Saturday, June 17, 2017

Update on the whole-stream nitrogen additions

This year we're adding nitrogen to the two cold and two warm streams. Six hundred kilos of ammonium nitrate fertilizer will do the job, delivered by the same float-valve drippers we used last year to add phosphorus. 



It's now mid-June and still early days for our nitrogen additions, but we're already playing spot the difference. Here are two shots taken two days ago of one of our warm streams. The left photo is just upstream of the nitrogen dripper, while the other shot is just downstream. Note the particularly lurid green clumps of Cladophora that start directly below the dripper.


Our isotope additions to the four streams will start in the next few days (depending on weather!), so watch this space.

New publication from Iceland project

Dan Nelson's first manuscript from his dissertation is now out in Global Change Biology. In it, we describe how our experimental warming of Stream 7 at Hengill by 3.8 degrees C changed the structure of its invertebrate community. Somewhat surprisingly, average body size increased. Across all of Hengill's streams we can obviously find taxa with a wide range in thermal preference. It just happens that many of the invertebrates with higher thermal preference are relatively large-bodied (snails and black flies, for example) and these groups responded strongly to our whole-stream warming manipulation. Conversely, many cold-adapted taxa are quite small (many midges are obvious examples) and these groups declined. These results show that shifts towards lower average body size with warming are not universal, and that the combination of diversity in thermal preference and dispersal ability will dictate how communities reassemble as ecosystems warm in the future. Well done to Dan for all the hard work he put in to reveal these patterns!

Tuesday, June 13, 2017

Update and Hot Pot



Hey Everyone!
My name is Heath Goertzen. I’m the undergrad REU student helping Lyndsie with the channels experiment this year. This blog post shouldn’t be anything complicated, just a quick update on the project so far and what we’ve been doing. I’ll also be adding a few pictures, just for posterity.

The channels have been operating quite smoothly (knock on wood) so most of what we’ve been doing is relatively simple maintenance and monitoring of channel operation, with some sampling for biomass along the way. We’ve also been spending some serious time standing over the hot pot being confused. Here’s a picture of it:

 It's the thing on the bottom, on the top is the warm pond

Now, that looks like a normal hot pot. For the first 3 years of the experiment, I’m told that this hot pot sat at a nice 40 degrees C and behaved itself. Notice the tragic use of past tense because this year, things have gotten weird. Conditions are changing day to day (perfect for scientific experiments based on consistency), so this post will probably be inaccurate by the time you see it. I’ll still fill you in on some of the more notable conditions we’ve seen. First, the hot pot got sad. See Lyndsie’s posts below mine for more but essentially, it wasn’t being a hotpot (more of a refreshing bath, really). Lyndise bailed it out (see below) and that helped at least get the temps back up. After that, the hot pot started warming in cycles. This involved it going from the original consistent temperature of 40 C to a potentially face-scalding 90 degrees C. It also started having cycles of activity that I can only describe as geyser-esque (note, I have no idea what I’m talking about and this is pure, blind speculation), wherein levels and temperature would both change over time (~1000 liters of water and 10 degrees C variability), with peak periods looking like this.

 Don’t put your face in it

 And low periods looking like this.

Still not a good idea to put your face in it

This conditional behavior caused some of the treatments to get more temp variation than was allowable, so we tried clearing a channel between the warm pond and the hot pot. The added inflow solved our level problem (yes!) but the temperature continued in cycles, which in turn perpetuated the variability (no!).

We finally blocked the same channel we had previously cleared (the one leading to the warm pond). It feels a bit like playing a game with three options wherein you’re probably going to lose no matter what you do, but you’re losing anyways so you may as well try something. Last I heard, blocking the flow has made some improvements and the hot pot was looking more consistent! I’d like everyone reading this to engage in some manner of good luck superstition. Rub a rabbit's foot, I'm serious. At this point we’ll take all the help we can get in maintaining consistency. Cheers and thanks for reading!

Saturday, May 27, 2017

2017 Channel Experiment Begins!

After nearly 3 weeks of setup and countless trips carrying equipment to our field site, the big day has finally arrived- the channel experiment has officially begun! The temperature treatments are maintaining nice 4C intervals, the water flow through the channels is consistent, and the nutrient drippers are delivering a steady supply of N and P to each channel. Now I just get to sit back, relax, and let my biofilm grow. :)

Here's a picture of the final setup, can you spot me?


Monday, May 22, 2017

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.


    Set up and ready for some bioifilm

Despite the setbacks it’s been a productive first week, and I’m looking forward to a fun and successful field season- one with lots of hot water!
Look at that steam... if only this was 1 km closer to our field site...