“The world is full of magic things, patiently waiting for our senses to grow sharper.” Yeats could have been talking about Environmental Chemist Peter Weiss-Penzias who was bicycling to work at UC-Santa Cruz one day when
he noticed the heavy, wet air pressed against his temples and spider webs sagging under glowing water droplets. He realized the ocean was, in effect, all around him. He stopped pedaling and stared into the white horizon. “What is fog?” he recalls wondering. “What’s in it?” |
Let me do an ecstatic geek dance before explaining further.*
People like this excite me. There’s always something to discover and you don’t have to be at a think tank or mountain in Sri Lanka, it might be found on your daily commute. I discovered a six-foot-tall hollyhock-like undescribed plant species in the forest meadow that was my backyard.
But there’s a dark side to Weiss-Penzias’ discovery.
“No witchcraft, no enemy action had silenced the rebirth of life in this stricken world. The people had done it to themselves.” Rachel Carson was speaking about humans, our propensity to do what is expedient or profitable and assume it is inconsequential to life on earth. Here’s where my joyous dance halts and I scream at industries and individuals: You must ensure safety by investigating short and long-term consequences before releasing it everywhere! Didn’t Carson’s lessons about DDT sink in? Did we really need lead-based paint, thalidomide, and Teflon?
The Daily Bucket is a regular feature of the Backyard Science group. It is a place to note any observations you have made of the world around you. Animals, weather, meteorites, climate, soil, plants, waters are all worthy additions to the Bucket. Please let us know what is going on around you in a comment. Include, as close as is comfortable for you, your location. Each note is a record that we can refer to in the future as we try to understand the patterns that are quietly unwinding around us.
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Weiss-Penzias discovered that fog picks up mercury pollution from the ocean and disperses it into the Santa Cruz Mountain fog habitat, where it is picked up by other organisms, including pumas (mountain lions), wolf spiders, and probably puma’s prey (often mule deer), understory plants, and other organisms. The mercury being cycled into fog probably was deposited into the ocean years ago due to burning coal and other human activities. It’s another lesson to humans that what we do now may dangerously reverberate into the future and cause troubles we do not imagine.
Because Weiss-Penzias indulged his moment of curiosity and allowed his senses to grow sharper, researchers learned that pumas in redwood forest can have toxic levels of mercury, sometimes 4 to12 times higher than the level considered safe for humans.
The path by which he discovered this information is a perfect example of following your curiosity to each new step. While mercury isn’t fairy dust, it is magic to discover something unknown, even toxic, that is literally right in your eyes.
First, he set up nets to condense fog into water and tested the water in his lab. Every sample had higher than ambient mercury levels.
“I didn’t believe it,” he says. “I was trying to figure out how we could have contaminated the sample somehow to get these high numbers.” So his team returned and collected more fog water, but the mercury was always there.
Still, he wasn’t sure what his findings might mean for the plants and animals in our foggy coastal habitats. “This was a source of a toxic compound to the environment that was new,” he says. “Here’s a mechanism that involves the air, the ocean and the land, and nobody knows anything about it.” [snip] Coastal fog is basically an extension of the ocean,” Weiss-Penzias says. “Mercury settles into the ocean from the atmosphere, but it also finds a way back out.”
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Although these data were curious, the mercury levels in the test samples were diluted — within what is considered safe limits for humans (e.g., in fish). But fog doesn’t just flow in and out of the coastal belt; redwood forest habitat depends on fog during the summer dry season. Redwoods take in water from fog via the leaves’ stomata.
To obtain sufficient moisture for photosynthesis and growth, redwoods reach into the air with leaves shaped like baseball mitts and capture the fog that rolls in by night and languishes through most mornings. "From 25 to 40 percent of the moisture in the system comes from fog," says Dawson, who has been studying the relationship between the coastal fog and the redwoods for two decades. Some of the fog simply covers the leaves and prevents evaporation. But some of it also enters the stomata, or tiny pores, on the leaves and is drawn down through the branches to the roots.T |
The ocean is the primary source of fog’s mercury, deposited from coal burning and probably historic mining.
Mercury is a highly toxic element that is released into the environment through a variety of human activities, including the burning of coal. In California, mercury mines in the coast ranges produced large amounts of elemental mercury for use in gold mining operations, leading to contamination of watersheds throughout the state. Bacteria in soil and sediments transform elemental mercury into methylmercury compounds that are especially toxic and readily absorbed by organisms. |
It’s far too late to remove the mercury from the oceans. As colder deep ocean water rises to the surface (due to winds blowing over the ocean that push away water), the mercury deposited into the ocean is brought to the surface. Weiss-Penzias notes
“Dimethylmercury. . .readily evaporates from the surface into the atmosphere, where it decomposes into monomethylmercury and gets into fog droplets. . . . the mercury that moves from ocean waters into fog is probably not fresh pollution, but the result of the historical legacy of mercury pollution from coal burning and other sources.”
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As usual with nature, the fog’s moisture doesn’t remain in the redwood trees but moves through the entire ecosystem, which exists because of the unique characteristics that create the fog.
Fog is not just a vital element for the redwoods—it's also crucial to the entire redwood forest ecosystem. Some of the moisture drips off the redwood leaves, landing on the forest floor to water the trees and young saplings. "It's not just a drip, drip, drip," says ecologist Holly Ewing of Bates College in Lewiston, Maine. . . . "The moisture can descend into the ground up to 35 centimeters deep, and that's a lot of water.”
The fog is a gift of the Pacific Ocean's California Current where winds create upwellings that bring cold, deep, nutrient-rich waters to the surface. Those nutrients incorporated into the fog then become a gift from one of the richest marine currents on Earth to the tallest forest on the planet. Fog rolls in not only bearing moisture but also nitrogen, phosphorus and some minerals.
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Redwood needles containing mercury (but not at levels toxic to humans) drop to the ground and provide the organic-rich forest litter that supports other organisms, such as wolf spiders. So Weiss-Penzias asked one his grad students to bring in samples.
“He would lay out cups in the forest, and the spiders would simply fall in,” Weiss-Penzias says. The team tested the spiders, and once again they found mercury—but this time at levels beyond the safe human health threshold.
The high mercury level in spiders doesn’t come from the fog droplets that bead on their webs. Instead, Weiss-Penzias says, spiders must consume mercury-laden prey.
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The process of concentrating toxins as they move through the food web is called bioaccumulation and Weiss-Penzias traced mercury using puma whiskers.
Predators metabolize fats, carbohydrates and proteins of their prey, and toxins, such as heavy metals, accumulate in the predator’s tissues. To evaluate the presence of mercury in pumas, Weiss-Penzias worked with Chris Wilmers, Director of the Santa Cruz Puma Project, using their collection of puma whiskers.
Like a human hair or a tree ring, a mountain lion whisker is a chemical archive that traces the cat’s health as the whisker grows. Mercury in particular sticks to hair-like tissues, Weiss-Penzias says, such as whiskers. As a mountain lion whisker grows, tiny amounts of the mercury from within the cat attach to the whisker.
Researchers don’t yet know how mercury might be affecting mountain lions, but research has clearly shown that it harms other large mammals. Mercury tangles up the enzymes that make important “cleaning molecules” in cells. These molecules are necessary to prevent natural but harmful byproducts from building up. . . .
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The next step in the discovery process is to determine how the pumas pick up mercury. Since mule deer are their usual prey, deer and plants they forage will be tested for mercury. “Coastal fog is basically an extension of the ocean,” Weiss-Penzias says. “Mercury settles into the ocean from the atmosphere, but it also finds a way back out.” The entire redwood forest habitat may be contaminated with mercury.
"There is so little data on this now, we're just trying to fill in the map to improve our understanding of the cycling of mercury in the environment," Weiss-Penzias said. "We want to know its sources and sinks and transformations."
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what magic things now
patiently wait in your fog
for discovery?
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* thank you, linsea, for bringing this story to my attention.