While studying biology at Sonoma State University, Gary Cherr indulged his childhood fascination with marine life. A longtime fisher, he finally had an intimate view of the organisms that once swam by him while he angled. Only this time, he was in a laboratory rather than on a fishing boat. He used electron microscopes to investigate the structure of octopus suckers and performed studies in Tomales Bay, monitoring the reproductive behaviors of fish in eelgrass beds.
“Sonoma State is only 35 to 40 minutes away from Bodega Bay, so as an undergraduate, we used to come out here all the time on field trips to the Bodega Marine Laboratory,” said Cherr, a professor in the College of Agricultural and Environmental Sciences’ Departments of Environmental Toxicology and Nutrition. “I always remember saying to myself, ‘Gee, I would love to work there someday.’”
Since 2009, Cherr has served as the director of the Bodega Marine Laboratory and as an associate director of the Coastal & Marine Sciences Institute. But he became an Aggie well before that. After completing a B.A. in Biology at Sonoma State University in 1979, he enrolled at UC Davis for graduate studies in the Zoology Department, a program within the Division of Biological Sciences, which later became the College of Biological Sciences.
“At the time, Davis was launching its relatively new aquaculture program,” said Cherr, noting that the program, while new, was already well-respected. “This was a whole new area of interest across the country.”
Ocean conservation starts at the molecular level
For four years, Cherr worked with the university’s white sturgeon aquaculture program, studying the fundamental cell biology of the program’s namesake fish. Specifically, Cherr investigated the fish’s reproductive cell biology to help better inform aquaculture practices in captive breeding programs.
After completing his Ph.D. in 1984, Cherr started postdoctoral work at the UC Davis Department of Obstetrics and Gynecology in the Medical School. In 1986, when the postdoctoral work wrapped up, he found an opportunity to join a new program at the Bodega Marine Laboratory. The work would combine Cherr’s interest in reproductive biology with environmental toxicology.
Since then, Cherr has worked on many projects, such as assessing oil spills in San Francisco Bay and pollution from pulp mills on the Samoa Peninsula near Eureka, Calif. Starting with the Bodega Marine Laboratory as a research scientist, he eventually moved into teaching, becoming a full professor in 1999.
“The current ongoing project that’s probably our biggest focus is part of a UC-wide center called CEIN, which stands for Center for Environmental Implications of Nanotechnology,” said Cherr. “It’s basically very interdisciplinary and we’re working together with industry to look at safe design of nanoparticles.”
A nanoparticle is generally considered “nano” when it’s less than 100 nanometers in size. “The most active are between 2 and 20 nanometers,” said Cherr. “They’re just a little bit larger than the diameter of a DNA helix, so they’re very tiny and often, they’re not very soluble.”
Nanoparticles are used in photovoltaic cells, electronics, biomedical imaging treatments, cosmetics, antimicrobials, and sunscreens, among many other products. Their inability to dissolve slowly in water makes them a potential environmental waste hazard to our oceans.
“The one thing that wasn’t understood was once these nanoparticles get released into the environment, there’s no bringing them back,” said Cherr. “So the idea of this program was to address the issue of nanotechnology taking off at such an exponential rate, and to try to keep the environmental science up to speed with industry, and to try to inform the industry regarding design in a safe way.”
For almost nine years, Cherr’s CEIN work has focused on the effects of nanoparticles on developing embryos and juvenile marine organisms, since they’re quite sensitive to such nanoparticles at these early stages.
“We’re looking at how these particles kind of differ from the traditional chemical bulk counterparts,” said Cherr. “The two we focus on a lot are the zinc compounds, because they’re used in sunscreen, and also copper, because the bottom of boats are painted with soluble copper and now nano-copper to prevent fouling.”
“That’s been used for decades and decades,” Cherr added about the copper chloride paint. “But now they’re starting to produce paints with copper nanoparticles and it’s been touted as a safer alternative because there is less soluble copper that goes into the environment, but nobody’s really studied the effect of the insoluble nano form until recently.”
Trojan horse invasions in sea urchins
Unlike bulk copper (copper chloride for example), copper nanoparticles aren’t very soluble. They linger in the water, where they can potentially be eaten by organisms like mussels and sea urchin larvae. In their larval form, sea urchins are mobile organisms, resembling triangular spaceships with calcium carbonate skeletal rods that help them swim and feed. If exposed to copper nanoparticles early in development, their skeletal rods don’t develop properly, becoming asymmetric and stubby.
“The embryos are alive but they really can’t feed efficiently or they can’t feed at all,” said Cherr. “It’s a really obvious morphological effect and it’s because this nano-copper has been taken up specifically by the cells that are responsible for forming those skeletal rods.”
This invasion of the sea urchin’s cells is known as the “Trojan-horse effect”. The nanoparticles themselves are not very toxic, but once inside the cell, the particles dissolve, becoming toxic and damaging the cell. “The embryos can defend themselves much better against the soluble copper, but when it’s particulate like this, they take it up and we see these unusual abnormalities in development,” said Cherr, noting that the abnormalities usually lead to death.
In bivalve mussels, copper nanoparticles accumulate inside the digestive gland and are excreted back into the environment via feces. Trace particles in the feces can spread to the sediment, where they can be eaten by marine worms and other bottom-dwelling organisms, impacting the food web.
“We’re still completing a lot of these studies,” he added. “But if these nanoparticles start to be used as a predominant chemical in the environment for this application, we need to know what the risks are.”