What’s Happening to Our Food?

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This story originally appeared in the winter 2025 issue of UC San Diego Magazine as “What’s Happening to Our Food?”

If you spend any time in San Diego, you know seafood anchors the local culinary scene. From Baja-inspired fish tacos and artfully prepared sushi to hearty surf-and-turf plates and fresh market catches, the options are endless.

Beyond its West Coast flavor, seafood also delivers a major economic kick. According to the most recent National Oceanic and Atmospheric Administration’s fisheries report, commercial and recreational fisheries in the U.S. generate an estimated $321 billion in sales annually and support roughly 1.7 million jobs. Seafood also offers numerous health benefits, serving as a heart-healthy source of lean protein, particularly species such as anchovies, mackerel and herring that are rich in omega-3 fatty acids.

Yet the vital seafood industry faces threats from pollutants, parasites and environmental changes that put both marine life and humans at risk. So, what’s happening to our food — especially our seafood — and how concerned should consumers be? 

Several scientists at Scripps Institution of Oceanography at UC San Diego are investigating these questions and more, with much of the work based at the Scripps Center for Oceans and Human Health on campus. Supported by the National Science Foundation and National Institutes of Health, the center is one of six nationwide focused on studying marine contaminants and nutrients, how ocean exposures affect human health, and ways to protect the public from risks.

Mercury mysteries

Amina Schartup, a marine biogeochemist at Scripps Oceanography, is studying mercury, a toxic heavy metal, in marine ecosystems. “My top research priority is understanding how mercury converts into the toxic form that accumulates in fish and what that means for us,” says Schartup. 

Her work explores how microbial communities convert mercury into highly toxic compounds like methylmercury, which accumulates in ocean food webs.

A global pollutant, mercury enters waterways from sources such as coal burning, gold mining, smelting and waste from consumer products. When this mercury is converted into methylmercury, it moves up the food chain from microscopic organisms to top predators, including humans. As a result, people who frequently eat marine predators such as tuna or swordfish can be exposed to unhealthy levels of mercury. In severe cases, mercury poisoning can cause neurological damage and symptoms such as nausea, vomiting, muscle weakness and seizures.

Despite the mercury concerns and health advisories, seafood remains an important and often sole source of micronutrients and protein for many people around the world. This makes it especially concerning if mercury levels continue to rise in our oceans and waterways. To address this, Schartup and colleagues from Scripps and UCLA recently developed an engineered bacterium capable of converting methylmercury into less toxic forms that our bodies can remove more easily. 

In a recent study, the team reported that the engineered microbe Bacteroides thetaiotaomicron removed methylmercury from the digestive tract of mice, reducing its levels in tissues and feces in as little as 12 hours. This discovery paves the way for developing human-targeted therapies — such as probiotics — that can remove methylmercury and prevent the neurological damage it causes in children who are exposed to high levels before birth.

The collaborative project bridged the fields of medicine, biology and oceanography to help provide a real-world solution to a public health challenge.

In a separate project, Schartup and Anela Choy, a Scripps biological oceanographer, have teamed up to study how nutrients and contaminants accumulate in marine food webs and how those concentrations may be impacted by changes in ocean temperature or other conditions. Their work, funded by the NSF and the National Institute of Environmental Health Sciences, uses modeling to simulate chemical cycling in the ocean and forecast future exposure risks. Through field studies, the team is incorporating data on deep-ocean fish to understand what’s happening far below the surface.

“Our goal is to collect valuable baseline contaminant and nutrient data on a diversity of deep-sea animals — all of which feed and connect marine food webs to sustainable fisheries and human societies,” says Choy. “This is particularly urgent, as the deep sea is Earth’s largest habitat, and it is currently facing major environmental changes and threats from human activities, including fishing and mining.”

For example, lancetfish — a deep-sea species that can grow over 7 feet in length — have slow digestion systems and tend to accumulate mercury. By studying this species and other deep-sea dwellers that serve as prey for commercially harvested fish, researchers gain a better understanding of how chemicals like mercury move through the food chain and end up on our plates. This information can help consumers, regulators and fisheries make smarter choices about seafood safety and sustainability.

Parasitic problems

Scripps scientists are also examining threats to freshwater fish and related public health concerns. 

Ryan Hechinger, a marine biologist and ecologist at Scripps, has spent much of his career uncovering the often-overlooked role of parasites in marine ecosystems. His research ranges from examining the small-scale effects of parasites on individual hosts to broader impacts, such as how much energy flows through parasites compared to predators in ecosystems.

“Studying parasites helps us better figure out general rules for how nature works,” says Hechinger. “For instance, by including parasites alongside other animals in our work, we’ve changed how people think about how energy flows in food webs and how those food webs are shaped.”

In a spring 2025 study funded by the NIH, Hechinger and his team made a startling finding: More than 90% of popular freshwater game fishes in Southern California carried a non-native parasite capable of infecting humans — a previously unrecognized public health risk in the U.S.

The parasites found in the study — two species of flatworms known as trematodes — typically cause gastrointestinal problems, weight loss or lethargy when they infect humans. In some rare and severe cases, the parasites have caused strokes or heart attacks. 

The trematodes were found in freshwater species, including largemouth bass and bluegill, collected from five popular fishing locations in San Diego County. 

Hechinger emphasizes that the risks posed by these parasites are easy to mitigate with proper food safety protocols. Fully cooking the fish or freezing it for at least one week if it’s intended to be eaten raw will likely kill the trematodes, according to guidelines by the U.S. Food and Drug Administration.

However, the researchers also analyzed 125 YouTube videos, with a combined total of nearly 5 million views, and found that 65% of the videos showed no signs of using proper cooking or freezing methods. This suggests that many people in the U.S. may be consuming freshwater fish without proper precautions, significantly increasing their risk of infection. 

Hechinger and team have since reached out to public health officials in several Southern California counties to alert them of their findings.

“I hope our study serves as a wake-up call,” says Hechinger. “We’re sharing what we know about these unfamiliar parasites to help protect people.”

Hechinger says public health officials can educate the public on how to prevent infection, inform doctors about the likelihood of local fish-borne trematodiasis cases and add trematode infections to the list of diseases that must be reported to public health agencies.

Hechinger would like to conduct follow-up studies to determine how widespread these parasites are in fish. His work is dependent on federal funding and, according to Hechinger, is “essential for identifying new public health threats.”

Educational opportunities

Alongside scientific research, a key component of the Scripps Center for Oceans and Human Health is community engagement. The center works to integrate the latest seafood science with practical resources, helping to keep the public safe while promoting the health benefits of sustainable seafood.

Expert-led classes in the newly completed demonstration kitchen at the Scripps Marine Conservation and Technology Facility will launch this academic year. 

The Kwok Family Innovation Kitchen will connect scientists with chefs, seafood fishers and harvesters, industry professionals, students, and the public to demystify seafood sustainability, sourcing and cooking. This state-of-the-art space accommodates up to 24 participants working alongside scientists, educators and chefs as they explore sustainable seafood topics and culinary techniques.

“The innovation kitchen is more than just a space — it’s a classroom, a test kitchen, a collaboration hub and a training ground for the future of sustainable seafood,” says Stuart Sandin, director of the Center for Marine Biodiversity and Conservation at Scripps, who co-leads programming for the kitchen with the Scripps Academic Department.

“This is an opportunity to advance our mission of ocean stewardship and human well-being,” says Sandin. “We’re excited to use this versatile space to connect with local community members, the broader public, students and our incredible alumni.”

Learn more at scripps.ucsd.edu.