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.

Saturday, November 3, 2012

Yes, We Are Still At It...And the Work Continues!

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.
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!
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
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?