Lichen central in air quality study


Lichens are playing a key role in an air quality study being conducted in the Skagway area by the National Park Service and the U.S. Forest Service.
Forest Service researcher Karen Dillman helped explain the study at a June 18 presentation by four USFS researchers, and a Klondike Gold Rush National Historic Park biologist.
“We’re observing air quality over time with the help of lichens,” Dillman said.
The two-year study started in April, and uses lichen to connect chemical analysis of the air with known air pollution, said biologist Dave Schirokauer. Schirokauer is the local NPS official in charge of the study.
Karen Dillman, a USFS researcher based in Petersburg, explained the lichen side of the study at its simplest.
“We collect lichen tissue and analyze it for contaminants,” Dillman said.
Forest Service lichen guru Linda Geiser, of Portland, said the samples will be dried, ground, and analyzed to see how much of a contaminant is in it. A sample with one percent of a substance would mean one percent of the total ground up matter was that substance, she said.
Schirokauer later said the samples would be sent to a lab at the University of Minnesota for the analysis.
To understand those percentages, Geiser said they developed normal levels based on what is typically found in a healthy area.
Those baseline thresholds were developed using data from across Alaska, including information from a similar study done in Skagway nine years ago, Schirokauer said.
They will be testing for about 28 elements, including nitrogen, sulfur, lead, mercury, and ammonia, he said.
He noted one of the most interesting elements they’re studying is mercury. Some comes from coal-fired power plants in Asia.
“We are looking at local sources, but it is not just local,” he said. “The mercury is a far-field contaminant.”
Mercury is problematic, he said, because once itís in the ecosystem, it stays. Micro-organisms naturally methylate it, a process that changes its make-up, and makes it fat-soluble. Generally, they do so as a side affect of other processes, not for survival, he said.
Once it is fat-soluble, mercury starts making its way through the food web, and accumulating in organisms, he said. Some trickles back out, but most stays in fish and their predators. The accumulation can cause health effects.
But Schirokauer did not think all the results would be as worrisome. Historically, lead levels were high from trucks and trains bringing ore to the port in the 1970s and 1980s. Schirokauer thought those would drop.
“I’m expecting the lead levels to have declined with the new procedure for (metals) transfer in place,” he said.
Other sources of the contaminants being studied include vehicle exhaust, mining, marine vessels, wood burning stoves, and diesel power, Dillman said.
Not all of the lichen analysis is based on chemistry.
The types of lichen present will also tell researchers about the area, Geiser said.
To study and collect the lichen, Schirokauer said the researchers flag ìcommunity centersî at each site. Most of the study of types living in the area is done in the 84 square foot centers, although Schirokauer said the actual collection area might cover an entire acre.
There are two community centers per site, he said. The idea is for each of the samplers, and all of the lichen, to have the same air at one site, he said.
Some lichens are nitrophiles, meaning they thrive when there is nitrogen around, said Forest Service researcher Sarah Jovan. They are usually orange and yellow, and live in areas with lots of nitrogen, she said.

A thoroughfall near Lower Dewey lake catches what falls through the air. Researchers check the thoroughfalls once per season. MD

Dillman said the lichen absent from the area can say as much as the lichen present.
Jovan gave the example of nitrogen-sensitive lichen. Some beard-like lichen can’t survive in nitrogen-rich environments. If those lichens are absent, it is an indicator that nitrogen is present.
Schirokauer said Skagway isn’t the only area with testing plots.
There are six in Skagway, and about 120 in the Tongass National Forest, Schirokauer said. Glacier Bay National Park and Sitka NHP are also part of the study, he said.
Schirokauer said the number of sites involved gives weight to the study.
“ìThat gives us an incredible statistical power to look at [the data] on a regional level,” he said.
Glacier Bay and Sitka are also using several sample methods, unlike the Tongass, which focuses solely on lichen, he said.
The samplers help the researchers figure out how the lichen relate to whatís in the air, Schirokauer said.
Using only lichens, they can see changes and elevated levels of contaminants, but donít know what that means for air quality, he said.
Two other methods – throughfall and passive air concentration samplers – look at a variety of nitrogen and sulfur oxides and acids.
The passive air concentration samplers catch the atmospheric chemistry ñ†everything in the air, from what is naturally there to pollution from cruise ships or coal plants, he said.
The actual sampler is a small piece of paper coated with an absorbent compound, he said. There is a separate filter and device for each contaminant ñ†seven total.
Schirokauer said those filters are collected and changed weekly for the entire collection season (mid-April to mid-May).
The throughfalls, named for their placement under trees, capturing whatever passes through the canopy, catch what falls out of the air, he said.
There are 12 throughfalls per sampling plot, he said.
Although the samplers are a good tool for measurement, Schirokauer thought they wouldnít be used with every study. But the lichen sampler probably will.
The researchers explained that lichens are used to study air quality for a number of reasons.
They have different sensitivity levels, so different pollution can be measured, Jovan said. They are also good indicators of what is happening in the ecosystem overall, she said.
“The degradation of lichens has a direct impact on forest health,” Jovan said. “We like to say that these organisms provide a lot of ecosystem services.”
Those services include nutrient cycling, providing nest material, and being food, said Dillman. They also have a lot of biodiversity (there are more than 500 types of lichen in Southeast Alaska), and are some of the first organisms to move into an area, she said.
Jovan said lichen respond quickly to changes, so they show what is going on now, not just what happened months ago.
Dillman said they collect what is in the air efficiently.
“Theyíre like sponges, so they get everything from the rain or the humidity in the air,” she said.
Eventually, the team will use the lichen and instrument data to create models that predict how certain levels of pollution will affect the ecosystem, said Jovan.