15N additions started in Iceland

Last night Dan Nelson and Jon Benstead started the 15N additions in the four streams along our landscape temperature gradient in Iceland. So for the next five days each stream will have TWO drippers going - one adding phosphorus and one adding 15N-enriched nitrogen at tracer levels. Lots of work ahead of us as we follow where all the isotope goes and find out whether adding phosphorus has an effect on nitrogen uptake and routing through the food web. Below is a shot of Stream 11 (our coldest stream), with the phosphorus dripper on the right and metering pump delivering the isotope on the left.