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Hard Times for Hard Shells: AAAS Fellow Tessa Hill Tackles the Threats to Our Oceans

Having a conversation about wildfires may be an unusual way to help educate people about climate change in our oceans. But for Northern California-based marine scientist and AAAS Fellow Tessa Hill, Ph.D., both topics are urgent and closely related. Deadly, fast-moving wildfires have touched nearly everyone in the region. And the fires’ link to climate change provides a non-threatening way for her to engage with her community about heat waves, both on land and in the oceans. 

headshot of Tessa Hill
Tessa Hill, Ph.D. Photo credit: DJ Putonen.

“Fundamental to my work in science is an understanding that we have to meet people where they're at, and that certainly applies around climate change,” says Hill, geochemist and oceanographer at the University of California, Davis Bodega Marine Laboratory.

“I think about what other people value, what drives them, what's important to them. Our ability to house people, the amount of money we have for public schools for kids, our air quality, every aspect of living here is impacted at this point by climate change. It's also an entryway to talk to people about the fact that this is not the future that we want,” notes Hill.

From warmer waters to harmful algal blooms, changes in the ocean are altering the lives of sea creatures, impacting the food people eat, and the waters where they relax and recreate with their families. Hill works to connect the dots with local residents about those effects, and the likely future threats to human health, local economies and the coastal way of life.

One focus of her research is ocean acidification. The ocean soaks up 25% to 30% of the carbon humans emit into the atmosphere, causing a fundamental change in the chemistry of the ocean. As that carbon dioxide sinks in, it lowers the pH of the water, causing ocean acidification. She explains how organisms like oysters, mussels, clams and coral reefs must use the natural chemistry of the water to build the components of their “hard parts.” A high pH means there are plenty of available building blocks. A lower, more acidic pH means their growth is more challenging, making sea animals weaker and more vulnerable. 

Tessa at an interview for a PBS show on ocean acidification, on the UC Davis Bodega Marine Reserve.
Tessa at an interview for a PBS show on ocean acidification, on the UC Davis Bodega Marine Reserve. Photo credit: D. Grabias.

In her search for climate solutions, Hill and her team have also explored how some of the Pacific Ocean’s plants are creating a healthier environment for other creatures, buffering ocean acidification and promoting carbon storage. They spent seven years collecting millions of data points, using remote instruments to monitor seagrasses along the California coast.

Their data showed that seagrasses can reduce local acidity by up to 30%. From sea turtles to sea horses and sea slugs, creatures in these marine forests likely benefit from a halo effect within an estuary. Additional restorative capabilities of these seagrasses include providing habitat components for a lot of other organisms and filtering out pathogens and toxins.

While the climate crisis is often viewed as a global challenge, with many people leaving answers to national governments and their vast resources, Hill and others in the Pacific Northwest have not waited for a federal rescue. More than a decade ago at a California conference on sustainable aquaculture, Hill met Terry Sawyer, a co-owner of the Hog Island Oyster Company. Their conversations about protecting both the bay and responsible shellfish farming led to an ongoing intellectual partnership.

At the oyster farm, Hill and her team collect temperature and salinity readings, as well as data on the oxygen content and pH. Hill uses those readings to understand how the environment of Tomales Bay is changing through time. On the industry side, Hog Island uses the same information to make immediate decisions about their shellfish farming operations—questions like when to put baby oysters out into the bay, when to harvest and when to investigate any worrying discoveries in the water.

With collaborations now at two Hog Island facilities, Sawyer says “Dr. Hill is a constant source of clear thinking and getting things done. We can work off each other to [convey] complicated messages that are clear enough for the general public.”

But Hill points out that even creative and successful local efforts like these fall far short of what the planet needs to tackle the climate crisis.

“We also need a significant government response to this problem, and it needs to be treated by our elected officials with the urgency that it deserves. We're frankly not seeing that yet. There's no amount of small-scale projects that will add up to be enough to address this without government intervention. We need both,” she says.

Tessa Hill with students at UC Davis Bodega Marine Reserve.
Tessa visiting the UC Davis Bodega Marine Reserve with students. Photo credit: K. Higgins, UC Davis Strategic Communications.

As Associate Vice Provost for Academic Programs in Public Scholarship and Engagement at UC Davis, Hill now spends much of her time on outreach, connecting scholars with each other and promoting their achievements. The 2020 AAAS Fellow credits a AAAS Leshner Public Engagement Fellowship for providing some of the tools that have equipped her for this role.

I walked away from that with a bigger vision about wanting to change the way that we approach public engagement at universities and wanting to support, not just my own public science, but also other scholars' efforts to really engage with communities around their research.

Hill says it is sometimes disheartening to see the human and environmental price already paid in vulnerable communities for the climate crisis that should have been confronted years ago. Yet, she perseveres.

“I think about the things that I love in the ocean, the things that I show my children and that I want them to be able to experience for their whole lives. I reconnect with that wonder and awe and appreciation for the ocean. That's what refuels me,” says Hill.

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Marsha Walton