Impacts of un-ionized ammonia in digested piggery effluent on reproductive performance and longevity of Daphnia carinata and Moina australiensis

In effluent treatment systems, a major concern is how to maintain culture of local zooplankton species (Daphnia carinata and Moina australiensis), particularly with the impact of un-ionized ammonia on their life cycle response. Hence the impact of un-ionized ammonia present in digested piggery effluent on the reproductive physiology and survival of D. carinata and M. australiensis was evaluated in this study. Both species were cultured in diluted digested piggery effluent and supplied with algae, Chlorella vulgaris as food. The effects of different un-ionized ammonia concentrations on total fertility, number of clutches, clutch size and survival were recorded every 24 h. The lethal concentration of unionized ammonia, with 50% survival after 24 h exposure to (24 hr LC50 values) un-ionized ammonia was determined for each species relative to total ammonia nitrogen, pH and temperature. M. australiensis had greater tolerance at higher levels of un-ionized ammonia than D. carinata. However, older neonates (< 48 h old) could survive at a higher concentration of un-ionized ammonia nitrogen (up to 2.8 mg/l D. carinata and 8.8 mg/l M. australiensis) than younger neonates (2.2 mg/l D. carinata and 7.5 mg/l M. australiensis). The net reproduction rates (R0) were derived from fertility and survival while the intrinsic rates of increases (r) were calculated with net reproduction rate and generation time. M. australiensis has a maximum R0 (189.84) and r (0.54) at 4.5 and 6.5 mg/l NH3–N, respectively, while D. carinata has a maximum R0 (100.46) and r (0.39) at 0.5 and 1.0 mg/l NH3–N. Hence, M. australiensis is a faster growing species than D. carinata when cultured in digested piggery effluent.