Total biovolume of major green algae and cyanobacterial species growing on nutrient-releasing CDS for 20 days in March and June. C = control, P = PO₄³⁻-P, N = NO₃⁻-N, A = NH₄⁺-N, NP = NO₃⁻-N + PO₄³⁻-P, AP = NH₄⁺-N + PO₄³⁻-P. Data bearing different letters for a particular time period, uppercase for March and lowercase for June, are statistically different from each other (p < 0.05, Tukey's HSD test).