Protecting coral 'nurseries' as important as safeguarding established coral reefs

When imagining corals, the picture that comes to mind is usually a stationary one: a garden of rock-like structures covering sections of the ocean floor.

Reef conservation efforts typically focus on preserving established coral and protecting them from known stressors such as pollution, overfishing and runoff from coastline populations.

However, new research near Miloliʻi in the southwestern part of the island of Hawaii, shows that identifying and protecting marine ecosystems both down-current and up-current of coral reefs, specifically areas where coral larvae are more likely to survive and thrive, is crucial to future coral conservation and restoration efforts -- especially as reefs face increasing pressure from the devastating effects of climate change.

The research, completed by Arizona State University scientists and their collaborators, appears in the current issue of Proceedings of the National Academy of Sciences.

Rachel Carlson, an ASU affiliate scientist and the study's first author, along with Greg Asner, director of ASU's Center for Global Discovery and Conservation Science, Larry Crowder, professor of oceans at Stanford University, and Robin Martin, associate professor with the ASU School of Ocean Futures in the Julie Ann Wrigley Global Futures Laboratory, collaborated on the project.

Additionally, the ʻĀkoʻakoʻa Reef Restoration Program, a regional effort that fuses cultural leadership, multi-modal education, advanced science and government engagement, backed the research.

Carlson says this type of collaborative work -- partnerships combining local, Indigenous knowledge and Western science -- is crucial to mapping out a future that ensures the survival of coral populations.

"There's a lot of Indigenous knowledge about coral spawning and fish populations in West Hawaii. In this study, we addressed an open question: How connected are coral populations between embayments along this coastline?" Carlson said. "What we essentially found is that the major factors in helping the coral keiki, known as larvae, settle down and survive are the nearshore current and the structure of the reef."

The study shows that the larvae more often settle in and inhabit areas with large boulders and uneven surfaces, or "chunky features," said Carlson, who is also a Chancellor's Postdoctoral Fellow at the UC Davis Bodega Marine Lab. Adult coral will spawn millions of larvae into the water column and those larvae prefer to settle in places with large knolls and boulders.

This discovery is good news: These kinds of seafloor features have been mapped via ASU's Global Airborne Observatory, a highly specialized aircraft that uses several types of remote sensing technologies to track both underwater and land-based habitats. This means that the researchers have the capability to help find and map priority reefs for conservation and restoration.

"This is foundational research in several important ways," said Asner, the study's senior author. "First, it gives us an understanding of the connectivity of different parts of reefs along our coastline and tells us the level of connectivity in the context of the birth, settlement and growth of corals miles apart. Second, our unique remote sensing capabilities can identify reef sites where coral restoration could be most viable in the future. Finally, these findings provide a critical building block for future restoration efforts by our ʻĀkoʻakoʻa team and collaborators."

The group's goal is to preserve and restore vitality to Hawaii's coral reefs and coastline health.

"We as lineal descendants of the Miloliʻi area have always relied on the reef for our ʻOhana (families). Our reef is our sustenance and is of enormous cultural value to us," said Kaʻimi Kaupiko, president of the nonprofit organization Kalanihale, which manages the Miloliʻi Community-Based Subsistence Fishing Area where the study took place.

Asner said the intertwined nature of reefs along Hawaii's coastlines is crucial to consider in reef protection strategies. Narrowing in on one area without consideration for the reproductive corridors of corals, he said, would be akin to worrying about planting trees in a certain place and not thinking about the forest as a whole. This sentiment is echoed by Martin, who said reef connectivity is an underutilized tool in reef restoration efforts globally.

"In Hawaii and worldwide, we're trying to figure out where we should place protections and restore areas to help reefs," Martin said. "This study is highly technical, but it needs to be part of that conversation and part of that work, because if you aren't protecting the upcurrent reefs, you are cutting off important reproductive areas."

Martin said reef restoration could, for example, expand a protected area of reefs beyond just the spots that have more dense coral coverage on the ocean floor; protection efforts would also be needed in the upcurrent path that the coral larvae traveled through before they settled in a new location.

Asner adds that this research could very well help conservation efforts expand to much greater distances than have been achieved previously.

"These kinds of studies of connectivity, flow and movement are needed because the west Hawaii island coastline is longer than the whole circumference of any other island," Asner said. "We have a lot of degraded reefs along our coastline, so knowing where and how to help baby corals thrive is fundamental to the ʻĀkoʻakoʻa restoration effort."

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To restore ecosystems, think about thwarting hungry herbivores

Re-establishing plantings of trees, grasses and other vegetation is essential for restoring degraded ecosystems, but a new survey of almost 2,600 restoration projects from nearly every type of ecosystem on Earth finds that most projects fail to recognize and control one of the new plants' chief threats: hungry critters that eat plants.

"While most of the projects took steps to exclude competing plant species, only 10% took steps to control or temporarily exclude herbivores, despite the fact that in the early stages these plants are like lollipops -- irresistible little treats for grazers," said Brian Silliman, Rachel Carson Distinguished Professor of Marine Conservation Biology at Duke University's Nicholas School of the Environment.

By not protecting plants in their early states, conservationists are missing out on great opportunity to significantly speed restoration, improve its outcomes, and lower its costs, he said.

"Our analysis of the surveyed projects shows that introducing predators to keep herbivore populations in check or installing barriers to keep them at bay until plantings become more established and less vulnerable, can increase plant re-growth by 89% on average," said Silliman, who helped conceptualize the study and was one of its coauthors.

Those gains are equal to or greater than the gains realized by excluding competing plant species, the new survey shows.

"This begs the question: Why aren't we doing it more?" he asks.

The new survey was conducted with input from an international team of researchers affiliated with 20 universities and institutions. They published their peer-reviewed findings Nov. 3 in Science.

Qiang He, professor of coastal ecology at Fudan University and a former postdoctoral research associate of Silliman's at Duke, co-led the study with Changlin Xu, a member of He's Coastal Ecology Lab at Fudan.

The survey's findings have far-reaching implications for efforts to restore vegetation at a time of climate change, He said.

"Herbivores' effects were particularly pronounced in regions with higher temperatures and lower precipitation," He noted.

All of which leads to one inescapable conclusion, Silliman said.

"If we want more plants, we have to let more predators in or restore their populations," Silliman said. "Indeed, the decline of large predators, like wolves, lions, and sharks, that normally keep herbivore populations in check, is likely an important indirect cause of high grazing pressures."

"Conventional restoration is slowing our losses, but it's not expanding vegetation in many places, and climate change could make that even more difficult," he said.

Using predators to keep herbivores in check at restored sites is a relatively untapped approach that could help us boost plant diversity and restore ecosystems that are vital to human and environmental health, in less time and at lower costs," Silliman said. "It's like learning a new gardening trick that doubles your yield."

Once a planting is established, the herbivores are essential too, he added. "Plants just need a small break from being eaten to get restarted making ecosystems. Once they establish, herbivores are key to maintaining plant ecosystem diversity and function."

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An unexpected doorway into the ear opens new possibilities for hearing restoration

An international team of researchers has developed a new method to deliver drugs into the inner ear. The discovery was possible by harnessing the natural flow of fluids in the brain and employing a little understood backdoor into the cochlea. When combined to deliver a gene therapy that repairs inner ear hair cells, the researchers were able to restore hearing in deaf mice.

"These findings demonstrate that cerebrospinal fluid transport comprises an accessible route for gene delivery to the adult inner ear and may represent an important step towards using gene therapy to restore hearing in humans," said Maiken Nedergaard, MD, DMSc, senior author of the new study, which appears in the journal Science Translational Medicine.

Nedergaard is co-director of the Center for Translational Neuromedicine at University of Rochester and the University of Copenhagen. The study was the product of a collaboration between researchers at the two universities and a group led by Barbara Canlon, Ph.D. in the Laboratory of Experimental Audiology at the Karolinska Institute in Stockholm, Sweden.

The number of people worldwide predicted to have mild to complete hearing loss is expected to grow to around 2.5 billion by mid-century. The primarily cause is the death or loss of function of hair cells found in the cochlea -- which are responsible for relaying sounds to the brain -- due to mutations of critical genes, aging, noise exposure, and other factors.

While hair cells do not naturally regenerated in humans and other mammals, gene therapies have shown promise and in separate studies have successfully repaired the function of hair cells in neo-natal and very young mice. However, as both mice and humans age, the cochlea, already a delicate structure, becomes enclosed in temporal bone. At this point, any effort to reach the cochlea and deliver a gene therapy via surgery risks damaging this sensitive area and altering hearing.

In the new study, the researchers describe a little understood passage into the cochlea called the cochlear aqueduct. While the name conjures images of monumental stone architecture, the cochlear aqueduct is thin boney channel no larger than a single strand of hair. Suspected to play a role in balancing pressure in the ear, new study shows that that the cochlear aqueduct also acts as a conduit between the cerebrospinal fluid found in the inner ear and the rest of the brain.

Scientists are developing clearer picture of the mechanics of glymphatic system, the brain's unique process of removing waste first described by the Nedergaard lab in 2012. Because the glymphatic system pumps cerebrospinal fluid deep into brain tissue to wash away toxic proteins, researchers have been eyeing it as a potentially new way to deliver drugs into the brain, a major challenge in developing drugs for neurological disorders.

Researchers have also discovered that the complex movement of fluids driven by the glymphatic system extend to the eyes and the peripheral nervous system, including ear. The new study represented an opportunity to put the drug delivery potential of the glymphatic system to the test, while at the same time targeting a previously unreachable part of the auditory system.

Employing a number of imagining and modeling technologies, the researchers were able to develop a detailed portrait of how fluid from other parts of the brain flows through cochlear aqueduct and into the inner ear. The team then injected an adeno-associated virus into the cisterna magna, a large reservoir of cerebrospinal fluid found at the base of the skull. The virus found its way into the inner ear via the cochlear aqueduct, delivered a gene therapy that expresses a protein called vesicular glutamate transporter-3, which enable the hair cells to transmit signal and rescued hearing in adult deaf mice.

"This new delivery route into the ear may not only serve the advancement of auditory research, but also prove useful when translated to humans with progressive genetic-mediated hearing loss," said Nedergaard.

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Global wetlands losses overestimated despite high losses in many regions

Sometime this spring or summer, the Supreme Court is expected to issue a case ruling that will legally define whether federal protections should be extended to wetlands outside of navigable waters. The justices might consider reading a new Stanford-led study that finds, although wetlands remain threatened in many parts of the world -- including the U.S., which accounts for more losses than any other country -- global losses of wetlands have likely been overestimated. Published Feb. 8 in Nature, the study's findings could help better explain the causes and impacts of wetland loss, enabling more informed plans to protect or restore ecosystems crucial for human health and livelihoods.

"Despite the good news that our results might imply, it remains urgent to halt and reverse the conversion and degradation of wetlands," said study lead author Etienne Fluet-Chouinard, a postdoctoral associate in Stanford's Department of Earth System Science at the time of the research. "The geographic disparities in losses are critical to consider because the forgone local benefits from drained wetlands cannot be replaced by wetlands elsewhere."

Rethinking wetlands

Now understood to be vital sources of water purification, groundwater recharge, and carbon storage, wetlands were long seen as unproductive areas teeming with disease-bearing insects and good only for draining to grow crops or harvest peat for fuel and fertilizer. Unrelenting drainage for conversion to human land uses, such as farmland and urban areas, in addition to alteration by fires and groundwater extraction, has made wetlands among the world's most threatened ecosystems in the world.

Accurately estimating the extent, distribution, and timing of wetland loss is key to understanding their role in natural processes and the impact of wetland drainage on the water and carbon cycles. A lack of historical data has hindered the effort, forcing scientists to make estimates based on incomplete collections of regional data on wetland loss.

"Wetlands purify our water, prevent flooding, and are biodiversity superheroes," said study co-author Rob Jackson, the Michelle and Kevin Douglas Provostial Professor of Energy and Environment in the Stanford Doerr School of Sustainability. "We need the best data possible to save what we have and know what we've lost."

A second chance

In a first-of-its-kind historical reconstruction, the researchers combed through thousands of records of wetland drainage and land-use changes in 154 countries, mapping the distribution of drained and converted wetlands onto maps of present-day wetlands to get a picture of what the original wetland area might have looked like in 1700.

They found that the area of wetland ecosystems has declined 21-35% since 1700 due to human intervention. That's far less than the 50-87% losses estimated by previous studies. Still, the authors estimate that at least 1.3 million square miles of wetlands have been lost globally -- an area about the size of Alaska, Texas, California, Montana, New Mexico, and Arizona combined.

"These new results allow us to better quantify changes in wetlands' sequestration of carbon from the atmosphere and emission of methane, another powerful greenhouse gas," said study co-author Avni Malhotra, a Stanford postdoctoral researcher at the time of the research.

The low estimate is likely the result of the study's focus beyond regions with historically high wetland losses, and its avoidance of large extrapolations -- characteristics of many previous estimates. The researchers note their estimate of losses is likely conservative because they constrained their analysis to available data, which is scarce for the years before 1850.

Despite what may seem to be good news, the researchers emphasize that wetland losses have been dramatically high in some regions, such as the U.S., which is estimated to have lost 40% of its wetlands since 1700 and accounts for more than 15% of all global losses during the study's time period. Although wetland conversion and degradation have slowed globally, it continues apace in some regions, such as Indonesia, where farmers and corporations continue to clear large swaths of land for oil palm plantations and other agricultural uses.

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Computer modelling aims to inform restoration, conservation of coral reefs

A UBC Okanagan research team has created a computer modelling program to help scientists predict the effect of climate damage and eventual restoration plans on coral reefs around the globe.

This is a critical objective, says Dr. Bruno Carturan, because climate change is killing many coral species and can lead to the collapse of entire coral reef ecosystems. But, because they are so complex, it's logistically challenging to study the impact of devastation and regeneration of coral reefs.

Real-world experiments are impractical, as researchers would need to manipulate and disrupt large areas of reefs, along with coral colonies and herbivore populations, and then monitor the changes in structure and diversity over many years.

"Needless to say, conducting experiments that will disturb natural coral reefs is unethical and should be avoided, while using big aquariums is simply unfeasible," says Dr. Carturan, who recently completed his doctoral studies with the Irving K. Barber Faculty of Science. "For these reasons, no such experiments have ever been conducted, which has hindered our capacity to predict coral diversity and the associated resilience of the reefs."

For his latest research, published recently in Frontiers in Ecology and Evolution, Dr. Carturan used models to create 245 coral communities, each with a unique set of nine species and each occupying a surface of 25 square metres. The model represents coral colonies and different species of algae that grow, compete and reproduce together while also being impacted by climate.

Crucially, he notes, all the key components of the model, including species' traits such as competitive abilities and growth rates, are informed by pre-existing, real-world data from 800 species.

The research team simulated various scenarios -- including strong waves, a cyclone or intense heat -- and then measured each model reef's resilience taking note of damage, recovery time and the quality of the habitat 10 years after the disturbance.

By running so many scenarios with computer modelling, the team found that more diverse communities -- those with species having highly dissimilar traits -- were most resilient. They were better at recovering from damage and had greater habitat quality 10 years after the disturbances.

"More diverse communities are more likely to have certain species that are very important for resilience," Dr. Carturan explains. "These species have particular traits -- they are morphologically complex, competitive and with a good capacity to recover. When present in a community, these species maintained or even increased the quality of the habitat after the disturbance. Contrastingly, communities without these species were often dominated by harmful algae at the end."

Coral diversity determines the strength and future health of coral reefs, he adds. Coral species are the foundation of coral reef ecosystems because their colonies form the physical habitat where thousands of fish and crustaceans live. Among those are herbivores, such as parrotfish and surgeonfish, which maintain the coral habitat by eating the algae. Without herbivores, the algae would kill many coral colonies, causing the coral habitat to collapse, destroying its many populations.

"What is unique with our study is that our results apply to most coral communities in the world. By measuring the effect of diversity on resilience in more than 245 different coral communities, the span of diversity likely overlaps the actual coral diversity found in most reefs."

At the same time, the study provides a framework to successfully manage these ecosystems and help with coral reef restoration by revealing how the resilience of coral communities can be managed by establishing colonies of species with complementary traits.

Looking forward, there are other questions the model can help answer. For instance, the coral species vital for resilience are also the most affected by climate change and might not be able to recover if strong climatic heatwaves become too frequent.

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