Mercury is a naturally occurring element that is released to the atmosphere by human activities—approximately 4000 metric tons each year. Coal combustion, gold mining, and other industrial processes are the main culprits.

Peter Weiss-Penzias, Ph.D., an associate researcher in the Department of Microbiology and Environmental Toxicology at UC Santa Cruz, will be talking about the danger of mercury to humans and wildlife in this Slugs & Steins alumni gathering.

He'll share his research into this neurotoxin that can bioaccumulate in food webs to reach levels that exceed dietary thresholds. Normally, this is a problem in aquatic systems where methylmercury is produced by bacteria and there are many levels in the food web (big fish eats the little fish). However, coastal fog like the kind we have in California acts as a sponge for methylmercury emissions from the ocean, and when this fog moves onshore and wets the forest with droplets, methylmercury from the ocean can enter the food web on land.

Weiss-Penzias's research on mountain lions in the Santa Cruz area showed that they had mercury concentrations that approached toxicological thresholds, with levels that were three times greater in their fur and whiskers compared with mountain lions from the Sierra Nevada Mountains. Deer in the Santa Cruz Mountains, which are the main food source of mountain lions, also contained higher concentrations of mercury compared to deer in the Sierra Nevada. Lichen, the symbiotic organism that lives on trees, also showed similar enhancements in mercury, which strongly suggested an atmospheric source (i.e. fog) since lichen lack roots and only absorb materials from the air.

Thus, although fog makes up a small portion of the water inputs to the Central Coast, it may play an outsized role in cycling mercury from the ocean to the land. 

Slugs & Steins

The Slugs & Steins speaker series is a monthly event hosted by the Silicon Valley chapter of the UCSC Alumni Association. It is a free, virtual event that is open to the general public.