We are a group of freshwater ecologists from the Biology Department at St. Catherine University in Saint Paul, Minnesota studying the effect of temperature and nutrient availability on metabolism and nitrogen fixation in geothermally active streams in the Hengill region of Iceland. This is a collaborative research effort with our partners from Montana State University, the University of Alabama, the University of Iceland, and the Institute of Freshwater Fisheries in Iceland. See links to our collaborators labs below.

Sunday, July 26, 2015

One small step for ARA, one giant leap for MIMS and N15


Not a bad day to measure nitrogen fixation on stream 9
We did it! Bree, Delor, Jill and I measured nitrogen fixation rates using acetylene reduction assays (ARA), membrane inlet mass spectrometry (MIMS), and N15 assimilation in 5 streams in the Hengill Valley in Iceland this past week.  Bree has a recent blog post that describes the ARA method, so be sure to check it out.  Now, we have added two additional methods to our research.  The days flew by and I learned a lot about each method and the various steps involved. I enjoyed seeing how the methods differ, but also how each one can help us to determine how much nitrogen fixation is really occurring in these streams!  I am excited to see what the results will tell us once we process our samples. Waiting for them will be the hardest part  - even worse than enduring the black flies in the field!

Stream 11 - finished!


Our task this coming week is to  sample the channel experiment using our three methods once again to measure nitrogen fixation. We will use the same techniques and determination that we had on the natural streams, but in the channel experiment our equipment will be "mini-sized" as we will be sampling from pretty tiny artificial streams - but 30 of them! We are all rested, hydrated, and ready for any weather as we gear up for this next major sampling effort.

Sunday, July 12, 2015

Measuring Nitrogen Fixation: The Acetylene Reduction Assay

Bree and Abbi taking gas samples.
There are often multiple answers to the same question.  Whether or not those answers are parallel and agree with one another is often a different story. We are interested in determining the rate of nitrogen fixation in stream ecosystems and understanding how rates are affected by temperature. The Hengill Valley in Iceland provides us with a unique natural ecological laboratory to ask our questions, with streams that span across a 25 degree Celsius temperature gradient, while maintaining similar flow, light, and water chemistry. However, what is "the true" rate?  Getting this answer is harder than it may first appear.

Nitrogen fixation is a process completed by cyanobacteria.  While they are the only group of organisms capable of this process, they are found all over the world, in water, soil, and sometimes in association with plants (e.g., legumes). Our work in Iceland focuses on species of algae in streams that fix nitrogen. These organisms have a competitive advantage in nitrogen poor environments, including our study streams where stream water is quite nitrogen poor. They are able to take nitrogen gas, which makes up about 78% of the atmosphere, and convert it (by the use of an enzyme known as nitrogenase) to a biologically available form of nitrogen, which is an important building block for amino acids, proteins, and many cellular processes! Think of it this way: if you needed ice cream, but there was none available, you could turn to cream, sugar, and ice and make your own, if you could get the ingredients and had the right equipment to combine them. This is what cyanobacteria do in order to make proteins - they access nitrogen from the air when other sources are not available.  Evolutionarily genius!
Measuring nitrogen fixation rates on stream 11 -
 the water is super cold!

So you may be thinking, “how on Earth can you figure out how much nitrogen gas is being taken from the atmosphere and converted into the biomass of these nitrogen fixing organisms?” Do not worry - I asked the same question.  In fact, I have learned that there are currently three methods that are used to determine the rate of nitrogen fixation. We have started to answer our question with a method known as the acetylene reduction assay. Now before you panic, let me break it down. This method uses acetylene gas as a "stand in" for nitrogen gas.  Recall that nitrogen gas comprises 78% of the atmosphere.  It is typically difficult to measure the uptake of such an abundant substance. We are fortunate, however, that the nitrogenase enzyme also reacts with acetylene gas (acetylene and nitrogen gas have similar triple-bonded molecular structures), which allows us to use it to gain an indirect estimate of nitrogen fixation. 

The video below shows me preparing acetylene gas filled balloons that we insert into a gas tight chamber.  The balloon is then popped to allow the gas to be readily available to the cyanobacteria.  It is important that we shake the chamber to dissolve the acetylene gas in the water. We take gas samples before and after an incubation period of 2 hours. The gas samples are  then run on a gas chromatograph (also in video), which is used to quantify the amount of different gases in the sample. If nitrogen fixation is occurring in the chamber, the concentration of acetylene will decrease while ethylene will increase, which is the gas by-product created from our acetylene when nitrogenase is active. However, there are also two more methods that we are using to measure nitrogen fixation rates.  How will the results from those methods compare to the acetylene reduction assay?  We can't wait to find out! If you have any questions, please leave us a comment, we would love to talk more about nitrogen fixation. More methods to come next week!




Friday, June 26, 2015

24-hour mission


By: Abbi White, Bree Vculek, and Hilary Madinger            

Last night we spent the night under the Icelandic midnight sun camping at our Hengill sampling sites. It was an unbelievably beautiful night! Sunday afternoon was a rare Icelandic sunny day and the night was a continuous sunset. We were even visited by Jill and Jon who delivered pizza, falafel, and chocolate (Sirius chocolate, an Islandic treat). Perhaps our experience wasn’t quite rustic…
The mission for our trip was to try collecting diel (24 hour - hence the overnight camping) water samples to calculate net nitrogen fixation. Every hour we collected water samples, temperature, and air pressure from the stream in two different places. When we are all done sampling, the water samples will fly back to Wyoming with Hilary to be analyzed on a membrane inlet mass spectrometer (MIMS). Then we will run the data through a model to estimate  net nitrogen fixation. The basic idea of how the model works is that using the temperature and air pressure measurements we can calculate what the expected dissolved gas concentrations of the stream would be if it was in equilibrium with the atmosphere. But streams are not at equilibrium because there are biological processes changing the dissolved gas concentration. So we will compare the dissolved gas concentration in our water samples with the concentration we expect due to temperature and pressure alone and the difference in the dissolved nitrogen = net nitrogen fixation!

Since we collected hourly samples, we also had time to do a bit of exploring in the valley. We went for a midnight hike up one of the mountains, kept our feet warm with mud from a hotpot, drank water from a spring head, and embraced nature for a night. We also squeezed in some additional stream measurements to help with our analysis. Overall, we had a great time together sampling and camping and highly recommend the experience. Now we are anxious to see how the results look.

Tuesday, June 16, 2015

Your Majesty


Upon my initial arrival to the Hengill Valley stream site, I felt as if I had stepped onto another planet. The rolling hills, volcanic rock, boiling and steaming earth, and shades of green, brown, and gold graced the landscape and captivated my attention. The smoky gray fog glistened with mystery. The land is majestic. The cool, crisp, mesmerizing breeze and running water quickly snapped me out of my trance and we proceeded to prepare the experiments that will be our summer's work.



Hengill Valley, Iceland
Fieldwork has always been my favorite part of research, which is a clear indication of my love for the field of ecology. Water? Sand? Mud? Count me in! Not only is our field site one of the most beautiful places I have ever laid my eyes on, I find the unpredictable weather, the physical and mental intensity of experimental innovation, and the long days away from civilization, to be quite appealing.




Photo by Jim Hood.  Experiment where we are warming
a cold stream to 5 different temperatures, while also adding
nitrogen to some to see how the algal communities respond.
All using geothermal heat!
So far, I have spent much of my time in the field working with the team on the stream channel experiment. This has been a big job, and it has been exciting to be a part of it. I have greatly enjoyed learning some engineering, plumbing, and aquatic ecology from Dr. Jim Hood (who arrived in Iceland in early May to get this experiment up and running) from Montana State University. I am repeatedly mesmerized by the geothermal activity of the Earth, and the way we can channel that energy to experimentally vary water temperatures.


Checking out the N-fixers in one of our warm streams with
Jill and Abbi.

Back in the lab, we have been prepping for the nitrogen fixation measurement procedures and practicing our technique.  We are anxious to get our sampling underway!  Soon....

We will start that part of our work next week.

Monday, June 8, 2015

Home Away from Home

I never tire of this view from the plane window as we make our way from the Twin Cities to Iceland.  In fact, despite the late hour, I can never sleep and always have my camera at the ready, as deep night flips to bright day before my eyes.  Then, Greenland comes into view, if we are lucky enough to have clear skies.  The clouds usually break as we cross from sea to land over Greenland, but sometimes it is difficult to discern the snow covered peaks from the clouds and I have to stare long and hard out the window before I discover that yes, I can see Greenland below!  I hope to visit there someday soon and expand some our research questions to aquatic environments in Greenland.  What an amazing place it must be.


Greenland comes into view.
Iceland continues to captivate me - an amazing country, people, and place to get to  know.  I am reading the Icelandic Sagas and continue to work on my Icelandic with local friends and the scientists at the Institute of Freshwater Fisheries, but some sounds and syllables seem impossible to replicate.  I will not give up...

We have a great team here this year from St. Kate's, Montana State University, and the University of Alabama, and I am really excited to work with such an energetic and dedicated crew. We have some big experiments in front of us and  more troubleshooting to do following the long winter, but, I look forward to the greening of the landscape that is starting to emerge, as well as the explosion of cotton grass, and the upcoming results of our work.  It is going to be a great summer.  



Hengill Valley - home away from home.
We have a big week coming up that will involve lots of intensive sampling with the whole team, as well as some camping at our field site.  Unfortunately, it also looks like we may encounter a lot of rain (see the forecast link on our blog site).  But, at least we will have light!  Current day length here is over 20 hours, but it never completely darkens.  So, that will help make navigating the streams at night easier, even though we may be pretty wet!  We will report back on our progress soon.  Here's to hoping for some good weather!