Mercury-Laden Fog Swirls Over California Coastal Cities
Picture San Francisco's Golden Gate Bridge and you probably imagine it enshrouded with fog. Fog is an iconic aspect of the Northern California climate, but many don't realize that this coastal fog is ladened with mercury.
Photo credit: Shutterstock
For the past five years, researchers from University of California, Santa Cruz and other institutions have been sampling fog in central California. Two years ago, the researchers expanded their scope to seven locations stretching from Monterey to Eureka as part of the FogNet project, which is funded by the National Science Foundation.
Researchers found the concentration of monomethyl mercury is 19 times higher in fog collected on land compared to rain. They told the San Francisco Chronicle that exposure levels are relatively low for humans, but the discovery still worried them.
“On a relative scale, the levels of mercury are quite low and of no health concern,” Peter Weiss-Penzias, a professor at UC Santa Cruz, told the Chronicle. “But it does bioaccumulate,” or build up in the food chain.
It's already well known that monomethyl mercury bioaccumulates in aquatic food webs, often making fish and other animals unsafe for human consumption. But there has been nothing in the scientific literature about mercury in the fog and its potential impact on terrestrial ecosystems until now.
"There haven't been reports of monomethyl mercury measurements in fog water in the scientific literature," Weiss-Penzias said. "But these elevated concentrations suggest that fog could be a significant source in coastal environments."
According to the Chronicle, "the scientists determined that mesoscale eddies—large, circular currents of water from the California current—are depositing dimethyl mercury into the fog, where acidic marine aerosols—particles left over from evaporated droplets of ocean spray—convert it into its monomethyl mercury form. That compound is then blown ashore in the fog, where it is deposited on the coastal landscape."
The source of monomethyl mercury in the ocean is debated, but emissions from coal-burning power plants "likely make a significant contribution," Weiss-Penzias said.
So far, researchers have shown that, at the highest periods of fog, mercury levels in wolf spiders along the coast exceeded the U.S. Food and Drug Administration’s three parts per million safety threshold.
“I would definitely not eat any spiders from foggy areas,” researcher Kenneth Coale jokingly told KQED Science.
And preliminary research on mountain lions showed that larger animals are susceptible too. They believe mercury levels in these large cats could be, on average, 10 times higher than those of their inland counterparts. They presented their latest findings at the fall meeting of the American Geophysical Union last month in San Francisco. They are currently writing up a report, which they plan to submit to Science.
The FogNet team said more research needs to be done to determine how dangerous the exposure is for humans and if other chemicals are making their way into the fog. They will continue to collect data through 2016. In the meantime, they said regulators may want to limit mercury pollution in the atmosphere.
“I am hopeful that when all the exposure routes are added up, we will see that we are receiving quite a burden,” Coale said, “and that perhaps we should be considering limiting [mercury] emissions, particularly from coal-fired power plants—not just from a climate change perspective, but from an ecosystem health perspective as well.”
For a more in-depth explanation of how fog transports mercury from the sea to land, watch this video showcasing research led by Coale at the Moss Landing Marine Labs:
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By Aaron W Hunter
A chance discovery of a beautifully preserved fossil in the desert landscape of Morocco has solved one of the great mysteries of biology and paleontology: how starfish evolved their arms.
The Pompeii of palaeontology. Aaron Hunter, Author provided<h2></h2><p>Although starfish might appear very robust animals, they are typically made up of lots of hard parts attached by ligaments and soft tissue which, upon death, quickly degrade. This means we rely on places like the Fezouata formations to provide snapshots of their evolution.</p><p>The starfish fossil record is patchy, especially at the critical time when many of these animal groups first appeared. Sorting out how each of the various types of ancient starfish relate to each other is like putting a puzzle together when many of the parts are missing.</p><h2>The Oldest Starfish</h2><p><em><a href="https://www.biorxiv.org/content/10.1101/216101v1.full.pdf" target="_blank" rel="noopener noreferrer">Cantabrigiaster</a></em> is the most primitive starfish-like animal to be discovered in the fossil record. It was discovered in 2003, but it has taken over 17 years to work out its true significance.</p><p>What makes <em>Cantabrigiaster</em> unique is that it lacks almost all the characteristics we find in brittle stars and starfish.</p><p>Starfish and brittle stars belong to the family Asterozoa. Their ancestors, the Somasteroids were especially fragile - before <em>Cantabrigiaster</em> we only had a handful of specimens. The celebrated Moroccan paleontologist Mohamed <a href="https://doi.org/10.1016/j.palaeo.2016.06.041" target="_blank" rel="noopener noreferrer">Ben Moula</a> and his local team was instrumental in discovering <a href="https://www.sciencedirect.com/science/article/abs/pii/S0031018216302334?via%3Dihub" target="_blank" rel="noopener noreferrer">these amazing fossils</a> near the town of Zagora, in Morocco.</p><h2>The Breakthrough</h2><p>Our breakthrough moment came when I compared the arms of <em>Cantabrigiaster</em> with those of modern sea lilles, filter feeders with long feathery arms that tend to be attached to the sea floor by a stem or stalk.</p><p>The striking similarity between these modern filter feeders and the ancient starfish led our team from the University of Cambridge and Harvard University to create a new analysis. We applied a biological model to the features of all the current early Asterozoa fossils in existence, along with a sample of their closest relatives.</p>
Cantabrigiaster is the most primitive starfish-like animal to be discovered in the fossil record. Aaron Hunter, Author provided<p>Our results demonstrate <em>Cantabrigiaster</em> is the most primitive of all the Asterozoa, and most likely evolved from ancient animals called crinoids that lived 250 million years before dinosaurs. The five arms of starfish are a relic left over from these ancestors. In the case of <em>Cantabrigiaster</em>, and its starfish descendants, it evolved by flipping upside-down so its arms are face down on the sediment to feed.</p><p>Although we sampled a relatively small numbers of those ancestors, one of the unexpected outcomes was it provided an idea of how they could be related to each other. Paleontologists studying echinoderms are often lost in detail as all the different groups are so radically different from each other, so it is hard to tell which evolved first.</p>
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