��������

By Victoria Bourne

Dan Barshis, Ph.D., was a sixth-grader at summer camp in Wisconsin when he first tried scuba diving. He recalls the panic that set in as his mask began to leak when he was fully submerged.

“Getting over the fear is a big thing,” Dr. Barshis said. With a better-fitting mask, he returned to the water, and all was well. Years later, one of his first open water dives was in Micronesia.

“A tropical island atoll just blew me away and I never looked back,” he said.

Now an associate professor of biological sciences at ��������, Dr. Barshis dives in countries around the world — Israel, Saudi Arabia, Japan — researching the impact of rising sea temperatures on some of the most beautiful and vulnerable underwater ecosystems: coral reefs.

Dr. Barshis came to ��������’s College of Sciences in December 2013. Through the lab that bears his name, he and his team of undergraduate and graduate students and postdoctoral researchers study the evolution of stress tolerance in marine invertebrates, with a focus on reef-building corals. Their research spans the fields of ecology, physiology, genetics and transcriptomics, a technique used to study molecular mechanisms.

American Samoa has been the primary location for Dr. Barshis’ research since 2003 when, as a Ph.D. student at the University of Hawai’i at Mãnoa, he began examining the resiliency of corals exposed to high temperature spikes during low tide in a small portion of the National Park of American Samoa.

“The initial question was, ‘Why do these corals look so happy? And are they any different from corals that don't experience these short temperature spikes?’” Dr. Barshis said.  “The answer was, yes, they're more resilient, and maybe have even evolved and adapted to those environments.”

Located in the Pacific Ocean, 2,200 miles from Hawaii, American Samoa is a group of islands that represent the southernmost territory of the United States. It’s home to 280 species of tropical reef-making coral out of nearly 1,000 documented worldwide.

In all, there are roughly 6,000 species around the world living in shallow and deep-water environments, including soft corals that do not build but are nevertheless vital to reef health and function.

In 2021, Dr. Barshis embarked on a comprehensive examination of coral reef resiliency in American Samoa as part of a multi-grant funded $7 million project. The effort included teams of international and U.S.-based researchers with focus areas stretching from the Caribbean to the Great Barrier Reef off the northeastern coast of Australia.

Reef-making corals are the architects of the sea. Through their clonal ability to replicate, they build a framework that supports a third of all marine biodiversity — not unlike terrestrial rainforests. Fish, invertebrates and even some mammals are supported by coral reefs.

"They're extremely important from an ecological standpoint,” Dr. Barshis said.

That biodiversity is a source of food for the millions of people who live near tropical coral reefs. Corals and the organisms found in reefs are also a source of bioactive compounds with pharmacological potential, representing an untold library of future discoveries that could benefit medical research, as well as ones that have already aided anti-cancer drugs and antibiotics, Dr. Barshis said.

Coral reefs create breakwaters, protecting coastlines from storms and wave erosion, and they provide an important source of recreational tourism dollars for many tropical economies.

They’re under threat from rising sea temperatures with spikes occurring more frequently and with more intensity over the last several years, resulting in coral bleaching, a whitening that is indicative of stress and potential threat to the otherwise long-lived organism. American Samoa has revealed pockets of hope — corals that have shown more resiliency.

“American Samoa coral reefs are still doing quite well, where other places are not,” Dr. Barshis said. “Last year, we had the hottest ocean temperatures on record, but compared to the last few bleaching events, it was one of the least extreme bleaching events in American Samoa.”

Bleaching is a combination of temperature and light stress; the biggest natural bleaching events occur during calm weather, when the water is very clear and temperatures are high, Dr. Barshis said.

Corals thrive from a symbiotic relationship with a tiny algae called dinoflagellates that live inside their tissues. The coral feeds off the sugars the algae produce through photosynthesis in exchange for shelter, nutrients and access to sunlight provided by the coral.

That already sensitive symbiosis breaks down with ocean warming and tends to fall apart, Dr. Barshis said. As the coral expels the little brown algae, they not only lose their energy supply but also the source of their brilliant pigmentation.  As the coral starves and dies, it turns white.

 “That's why it's called bleaching," Dr. Barshis said. "There's a lot of interest in what makes some corals more resistant to bleaching than others."

Using a portable lab co-developed by Dr. Barshis he and his team have run thousands of coral samples through short temperature challenges. He likened it to a cardiac stress test one might get at a doctor’s office. 

The CBASS is custom-made, constructed from restaurant-grade food storage containers with temperature sensor controllers that activate the chiller or heater depending on a set point determined by the researchers. Lights enable the team to replicate levels of daylight.

The researchers measure how well the algae are able to convert light energy into chemical energy and look for signs of bleaching.

In the last few years, the CBASS has been deployed all around the main island of Tutuila in American Samoa trying to assess as many different sites and coral individuals as possible. The goal is to learn a lot more about how different environmental conditions and genotypes affect resilience, and what genes might be under selection for increasing thermal tolerance. 

“What we're learning are ways to diagnose and find the most resilient coral individuals and species,” Dr. Barshis said. “What I'm moving towards is then using those in a nursery, growing them and putting them in live genetic banks to preserve that genetic diversity.”

Dr. Barshis’ work in America Samoa produced by The World.

“Research like Dan’s is important,” Sana Lynch, who coordinates the Coral Reef Advisory Group, said in the piece, “because we can use our coral diversity and hopefully expand the findings here to other places to increase coral abundance.”

Thanks to CBASS’ portability – Dr. Barshis said it fits in about seven suitcases – he and his team have run standardized and replicable experiments from a wooden live-aboard dive boat in Djibouti, across the Saudi Arabian Red Sea and on a hotel balcony in the Galapagos.

Through an exchange fellowship last summer, Dr. Barshis visited Okinawa, Japan, where he had an opportunity to work beside researchers from the University of the Ryukyus to survey and test species of corals residing in ecosystems starting from 130 feet or so below the ocean surface.

“The more places that we can run these same experiments, the more we can directly compare the data,” Dr. Barshis said. “We're trying to build a global database of tolerance limits, which we haven't been able to do before because we haven't been able to run the exact same experiment with the same equipment measuring the same thing in different places.”

Dr. Barshis said he’s pivoting his research lens in the direction of active restoration to increase the resilience of some reefs that are more sensitive to stress but added he’s not necessarily advocating for relocating live American Samoa coral to far flung places such as the Great Barrier Reef.

“What I've found is that if you look closely enough, you'll find resilient corals and genotypes locally in little pockets here and there.”

Did you know?

�������� is home to one of about 10 technical rebreather diving research programs in the country, and one of only about 20 worldwide. Dr. Barshis started the program in 2014. It’s part of the University’s decades-old for faculty, staff and students who are conducting underwater scientific research.