The case of the missing oxygen: Foster Scholar Kate Hewett studies hypoxia in national marine sanctuaries

By Yaamini Venkataraman

November 2018

Not every marine scientist has the same origin story. Some are instantly enthralled by the ocean and its many inhabitants at a ripe young age. For others, a lightbulb goes off while sitting in an undergraduate class. Dr. Nancy Foster Scholar Kate Hewett grew up on the islands of Micronesia, but did not consider a career in marine sciences until graduate school. While working as an environmental engineer in Boston, Massachusetts, she decided to go back to school to develop a deeper understanding of the environmental problems she encountered at work. In her classes, the complicated physics associated with coastal zones pulled at Hewett’s engineering heartstrings.

Now she studies ocean dynamics at Cordell Bank and Greater Farallones national marine sanctuaries. As a University of California, Davis Ph.D. student, Hewett uses data from moored sensors to monitor and understand oxygen dynamics in sanctuary waters. She’s interested in understanding those dynamics in northern California national marine sanctuaries, as well as how factors can change and drive low-oxygen conditions that threaten marine life.

“I’m motivated to study oxygen dynamics because oxygen impacts everything,” Hewett says. “It impacts recreation, tourism, and physiology.”

On the West Coast, ecosystems along the California Current system experience seasonal upwelling, when strong, persistent northwesterly winds drive cold, deep waters toward the surface. Because these upwelling events can influence the amount of oxygen in the water, Cordell Bank and Greater Farallones national marine sanctuaries monitor oxygen content in collaboration with University of California, Davis’ Bodega Marine Lab.

With five years and counting of data from moorings, Hewett can pick out patterns and trends, separating natural fluctuations from abnormal conditions. Hewett’s goal is to understand when and why the sanctuaries experience hypoxia – low oxygen conditions – so that sanctuaries can be more prepared for these events when they occur.

Hewett has found that low-oxygen events off the California coast are linked with wind patterns. When winds relax, ocean waters are not as thoroughly mixed. The water separates into distinct layers, and low-oxygen events start to crop up along the coast. Because different locations have distinct physical processes that control water chemistry and circulation, Hewett emphasizes that intensity of hypoxia events can vary at her study locations.

Ocean warming also influences the amount of oxygen in the water. As the ocean warms, it holds less oxygen. Warming also enhances stratification and slows overall ocean circulation, which affects ocean oxygen content. Hewett notes that these changes are not only major concerns when studying hypoxia, but also for the organisms that live in the sanctuary. Corals, fish, and shellfish still need oxygen to survive, and are at risk during hypoxic events.

“To make smart decisions, we need to understand the conditions that our resources are experiencing,” Hewett says. “If we want to manage national marine sanctuaries, we need to know what the stressors are so we can alleviate the local expression of global change.” While managers of sanctuaries like Cordell Bank and Greater Farallones cannot control all impacts caused by global climate changes — or control wind patterns to alleviate hypoxic events — they will be better equipped for dealing with local hypoxic events brought on by human impacts like pollutants.

Ocean processes and hypoxia are foreign concepts for most, but Hewett makes a point to share the same magic that got her hooked with the public. She’s a scientist-in-residence at the Exploratorium in San Francisco. Hewett collects oceanographic data from the museum’s wired pier in San Francisco Bay, helps the museum with sensors, and trains their docents. She also interns at Cordell Bank National Marine Sanctuary and participates in after-school events, at open houses, and even at the California Academy of Sciences.

“We need a lot of people thinking about these big problems, and making science accessible should be the responsibility of all scientists,” Hewett says. “[We should] be accessible so people can understand the work we are doing because it impacts [their] lives, and they’re also paying for [our research].”

Just like Hewett feels responsible for bringing her research to the public, she believes the National Marine Sanctuary System does the important job of bringing the ocean to masses.

“The ocean is our own outer space,” Hewett says. “We haven’t really explored all of it, and it can seem really inaccessible. [National marine] sanctuaries are important because they give people a sense of place. To get people to care about something, you have to make it personal. The sanctuaries do that.”

Hewett’s Dr. Nancy Foster Scholarship is funded by the NOAA Ocean Acidification Program.

Yaamini Venkataraman is a volunteer social media intern for NOAA’s Office of National Marine Sanctuaries and a graduate student at the University of Washington.