Tolerance of un-ionized ammonia in live feed cultures of the calanoid copepodAcartia tonsaDana

Abstract

Optimal water quality is considered as being a restriction for marine copepod cultures for live feed. There is a lack of knowledge on the water‐quality conditions in copepod cultures and the effect on copepods. Few studies have investigated the effect of ammonia on copepods, and fewer reports No Observed Effect Concentrations (NOEC) and Lowest Observed Effect Concentrations (LOEC), which provides safety levels before cultures are affected. This study investigates the tolerance of Acartia tonsa nauplii and adults to ammonia, using mortality as the endpoint after 24, 48 and 72 h of exposure. Nauplii were exposed to levels from 0 to 5127 μg NH3 L−1 and adults to levels from 0 to 8481 μg NH3 L−1. Nauplii NOEC was 30 μg NH3 L−1 and LOEC was 81 μg NH3 L−1. Adult NOEC was 477 μg NH3 L−1 and LOEC was 1789 μg NH3 L−1. 50% Lethal Concentrations (LC50) for nauplii of 48 and 72 h was 1257 and 220 μg NH3 L−1. LC50 for adults was 2370 (24 h), 972 (48 h) and 770 (72 h). Combining NOEC with excretion rates of NH4/NH3 a model was developed to calculate densities in batch cultures. We recommend that for batch cultures of A. tonsa, NH3 is kept below NOEC for nauplii and that levels of NH3 together with pH are monitored weekly.

Homeostatic swimming of zooplankton upon crowding: the case of the copepod Centropages typicus

“…Similar values can be reached also in artificial conditions when a large number of individuals is needed for experimental trials [12], for aquaculture purposes [13][14][15] or when recording the motion of copepods [16]. As a drawback, high densities may impair copepod fitness, reducing food availability and egg production while increasing mortality [17][18][19], boosting the concentration of metabolic products and reducing water quality [20], and decreasing the respiration rate [15]. In addition, increasing copepod abundance can favour the transfer of oil droplets to lower trophic level by direct manipulation and egestion [21].…”

Effects of Temperature and Salinity on Egg Production, Hatching, and Mortality Rates in Acartia ohtsukai (Copepoda, Calanoida)

“…On the other hand, Støttrup et al (1986) reported that the daily copepod mortality rate of A. tonsa was constant at 5% in the optimal salinity gradient, but it increased by about 50% or more in high salinity with values above 25 psu (Medina and Barata, 2004). It is not practical to accommodate more than 50% mortality of live prey in mass production (Jepsen et al, 2015). The mortality of A. ohtsukai observed for 10 days showed a low rate of less than 25% on average at all water temperatures and salinities except at salinity values of 10 and 15 psu at a water temperature of 10 • C. Further, extensive salinity changes, except for a high salinity value of 33 psu, did not significantly affect HS in A. ohtsukai over 48 h. However, in the low temperature (10 and 15 • C) experiment, no eggs were produced at salinities of 10, 15, and 33 psu.…”

Eggs of the copepod Acartia tonsa Dana require hypoxic conditions to tolerate prolonged embryonic development arrest

“…1b and c, where the viability of eggs is constant for samples with much higher egg abundances than in the long term experiment. In dense static A. tonsa cultures, the level of ammonia can reach toxic limits due to the pH dependent equilibrium between NH 4 /NH 3 [43]. The release of NH 4 /NH 3 from A. tonsa eggs is unknown, but expected to be negligible.…”

“…The culture was started at the Danish Institute for Fisheries and Marine Research and has been continuously maintained for > 35 years without being restocked with wild animals. The physiology and ecology of the culture has been described in several publications [15, 16, 20, 29, 30, 41, 43].…”