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Add To Calendar 21/02/2017 14:00:0021/02/2017 14:20:00America/ChicagoAquaculture America 2017EVALUATION OF SODIUM HYPOCHLORITE IMMERSION PROTOCOLS FOR THE DISINFECTION OF Acartia tonsa AND Parvocalanus crassirostris CULTURES Room 11The World Aquaculture Societyjohnc@was.orgfalseanrl65yqlzh3g1q0dme13067DD/MM/YYYY

EVALUATION OF SODIUM HYPOCHLORITE IMMERSION PROTOCOLS FOR THE DISINFECTION OF Acartia tonsa AND Parvocalanus crassirostris CULTURES

Adam Daw*, Brie Sarkisian, Reginald Blaylock, and Eric Saillant
 
 Thad Cochran Marine Aquaculture Center
 Gulf Coast Research Laboratory, University of Southern Mississippi
 Ocean Springs, MS 39564
 Adam.daw@usm.edu

Contamination of live feed cultures by unwanted organisms can have major negative impacts on hatchery production.  The calanoid copepods Acartia tonsa and Parvocalanus crassirostris are major candidates as live feeds for marine aquaculture. Cultures of these two copepod species are commonly contaminated by a variety of bacteria, protists, algae, and rotifers, and protocols for their easy disinfection/re-isolation are essential for maintaining consistent production and reducing manpower and costs.

Previous work has demonstrated the effectiveness of a variety of antibacterials on copepod eggs, however protozoa also can reduce the productivity of copepod cultures by outcompeting the copepods for food, attaching to the copepods (occasionally being parasitic), and fouling culture tanks. To evaluate the effectiveness of sodium hypochlorite (bleach) for the control of protozoa in cultures of Acartia tonsa and Parvocalanus crassirostris, we exposed eggs of the two species to a range of bleach concentrations (25, 50, 100, 200 and 400 ppt total chlorine, Cl2) over a range of exposure durations (15 sec, 5, 15 and 30 min). Each treatment was replicated three times. For each treatment, copepod eggs were mixed with a concentrated protozoa culture containing Euplotes sp. and Euglena sp., exposed to each treatment, then rinsed three times with filtered saltwater. Water from the last rinse was tested for residual chlorine to confirm that all chlorine had been removed. Protozoa were visually observed after the rinses and then 40 hours post-exposure. Copepod egg hatch percentage was evaluated 40 hours after exposure. Results show that a bleach concentration of 50 ppt and above is effective in killing protozoa for all durations tested. For both species of copepods, egg hatch was negatively related to bleach concentration, and the correlation was stronger for the longer exposure durations. Eggs of both copepod species were able to survive exposure to a relatively high level of bleach (400 ppt) for a short period of time (15 sec.), but almost complete mortality (> 90%) was observed when exposure to high concentrations lasted 15 min or more. Differences in percent egg hatch between the two species at many of the treatment levels indicates that P. crassirostris is more sensitive to the exposure duration and bleach concentrations tested than A. tonsa.

This study showed that a 15 sec exposure to 50 ppt bleach was sufficient to control protozoa. This protocol would allow cost effective disinfection of large numbers of copepod eggs simultaneously, which can be useful when starting fresh cultures. However, because of the differences in bleach tolerance noted in the eggs of the two copepod species, the optimal bleach concentration and exposure duration may need to be adjusted in order to apply this method to other copepod species.

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