Researchers from the University of Washington School of Aquatic and Fishery Sciences have discovered that ocean acidification impacts the ability of some oysters to pass down “memories” of environmental trauma to their offspring.

The two papers were published in December in Ecological Applications and the Journal of Shellfish Research.

“Warming and acidifying oceans negatively influence many marine species. However, some species that live in extreme environments, such as the intertidal, may be more resilient than others to these changes,” said Laura Spencer, one of the two lead authors and a graduate student in aquatic and fishery sciences. “Some species may even be able to pass on memories of harsh conditions to their offspring, making them more capable of surviving in similarly harsh environments.”

Researchers studied two species of ecologically and commercially valuable oysters found throughout Puget Sound: the Olympia oyster and the Pacific oyster. Although oyster larvae are sensitive to acidifying oceans, adult oysters commonly occur in intertidal areas and estuaries where they must endure constantly fluctuating water conditions.

It is this hardiness that has researchers hopeful that oysters can withstand an increasingly acidic ocean. If their resilience to stressors can be passed down to their offspring, it could promote an increased tolerance among the future population.

In Spencer’s study, Olympia oysters were exposed to a combination of elevated temperatures and acidified conditions during winter months, mimicking what might happen under climate change. The higher water temperatures caused the oysters to spawn earlier; however, these effects were canceled out when combined with acidified conditions. Researchers then reared and transplanted the exposed oysters’ offspring to four estuaries in Puget Sound. They observed that the offspring whose parents were exposed to acidified conditions in the lab had higher survival rates in two of the four bays.

“We found that Olympia oyster adults were relatively resilient to acidification and warming when exposed during the winter,” said Spencer. “Most interestingly, we found evidence that adult exposure to acidified conditions can benefit offspring by improving survival.”

This carryover effect demonstrates that the experiences of oyster parents have a direct impact on how their offspring perform, and juvenile oysters may be more resilient in certain environments when their parents have been pre-conditioned by similar stressors.

In the other study, adult Pacific oysters were similarly exposed to acidified conditions in the lab. The oysters were then placed back in ambient water to recover before spawning. Researchers observed that the embryonic and larval offspring of female oysters exposed to these experimental conditions experienced poorer survival than a similar control group.

“The conditions one generation of Pacific oysters experience can affect how their children perform,” said lead author Yaamini Venkataraman, a graduate student in aquatic and fishery sciences. “Even if oysters are not in stressful conditions when they reproduce, their previous stressful experiences can impact their offspring.”

These two contrasting results are both encouraging and concerning to Washington’s shellfish industry, which generates nearly $150 million a year and provides over 2,700 jobs. While one study revealed that juvenile Olympia oysters benefited and experienced a survival advantage due to parental exposure to acidified conditions, the other study showed the embryonic and larval survival of Pacific oysters decreased with parental exposure. The authors believe these differing results could be species-specific or because the experiments focused on different life stages of oysters.

Nevertheless, determining how and why some species, such as the Olympia oyster, tolerate ocean acidification and warming helps inform where to focus conservation resources and how to improve growing methods, said Spencer.

“We needed to broaden our understanding of environmental memory when thinking about how oysters or other organisms will persist in the face of climate change,” explained Venkataraman. “The aquaculture industry is part of the fiber of Washington, and understanding how oysters will respond to changes in their environment, like more acidic water conditions, across multiple generations is crucial to sustaining the industry.”

This recent research shows that as the world’s oceans warm and become more acidic due to climate change, species tolerance or sensitivity can’t be defined by looking solely at one generation of oysters.

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Although Mr. Pudey’s walk was found to be only 3.3 times more variable than a normal walk, the research team agreed with the Minister’s decision that he had a promising silly walk that was deserving of a Research Fellowship.

The team points out how bureaucratic inefficiency can be likened to that of the peer-review process associated with academic research in the health sciences, particularly when applying for funding. Applying for a federal grant is extremely time consuming and can take months to prepare. An application may require a 150-page proposal followed by a review by a panel of researchers, who are often flown in for the occasion. Peer review protocols often require that the panelists must reach a consensus of 75 percent or more to approve a proposal.

By contrast, the Dartmouth team points out how the National Health and Medical Research Council of Australia pioneered a streamlined grant application process in 2013, which resulted in an estimated savings in 2015 of $A2.1-$4.9 million per year.

“The peer review research process has become rather unwieldy,” said Nathaniel J. Dominy, the Charles Hansen Professor of Anthropology, who co-authored the study with Erin E. Butler, who was a postdoctoral fellow at the Neukom Institute at Dartmouth at the time the research was conducted. “If the process was streamlined and grants were awarded more quickly, researchers could start their work earlier, accelerating the timeline for research. Similarly, grant administrators would recoup time and money, which could potentially free up more money for research funding,” explained Dominy.

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The research used a computer model of gas bubbles flowing through hydrate deposits, a common phenomenon which according to existing models, should not be possible based on physics. The new model helps explain how some deposits grow into massive natural gas hydrate reservoirs, such as those found beneath the Gulf of Mexico.

A paper describing the research was published Feb.16, 2020, in the journal Geophysical Research Letters.

Gas hydrates are an icy substance in which gas molecules, typically methane, become trapped in water-ice cages under high pressure and low temperature. They are found widely in nature, house a substantial fraction of the world’s organic carbon and could become a future energy resource. However, many questions remain about how hydrate deposits form and evolve.

One such question was raised by observations in the field which spotted methane flowing freely as a gas through hydrate deposits in the subsurface. What puzzled scientists is that under conditions where hydrates occur, methane should only exist as a hydrate, not as a free gas. To solve the mystery of the free flowing gas, a team of UT researchers led by Dylan Meyer, a graduate student at the UT Jackson School of Geosciences, recreated in the lab what they saw in the field.

Using this data, they hypothesized that as hydrate forms in a deposit it also acts as a barrier between gas and water, restricting the speed at which new hydrate forms, and allowing much of the gas to bubble through the deposit. They developed this idea into a computer model and found that the model matched experimental results. When scaled up, they also matched evidence from field studies, making it the first model of the phenomena to successfully do both. Crucially, the model suggests that gas flowing through the subsurface can accumulate into large, concentrated hydrate reservoirs, which could be suitable targets for future energy sources.

“The model convincingly reproduces a range of independent experimental results, which strongly support the fundamental concepts behind it,” said Meyer. “We believe this model will be an essential tool for future studies investigating the evolution of large, highly concentrated hydrate reservoirs that experience relatively rapid gas flow through porous media.”

The study is the first time this kind of model has been built using data from experiments designed to mimic the gas flow process. The team produced their own hydrate deposit in the lab using a mixture of sand, water and gas and recreating the extreme conditions found in nature. Their efforts provided them with realistic and relevant data from which to develop their model.

Co-author Peter Flemings, a professor at the Jackson School, said that understanding how methane gas travels through hydrate layers in the subsurface is important for understanding methane’s role in the carbon cycle and its potential contribution to global warming.

“The paper gives an elegant and simple model to explain some very challenging experiments,” said Flemings.

The study’s experiments were conducted in specialized labs at the Jackson School, but the model was the result of a cross-campus collaboration between two UT schools, the Jackson School and the Cockrell School of Engineering.

Meyer, Flemings and Kehua You, a research scientist at the University of Texas Institute for Geophysics (UTIG), had developed the original computer code to explain their experimental results, but it wasn’t until they teamed up with David DiCarlo, an associate professor at the the UT Cockrell School of Engineering, who showed them how the results could be presented using analytical math, that they could successfully tackle the problem in a way that mirrored what they were seeing in nature.

The paper is the culmination of Meyer’s graduate research and builds on two previously published papers that focused on the results of his lab experiments. Meyer graduated in 2018 with a doctoral degree from the Jackson School and is now a postdoctoral researcher at Academia Sinica in Taipei.

The research was funded by the U.S. Department of Energy (DOE) and is part of a broader partnership between the DOE and The University of Texas at Austin to investigate methane hydrate deposits in the Gulf of Mexico.

Many of the lab experiments that fed into the current study were performed by Meyer at the UT Pressure Core Center, a laboratory at the Jackson School equipped to store and study pressurized cores taken from natural methane hydrate deposits in 2017 and which remains the only such university-based facility.