Water conditions and chemistry. A Hydrolab minisonde (Hach Hydromet) was
attached to the end of the tubing to record dissolved oxygen, temperature and
specific conductance during deployment. Nitrate, sulfate and chloride were
measured by ion chromatography at the University of New Hampshire Water
Quality Analysis Laboratory. Iron was measured by a modified ferrozine
protocol16,40. Values for other chemical species used in the model but not directly
measured were manually interpolated from previous measurements.
DNA extraction. DNA from half of the 2012 samples and all the 2013 samples was
extracted with a PowerWater DNA extraction kit (MoBio Laboratories). The
manufacturer’s protocol was followed, except for the addition of proteinase K and