Field Work Begins with an Exciting Experiment

Meet Tanner Williamson - a graduate student from
Montana State U. and his channel experiment.  We will be
working closely with Tanner and undergraduate student
Ellie Zignego to pair N2-fixation measurements with
estimates of algal metabolism and nutrient uptake.

The 2013 field season has officially begun for the St. Kate's crew.   This year, we are working closely with the Montana State team led by Tanner Williamson, a graduate student who is conducting an elegant experiment that will assess the effect of increasing temperature on algal species composition, biomass, and metabolism, as well as nutrient content.  Tanner has been in Iceland since early May and has been working with the University of Alabama team (Phillip Johnson who designed and built the heat exchangers and Alex Huryn who designed and built the incubation chambers) to get this experiment set up and operating well as the peak summer growing season approaches.  We will be working with Tanner to support his measurements and help out wherever we can.  We will also piggyback onto his data collection and measure nitrogen fixation rates during each sampling period so that we can compare nitrogen fixation rates with Tanner's estimates of photosynthesis and respiration across the temperature gradient, as well as the uptake rate of essential nutrients from the stream water, including nitrogen and phosphorus.  

Experimental channels with 5 temperature treatments -
ambient, +5, +10, +15, +20 degrees C.
Three channels are maintained at each temperature.

In this experiment, cold water is piped from a nearby cold stream (~ 6 degrees Celsius) and split into 3 separate faucets so to speak - one that remains cold, a second where cold water is passed through a heat exchanger that sits in a warm pool (~ 25 degrees C) which warms the water as it passes through coiled tubing within the pool, and a third pipe that runs the cold water through a heat exchanger sitting within a boiling hot pot (~80 degrees C).   These three "faucets" are then used to create a temperature gradient comprised of 5 temperature treatments - ambient (temperature of the cold stream), +5,+10,+15, and +20 degrees C.  Water at these set temperatures is then piped into small artificial channels, with three channels maintained at each of the 5 temperature conditions, for a total of 15 channels.  These little channels require quite a bit of maintenance on Tanner's part to keep the flow rates consistent and to ensure that the mixing of water from the various inlets maintains the appropriate temperature gradient.  So far, they are working extremely well and have remained steady with consistent temperature increases across the treatments.

Close up of basalt
tiles in the channels

First field day measuring metabolic rates associated
with algae and microbes that have colonized the tiles
after 4 weeks.  It was quite rainy and windy!

We arrived just before the first sampling period, scheduled for 4 weeks after Tanner had placed clean basalt tiles into the channels to provide a colonization surface for the resident algae and microbial community.  Upon inspection you could see that the tiles were beginning to turn green, with a visible effect of the temperature treatments, so it was time to collect the first initial set of data.  Our first planned field day was canceled due to bad weather, which has to be pretty bad to cancel a field day (it was very foggy with low visibility and lots of rain), but we have been out in the field for the past 3 days now and we been fortunate to have sunny skies for the most part.   The first day we measured photosynthesis and cellular respiration on sets of tiles from each of the experimental channels, followed by nutrient uptake (both nitrogen and phosphorus) yesterday and today.  It has simply been beautiful out - so nice in fact, that one might be tempted to think that you no longer need to bring heavy rain gear to the field.  Ah....but one should never give in to such thoughts at Hengill, as sunny skies can turn to cold wind and heavy rain in a blink of an eye!

Beautiful sunny day with Ellie, Tanner, Jill, Aimee,

David and Jackie.  Tile sampling, day 2.

We are also in the process of setting up our gas chromatograph and we expect to measure N2-fixation on the tiles early next week.  So, we are off and running!  More from Aimee and Jackie soon - when they can get a break from field work - but on such a beautiful sunny day it is best to be outside!  In the meantime, hope you enjoy our new slideshow (above) with some  photos from our first week.