The Hengill Diaries: A slow but steady start

My first week back in Hengill has gone exactly as expected, full of both small achievements and some interesting challenges.

This summer I will be running our fourth and final side-stream channel experiment, in which we will investigate the effects of climate change and nutrient pollution on stream ecosystem processes, such as carbon fixation and the cycling of associated nutrients. To do this we’ll culture biofilms in side-stream channels along a temperature gradient of 5C-25C (41F-77F), while adding N and P at varying concentrations and ratios. This will allow us to understand if the concentration of a nutrient, or its relative availability to other nutrients, influences how biofilms and their coupled ecosystem processes respond to temperature.

However, before we can answer these questions the channels need to be up and running, which is proving more difficult than anticipated. Although the PIs spent the last two weeks getting the infrastructure in place and securing a constant supply of water to our site, the hot pot that warms our water is refusing to stay hot. Last year the pool was consistently around 45C; this year it struggles to hit 40C and seems unable to maintain a heat source.

If a hot pot doesn't produce hot water, is it really a hot pot?

These are the questions that keep me up at night.

I’m currently testing out a few ideas to get the heat back. Draining the hot pot completely results in an inflow of warmer water- sometimes the incoming water is 70C- that’s 158F! However, once the pool refills the pressure from the water seems to “shut off” the heat vent, and the water begins to cool. Keeping the water levels lower in the hot pot may therefore help us maintain a constant supply of hot water. I’ll be keeping an eye on the temperature in the coming days, bailing water as needed, and hoping for the best.

"The Belly of the Beast"-

a rare glimpse into the inner-workings our volatile hot pot after I removed over 1500 L of water

Meanwhile, I’m continuing to put the final touches on the rest of the experiment. Beth and Filipa, two Master’s students from Imperial College London, lent a hand carrying out tiles to the site, which I use as the “rocks” in my experiment for the biofilm to grow on. We spent the afternoon lining the channels with the tiles, and their help sped up the process considerably.