September 25, 2014

Glacier Ice Worms in Action

Posted by Mauri Pelto

On glaciers in the coastal ranges of the Pacific Northwest glacier ice worms thrive. Their diet as far as we have seen from looking in their gut is algae. They cannot survive during daylight hours on the surface of the snow with even indirect solar radiation. They can survive on the surface of glacier ice if bathed in meltwater. When we leave the edge of a glacier and cross onto a snowfield that persists in many years, the number of ice worms plummets from 100-400 worms/square meter to zero within 20 m. This suggests that ice worms do not tend to roam off glaciers. There movement is relatively vertical, so they cannot migrate around a glacier to remain on a snowcovered section. Since their diet is largely algae, which can thrive in snowpack, what happens to this diet when the snowpack is lost and they have to exist on the glacier ice? If this period of existence on the ice is expanded due to earlier snow melt, is this a significant stress? This latter question is what I was pondering while observing and filming the ice worms on the surface of Sholes Glacier on August 11th, 2014. The snowpack had been lost and yet there was still at least 7 weeks left in the melt season. The snowpack had been lost in 2013 in early August as well. In 2014 monitoring the ice worm population in the same location as every year, the numbers were the lowest we had seen since 2005 also a low snowpack year following a low snowpack year. The population did rebound in 2007 and 2008 with better snowpack. The data does not answer the question, but is suggestive that repeated low snowpack occurring with significant periods left in the melts season may reduce glacier ice worm populations. You may think why does that matter, but in fact on Sholes Glacier the population of glacier ice worms based on our surveys is approximately 200 million. The process of answering this question will continue.

For an overall assessment of ice worms.