List of time-averaged concentrations (ng.L⁻¹) of herbicides found over one month's deployment at four sites in Keppel Bay and their photosystem II inhibition potential based on relative potency (potency factor^*) with respect to the reference diuron.

Photosystem II equivalent concentrations (PSII-HEq) were calculated for each site by summing the PSII-HEq for individual herbicides**. Relative potency factors of each of the herbicide with respect to the reference diuron, in terms of PSII inhibition. PSII-HEq were calculated by summing individual PSII-HEq for each herbicide derived by multiplying the time-averaged concentration in water by the relative potency with respect to the reference herbicide diuron [37].