Pomacentrus amboinensis embryos were exposed experimentally, to a range of concentrations of the organophosphorus insecticide chlorpyrifos and monitored for survival and sublethal effects. Eggs from a single clutch were obtained from the captive breeding program at James Cook University and transferred to aquaria at the Australian Institute of Marine Science.
Appropriate amounts of chlorpyrifos were added to 50 µL of acetone and 700 ml of 1 µm filtered seawater to produce treatment solutions with concentrations of 50, 125, 250, 500, 750, 1000, 1250, 2000 µg/L. A control, which contained 50 µL of acetone in seawater was also used. Water quality parameters were monitored throughout the experiments (dissolved oxygen >85% saturation, pH 8.1±0.1, temperature 27±1°C, salinity 33.3±0.2 0/00).
Toxicity tests were carried out using healthy fertilised eggs, less than 10 hours old. Twenty randomly selected eggs were placed in each of three replicate 900 ml treatment chambers for each chlorpyrifos concentration. Numbers of dead, immobilised or abnormal embryos were counted after 72 and 120 hours and dead embryos removed. Heart rates were measured over a 1 minute period for 5 embryos from each treatment after 96 hours, using a Hi-8 video system connected to a stereo dissecting microscope.
On completion of hatching, numbers of normal, dead, or deformed larvae were counted and the percentage viable hatch calculated for each replicate. Surviving larvae were killed and their standard lengths measured. The experiment was terminated at 144 hours, as all eggs had hatched and mortality was extremely high at the highest concentrations.