Removal Of Free-Living Ciliates From Stock Cultures Of Two Calanoid Copepods With Sodium Hypochlorite

Eggs of Acartia tonsa and Parvocalanus crassirostris were contaminated with ciliates (Euplotes sp.) and exposed to five concentrations of sodium hypochlorite (25, 55, 105, 205, and 405 mg/L) for durations of 15 s, 5 min, 15 min, or 30 min to assess the efficacy of household bleach for removing the ciliates. Eggs from each exposure treatment were incubated for 40 h (A. tonsa) or 12 h (P. crassirostris) to assess hatch. The presence of living ciliates was evaluated after incubation, and the egg hatch rate (%) for the copepods was estimated for each treatment and in controls. Exposure to 105 mg/L total chlorine for 15 s killed all of the ciliates and reduced the copepod hatch rate by less than 26% with respect to controls in both species. Exposure to 55 mg/L for 15 min or 25 mg/L for 30 min also killed the ciliates and achieved a mean copepod hatch rate of 38.5% and 58.1% of the control-group hatch rate, respectively, in A. tonsa. Treatments for 5 min or longer reduced the hatch rate for P. crassirostris eggs by at least 76% at all of the concentrations that we tested.