By Dr. David Wartinbee, for the Redoubt Reporter
Years ago as a graduate student studying in the Beartooth Mountains of Wyoming, I first encountered what was called “watermelon snow.” Many of the snow piles above 10,000 feet had an unusual, reddish-pink color. When approaching them, there was an odor similar to a fresh watermelon, and when we tried tasting it, there was even a hint of watermelon taste. It wasn’t sweet like a flavored snow cone but, yet, a hint of watermelon was good enough to justify the name. Our professors told us there were algae in the snow, and since we were working on bugs, we considered it kind of an anomaly and let it go.
We are not the first to this occurrence. Supposedly there are reports of red-colored snow from the early Greeks. The red-colored algal cells causing the color were probably first seen in the early 1800s as microscopes were being refined.
Recently, while flying over the west side of Cook Inlet, I noticed snow piles with pink ridges and was reminded of the “watermelon snow” I had seen so many years ago. I decided it was time to look at the snow under a microscope and learn more about these algae. A friend mentioned that he has seen snow piles with distinct pink coloration in Hatcher Pass, so I made a special trip to gather some specimens.
Watermelon snow can be seen all over the world and is caused by basically the same species of alga. I put some
reddish-colored water from the melting snow under a microscope and peered within. There were bright-red alga cells all over the place. These cells are a green alga named Chlamydomonas nivalis. While the alga cells contain photosynthetic green-colored chlorophylls, their abundant red carotenoid pigments overpower the others and create the distinct red color. These carotenoid pigments serve as protection from deadly ultraviolet rays that are in great abundance at high elevations.
The alga cells in the genus Chlamydomonas are well known for having a pair of flagellae (long, mobile, whiplike appendages) that enable them to move throughout the water column. However, what we see under the microscope are known as aplanospores, or “resting cells,” and then have no flagellae. These algal cells are hanging out in the snow, soaking up the sun, photosynthesizing and using nutrients that have been trapped in the snow.
Once the snow melts, these resting cells will go into a dormant state. Dormant cells can remain in place or be dispersed by winds. The dormant cells get covered with snow again and are well suited for survival in icy cold conditions. Warmer spring temperatures, meltwater in the snow and increased light cause them to germinate and form special cells with flagellae. These flagellated cells swim toward the light and end up on top of the snow. Once again, they form the red-colored aplanospore cells (resting cells) that give the characteristic watermelon-red color.
There have been some concerns about eating watermelon snow and caution about it causing gastrointestinal upset.
The cells themselves are not considered toxic or poisonous. However, after seeing all the detritus, fungal hyphae, fungal spores, dust, bacteria, nematode worms and grit that is mixed in the snow and with these algae, I can understand why it might make someone ill. Personally, I am through tasting watermelon snow. Check out the picture with these algal cells surrounded by masses of detritus that has collected in the snow over a period of many months.
Some other cryophilic (cold-loving) creatures found in high-elevation snow piles are springtails, nematode worms and the famous annelid “ice worms.” All of these tiny animals are believed to feed to some extent on Chlamydomonas nivalis cells within the snow.
When you get the opportunity, look at high-elevation snow piles and feast your eyes, if not your mouth, on this
unusual alga that causes the red color of what we call “watermelon snow.”
David Wartinbee, Ph.D, J.D., is a biology professor at Kenai Peninsula College’s Kenai River Campus. He is writing a series of columns on the biology of the Kenai River watershed.