheries resources. They ban fishing on part of their reefs for a few years, and then open these closures when village elders believe fish behavior has changed and fish populations have recovered. They then close a different part of their reefs, and repeat the process.

The researchers found that these rotational practices resulted in more than twice as many fish on the closed reefs as compared to open ones, and the closures made fish less scared of people and easier to catch. But the researchers did caution that this short term boost in fish numbers may not be enough to stop the overall impact of fishing.

Globally, more than 500 million people depend on coral reefs for food, income, and coastal protection. Balancing community needs with environmental needs can be tricky business.

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Positive community action can help coral reef health

Photo, posted October 11, 2011, courtesy of Paul Toogood via Flickr.

Earth Wise is a production of WAMC Northeast Public Radio.

Pesticides In The Great Barrier Reef

November 7, 2019 By EarthWise Leave a Comment

Australia’s Great Barrier Reef is one of the greatest natural wonders in the world and it has been under siege by warming waters and ocean acidification. Widespread coral bleaching has damaged or destroyed large portions of the 1,400-mile long coral reef system. But the effects of climate change are not the only threat to the reef. Pesticides found in waterways that flow into the Great Barrier Reef are another serious problem.

According to a new study by the University of Queensland, the combined toxicity of 22 of the most common pesticides that flow into the Reef are not meeting pollution reduction targets.

Different pesticides affect different organisms. Herbicides affect organisms that photosynthesize such as seagrass, corals, mangroves, and algae. Insecticides affect insect larvae in freshwater, and crustaceans such as crabs, prawns, and lobsters. Previous assessments have only examined individual pesticides and only for limited times. The new study has utilized a methodology that estimates the combined toxicity of multiple pesticides found in the waterways that discharge into the Reef and does it for the entire wet season.

The research revealed that the pesticide reduction target set in the Australian Government’s Reef 2050 Water Quality Improvement Plan is not being met. Only one natural resource management region – the Cape York region – was found to be meeting its target.

By having estimates of the risk posed by pesticides in the various regions and individual waterways, governments, farmers, and conservationists can see which areas pose the greatest risk and where to maximize efforts. Stakeholders have to come together to reduce pesticide concentrations through better management practices and by using less toxic pesticides.

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High pesticide concentrations continue to enter Great Barrier Reef

Photo, posted July 29, 2010, courtesy of Kyle Taylor via Flickr.

Earth Wise is a production of WAMC Northeast Public Radio.

Refugee Corals

August 30, 2019 By EarthWise Leave a Comment

As climate change warms the ocean, subtropical environments are becoming more favorable for corals than the equatorial waters where they traditionally thrived. As a result, drifting coral larvae are settling and growing in new regions.

According to new research in the journal Marine Ecology Progress Series, the number of young corals on tropical reefs has declined by 85% over the past 40 years. At the same time, the numbers on subtropical reefs has doubled.

Only certain types of coral can reach these new subtropical locations. That depends on how far the microscopic larvae can swim and drift on currents before they exhaust their limited fat stores. Thus, the reef ecosystems that develop have new blends of species that have previously never coexisted. It is not clear how long it will take for the new systems to reach equilibrium.

Coral reefs are complicated systems that depend on the interplay between species to enable their healthy functioning. Apart from the corals themselves, there are the coraline algae that symbiotically coexist with them. How all of this will play out in these evolving ecosystems is unknown.

In the meantime, the research has found that these refugee corals are settling at latitudes up to 35 degrees both north and south of the equator. It is no longer so clear what constitute native species in the reefs. It remains to be seen whether new reefs in subtropical oceans can support the incredible biodiversity seen in tropical reefs. But ultimately, these changing ecosystems could potentially bring new resources and opportunities, such as fishing and tourism, to places where they never existed before.

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Coral Reefs Shifting Away from Equatorial Waters

Photo, posted March 22, 2011, courtesy of Simone Lovati via Flickr.

Earth Wise is a production of WAMC Northeast Public Radio.

How Much CO2 Can The Oceans Hold?

May 2, 2019 By EarthWise Leave a Comment

The carbon dioxide that enters the atmosphere doesn’t necessarily stay there. As part of the natural carbon cycle, much of it goes into plants, soil and, very significantly, the ocean. In fact, the world’s oceans are a sink for human-generated carbon dioxide without which the extent of global climate change would be far worse.

Oceans takes up CO2 in two steps: first the CO2 dissolves in the surface water. Then, the ocean’s overturning circulation distributes it. Currents and mixing processes transport the dissolved CO2 from the surface deep into the ocean’s interior, where it accumulates over time.

A long-standing priority for climate researchers is to determine how much of the CO2 we produce is being absorbed by the oceans and, ultimately, how much can they hold?

An international team of scientists has recently provided some answers. As reported in Science, the researchers have determined that the oceans have taken up from the atmosphere as much as 37 billion tons of human-made carbon between 1994 and 2007. This figure corresponds to nearly a third of all the anthropogenic CO2 emitted during that time.

Furthermore, they found that the percentage of CO2 taken up by the oceans has remained relatively stable compared to the preceding 200 years even as the absolute quantity has increased. So, evidently, the oceans’ capacity for carbon dioxide has not yet been saturated.

That’s the good news. The bad news is that putting all that CO2 into the oceans has a steep price: the dissolved CO2 acidifies the water. The consequences for a wide range of marine life including coral reefs are serious and getting worse. We need to drastically reduce carbon emissions.

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Ocean sink for human-made carbon dioxide measured

Photo, posted November 5, 2018, courtesy of Flickr.

Earth Wise is a production of WAMC Northeast Public Radio.

Another Problem For Coral Reefs

April 5, 2019 By EarthWise Leave a Comment

Coral reefs around the world have been suffering in recent years from warming ocean temperatures as well as from increasing ocean acidification. Corals are very sensitive organisms that can only tolerate relatively slight changes in their environment. Thus, the majority of reef-building corals are found in tropical and subtropical waters with favorable conditions.

New research has confirmed that drastic changes in ocean salinity from, for example, severe freshwater flooding, provoke similar stress responses in corals as the heating that has resulted in freshwater bleaching and, eventually, coral death.

The coast of northeast Queensland in Australia has experienced abnormal monsoon-related freshwater flooding that caused extreme and sudden changes in the ocean salt concentration. In places, nearshore reefs were exposed to water with only half the normal ocean salinity. The result has been a shock response in corals that prevents normal cell function. Unlike their response to heat stress, corals exposed to reduced salinity experience a complete collapse of their internal cellular protein balance.

The central Great Barrier Reef has actually been relatively free from mass thermal bleaching events this Australian summer, but many coastal reefs instead have been battling dramatic changes in water conditions as a result of massive plumes of floodwater.

The wild weather in Australia is undoubtedly associated with the changing climate and this new research shows that it is leading to yet another threat to the world’s coral reefs. With the frequency and severity of heavy rainfall and runoff events predicted to continue to increase over the next few decades, proactive measures to increase the resiliency of coral reefs are needed more than ever.

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Reduced salinity of seawater wreaks havoc on coral chemistry

Photo, posted December 12, 2010, courtesy of Gareth Williams via Flickr.

Earth Wise is a production of WAMC Northeast Public Radio.

Disease On Coral Reefs

February 19, 2019 By EarthWise Leave a Comment

The warming oceans have led to bleaching events in coral reefs around the world, but bleaching is not the only problem corals face. Disease outbreaks are also becoming more frequent, severe, and widespread.

Many factors are contributing to the problem, including pollution and nitrogen runoff from fertilizers and coastal sewer and septic systems. However, the key culprit is likely the steadily increasing ocean temperatures, which are the cause of coral bleaching. Elevated water temperatures can cause coral polyps to expel the algae that sustains them and gives them color.

According to scientists, bleaching makes corals more susceptible to illness. In the Caribbean, a coral disease hotspot, about 80% of coral cover has disappeared, largely from outbreaks of “white band disease”, so called because of a white band of dead tissue that forms in affected corals. Two crucial reef-building species, elkhorn and staghorn coral, are now nearing extinction in the regions. The reef extending along the Florida coastline is the third largest reef ecosystem in the world and nearly 35% of it has been lost to disease.

Estimates are that disease outbreaks have wiped out at least 6% of the corals on the Great Barrier Reef in Australia. In that region, diseases are more prevalent in areas where corals were damaged by fishing and other human activity because wounded coral provides an entry point for pathogens and bacteria.

In the face of climate change and mounting disease outbreaks, scientists are scrambling for solutions to stave off catastrophe. Assisting the migration of hardier coral species and breeding so-called “super corals” are among the strategies being pursued. It is unknown whether these and other forms of intervention can be used on a wide enough scale to really make a difference.

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