Advancing towards sustainability: turning carbon dioxide and water into acetylene

Scientists develop an environmentally friendly method to electrochemically synthesize an essential industrial gas

Peer-Reviewed Publication

DOSHISHA UNIVERSITY

 

IMAGE: 

ACETYLENE IS WIDELY USED IN ACROSS MANY INDUSTRIES, INCLUDING THE PRODUCTION OF RESINS AND PLASTICS LIKE PVC. REALIZING AN ENVIRONMENTALLY FRIENDLY TECHNIQUE TO SYNTHESIZE IT WOULD REPRESENT A MASSIVE STEP TOWARDS BUILDING SUSTAINABLE SOCIETIES.

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CREDIT: YUTA SUZUKI FROM DOSHISHA UNIVERSITY, JAPAN

Reaching sustainability is one of humanity’s most pressing challenges today—and also one of the hardest. To minimize our impact on the environment and start reverting the damage humanity has already caused, striving to achieve carbon neutrality in as many economic activities as possible is paramount. Unfortunately, the synthesis of many important chemicals still causes high carbon emissions.

Such is the case of acetylene (C2H2), an essential hydrocarbon with a plethora of applications. This highly flammable gas is used for welding, industrial cutting, metal hardening, heat treatments, and other industrial processes. In addition, it is an important precursor in the production of synthetic resins and plastics, including PVC. Since the production of C2H2 requires fossil fuels as feedstock, a more environmentally friendly synthesis route is urgently needed.

Against this backdrop, a research team based on an academia–industry collaboration between Doshisha University and Daikin Industries, Ltd., Japan, has been developing a new and very promising strategy to produce C2H2 using carbon dioxide (CO2) and water (H2O) as raw materials. Their latest study, which included Assistant Professor Yuta Suzuki from Harris Science Research Institute and Professor Takuya Goto from the Department of Science of Environment and Mathematical Modeling of Graduate School of Science and Engineering, both at Doshisha University, and Tomohiro Isogai from Technology and Innovation Center at Daikin Industries Ltd., was made available online on January 25, 2024, and published in Volume 12, Issue 5 of ACS Sustainable Chemistry & Engineering in February 2024.

The proposed approach is based on the electrochemical and chemical conversion of CO2 into C2H2 by using high-temperature molten salts, namely chloride melts. One key aspect of the process is that it leverages metal carbides, which are solids composed of carbon atoms and metal atoms, as a pivot point in the conversion. “In our strategy, CO2 is first converted to metallic carbides such as CaC2 and Li2C2, which deposit onto one of the electrodes,” explains Dr. Suzuki. “Then, these metal carbides react with H2O, generating C2H2 gas.”

To achieve higher energy efficiency out of this method, the team had to test various configurations, including different electrode materials and molten salt compositions. After a series of comprehensive experiments, including cyclic voltammetry, carbon crystallinity analysis, and X-ray diffraction, they determined that a NaCl−KCl−CaCl2−CaO melt saturated with additional CaCl2 in a CO2 atmosphere yielded the best results. This particular melt led to the selective formation of CaC2 around the cathode, which achieved better results than melts including lithium.

This innovative strategy offers important advantages over conventional synthesis pathways for C2H2. First, the electrodes can be reused after a simple reconditioning treatment since the desired reaction occurs on the deposited metal carbides rather than directly on the electrode surfaces. Another advantage, and perhaps the most notable, is the direct use of CO2 as feedstock to produce an industrially useful and valuable chemical.

“The proposed approach represents a promising technology for realizing a sustainable resource and energy cycle without relying on fossil fuels,” highlights Prof. Goto. Adding further, he says, “In the future, this same technique could be used as a carbon negative emission technology by extracting carbon dioxide from the air and using it as a raw material, particularly in combination with direct air capture processes.”

With any luck, further research on this exciting method will lead to both economically and environmentally viable ways to produce important resins and chemicals from CO2, paving the way to sustainable societies. Ultimately, these efforts would enable us to live in harmony with the environment while maintaining many of the positive aspects of our modern way of life.

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About Assistant Professor Yuta Suzuki from Doshisha University, Japan
Dr. Yuta Suzuki holds a Ph.D. degree in Engineering and a Master’s degree in Mathematics, Physics, and Environmental Sciences, both of which he obtained from Doshisha University. He currently serves as an Assistant Professor at Harris Science Research Institute of Doshisha University. He specializes in energy science, resource engineering and production, and nanotechnology, with a focus on inorganic and coordination chemistry. He has published over 15 papers on these topics and holds several patents in related technological developments.

About Professor Takuya Goto from Doshisha University, Japan
Prof. Takuya Goto serves as a Professor at the Department of Science of Environment and Mathematical Modeling, Graduate School of Science and Engineering at Doshisha University, Japan. He obtained his Ph.D. in energy science from Kyoto University, Japan. Prof. Goto has over 90 publications to his credit. His laboratory primarily conducts research in the area of energy science, nuclear engineering, inorganic chemistry, and electrochemistry.

Funding information
This work was partially supported by JSPS KAKENHI grant number JP22K14700.

JOURNAL

ACS Sustainable Chemistry & Engineering

DOI

10.1021/acssuschemeng.3c08139 

METHOD OF RESEARCH

Experimental study

SUBJECT OF RESEARCH

Not applicable

ARTICLE TITLE

New Route of Acetylene Synthesis via Electrochemical Formation of Metal Carbides from CO2 in Chloride Melts

 

Scientists extract genetic secrets from 4,000-year-old teeth to illuminate the impact of changing human diets over the centuries

Peer-Reviewed Publication

TRINITY COLLEGE DUBLIN

 

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KILLURAGH CAVE, IRELAND.

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CREDIT: CREDIT SAM MOORE, OWNER MARION DOWD.

Researchers at Trinity College Dublin have recovered remarkably preserved microbiomes from two teeth dating back 4,000 years, found in an Irish limestone cave. Genetic analyses of these microbiomes reveal major changes in the oral microenvironment from the Bronze Age to today. The teeth both belonged to the same male individual and also provided a snapshot of his oral health.

The study, carried out in collaboration with archaeologists from the Atlantic Technological University and University of Edinburgh, was published today in leading journal Molecular Biology and Evolution. The authors identified several bacteria linked to gum disease and provided the first high-quality ancient genome of Streptococcus mutans, the major culprit behind tooth decay. 

While S. mutans is very common in modern mouths, it is exceptionally rare in the ancient genomic record. One reason for this may be the acid-producing nature of the species. This acid decays the tooth, but also destroys DNA and stops plaque from fossilising. While most ancient oral microbiomes are retrieved from fossilised plaque, this study targeted the tooth directly. 

Another reason for the scarcity of S. mutans in ancient mouths may be the lack of favorable habitats for this sugar-loving species. An uptick of dental cavities is seen in the archaeological record after the adoption of cereal agriculture thousands of years ago, but a far more dramatic increase has occurred only in the past few hundred years when sugary foods were introduced to the masses. 

The sampled teeth were part of a larger skeletal assemblage excavated from Killuragh Cave, County Limerick, by the late Peter Woodman of University College Cork. While other teeth in the cave showed advanced dental decay, no cavities were visible on the sampled teeth. However, one tooth produced an unprecedented amount of S. mutans DNA, a sign of an extreme imbalance in the oral microbial community.

“We were very surprised to see such a large abundance of S. mutans in this 4,000-year-old tooth,” said Dr Lara Cassidy, an assistant professor in Trinity’s School of Genetics and Microbiology, and senior author of the study. “It is a remarkably rare find and suggests this man was at a high risk of developing cavities right before his death.”

The researchers also found that other streptococcal species were virtually absent from the tooth. This indicates the natural balance of the oral biofilm had been upset – mutans had outcompeted the other streptococci leading to the pre-disease state.

The team also found evidence to support the "disappearing microbiome" hypothesis, which proposes modern microbiomes are less diverse than those of our ancestors. This is cause for concern, as biodiversity loss can impact human health. The two Bronze Age teeth produced highly divergent strains of Tannerella forsythia, a bacteria implicated in gum disease.

“These strains from a single ancient mouth were more genetically different from one another than any pair of modern strains in our dataset, despite the modern samples deriving from Europe, Japan and the USA,” explained Iseult Jackson, a PhD candidate at Trinity, and first author of the study. “This represents a major loss in diversity and one that we need to understand better.” 

Very few full genomes from oral bacteria have been recovered prior to the Medieval era. By characterising prehistoric diversity, the authors were able to reveal dramatic changes in the oral microenvironment that have happened since. 

Dr Cassidy added: “Over the last 750 years, a single lineage of T. forsythia has become dominant worldwide. This is the tell-tale sign of natural selection, where one strain rises rapidly in frequency due to some genetic advantage it holds over the others. T. forsythia strains from the industrial era onwards contain many new genes that help the bacteria colonise the mouth and cause disease.

“S. mutans has also undergone recent lineage expansions and changes in gene content related to pathogenicity. These coincide with humanity’s mass consumption of sugar, although we did find that modern S. mutans populations have remained more diverse, with deep splits in the S. mutans evolutionary tree pre-dating the Killuragh genome.” 

The scientists believe this is driven by differences in the evolutionary mechanisms that shape genome diversity in these species.

“S. mutans is very adept at swapping genetic material between strains,” said Dr Cassidy. “This means an advantageous innovation can be spread across S. mutans lineages like a new piece of tech. This ability to easily share innovations may explain why this species retains many diverse lineages without one becoming dominant and replacing all the others.”

In effect, both these disease-causing bacteria have changed dramatically from the Bronze Age to today, but it appears that very recent cultural transitions in the industrial era have had an inordinate impact.

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An EXAMPLE of a tooth prior to ancient DNA sampling. Note this was not the tooth sampled in the study.

CREDIT

Dr Lara Cassidy, Trinity.

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JOURNAL

Molecular Biology and Evolution

What Bronze Age teeth say about the evolution of the human diet

OXFORD UNIVERSITY PRESS USA

 

IMAGE: 

KILLURAGH CAVE, COUNTY LIMERICK, IRELAND.

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CREDIT: SAM MOORE AND MARION DOWD/MOLECULAR BIOLOGY AND EVOLUTION

A new paper in Molecular Biology and Evolution, published by Oxford Univeristy Press, uncovers well-preserved microbiomes from two 4,000 year old teeth in a limestone cave in Ireland. These contained bacteria that cause gum disease, as well as the first high quality ancient genome from S. mutans, an oral bacterium that is one of the major causes of tooth decay.

These discoveries allowed the researchers to assess the impact of past dietary changes on the oral microbiome across millennia, including major changes coinciding with the popularization of sugar and industrialization. The teeth, both derived from the same Bronze Age man, also provided a snapshot of oral health in the past, with one tooth showing evidence of microbiome dysbiosis.

Microbial DNA extracted from ancient human teeth can provide information on the evolution of the oral microbiome. How did our ancestors’ mouths differ from our own and why? The excellent preservation of DNA in fossilized dental plaque has made the oral cavity one of the best studied aspects of the ancient human body. However, scientists have retrieved very few full genomes from oral bacteria from prior to the Medieval era. Researchers have limited knowledge about prehistoric bacterial diversity and the relative impact of recent dietary changes compared to ancient ones, such as the spread of farming starting about ten thousand years ago.

S. mutans is the primary cause of dental cavities and very common in oral microbiomes. However, it is exceptionally rare in the ancient genomic record. One reason for its rarity could be its acid-producing nature – this acid causes the tooth to decay but also degrades DNA and prevents plaque from mineralizing. The absence of S. mutans DNA in ancient mouths could also reflect less favorable habitats for the species across most of human history. Archaeologists have observed an uptick in dental cavities in skeletal remains following the adoption of cereal agriculture, but cavities become much more common in the Early Modern period, beginning about 1500 AD.

The sampled teeth were among a large assemblage of skeletal remains excavated from a limestone cave at Killuragh, County Limerick, by the late Peter Woodman of University College Cork. While other teeth in the cave showed advanced dental decay there was no evidence of caries on the sampled teeth. Nevertheless, one tooth root yielded an unprecedented quantity of mutans sequences.

“We were very surprised to see such a large abundance of mutans in this 4,000 year old tooth” said Lara Cassidy, an assistant professor at Trinity College Dublin and senior author of the study. “It is a remarkably rare find and suggests this man was at high risk of developing cavities right before his death.”

The cool, dry, and alkaline conditions of the cave may have contributed to the exceptional preservation of S. mutans DNA, but its high abundance also points to dysbiosis. The researchers found that while S. mutans DNA was plentiful, other streptococcal species were virtually absent from the tooth sample. This implies that the natural balance of the oral biofilm had been upset – mutans had outcompeted the other species leading to a pre-disease state.

The study lends support to the “disappearing microbiome” hypothesis, which proposes the microbiomes of our ancestors were more diverse than our own today. Alongside the S. mutans genome, the authors reconstructed two genomes for T. forsythia – a bacteria involved in gum disease – and found them to be highly divergent from one another, implying much higher levels of strain diversity in prehistoric populations.

“The two sampled teeth contained quite divergent strains of T. forsythia” explained Iseult Jackson, a PhD candidate and first author of the study. “These strains from a single ancient mouth were more genetically different from one another than any pair of modern strains in our dataset, despite these modern samples deriving from Europe, Japan, and the USA. This is interesting because a loss of biodiversity can have negative impacts on the oral environment and human health.”

The reconstructed T. forsythia and S. mutans genomes revealed dramatic changes in the oral microenvironment over the last 750 years. In recent centuries, one lineage of T. forsythia has become dominant in global populations. This is the tell-tale sign of a selective episode – where one strain rises rapidly in frequency due to some genetic advantage. The researchers found that post-industrial T. forsythia genomes have acquired many new genes that help the bacteria colonize the oral environment and cause disease.

S. mutans also showed evidence of recent lineage expansions and changes in gene content, which coincide with the popularization of sugar. However, the investigators found that modern S. mutans populations have remained more diverse than T. forsythia, with deep splits in the mutans evolutionary tree pre-dating the Killuragh genome.  They believe this is driven by differences in the evolutionary mechanisms that shape genome diversity in these species.

“S. mutans is very adept at swapping genetic material across strains.” said Cassidy “This allows an advantageous innovation to be spread across mutans lineages, rather than one lineage becoming dominant and replacing all others.”

In effect, both these disease-causing bacteria have changed dramatically from the Bronze Age to today, but it appears that very recent cultural transitions, such as the consumption of sugar, have had an inordinate impact.

The paper, “Ancient genomes from Bronze Age remains reveal deep diversity and recent adaptive episodes for human oral pathobionts,” is available (at midnight on March 27th) at https://academic.oup.com/mbe/article-lookup/doi/10.1093/molbev/msae017.

Direct correspondence to: 
Lara Cassidy
Smurfit Institute of Genetics
Trinity College Dublin
Dublin 2, IRELAND
cassidl4@tcd.ie

To request a copy of the study, please contact:
Daniel Luzer 
daniel.luzer@oup.com

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JOURNAL

Molecular Biology and Evolution

DOI

10.1093/molbev/msae017 

METHOD OF RESEARCH

Content analysis

SUBJECT OF RESEARCH

People

ARTICLE TITLE

Ancient genomes from Bronze Age remains reveal deep diversity and recent adaptive episodes for human oral pathobionts

ARTICLE PUBLICATION DATE

27-Mar-2024

 

Scientists warn: The grey seal hunt is too large

Peer-Reviewed Publication

UNIVERSITY OF GOTHENBURG

 

IMAGE: 

THE GREY SEAL IN THE BALTIC SEA WAS HIGHLY ENDANGERED, AT THE END OF THE 1970S THERE WERE ONLY 5,000 ANIMALS LEFT OUT OF THE ORIGINAL 90,000. SINCE THEN, THE SEAL POPULATION HAS RECOVERED AND TODAY AMOUNTS TO A TOTAL OF ABOUT 55,000 ANIMALS. BUT NOW IT MAY AGAIN BE THREATENED IF LICENSED HUNTING IS NOT COORDINATED BETWEEN THE COUNTRIES.

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CREDIT: DAIRE CARROLL

Researchers at the University of Gothenburg warn that today's hunting quotas of about 3,000 animals pose a risk to the long-term survival of the grey seal in the Baltic Sea. The conclusions of this new study are based on statistics from 20th century seal hunting and predictions of future climate change.

After decades of hard hunting and environmental contamination by toxins such as PCBs, there were only 5,000 grey seals left in the entire Baltic Sea by the 1970s, falling from an initial size of more than 90,000 at the beginning of the century. Since then, the population has partially recovered, and today stands at around 55,000 animals for all countries combined.

Baltic grey seals are genetically isolated from the closest grey seal populations in the Atlantic. They are generally slightly smaller and, unlike solely land breeding seals found in the British Isles, can give birth to young on both drift ice and on land. The population is now facing new challenges in a world with a warming climate and a shortage of appropriately sized prey fish. Using a mathematical model, the researchers showed that increased seal hunting could cause the population to decline once more.

"It has taken three generations for the grey seal to recover. The seal population is now growing, but our research shows that, if the current hunting quota of 3,000 animals per year is met, the survival of the grey seal in the Baltic Sea will once again be threatened," says Daire Carroll, Associate researcher at the University of Gothenburg and lead author of the study published in the Journal of Animal Ecology.

At present, about 1,500 seals are killed each year in the Baltic Sea.

The hunting quota must be reduced

The researchers created a mathematical model for grey seal population growth and examined several different scenarios for the future. They tested the effect of different hunting pressures, different levels of food availability, and the consequences of less sea ice.

"We saw that killing 3,000 seals each year always led to a decrease in seal population size, even in the most optimistic scenarios for the climate and marine environment. Our conclusion is that the current hunting quota in the Baltic Sea is unsustainable. If the seal population is to continue to recover, the maximum number that can be hunted is 1,900 animals. But if there are other environmental changes that have a negative impact on population, that figure should also be reduced," says Daire Carroll.

The countries around the Baltic Sea have agreed that the grey seal population should be allowed to recover after coming close to extinction in the 20th century due to hunting and environmental contamination. Conflict with fisheries during this period led to a bounty on seals. A biproduct of this is that there are detailed statistics on how many seals were killed each year. Researchers at the University of Gothenburg were helped by their colleagues at the Swedish Museum of Natural History in Stockholm to produce data on the development of the grey seal in modern times. Thanks to the fact that seals are now used as an environmental indicator for the Baltic Sea, there is good data on the seals' numbers, fertility, and health.

Advantage of breeding on ice

"We created a model of how the seal population would have grown over the last 20 years if there had been no hunting. In this way, we can estimate the long-term effect of today's hunting quotas on the seal population. We have also simulated what a warmer climate would mean for the grey seal," says Daire Carroll.

Baltic grey seal pups have a greater chance of survival if they are born on sea ice instead of on land. On ice floes, mothers and pups can spread out over a larger area and the pups face fewer threats from other predators, humans, or infections that are easily spread in dense seal colonies on land.

As the seal population has grown, so has the conflict with the fishing industry, and in 2020, the protective hunt was supplemented with a licensed hunt in Finland and Sweden. In total, more than 3,000 animals could potentially be killed.

"The culling of individual seals that visit or destroy fishing gear has always been allowed and is not problematic for the survival of the population. It was a few hundred individuals per year and did not affect entire groups of seals. But the new licensed hunting, it is different, it risks hitting the survival of the grey seal hard," says Karin Hårding, Professor of Ecology at the University of Gothenburg and co-author of the study, who has been researching seals since the late 1980s.

Researchers at the University of Gothenburg warn that today's hunting quotas of about 3,000 animals pose a risk to the long-term survival of the grey seal in the Baltic Sea. The conclusions of this new study are based on statistics from 20th century seal hunting and predictions of future climate change.

After decades of hard hunting and environmental contamination by toxins such as PCBs, there were only 5,000 grey seals left in the entire Baltic Sea by the 1970s, falling from an initial size of more than 90,000 at the beginning of the century. Since then, the population has partially recovered, and today stands at around 55,000 animals for all countries combined.

Baltic grey seals are genetically isolated from the closest grey seal populations in the Atlantic. They are generally slightly smaller and, unlike solely land breeding seals found in the British Isles, can give birth to young on both drift ice and on land. The population is now facing new challenges in a world with a warming climate and a shortage of appropriately sized prey fish. Using a mathematical model, the researchers showed that increased seal hunting could cause the population to decline once more.

"It has taken three generations for the grey seal to recover. The seal population is now growing, but our research shows that, if the current hunting quota of 3,000 animals per year is met, the survival of the grey seal in the Baltic Sea will once again be threatened," says Daire Carroll, Associate researcher at the University of Gothenburg and lead author of the study published in the Journal of Animal Ecology.

At present, about 1,500 seals are killed each year in the Baltic Sea.

The hunting quota must be reduced

The researchers created a mathematical model for grey seal population growth and examined several different scenarios for the future. They tested the effect of different hunting pressures, different levels of food availability, and the consequences of less sea ice.

"We saw that killing 3,000 seals each year always led to a decrease in seal population size, even in the most optimistic scenarios for the climate and marine environment. Our conclusion is that the current hunting quota in the Baltic Sea is unsustainable. If the seal population is to continue to recover, the maximum number that can be hunted is 1,900 animals. But if there are other environmental changes that have a negative impact on population, that figure should also be reduced," says Daire Carroll.

The countries around the Baltic Sea have agreed that the grey seal population should be allowed to recover after coming close to extinction in the 20th century due to hunting and environmental contamination. Conflict with fisheries during this period led to a bounty on seals. A biproduct of this is that there are detailed statistics on how many seals were killed each year. Researchers at the University of Gothenburg were helped by their colleagues at the Swedish Museum of Natural History in Stockholm to produce data on the development of the grey seal in modern times. Thanks to the fact that seals are now used as an environmental indicator for the Baltic Sea, there is good data on the seals' numbers, fertility, and health.

Advantage of breeding on ice

"We created a model of how the seal population would have grown over the last 20 years if there had been no hunting. In this way, we can estimate the long-term effect of today's hunting quotas on the seal population. We have also simulated what a warmer climate would mean for the grey seal," says Daire Carroll.

Baltic grey seal pups have a greater chance of survival if they are born on sea ice instead of on land. On ice floes, mothers and pups can spread out over a larger area and the pups face fewer threats from other predators, humans, or infections that are easily spread in dense seal colonies on land.

As the seal population has grown, so has the conflict with the fishing industry, and in 2020, the protective hunt was supplemented with a licensed hunt in Finland and Sweden. In total, more than 3,000 animals could potentially be killed.

"The culling of individual seals that visit or destroy fishing gear has always been allowed and is not problematic for the survival of the population. It was a few hundred individuals per year and did not affect entire groups of seals. But the new licensed hunting, it is different, it risks hitting the survival of the grey seal hard," says Karin Hårding, Professor of Ecology at the University of Gothenburg and co-author of the study, who has been researching seals since the late 1980s.

The grey seal in the Baltic Sea is affected by climate change. Reduced sea ice makes it harder for the grey seal's young to survive.

CREDIT

Daire Carroll

Daire Carroll, Associate Researcher at the University of Gothenburg.

CREDIT

Karin Hårding

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JOURNAL

Journal of Animal Ecology

DOI

10.1111/1365-2656.14065 

METHOD OF RESEARCH

Data/statistical analysis

ARTICLE TITLE

120‐years of ecological monitoring data shows that the risk of overhunting is increased by environmental degradation for an isolated marine mammal population: The Baltic grey seal

ARTICLE PUBLICATION DATE

27-Mar-2024

 

Severe hurricanes boost influx of juveniles and gene flow in a coral reef sponge

Study first to show recolonization by rope-like Caribbean sponge post-storms using genetic analyses

FLORIDA ATLANTIC UNIVERSITY

 

IMAGE: 

FOR THE STUDY, SCUBA DIVERS COLLECTED SMALL SAMPLES OF THE THIN PURPLE MORPHOTYPE SPONGES 14 AND 22 MONTHS AFTER THE TWO CATEGORY 5 HURRICANES IN ST. THOMAS.

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CREDIT: KARLI HOLLISTER

Named for its ropy-looking long branches, Aplysina cauliformis, a coral reef sponge, provides a critical 3D habitat for marine organisms and helps to stabilize the foundation of coral reefs. However, these upright branching sponges are highly susceptible to breaking during storms, which increases sponge fragmentation and contributes to population clonality and inbreeding.

Many sponges can survive severe damage and undergo frequent fragmentation, which is considered a mechanism for asexual reproduction. While fragmentation is a commonly utilized reproductive strategy in rope sponges, they also can reproduce sexually by producing larvae. How and whether they recolonize following extreme weather events is critical for the restoration and resilience of coral reef ecosystems.

Hurricanes Irma and Maria – both in 2017 – were two rapid succession storms that provided researchers from Florida Atlantic University’s Harriet L. Wilkes Honors College and Harbor Branch Oceanographic Institute, and collaborators from the University of the Virgin Islands, the University of Mississippi and the University of Alabama, with a unique opportunity to address a priority concern – the resilience of coral reef sponge populations after severe hurricanes. 

The researchers are the first to evaluate substrate recolonization by sponges in the U.S. Virgin Islands after these two catastrophic storms using genetic analyses to understand how much clonality verses sexual recruitment occurs on coral reefs post-storms. To date, studies of storm impacts have largely focused on scleractinian or stony corals.

Results of the study, published in the journal Molecular Ecology, reveal that populations of clonal marine species with low pelagic dispersion, such as A. cauliformis, may benefit from increased frequency and magnitude of hurricanes to maintain genetic diversity and combat inbreeding, enhancing the resilience of Caribbean sponge communities to extreme storm events.

The A. cauliformis population before the hurricanes was highly clonal but shifted to greater sexual reproduction for recolonization after the hurricanes, with 85 percent of sexual reproduction mainly due to local larval recruitment. Major storm events favored sponge larval recruitment but did not increase the genetic diversity.   

“Branching coral populations exposed to intermediate or low storm frequencies are known to have primarily sexual populations, whereas sites with the highest storm frequencies have mostly clonal populations,” said Andia Chaves Fonnegra, Ph.D., principal investigator and an assistant professor of biology in FAU’s Harriet L. Wilkes Honors College and Harbor Branch. “In contrast, our findings showed greater recruitment of sexually derived sponge larvae than clones arising from fragmentation/regeneration after these extreme events, maintaining genetic diversity. Because A. cauliformis sponges reproduce both asexually via fragmentation and sexually, interactions between these mechanisms may maximize their dispersal efficiency and their likelihood of successfully recolonizing habitats.” 

Larval recruits (genets) and fragments (ramets) were detected at all St. Thomas sampling locations post-hurricane, indicating a potential for rapid population recovery for this species that was not affected by site physiography.

At all sites combined, 65.8 percent of the pre-hurricane adult sponges were genets compared to 85.1 percent of the post-hurricane juveniles. This suggests that recolonization of A. cauliformis after the hurricanes was largely due to sexual reproduction, with gene flow across distances up to 60 kilometers, between St. Croix and Buck Island in St. Thomas, detected among the study sites.

For the study, scuba divers collected small samples of the thin purple morphotype sponges 14 and 22 months after the two Category 5 hurricanes in St. Thomas. Researchers then extracted genomic DNA from the sponge samples using a genotyping method based on sequencing uniform fragments called 2b-RAD. This emerging method is used for mapping, population genetics, genetic mapping and estimating alleles. Genetic diversity was estimated for the pre-hurricane (adults) and post-hurricane (adults and juveniles) populations as expected (He) and observed (Ho) heterozygosities with inbreeding coefficient (FIS) and compared.

“Over short time scales, intermittent disturbances such as hurricanes can alter the structure and function of the coral reef benthic community and impact recovery time,” said Chaves Fonnegra. “However, as we have demonstrated in our study, storm events don’t affect all reef species equally and can promote diversity by creating open substrate for larval attachment and recruitment.”

Given predictions of more frequent intense hurricanes as climate continues to change, it is likely that major disturbances such as the unprecedented landfall of the two Category 5 hurricanes in St. Thomas will continue to influence the population structure of coral reef species and their ecological interactions.

Study co-authors are Iris Segura-Garcia, Ph.D., first author and a former postdoctoral fellow in the Chaves Fonnegra Lab; Julie B. Olsen, Ph.D., a professor of biological sciences, University of Alabama; Deborah J. Gochfeld, Ph.D., principal scientist, Department of Biomolecular Studies, the University of Mississippi; and Marilyn E. Brandt, Ph.D., research associate professor, University of the Virgin Islands.  

This research was funded by Chaves Fonnegra start-up funds and a National Science Foundation RAPID grant (OCE-1807807, Gochfeld, OCE-1808233, Olson and OCE1810616, Brandt).

- FAU -

About Florida Atlantic University:
Florida Atlantic University, established in 1961, officially opened its doors in 1964 as the fifth public university in Florida. Today, the University serves more than 30,000 undergraduate and graduate students across six campuses located along the southeast Florida coast. In recent years, the University has doubled its research expenditures and outpaced its peers in student achievement rates. Through the coexistence of access and excellence, FAU embodies an innovative model where traditional achievement gaps vanish. FAU is designated a Hispanic-serving institution, ranked as a top public university by U.S. News & World Report and a High Research Activity institution by the Carnegie Foundation for the Advancement of Teaching. For more information, visit www.fau.edu.

 

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JOURNAL

Molecular Ecology

DOI

10.1111/mec.17307 

METHOD OF RESEARCH

Meta-analysis

SUBJECT OF RESEARCH

Animals

ARTICLE TITLE

Severe hurricanes increase recruitment and gene flow in the clonal sponge Aplysina cauliformis