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Tucked away in back rooms above the dinosaur skeletons and gawking school groups at the Academy of Natural Sciences of Drexel University in Philadelphia a series of file cabinets and drawers houses a whole lot of something you can’t see. This is the second-largest diatom herbarium in the world (behind only London’s Natural History Museum). Although a file cabinet or a hundred doesn’t sound all that sexy, the collection could help provide a way to sniff out some very controversial water quality problems.
Diatoms, single-celled algae characterized by a hard cell wall made of silica—essentially a glass shell—are found in almost every body of water on the planet. Marina Potapova, curator of the Academy’s herbarium, says there are so many of these surprisingly beautiful little organisms that their photosynthesis produces an amazing percentage of all the oxygen on the planet. “Every fifth breath you take is because of these guys,” she says. Diatoms’ are very particular when it comes to what’s in their watery homes—from salinity and pH to specific levels of nutrients and chemicals—which has made them a useful tool for measuring water quality. In Pennsylvania this is a hot-button issue, thanks to the boom in hydraulic fracturing, or fracking, for natural gas.
There have been a number of reports of spills, fish kills and other issues affecting rivers, streams and underground aquifers around the state, but whether or not standard natural gas practices result in meaningful water disturbances remains an open question. Proprietary mixes of chemicals and water known as fracking fluid could potentially leak into water supplies, as could methane itself, although industry says there isn’t much to worry about. The U.S. Environmental Protection Agency is set this year to release its long-awaited report on fracking, but questions about methods and timing have dogged that effort. The EPA has not used diatoms as part of its assessment, although some experts think the algae could play a role in measuring fracking’s toll on the region.
The specific set of diatoms that appear in a given water sample can reveal a lot about it. This group of diatoms, say, is known to thrive in clean, untouched streams whereas this other group tends to live where nitrogen or phosphorus levels are high or where various potentially dangerous chemicals are concentrated. By counting the relative abundance of various species and comparing them with references like the herbarium hidden above the dinosaurs in Philly, one can determine water quality.
Potapova has begun some work in western and northern Pennsylvania cataloguing these “assemblages” of diatoms to look for disturbances. In the western part of the state she says the waterways she looked at already showed signs of severe damage, although this was almost certainly due to earlier mining activity. In the north-central, part of Pennsylvania, Potapova looked at some much more pristine streams and rivers in anticipation of fracking arriving in—believe it or not—state parks and forests.
One of the challenges associated with diatom-based observations, though, is a taxonomical one that seems to fit right in among the endless samples at the herbarium. (There are about a quarter million tiny sample jars containing water and diatoms and another quarter million slides mounted with specific species.) Biologists sometimes aren’t entirely sure what constitutes a diatom species. Up until the early 1980s or so experts estimated that there were around 100,000 species. But now, after researchers started to see differences in various traits that had gone unnoticed before, Potapova says she can’t even offer an order of magnitude. “It could be anywhere from that 100,000 number up to, say, 10 million! It definitely adds to uncertainties,” she adds.
And because we have catalogued so few of those species, the handful of researchers out there looking for diatoms tend to find new ones all the time. Potapova herself has described about 30 new species. Another part of the problem is that methods of “describing” have changed since the early 1800s when the herbarium’s first samples were collected. One ongoing project—largely delegated to students, of course—is to go through all of those file drawers and enter each sample, some lovingly drawn in 150-year-old notebooks, into a database. Sometimes it is hard to determine if a “new” species is actually one already in those notebooks or whether what was considered one species before is more accurately described as two or three or even more different diatoms.
Still, even without a perfect record of which diatom species live where and under what conditions, the organisms could provide at least a backup or complementary method of water quality assessment as fracking expands apace in Pennsylvania. Jasmine Saros, a diatom researcher at the University of Maine, Orono, hasn’t looked specifically at fracking-related issues but agreed the tiny algae could be extremely useful. “Diatoms are very sensitive to changes in their environment,” she says. “As a result, changes in diatom species often occur before we can detect some chemical changes.” For example, she says, in mountain lakes in the western U.S. we see that air pollution causes alterations in diatom species years before we can detect chemical changes. If we rely on chemical signatures alone and do not include the more sensitive biological monitoring, “we may not detect ecosystem changes until greater impacts occur,” she notes, adding that biological variations at the base of the food web, including diatoms and other algae, often have serious effects higher up that chain.
Potapova agrees, saying that the chemical analyses related to fracking are obviously important but that adding a biological element would give a clearer picture of the true nature of any water quality problems. Small pulses of chemical disturbances in particular might not register in standard testing, yet biological methods could pick them up. A spokesperson for the EPA says they have not discussed using diatoms in the official fracking water-quality study but that continuing work will involve literature searches that would potentially let diatom studies in.
“We are concerned, we are environmentalists,” Potapova says, gesturing around at the collection of file cabinets and the researchers who use them. “I am sure [fracking] is having an effect. We have to be concerned.”
