Beyond Google

Long gone are the days of the dictionary, encyclopedia, handheld map, and textbook. When curious minds inquire, they now instead proclaim, “I will Google it”. Google happens to be one of the most widely used search engines in the world. As a highly inquisitive individual myself, I often turn to my iPhone on a daily basis to enter something into Google. After all, knowing how and where to find information is becoming a more important skill than memorization and the internet has made information more accessible than ever before.  What has really struck me about our Iceland research is that the questions we are asking are in fact “beyond Google".

Bree and Abbi preparing chambers

Now, that might sound like common sense – of course you are doing research to gain new knowledge, generate information, and maybe even create paradigm shifts. But this reality hit me like a brick. What do you mean Google no longer contains the answers to my questions about nitrogen fixation, ecological stoichiometry, or metabolic theory?! Of course much is known about these topics and previous research has guided and shaped our questions and hypotheses, but many of the answers remain in the water.

So here I am in Iceland, going “beyond Google.” Our research is in full force as we strive to understand how important biogeochemical processes drive both the structure and function of stream ecosystems. I have learned that the work we have embarked on will provide novel information and that our findings will ultimately shape thinking, teaching, policy, and ultimately add to the wide world of Google. That is all for now! Stay tuned for some exciting results that will take you beyond Google!

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.

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!