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.