Impact of the herbicides 2,4-D and diuron on the metabolism of the coral Porites cylindrica.

This study investigates the effects of two herbicides on the hermatypic coral Porites cylindrica. The herbicides tested were 2,4-D and diuron, since they are commonly used and have different toxic characteristics. Corals were exposed to 10 and 100 mg l(-1) 2,4-D, and to 10, 50 and 100 micro g(-l) diuron for 48 h respectively, and the effects were measured using an oxymeter and a diving PAM fluorometer. Coral gross primary production rate, gross primary production to respiration ratio and effective quantum yield were significantly reduced when exposed to 100 mg l(-1) 2,4-D while respiration seemed unaffected. All three concentrations of diuron caused a significant reduction in all measured parameters except respiration and maximum fluorescence yield, where a significant reduction was detected at 50 and 100 micro g(-1) diuron, respectively.