Carbon, nitrogen, and phosphorus stoichiometric response to hydrologic extremes in a tributary to Lake Erie, USA

Anthropogenic activities are a major cause of water quality impairment. We evaluated how hydrologic extremes (5th and 95th percentile of flow) affect carbon (C), nitrogen (N), and phosphorus (P) stoichiometry in a tile-drained agricultural tributary to Lake Erie. Water samples collected (2003–2009) from three sites along one agricultural drainage ditch and its receiving third-order stream were analyzed for C, N, and P. The C/N/P concentrations were transformed to compare against the Redfield ratio (106:16:1 C/N/P), ideal for algal proliferation. Nitrogen was depleted relative to C and P at two sites on the agricultural ditch during extreme low-flow conditions, whereas P was depleted to C and N at the third. Tile drainage N and P losses during high flows shifted stoichiometry toward the Redfield ratio. Stoichiometry in the third-order stream was near the Redfield ratio at both hydrologic extremes, likely from wastewater treatment plant effluent.