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| Life in the lab, packed with our Iceland containers and samples! |
We are hard at work in the lab this
fall. Delor has been spending most of her time preparing our dried algae
samples for isotopic analysis. This method will give us a second, and more direct,
estimate of nitrogen fixation rates across the stream temperature gradient from the samples we collected in Iceland this summer. I will let her update you more on that soon, but
know that it is quite a time intensive process that requires Delor to mill each of the
dried samples of algae into a fine powder and then weigh very small amounts of
the powder into teeny tiny tin capsules before they can be run on the isotope
ratio mass spectrometer to find out how much 14N and 15N (the two isotopes of
nitrogen) they contain. It it quite tedious and at the same time
requires great attention to detail to make sure that the samples are carefully
prepared and that the weights are accurately recorded. She has milled and
weighed more than 200 samples and we expect to have all of the isotope data
sometime this coming week! We are really excited to start analyzing them
and begin exploring the patterns that emerge from the data.
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Is it Anabaena or Anabaenopsis? Turns out the
community is quite diverse,with a mix of these
cyanobacteria species and diatoms too! |
Bayley will be working with the data we will be getting this week as
well, but her interest in the results focuses instead on the carbon and
nitrogen content of the algae and how it changes across the temperature
gradient. She has been spending time reading up on the scientific literature that
explores the concept of "ecological stoichiometry", or the carbon to
nutrient ratios of organisms, the factors that can cause these ratios to vary,
and why they are important. She has also undertaken the tedious task of
calculating the rock areas associated with the epilithic (attached to rocks)
algal samples we collected this summer, which we will need to scale up our
nitrogen fixation estimates from our small chambers to whole streams.
Bayley will also be the first from our research team to present results in a
public forum, as she will present the stoichiometry data in an oral
presentation in the St. Catherine Biology Department Symposium in mid-December.
We are looking forward to her presentation and the story revealed by the
results!
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A sample that exhibits some of the amazing (and beautiful!)
diversity of nitrogen-fixers in our study streams. Here we
see Anabaena spp. (the short chains of pearls) as well as
several diatom species (those with the intricate glass
cases) including Epithemia and Rhopalodia spp. with
cyanobacteria housed within
the diatoms themselves! Photo by P.C. Furey |
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This is an image of Nostoc, one of the dominant
nitrogen-fixers, captured from one of our samples.
Photo by P.C. Furey |
We are also very excited by our developing work
with Dr. Paula Furey, a long-time collaborator of mine and colleague in the
Biology Department. Dr. Furey is an expert in algal identification and
taxonomy and she is working to identify the incredible diversity of
nitrogen-fixers in our Iceland samples that come into view under the
microscope. The images she is capturing are truly amazing and remind us
that the plant diversity we see when looking at a tropical forest or native
prairie ecosystem is certainly matched by algal and microbial species at the
micro-scale. It is neat to see the new images as they emerge each week in
the lab and to think about these species in relation to the nitrogen fixation
rates we have measured. Given the species diversity, we want to know
which ones are primarily responsible for the high nitrogen fixation rates we
have observed. Who is fixing all of that nitrogen?
