Tolerance response to ammonia and nitrite exposure in larvae of two marine fish species (gilthead seabream Sparus aurata L. and Senegal sole Solea senegalensis Kaup)

Abstract

Gilthead seabream Sparus aurata L. and Senegal sole Solea senegalensis Kaup are two species of ®sh that are of primary importance in Mediterranean aquaculture. In the present study, the larvae of these species were exposed to different concentrations of total ammonia and nitrite for 24 h to examine the toxicity of both nitrogenous compounds to larvae under rearing conditions. The non-ionized ammonia (NH 3 ) and nitrite (NO 2 ± ) 24-h LC 50 values were 0.24 p.p.m. and 1997 p.p.m., respectively, in 12day-old S. aurata larvae. According to the criteria of 10% of LC 50 value, the rearing water for gilthead seabream larvae has to have levels below 0.024 p.p.m. non-ionized ammonia and 200 p.p.m. nitrite-N to be safe. In 7-day-old S. senegalensis larvae, the non-ionized ammonia (NH 3 ) 24-h LC 50 value was 1.32 p.p.m. No deaths occurred when S. senegalensis larvae were exposed to nitrite concentrations of up to 2000 p.p.m. for 24 h. Both species showed different tolerance levels to the two nitrogenous compounds and also showed differences in resistance to toxicity tests. S. senegalensis larvae were more resistant. This is probably associated with the greater amount of mucus in their skin.

Effect of some rearing systems on growth and development of the Egyptian sole (Solea aegyptiaca Chabanaud, 1927) larvae.

“…The growth rate for larvae has been increased gradually with increasing temperature until 20 °C then decreased. These results agreed with most studies on biological development and temperature in Senegal sole as many authors have used a constant temperature of 20 ºC (Martinez et al, 1999;Parra and Yufera, 1999;Ribeiro et al, 1999;Yufera et al, 1999;Canavate et al, 2006;Sanchez et al, 2010;Salas-Leiton et al, 2011, 2012. The Senegal sole (Solea senegalensis) is a flatfish adapted to temperate waters of around 20-21 ºC (Drake et al, 1984).…”

Weaning of Senegalese sole (Solea senegalensis) postlarvae to an inert diet with a co-feeding regime

“…According to Person-Le Ruyet (1997), unionized ammonia (NH 3 ) corresponds to 2-4% of TAN in saltwater. Using these reference values, the concentration of NH 3 obtained for the higher value observed in the present study corresponds to 0.03-0.05 mg NH 3 L -1 , well below the value of 0.13 mg L -1 recommended by Parra and Yúfera (1999) to prevent deaths.…”

“…The TAN concentration in water was kept lower than 1 mg L -1 for both treatments, although postlarvae from the Artemia treatment were exposed for two hours above this value (1.28 mg TAN L -1 ). Parra and Yúfera (1999) observed that total mortality was attained when Senegalese sole larvae were exposed to 80 mg L -1 of ammonia (TAN). Based on water temperature, oxygen and pH, these authors calculated a 24-h LC 50 (NH 3 ) of 1.32 mg L -1 for this species (1.6% of TAN).…”

“…According to Parra and Yúfera (1999), fluctuating levels of TAN may have a more toxic effect than a continuous exposure.…”

Ammonia/ammonium dissociation coefficient in seawater: A significant numerical correction

“…To highlight this, two examples have been chosen, although many more are likely to exist within the literature: (i) aquaculture studies; and (ii) airsea NH 3 flux studies. These examples have been chosen in part because many research groups (including our own) have used the Khoo et al [1] equation as part of aquaculture studies [12,13] and air-sea NH 3(g) exchange studies. [14][15][16] (i) It has been shown that NH 3 is toxic to many organisms above certain threshold levels.…”