Repeated-measures analysis of variance of total phytoplankton biomass, chlorophyll a, chlorophyll a : biomass ratio, and biomass of major algal groups.

Probability (p) values were calculated for treatment and treatment-time interaction effects. Tukey’s HSD post hoc results represent mean treatment values ordered from largest to smallest and significant differences (>) at α = 0.05, for urea (U), nitrate (NO), ammonium (NH), and the control (C). If a treatment falls on both sides of a “>” this indicates no significant difference from the treatments on either side. All phytoplankton biomass (mg L−1) data, but not chlorophyll a concentrations (µg L−1), were log10(x+1) transformed prior to analysis to meet assumptions of normality. Probabilities were not corrected for number of comparisons. See Methods for additional information.