Opinion
Local Knowledge: Life Needs CHNOPS
The surprising impact of remnant organic compounds from hundreds of millions of years past
By Paul Swenson EBS COLUMNIST
What a great acronym, CHNOPS. You are 98% CHNOPS, even when you’re not drinking. This little mnemonic—a way of remembering a concept that is being taught—stands for: Carbon, Hydrogen, Nitrogen, Oxygen, Phosphorus and Sulphur.
These six elements, all non-metals, are found in the upper left-hand corner of a periodic table. Their covalently bonded organic compounds make up the vast majority of life on Earth. Every living organism uses these six elements to make DNA, RNA, proteins, fats, carbohydrates and other necessary compounds.
We humans cannot synthesize many of these important molecules, so we depend on other organisms to do the work for us. That makes us the consumers, and other organisms, especially plants, the producers. Plants take the ingredient list of CHNOPS, along with the energy of the sun, to make carbohydrates, fats and amino acids.
For plants, five of the six elements are easily accessible but nitrogen is not. This seems surprising since 78% of the atmosphere surrounding plants is diatomic nitrogen gas, N2. The difficulty arises because the two nitrogen atoms are bound together by triple covalent bonds. This arrangement takes so much energy to decompose that N2 is basically inert. So a plant has to find sources of nitrogen found in other compounds where it is accessible.
Most common compounds that provide plant-available nitrogen are nitrates and ammonium. These two ions are found in most fertilizers and animal waste, and have naturally occurring sources. There are many articles that address the human sources of nitrogen in our local water resources. The late summer algae blooms in the West Fork of the Gallatin River and the main stem of the Gallatin down stream of Big Sky are usually attributed to human activities in this watershed.
While I am confident human impacts do increase the nitrate load in the water, there are also many natural sources that contribute nitrates, ammonium and phosphorus to a creek. Taylor Fork, just over the hill 10 miles south of Big Sky, is a watershed with approximately the same size catchment basin, and almost identical geology. But it lacks the development found in Big Sky. Therefore, when algae blooms occur in this creek the sources of nutrient load must be primarily natural. So where is this natural “pollution” coming from?
Underlying most of both watersheds is the 100-million-year-old Thermopolis Shale. It is an easily eroded, dark gray to black, finely bedded rock that when wet, creates a black sticky mud experienced walking around the Hummocks trail system, Yellow Mule trails, or the first mile of Beehive Basin trail. Except for the headwaters of creeks in the Spanish Peaks, or Taylor Range, the rest of the streams run through this shale.
A black shale like the Thermopolis is produced in a marine environment where there is a lot of organic activity in the water column. When organisms die, they fall to the ocean floor where they produce a black, stinky mud that gets thicker and thicker over time. The nitrogen compounds contained in the mud becomes trapped in the rock. Then millions of years later, they’re released back into the environment when the shales are eroded.
Soils that are produced from eroded shales have a nitrogen/nitrate component that can be as high as 1 gram of nitrogen per kilogram of soil. That is a lot! So ground water and surface runoff can transport this plant-accessible nitrogen to creeks which—along with lower flows, higher temperatures, and more sunlight—increase the growth of algae during the later parts of summer.
Aside from nitrogen, phosphate compounds foundin household detergents can create similar algae blooms. Many states have banned the use of phosphate-based detergents, with a nationwide ban looming on the horizon.
But Big Sky has a natural source of phosphate pollution. The 270-million-year-old Permian Phosphoria Formation is exposed along Levinsky Ridge, Tick Ridge, then across North Fork, Beehive Creek and into the Madison Valley. It is also exposed on Buck Ridge, Cedar Ridge, Pioneer Mountain and other locations. As its name indicates, it contains a high phosphate concentration and is mined in Idaho.
As the phosphate rich rocks of this formation are eroded and weathered, water soluble phosphate compounds are carried into the ground water then to the creeks. Just as with the shales, the Phosphoria Formation is also exposed up Taylor Fork contributing added nutrients to its water.
Now that winter is settling in for the next few months, the discussions over algae blooms, water issues, sewer issues and development will take the back burner. Powder days, tram laps, hang time and frigid weather will command our attention. But when an order of schnapps shots comes ‘round, remember: CHNOPS shots keep you going. And maybe next summer, the region’s sources of natural pollution can be revisited.
Paul Swenson has been living in and around the Big Sky area since 1966. He is a retired science teacher, fishing guide, Yellowstone guide and naturalist. Also an artist and photographer, Swenson focuses on the intricacies found in nature.
