Coral Art: Drawing out the secrets of coral reef resilience to high ocean temperatures
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Victoria Glynn’s illustrations show the complex relationships between the coral animal, and the algae and bacteria that live with the coral. Taken together, this is called the coral holobiont. To understand resilience—how easily corals recover or respond to changes in their environment— it helps to be able to imagine all the different organisms that may play a role.
view moreCredit: Credit: Victoria Glynn
When Victoria Glynn came to Panama to study the effects of extreme ocean temperatures on coral reefs at the Smithsonian Tropical Research Institute (STRI) as a pre-doctoral fellow in professor Rowan Barrett’s lab at McGill University, she drew corals to explain her work to kids. Now, her illustrations help broader audiences reach an “Ah ha!” moment as she explains how corals from more variable ocean environments may be better equipped to survive rising ocean temperatures than corals from more stable environments—in a paper published in Current Biology.
Ask someone to draw a coral and they might draw a lump or a deer-antler shape, maybe with some fish or shells to illustrate its sea-floor setting. But Victoria’s drawings are much more intricate…because corals consist of the coral animal and its skeleton; the symbiotic algae, for energy capture; and a host of tiny bacteria…its microbiome--like we have in our guts, responsible for a lot of other functions. Scientists call this the coral holobiont, from the Greek for ‘the whole living thing’.
"Most people know that our gut microbiome plays a major role in our health, depending on our diet and the microbes we have. In many ways, corals are not so different," Victoria, now a post-doctoral associate at the University of Vermont, explains. "Their survival is intricately tied to their microbiomes. When I explain how corals stay healthy as their environment changes, I hope my drawings help people see just how complex they really are, and why it’s crucial to consider all the organisms involved: the coral animal, their symbiotic algae and the bacterial microbiome."
To survive, coral and their algae maintain a tight relationship, but when ocean water gets too hot, the algae often jump ship, leaving just the white coral skeleton behind, a phenomenon called coral bleaching.
Victoria did her doctoral work in Panama as part of the Rohr Reef Resilience Project led by Sean Connolly, STRI staff scientist. STRI’s location gives researchers easy access to the Tropical Eastern Pacific, an area of ocean extending from Ecuador’s Galapagos Islands north to Costa Rica’s Cocos Islands. This is a perfect natural laboratory for learning how corals respond to temperature extremes.
Project scientists take advantage of the frigid ocean currents that come to the surface in the Gulf of Panama to ask if corals growing there are more resilient to temperature extremes than corals in other places where temperatures are not so extreme, and why. In this study, they asked three big questions: How do high ocean temperatures affect the relationship between the coral animal and its algal partner? And what about its bacterial microbiome? And do these relationships explain how some corals are better able to survive at high temperatures?
The group sampled cauliflower corals (Pocillopora spp.) in the Gulf of Panama (where there are yearly temperature fluctuations) and in the Gulf of Chiriquí (nearby but with more stable year-round temperatures) and then ran an experiment to see what happens when they turn up the heat.
“We exposed corals to rapid heat stress in tanks on the yacht and, as the temperature climbed, we took samples so we could extract the DNA of the corals, their algae, and bacteria,” said Victoria. “This way, we gained insights into the relationships between the corals and the different members of their microbiome as the temperature rose.”
The corals themselves: Genetically, the corals from the two sites were similar, indicating that they must disperse easily along the coast, mixing different populations; but the few genetic differences between corals at the two sites may be important. The authors think that there could be differential selection on genes previously associated with the ability to resist thermal stress, with more ability to resist stress in the corals from the more variable Gulf of Panama.
The algae: The dynamics for the algae surprised them. In earlier experiments, at high temperatures, corals shifted to a different genus of algae that was more heat tolerant, but in this experiment, some corals kept their original algal partner.
The bacteria: The bacterial microbiome from corals at both sites was disrupted by higher temperatures, rapidly entering a disease-like state. But compared to previous studies on Australia’s Great Barrier Reef, the corals from the Gulf of Panama had less stable microbiomes at high temperatures.
The Australian experiments lasted longer—from weeks to months—and corals experienced temperatures ~4-5°C above their mean monthly maximum temperature, which can be thought of as the average hottest temperatures experienced. In the Panama experiment, which were less than 24 hours long, corals were exposed 10.5°C above their mean monthly maximum temperatures, and the microbes associated with the corals changed to a more diseased state at around 7.5°C above the hottest average temperatures.
To disrupt the relationship between corals and their bacteria, it took higher temperatures that the temperatures it took to stress out the coral animal itself, suggesting that for the Pocillopora corals in Panama, it’s more likely that a coral will die at high temperatures even before its microbiome is severely affected.
Overall: At the highest temperatures, the corals collected from the Gulf of Panama, where temperatures are more variable, handled the heat better. But corals from the stable-temperature environment struggled when they were heated.
The team’s findings support the idea that the Tropical Eastern Pacific’s naturally variable environments may contribute to these corals’ enhanced ability to withstand heat. This may explain why these reefs were able to bounce back after the catastrophic 1982 El Niño Southern Oscillation event.
“Coral reefs cover just 0.1% of Earth's surface but they support around 25% of all marine life. Reefs also provide critical services to more than a billion people globally, through fisheries, tourism, coastal protection, and cultural significance. As ocean temperatures continue to rise, coral reefs are increasingly under threat,” said Victoria. “Understanding what makes some corals more resilient to warming oceans will be essential for guiding conservation efforts, protecting coastal communities, and safeguarding biodiversity. When we think about these complex organisms, we need to get away from two-partner thinking and view them as an integrated whole,” said Victoria, “my artwork helps me do that, and also lets me share my love for the beauty of nature, and my passion for conserving the underwater world.”
Funding for the CBASS experiment was provided by the Mark and Rachel Rohr Foundation. Additional support was provided to lead author Victoria Glynn through a Fulbright U.S. Scholar Grant and a Vanier Canada Graduate Scholarship, which supported the molecular work, data analysis, and manuscript preparation. Further support came from the Smithsonian Tropical Research Institute, NSERC, and others.
About the Smithsonian Tropical Research Institute
Headquartered in Panama City, Panama, STRI is a unit of the Smithsonian Institution whose mission is to understand tropical biodiversity and its importance to human welfare, trains students to conduct research in the tropics and promotes conservation by increasing public awareness of the beauty and importance of tropical ecosystems. Watch STRI’s video and visit the institute on its website and on Facebook, X and Instagram for updates.
Victoria Glynn’s illustrations show the complex relationships between the coral animal, and the algae and bacteria that live with the coral. Taken together, this is called the coral holobiont. To understand resilience—how easily corals recover or respond to changes in their environment— it helps to be able to imagine all the different organisms that may play a role.
JOURNAL
Current Biology
Method of Research
Experimental study
Article Title
The role of holobiont composition and environmental history in thermotolerance of Tropical Eastern Pacific corals
Article Publication Date
5-Jun-2025
HE/SHE/THEM
Sex-changing fish quick to assert dominance
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A female spotty/paketi (an endemic species of wrasse) in the Gemmell Lab at the University of Otago. Credit: Gemmell Lab
view moreCredit: Gemmell Lab, University of Otago
University of Otago – Ōtākou Whakaihu Waka scientists have discovered that it takes mere minutes for a species of sex-changing fish to develop dominant behaviour after a change in the pecking order.
The new study led by the Department of Anatomy and published on Proceedings of the Royal Society B, examines the New Zealand spotty, or paketi, a fish that can change from female to male during adulthood in response to a change in social hierarchy.
It found that the sex change process begins almost immediately when a dominant spotty is removed from a group.
Lead author Haylee Quertermous, a PhD Candidate in the Department of Anatomy, says although the full sex change process takes weeks, it only takes minutes for a second-ranked fish to take advantage of the power vacuum and assert dominant behaviours.
“The aggressive behaviours (called ‘rushes’) involved the dominant fish swimming rapidly towards subordinate individuals,” she says.
“Sometimes the dominant fish will make physical contact with the subordinates, including taking bites at them, usually around their tail and fins. These aggressive behaviors are usually accompanied by the subordinate quickly swimming away (‘escaping’) from the dominant fish.”
While she expected to be able to see behavior changes within an hour of removing the dominant fish, she was surprised by just how rapid the change could be.
“In many of the tanks, second-ranked fish increased their aggression within just a few minutes after removal of the dominant fish.”
She cautions the dominant behaviour that accompanies a female to male sex change in spotties does not indicate a change from typically ‘female’ to ‘male’ behaviour, as other sex-changing fish species such as clownfish for example, change from male to more dominant female fish.
The researchers observed that spotties form linear dominance hierarchies based on size, with larger individuals dominating smaller ones.
They sought to determine which fish in the hierarchy were more likely to change sex when the opportunity arose.
Results show dominant, larger fish are more likely to change sex, and when social hierarchies are disrupted, less dominant fish can quickly change their behavior to seize new opportunities.
The study also delved into the neural mechanisms underlying spotties’ social interactions, finding that the social decision-making network in the fish brain is highly involved in establishing dominance.
Fish that attained dominant positions showed significant differences in this network compared to fish of all other ranks.
Dr Kaj Kamstra, who led the neurobiological aspects of the research, says the findings provide valuable insights into the complex interplay between social behavior and neural processes in these fish.
“They also highlight the importance of social context in shaping individual behavior, shedding light on the evolution of social behavior and the flexibility of brain mechanisms in adapting to changing social environments.
“The research has broader implications for understanding social dynamics in other species, even humans.”
The findings can be applied to other species of sex-changing fish where social dominance appears to be the most common trigger for sex change, and could prove beneficial for aquaculture and open water fisheries, with many commercial valuable fisheries dependent on fishes that change sex, for example, New Zealand’s blue cod.
Journal
Proceedings of the Royal Society B Biological Sciences
Method of Research
Experimental study
Subject of Research
Animals
Article Title
Behavioural and neural correlates of social hierarchy formation in a sex-changing fish
New study quantifies fish slaughter pain and cost-effectiveness of welfare solutions
Measuring the welfare footprint of animal farming practices is now possible, and can transform welfare standards
Welfare Footprint Institute
June 5, 2025 – A new study in Scientific Reports reveals the hidden pain of fish during slaughter and offers practical solutions to improve their welfare. Focusing on rainbow trout, the research quantifies pain in air asphyxia—a common slaughter method—using the innovative Welfare Footprint Framework (WFF). With up to 2.2 trillion wild and 171 billion farmed fish killed annually, the findings highlight an opportunity for welfare reforms on a massive scale.
The study shows rainbow trout endure an average of 10 minutes of intense pain during air asphyxia, with estimates ranging from 2 to 22 minutes depending on factors like fish size and water temperature. This translates to approximately 24 minutes of pain per kilogram of fish. These estimates are based on a comprehensive review of existing research to assess the intensity and duration of pain and distress experienced by the fish.
Crucially, the study also assesses the cost-effectiveness of interventions. If implemented properly, electrical stunning could avert 60 to 1,200 minutes of moderate to extreme pain for every U.S. dollar of capital cost. Percussive stunning offers high welfare potential as well, though challenges remain in achieving consistency in commercial settings. The study also notes that pre-slaughter practices such as crowding and transport – often overlooked – are likely to even cause greater cumulative suffering than the slaughter itself.
At the heart of this study is the Welfare Footprint Framework (WFF), developed by the Center for Welfare Metrics, a novel method that quantifies animal welfare by estimating the total time animals spend in various states of suffering or well-being. By assigning time-based values to subjective experiences, the WFF allows for direct comparisons between different animal welfare interventions, much like environmental footprints or health impact assessments in human contexts, in familiar terms that anyone can understand.
Dr. Wladimir Alonso, who conceptualized the method, explains, "The Welfare Footprint Framework provides a rigorous and transparent evidence-based approach to measuring animal welfare, and enables informed decisions about where to allocate resources for the greatest impact."
This study’s results could help shape regulatory discussions, improve certification standards, and guide welfare investments that deliver the greatest benefit per dollar spent.
Publication: Schuck-Paim et al. (2025). Quantifying the welfare impact of air asphyxia in rainbow trout slaughter for policy and practice. Scientific Reports. DOI: 10.1038/s41598-025-04272-1
For more information: media@welfarefootprint.org.
The Welfare Footprint Framework is freely available for research and policy use at welfarefootprint.org.
Journal
Scientific Reports
Method of Research
Data/statistical analysis
Subject of Research
Animals
Article Title
Quantifying the welfare impact of air asphyxia in rainbow trout slaughter for policy and practice
Article Publication Date
5-Jun-2025
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