Mapping corals from the sky guides reef conservation

December 14, 2020

Coral reefs are one of the most biodiverse ecosystems on the planet supporting an estimated 25% of all marine species. These biologically rich ecosystems are threatened by multiple stressors, from warming ocean temperatures brought on by climate change to increases in water pollution from coastal development.

According to current estimates, 75% of the world’s coral reefs could face critical threat levels by 2050. Scientists widely agree that immediate and well-targeted action must be taken to preserve coral reefs for future generations. However, without a clear understanding of where live corals are found, management and conservation efforts will remain hampered at best and ineffective at worst. Global Airborne Observatory The Arizona State University Global Airborne Observatory on a mapping mission over north Maui Island coast. Download Full Image

Previous work to assess live coral cover has been constrained by technical limitations inherent to available surveillance approaches. For instance, detailed field-based surveys are geographically limited, while satellites cannot track corals at resolutions detailed enough for many types of management activities.

Airborne technologies, however, can collect enormous tracts of contiguous high-resolution data within a single survey, providing insights into both coral health and extent. If the resulting maps can indicate the location of live corals, then specific strategies can be created to preserve, protect and restore them.

A critical case in point is the Hawaiian Islands, an icon of the natural world and the modern-day stresses underway on reef ecosystems. Coastal development has resulted in hot spots of sedimentation, waterborne pollutants and reef removal, while fishing and other resource uses have generated declines in reef resilience. Marine heatwaves, driven by a warming global climate, have also periodically engulfed the Hawaiian Islands, with the 2015 and 2019 coral bleaching events being the most recent. The 2015 event caused widespread coral death, but the geographic extent of coral loss or resistance has remained poorly understood, as it has in reef regions throughout the world.

Using a new airborne mapping approach developed by researchers at Arizona State University’s Center for Global Discovery and Conservation Science, the geographic distribution of live corals was, for the first time, quantified to 16 meters (52.5 feet) of water depth across the main Hawaiian Islands. The study was published Dec. 14 in Proceedings of the National Academy of Sciences of the United States of America.

“We undertook this first-ever mapping of a large archipelago to determine where corals live in Hawaiian waters despite repeated heatwaves and problematic coastal development issues,” said Greg Asner, lead author of the study and director of the Center for Global Discovery and Conservation Science. “It’s this basic information that is needed by partner organizations to drive more cost-effective protections, restoration activities, and public engagement.”

The mapping data were collected by the ASU Global Airborne Observatory, an aircraft-based laboratory developed by Asner and his team that houses advanced Earth-mapping technology. By combining laser-guided imaging spectroscopy and artificial intelligence, the new approach reveals unprecedented views of coral reefs below the ocean surface. The maps show where live corals persist as well as areas of degraded reef.

“Operational mapping of live coral cover within and across Hawaii’s reef ecosystems affords opportunities for managers and policymakers to better address reef protection, resilience and restoration,” said Brian Neilson, head of Hawaii’s Division of Aquatic Resources and study co-author. “With these new maps, we have a better shot at protecting what we have while focusing on where to improve conditions for corals and the myriad of species that depend upon corals.”

The team’s mapping of live corals was integrated with geospatial information on coastal and marine activities, and computer algorithms were used to estimate which factors most closely predict where corals are currently found on Hawaiian reefs. The results of the analysis revealed that nearshore development has a major negative relationship with live corals.

“Never before has there been such a detailed and synoptic view of live corals at this scale,” said co-author Jamison Gove of the National Oceanic and Atmospheric Administration. “These findings are foundational for developing place-based conservation and management strategies to promote reef persistence and mitigate further losses in corals across Hawaii.” 

The new mapping approach also pointed out areas where corals show resilience to human-driven environmental stressors. These regions of coral survival, deemed "refugia," suggest that some corals and some sites are more resilient, and are thus prime locations for enhanced coral conservation. Garnering a greater understanding of coral survivorship could also alter predictions of whether corals will survive in the current and future ocean climate.

“We are trying to make major leaps on the science and technology side to directly address coral reef conservation and management challenges, starting in the Hawaiian Islands,” Asner said. “Our hope is that these outcomes will grow the discussion among communities, environmental managers and elected officials, without which, we will continue to lose coral reefs right before our eyes.”

The study was supported by the Lenfest Ocean Program and The Battery Foundation. 

Heather D'Angelo

Communications director, Center for Global Discovery and Conservation Science

How and why microbes promote and protect against stress

ASU professor uses evolutionary theory to examine relationship between microbes in the human body and stress

December 14, 2020

More than half of the human body is not actually human: The body hosts approximately 100 trillion microbes. These bacteria, yeast and viruses, which make up the human microbiome, affect more than physical health. They also influence behavior and emotions.

Some microbes prosper when the body is under stress, while other microbes contribute to buffering the body against stress. Athena Aktipis, associate professor of psychology at Arizona State University, used evolutionary theory to examine the reciprocal relationship between microbes in the human body and stress. The paper was published in BioEssays on Dec. 7. The human body and the 100 trillion bacteria, yeast and viruses that make up the microbiome have a reciprocal relationship that can be illustrated by the evolutionary goals of microbes. A microbe that prospers when the body is under stress is shown: It uses the increase in blood glucose levels that accompany stress to rapidly replicate. Graphic by Neil Smith. Download Full Image

“Microbes have access to physiological systems that can give them the power to stress us out, and there is evidence that contributing to the human body’s stress response serves their evolutionary goals,” Aktipis said. “This means that microbes can potentially change our physiology to keep the stress response going, ensuring their access to resources so they can proliferate.

"One example of a microbe that can benefit from host stress is the bacterium E. coli. We call microbes like these ‘stress microbes,’ and the microbes that can provide resilience against stress, like some species of Lactobacillus, ‘resilience microbes’ because there is evidence that they affect our physiology in these ways, possibly for their own evolutionary benefit.”


Stress-loving microbes both contribute to and benefit from the physiological changes that happen in the human body in response to stress, such as high blood glucose levels, increased permeability of the intestines and suppressed immune system responses. These microbes use what evolutionary biologists call a fast life history strategy. Organisms with fast life histories benefit from big bursts of resources, like the increase in blood sugar that happens when people experience stress, and also replicate quickly and – in the case of microbes – without regard for their host. But the body only benefits from the stress response in specific situations, like escaping danger. In other situations, the body does not benefit from the stress response, setting up a figurative tug-of-war between host and microbe.

“All organisms have their own evolutionary interests, and different resources and environments lead to optimal survival and reproduction," Aktipis said. "What is best for the host is not always what is best for the microbe, and we think this is what might be going on with some pathogenic ‘stress microbes.’ Sometimes the host response can lead to escalation of the conflict, which can lead to chronic inflammation as the host’s immune system tries in vain to deal with microbes that are causing a problem in the body. Stress can encourage this kind of dysregulated environment in the host that allows some microbes to thrive.”

Video by ASU Department of Psychology

Not all microbes in the microbiome benefit from a stressed host. Many do better in a stable environment, relying on a slow life history strategy that prioritizes surviving over reproducing. Microbes like these both alter and benefit from physiological processes that help protect the host from stress. Some, like Lactobacillus reuteri, contribute to increased production of the hormone oxytocin, which is associated with feeling calm and connected with others. 

“Microbes alter host behavior – whether it be by promoting stress or contributing to resilience against it – in ways that increase the odds they will be able to reproduce,” Aktipis said. “The composition of our microbiomes influences us in myriad ways: It can change the way we feel in terms of stress and our mental health and influence how we respond to the world around us. But it is a two way street; the way we behave — including what we eat, whether we exercise, and how we manage our stress — also affects the composition of our microbiomes. By changing our behavior, we can affect which microbes are thriving inside us.” 

Diego Beltran, a psychology graduate student, also contributed to the paper.

Science writer, Psychology Department