Acute and chronic un-ionized ammonia toxicity to ‘all-fish’ growth hormone transgenic common carp(Cyprinus carpio L.)

Ammonia is toxic to fish in natural and artificial waters.We evaluated the acute(96 h) and chronic(21 d) toxicity of un-ionized ammonia to GH transgenic common carp(Cyprinus carpio L.) and non-transgenic common carp using a static-renewal bioassay.The 24,48,72 and 96 h median lethal concentrations(LC50) of un-ionized ammonia were slightly lower in transgenic carp(2.64,2.44,2.28 and 2.16 mg N/L,respectively) than in non-transgenic carp(2.70,2.64,2.52 and 2.33 mg N/L,respectively).Similarly,the median lethal time(LT50) was significantly shorter for transgenic carp(1.41,7.91 and 117.42 h) than for non-transgenic common carp(2.53,14.06 and 150.44 h) following exposure to 3.86,3.29,or 2.09 mg N/L,respectively.Moreover,the mortality of transgenic carp was significantly higher than that of non-transgenic carp at all un-ionized ammonia concentrations((0.91 ± 0.12),(0.48 ± 0.06) and(0.12 ± 0.01) mg N/L) during the 21 d chronic toxicity test.Our results suggest that GH transgenic carp are less tolerant of unionized ammonia than non-transgenic carp.Our data are useful for evaluating potential environmental risk,optimizing stocking density in intensive aquaculture and establishing water quality criteria for ammonia in aquaculture.

Ammonia is toxic to fish in natural and artificial waters. We evaluated the acute （96 h） and chronic （21 d） toxicity of un-ionized ammonia to GH transgenic common carp （Cyprinus carpio L.） and non-transgenic common carp using a static-renewal bioassay. The 24, 48, 72 and 96 h median lethal concentrations （LCs0） of un-ionized ammonia were slightly lower in transgenic carp （2.64, 2.44, 2.28 and 2.16 mg N/L, respectively） than in non-transgenic carp （2.70, 2.64, 2.52 and 2.33 mg N/L, respectively）. Similarly, the median lethal time （LTso） was significantly shorter for transgenic carp （1.41, 7.91 and 117.42 h） than for non-transgenic common carp （2.53, 14.06 and 150.44 h） following exposure to 3.86, 3.29, or 2.09 mg N/L, respectively. Moreover, the mortality of transgenic carp was significantly higher than that of non-transgenic carp at all un-ionized ammonia concentrations （（0.91± 0.12）, （0.48 ± 0.06） and （0.12 ±0.01） mg N/L） during the 21 d chronic toxicity test. Our results suggest that GH transgenic carp are less tolerant of un-ionized ammonia than non-transgenic carp. Our data are useful for evaluating potential environmental risk, optimizing stocking density in intensive aquaculture and establishing water quality criteria for ammonia in aquaculture.